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THE EFFECTS OF ACUTE PSYCHOLOGICAL STRESS ON CARDIOVASCULAR
REACTIVITY AND RENAL EXCRETION IN A SAMPLE OF NON-SMOKERS
A SSRC Funded Research Study
Matthew C. Scanlin
May 2008
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Abstract
A number of studies have reported that activation of the sympathetic nervous
system (SNS) by psychological stress can detrimentally affect the cardiovascular and
renal systems. When the SNS is activated by psychological stress, the release of
catecholamines increase cardiovascular reactivity and stimulate the renin-angiotensinaldosterone system (RAAS), causing the kidneys to retain sodium and water. These two
responses contribute to the observed increases in blood pressure, which can damage
organs such as the kidneys and the heart as well as others. Therefore, psychological
stress is a contributing risk factor for cardiovascular disease (CVD) and kidney disease.
Cardiovascular disease is the number one cause of death in America and kidney disease
can be terminal as well. Patients presenting with either condition often have the other or
a higher risk of developing it.
The current study assessed the effects of psychological stress on cardiovascular
reactivity and renal excretion. Cardiovascular reactivity (HR, SV, CO, SBP, DBP, MAP,
& TPR) was measured by bio impedance technology and renal excretion was assessed by
urine test strips, graduated cylinders, and hydrometers. Twenty healthy, nonsmoking
participants (10 males, 10 females), 19-22 years of age, were assigned randomly to either
a stressed condition (n=11) or a non-stressed condition (n=9). Each participant attended
two sessions: a pre-testing session consisting of a urine sample collection and
questionnaires and a testing session twelve hours later. The testing session measured
cardiovascular reactivity and affect (Visual Analog Scale) during a 10-minute baseline
period, a 6-minute Paced Auditory Serial Addition Task (PASAT), and a 16-minute
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recovery period. During the testing session, urine was collected before the start of the
baseline period and after the recovery period.
Repeated measures ANOVA revealed significant Task effects for each
cardiovascular variable measured (p< .05), such that during the PASAT, HR, CO, SBP,
DBP, MAP, & TPR were significantly increased and PEP and SV were significantly
decreased as compared to the baseline task. The study also found significant Task x
Condition interactions for HR, SBP, DBP, MAP, and PEP (p<. 05), such that participants
in the stressed condition demonstrated greater increases in HR, SBP, DBP, & MAP and
greater reductions in PEP from baseline to PASAT as compared to participants in the
non-stressed condition. No significant Condition effects were found for cardiovascular
reactivity. In regards to renal excretion, no main effects for Task or Condition and no
Task x Condition effects were found. These findings demonstrate that acute
psychological stress affects the cardiovascular system but may not affect the kidneys.
Introduction
Overview
Acute psychological stress can activate the sympathetic nervous system (SNS),
causing the release of the catecholamines, epinephrine and norepinephrine (Pike, et al.,
1997). These hormones affect the cardiovascular system, by increasing heart rate (HR)
and blood pressure (BP). The stimulation of the SNS by acute psychological stress has
also been shown to affect the kidneys, as indicated by the increase in plasma levels of
renin (Clamage, Vander, & Mouw, 1977). Renin contributes to the renin-angiotensinaldosterone biochemical pathway, leading to increases in BP due to increases in total
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peripheral resistance (TPR), the degree of constriction of the smooth muscles in the blood
vessels, as well as increased water retention (Givertz, 2001).
The increase in BP, resulting from the effects of SNS stimulation on the
cardiovascular and renal systems, can cause damage to organs, the heart and kidneys
included. Therefore, it is believed that psychological stress is a risk factor cardiovascular
disease (CVD) and kidney disease. Cardiovascular disease is the number one cause of
death in the U.S. according to the American Heart Association (AHA, 2003), contributing
to the death of one citizen every 35 seconds (Thom et al., 2006). Kidney disease is
another large health care concern, afflicting 10.9 million Americans (National Kidney
Disease Education Program: Final Strategic Plan, 2001). Given that psychological stress
can contribute to the risk for both diseases, it is important to study the effects of acute
psychological stress on both the cardiovascular and renal systems. Therefore, before the
current study is discussed a brief overview will be provided on psychological stress and
the various physiological responses it elicits.
Definition of Psychological Stress
Stress has two prominent working research definitions. Selye has defined stress
as a nonspecific response to any emotion or physical stressor (Selye, 1956, 1976, 1982;
as cited in Brannon & Feist, 2007). Responses to these stressors involve the nervous,
endocrine, and immune systems. The response of the body to a stressor was deemed by
Selye the “general adaptation syndrome (GAS).” The Gas was composed of three stages
which a person moves through in response to a stressor. The “alarm” stage is the
person’s initial reaction to a stressor, where the person physically prepares for the
stressor. Then the resistance stage occurs where the person attempts to cope with the
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stressor. If the person fails to adapt the person may eventually enter the exhaustion stage,
where an individual may become ill or die.
Lazarus and Folkman established a definition of psychological stress being a
relationship between the person and environment (Lazarus & Folkman, 1984; as cited in
Brannon & Feist, 2007). In this relationship psychological stress is mediated by both the
cognitive appraisal and coping abilities of an individual. Cognitive appraisal is how
threatening the person views the psychological stressor. A person first appraises an event
as either stressful or not, then judges the amount of resources available to cope with the
event if deemed stressful, and then reappraises the event as stressful or not in light of the
available coping resources. Coping is to what extent the person will be able to manage
the appraised stressor. Our body has physiological mechanisms in place to help us cope
with stressors. When presented with stressors, our body is capable of releasing specific
hormones to alter our physiology to better face the stressor. This is commonly referred to
as the fight or flight response. Three biological systems are involved in this response,
each releasing their own hormones and together they help the body cope with stressors.
What follows is a description of the three systems: the renin-angiotensin-aldosterone
system (RAAS), the hypothalamic-pituitary-adrenocortical (HPA) system, and the
sympathetic adrenal medulla system (SAM).
Stress Response of the Renin-Angiotensin-Aldosterone System (RAAS)
To discuss the stress response of the RAAS, which is initiated by the kidney, it’s
essential to first establish the literature’s findings on SNS activity in the kidney. The
central nervous system (CNS) is able to communicate with the kidney sympathetically
via renal nerves. The kidney is imperative to cardiovascular function, in that it regulates
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the composition and volume of the body fluids. The kidney responds to signals from
mechanosensitive and chemosensitive receptors to maintain homeostasis in body fluids.
Not only can the CNS communicate with the kidney, but the kidney has sensory fibers
that send signals from sensory receptors on the kidney to the CNS. This acts as feedback
system to ensure homeostasis is maintained (Dibona, & Kopp, 1997). It’s important to
discuss the physiology of the kidney’s connection to the SNS because when the stress
response is discussed it will make reference to the physiology of the kidney and its SNS
innervation discussed below.
It has been shown that the renal nerves are important to maintaining homeostasis
of the body fluid. A study of nondiuretic rats by Bellow-Reuss, Colindres, PastorizaMuÑoz, Mueller, and Gottshalk (1975) found that denervation of the left kidney
significantly increased urine volume and sodium excretion in comparison to the
innervated right kidney. Thus in the absence of the renal nerves, diuresis and natriuresis
occurs, demonstrating the renal nerves involvement in body fluid homeostasis.
To further elaborate upon this finding it’s important to note a study by
Wågermark, Ungerstedt, and Ljungqvist (1968) which found that the walls of the
juxtaglomerular arterioles, blood vessels that branch off of the kidneys’ arteries, contain
granulated cells believed to contain renin and are believed to be directly connected to the
SNS. The nerve fibers of these renin containing arterioles are similar to other nerve
fibers in the human body which contain norepinephrine, a neurotransmitter of the SNS.
Therefore, it can be concluded that this study provides an explanatory mechanism for the
release of renin in response to SNS stimulation.
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A study demonstrating this mechanism was performed by La Grange, Sloop, and
Schmid (1973), who found that stimulation of the renal nerves of dogs resulted in
significant decreases in sodium excretion, meaning there was an increase in sodium
reabsorption by the kidney. In addition, the study demonstrated that renal nerve
stimulation resulted in increased renin production by the kidney (La Grange, Sloop, &
Schmid, 1973). Therefore the increased sodium reabsorption could be attributed to the
increased renin production which could have activated the renin-angiotensin-aldosterone
system (RAAS), producing aldosterone, to induce the sodium reabsorption observed.
Another study by Bunag, Page, and McCubbin (1966) confirmed these findings in
the above study. They found that inducing hemorrhage in anesthetized dogs caused the
release of renin. This release of renin was prevented by ganglion blockade or local
anesthesia in the renal nerves, indicating the involvement of the renal nerves in the
release of renin. Furthermore, they observed increases in renin after infusions of
norepinephrine, a common SNS neurotransmitter. These two observations, again
contribute to the support of renal nerve involvement in the SNS’ release of renin. In
addition, stimulation of the renal nerve has been observed to cause increases in
norepinephrine in the renal plasma (Bradley, & Hjemdahl, 1984). Norepinephrine, a
neurotransmitter and catecholamine affects the function of the kidney by attaching to
alpha and beta adrenergic receptors (adrenoceptors) located on multiple parts of the
kidney and releasing renin (Winer, Chokshi, Yoon, & Freedman, 1969).
It is important to also note that sympathetic nerve activity is not a global process.
It’s believed that most organs are innervated by the SNS and that they are controlled
regionally as opposed to globally. For example, when cardiac baroreceptors are activated
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in the left atrium, they increase cardiac sympathetic nerve activity, but decrease efferent
renal nerve sympathetic activity, while leaving other nerves unchanged (Karim, Kidd,
Malpus, & Penna, 1972). Thus the SNS doesn’t cause the same systematic changes on all
nerves innervating different organs, but rather changes the action of each one
independently. So global measures of SNS activity such as plasma norepinephrine, renin,
and other hormones or muscle sympathetic nerve activity may not be reliable indicators
of regional SNS activity in the kidney. Still these are the most common measures used
because they are the most practical measures to attain in studies of stress reactivity.
The stimulation of the SNS as well as renal hypoperfusion, a reduction in blood
flow reaching the kidney, and decreased sodium delivery to the kidneys can activate the
renin-angiotensin-aldosterone system (RAAS) by releasing renin from the
juxtuloglomerular cells, renin-containing cells in the kidney. Renin then cleaves
angiotensinogen, an enzyme produced in the liver, giving rise to angiotensin I.
Angiotensin I circulates to the lungs, where it is then converted to angiotensin II by
angiotensin converting enzyme (ACE). Angiotensin II is important because it continues
the RAAS biochemical pathway but it can also independently bind to angiotensin II type
1 and type 2 receptors, leading to sodium and water retention in the kidney and
vasoconstriction in the vasculature. Angiotensin II perpetuates the RAAS by being
converted to aldosterone in the adrenal cortex. Aldosterone is the final hormone product
of the RAAS and it, like angiotensin II, also promotes sodium and water retention in the
kidney (Givertz, 2001). Aldosterone production can also result from the release of
ACTH (Skowronski, & Feldman, 1994), which is part of the next system discussed
below, the hypothalamus-pituitary-adrenal system. The RAAS which begins in the
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kidney with the release of renin, influences the stress response along with other systems
in the body.
Hypothalamus-Pituitary-Adrenal System’s Contribution to the Stress Response
The hypothalamus-pituitary-adrenal (HPA) system is activated by the SNS
stimulation and like the RAAS contributes to increases in BP in response but it also
increases HR. The hypothalamus is part of the central nervous system and it creates
hormones within its neurons and releases them in response to signals sent by other
neurons from higher brain centers that respond to environmental signals. The
hypothalamus releases corticotrophin-releasing hormone (CRH), which than travels via
the blood to the anterior pituitary to produce ACTH which stimulates the adrenal cortex
to release cortisol (Hiller-Strumhőfel, & Bartke, 1998) and aldosterone (Skowronski, &
Feldman, 1994). Cortisol causes an increase in HR, BP, and glucose metabolism and
aldosterone increases BP through the retention of water in the kidney.
Stress Response of the Sympathetic-Adrenal-Medulla (SAM) System
The sympathetic nervous system has already been mentioned to have an effect on
the RAAS but it contributes to the stress response in one other key way. The
hypothalamus can communicate directly with muscles and body organs by sending
signals through nerves of the autonomic nervous system rather than relying on hormones
to send a message. The medulla of adrenal gland is directly innervated by the SNS. In
response to SNS stimulation the adrenal medulla can release catecholamines, such as
norepinephrine and epinephrine. The catecholamines are partially responsible for the
increased vasoconstriction observed in blood vessels, as well as the increased HR, and
CO observed in response to stress. The SNS can as mentioned above cause the release of
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renin from the kidney, which can then cause affect the cardiovascular system via the
RAAS. Additionally, the stimulation of the SNS can also release norepinephrine from
the central nervous system to affect receptors on the heart (al’ Absi, Wittmers, Erickson,
Hatsukami, & Crouse, 2003). So in conclusion psychological stimulation of the SNS
affects the body in three ways: it activates the RAAS, the adrenal medulla, and receptors
on the heart.
Psychological Stress Induced Renal Reactivity
The major contribution of the kidneys to the stress response is the release of renin
in response to SNS arousal. The renin than activates the RAAS, a long biochemical
cascade, which cause increases in BP in two ways, it can directly constrict the vasculature
and it can cause the retention of water increasing plasma volume in the blood. A study
by Clamage, Vander, and Mouw (1977) studied the effects of several psychosocial
stimuli on PRA in normotensive, healthy subjects. The study tested 12 (six males, six
females) healthy, normotensive, male and female participants, ranging in age from 19-24
years of age. Subjects were screened for and excluded from the study if they had cardiac
or kidney diseases and prescriptions for certain medications.
The experiment assigned subjects to one of two possible protocols, each of which
had two conditions, an experimental and a control condition, which occurred on separate
days. The subjects of the first protocol had to participate in an experimental session
including a rotated letters test (3.5 min), stroop color test (2.5-6.0 min), neisner search
test, which has subjects search for specific letters amounts a group of letters (3.0 min),
grammatical reasoning (4.0 min), and mental arithmetic (4.0 min). All responses had to
be read aloud and the experimenter reported when participants were wrong and told them
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to do better. The other day was a control where subjects read magazines for 95 minutes.
If subjects were in protocol two, they participated in one or two control sessions lasting
90 min each and consisted of reading magazines. The experimental day for protocol two
included a 90 min movie “The Glass House.” PRA, HR, and BP were measured during
the control and experimental sessions in each protocol.
All experimental stressors, the puzzles and the movie, caused a significant
increase in SBP but no significant increase PRA. However, subjects were told in advance
that they would be performing puzzles in the puzzle protocol and this resulted in higher
PRAs that were strongly correlated with anxiety. This provides some evidence for a link
between psychological stress and increased PRA.
A previous study by Syvalahti, Lammintausta, and Pekkarinen (1976) confirms
the above finding that acute psychological stress can significantly increase PRA. This
specific study measured PRA in 131 healthy volunteer, medical students, who were
exposed to the psychological stress of a pharmacology examination, and 83 control
subjects, who had no test. The study recruited 89 students (52 male and 37 female) who
were taking a written pharmacology test and 42 students (30 male and 12 female) taking
an oral pharmacology test. After 10 minutes, blood samples were collected from students
taking the oral exam, which lasted 26 to 130 minutes (mean 83 minutes). In the written
exam, blood samples were taken anywhere between 25-200 minutes from the start. After
a half hour lecture, blood was withdrawn from 83 medical students (48 male 35 female)
in the control group.
The study found that PRA increased significantly after either a written or oral
exam in medical students. However the mean values of the PRA values were within
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normal ranges. This increase in PRA in response to acute psychological stress was
attributed to stimulation of the SNS.
These increases in PRA in response to acute psychological stress may contribute
to the observed increases in BP in response to acute psychological stress. Furthermore,
this mechanism for increased BP may be one way people develop hypertension
(diagnosed chronic high BP condition). This notion is supported by a study performed by
Baumann, Ziprian, Godicke, Hartrodt, Naumann, and Lauter (1973). Their study found
that HR, BP, and PRA increased significantly in response to acute psychological stress in
both normotensive subjects and subjects with essential hypertension (early stages of
hypertension) but increased significantly more so in the subjects with essential
hypertension.
This study included 30 participants with essential hypertension and 20
normotensive participants. All subjects were between 15 and 20 years of age and were
male. All subjects spent the night in the lab to acclimate to the setting. Immediately
before the beginning of the experiment, subjects were connected to cardiovascular
equipment known as a Physiomat (Rentsch & Co., Pirna, GDR). They then had an IV
performed on them 30 mins prior to the stress task so that blood samples of PRA could be
collected at various time points before and after the stressor. After a 30 minute baseline
period, subjects were exposed to a mental arithmetic, psychological stress task for
upwards of 14 mins. Afterwards subjects rested in a sitting position for 30 mins and then
had to rest in a standing position for 1.5 hrs.
The study determined that both groups of subjects had a significant increase in the
means for BP and HR between the baseline and stress conditions but that the participants
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with essential hypertension had a significantly greater increase in these means. In regards
to mean PRA, it also significantly increased in both groups in response to the stressor but
it did not increase significantly more in the hypertensive subjects as compared to the
normotensive subjects until the beginning of the standing recovery period, which began
30 mins after the stressor and lasted for 1.5 hours. These results provide an explanatory
mechanism for how psychological stress could contribute to the differences between
normotensive and hypertensive people. Overall, it seems one mechanism by which acute
psychological stress increases BP could be by increasing PRA. As already discussed in a
previous section, an increase in PRA can then activate the RAAS to induce the retention
of water and the constriction of the vasculature, both of which subsequently increase BP.
Psychological Stress Induced Cardiovascular Reactivity
One study by Sloan, Shapiro, Baciella, Bigger, Lo, and Gorman (1996)
investigated cardiovascular reactivity to psychological stress. The study found
significant increases in norepinephrine (NE), HR, SB, and DBP. The study was
performed on thirty-four (31 men, 3 women) participants with a mean age of 37.8± 13.35
years. Subjects were determined to be healthy with no history of cardiac disease or
medication use. Subjects were attached to EKG leads in the morning after a light
breakfast. Then an IV was established in an arm for blood sampling. Subjects rested for
30 minutes, then underwent a 5 minute baseline, followed with a 5 mental arithmetic and
two five minute recovery periods.
The study found that the mental arithmetic (the psychological stressor) induced
significant increases between baseline and mental arithmetic in NE, HR, and SBP and
DBP. These results indicate that psychological stress can affect the heart, most likely
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through the release of norepinephrine into the blood from the adrenal gland in response to
SNS stimulation by psychological stress.
Another study by Patterson, Marsland, Manuck, Kameneva, and Muldoon (1998),
performed shortly after the previous study, reinforced its findings. This study utilized 29
healthy, nonsmoking men between the ages of 18 and 30 years with no history of CVD.
An automated BP cuff was placed on one arm of each subject to measure HR, SBP and
DBP during 2 tasks: a 30 min baseline and a 5 min task consisting of public speaking, for
participants in the stressed condition, and rest for participants in the non-stressed
condition. The mean values for HR, SBP, and DBP in the participants exposed to the
stressor increased significantly in comparison to their mean values at baseline. In the
participants not exposed to the stressor, no significant differences were observed in these
values. This study provides further evidence that the cardiovascular system can be
affected by acute psychological stress.
These acute increases in HR and BP in response to acute psychological stress are
believed to occur because of their evolutionary advantage. Our ancestors needed this
mechanism to ready them to defend against threats. But in our modern society this
mechanism is maintained even though it exceeds our needs in response to acute
psychological stressors we face daily. If acute stressors occur repetitively they can
become chronic stressors. Chronic stress is maladaptive because it chronically elicits
these cardiovascular responses which can jeopardize a person’s health.
A study by Kaplan, Manuck, Clarkson, Lusso, and Taub (1982) demonstrates the
detrimental effects of chronic psychological stress on the cardiovascular system. They
performed a study on 30 Cynomolgus monkeys, with an average age of 7.5 years. They
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were all fed a diet intending to mimic a typical North American diet, with 43% of the
calories coming from fat. The monkeys were split into two groups of 15. One group was
in an unstable condition, meaning the monkeys in this group were constantly being
removed from their peers and being placed with new monkeys. Monkeys are very social
creatures and having to constantly reassert themselves in a social hierarchy is believed to
be psychologically stressful for them. In the first 12 months of the 22 month study, the
monkeys in the unstable condition were exposed to new monkeys every 12 weeks. For
the last 10 months of the study, these monkeys were exposed to new monkeys every 4
weeks. The remaining 15 monkeys not in the unstable condition were placed with
monkeys that they stayed with throughout the entirety of the 22 month period.
At the end of the 22 months, all the monkeys in those 2 conditions were killed.
Cross sections were taken from their coronary arteries. The researchers observed a
significantly greater degree of atherosclerosis in the cross sections from the monkeys in
the unstable condition. Atherosclerosis is plaque build up along the walls of arteries.
This occurs as part of an inflammatory response to damage occurring to these walls.
High BP can damage the walls and in response plaque builds up and thickens the wall of
the arteries. The significant increase in atherosclerosis in these monkeys was attributed
to the likelihood that the chronic psychological stress, experienced by these monkeys
constantly having to reassert themselves in a social hierarchy, caused BP to increase and
subsequently damage the walls.
In order to confirm it was the increase in BP, in response to chronic psychological
stress induced by stimulation of the SNS, that damaged the vasculature, a follow up study
was performed by Kaplan, Manuck, Adams, Weingand, and Clarkson (1987). This study
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placed 30 monkeys in an unstable condition, where they were introduced to new monkeys
every month. The 30 monkeys were split into 2 groups, with the first receiving
propanolol, a beta-blocker which blocks the beta receptors of the cardiovascular system
to prevent epinephrine and norepinephrine from mediating their effects. The second
group received no propanolol. All monkeys received a similar diet as the one from the
previous study. At the end of 26 months, the monkeys were killed and cross sections of
their coronary arteries were taken.
When comparing the two groups, the researchers found that the monkeys treated
with the beta-blocker had significantly less atherosclerosis than the monkeys without the
beta-blocker. This indicated that the SNS was being stimulated, most likely by the
chronic stress, and causing the release of epinephrine and norepinephrine, which when
left unblocked by propanolol, still caused increases in BP that damaged the arteries of
these monkeys. When the propanolol was present, the monkeys’ arteries could not be
damaged as easily. Therefore atherosclerosis was significantly reduced in these monkeys
on beta-blockers. This finding suggests that chronic psychological stress can have
detrimental affects on the body. If atherosclerosis becomes to severe a heart attack or
stroke can occur when arteries connected to these organs become occluded.
Psychological stress can mediate detrimental effects on both the kidneys and the
cardiovascular system. Damage to these organs and others can occur in response to
chronically high BP occurring from chronic psychological stress. Kidney disease and
CVD can result from such damage. These two diseases are huge health care concerns
both because of the amount of people afflicted by them and because of how much they
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cost to treat. Therefore, more research is needed to continue to clarify how these two
organs respond to psychological stress.
Specific Aims and Hypotheses
The research thus far indicates that acute psychological stress can cause the
cardiovascular system to increase HR and BP and the kidneys to increase the release of
rennin, which can also lead to an increase in BP. However, the research available that
considers how both of these organ systems respond to psychological stress is limited.
Therefore, this study aimed to further investigate the effects of acute psychological stress
on the cardiovascular system and kidneys. The current study measured cardiovascular
reactivity and renal excretion, an indirect measure of RAAS reactivity, in participants
exposed to an acute psychological stressor and participants not exposed to an acute
psychological stressor. Based on the previous literature it was hypothesized that:
1) Participants in the stressed condition would experience a greater increase in
cardiovascular reactivity as compared to participants in the non-stressed
condition.
2) The study explored for differences in the volume of urine excreted between the
participants in the stressed and non-stressed conditions, which would be
indicative of a difference in SNS arousal.
3) The study also explored for differences between participants in the stressed
and non-stressed conditions in specific gravity of the urine excreted, which would
be indicative of a difference in SNS arousal
Methods
Participants
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Twenty healthy participants (10 males and 10 females) between the ages of 18
and 22 years (mean= 20.75 ± .967) were recruited via flyers from the student population
and local community at St. Michael’s College in Colchester, VT (Appendix A). To take
part in the current study, all participants had to meet the following standards: a) 18-35
years of age, b) good physical health as indicated by absence of chronic or acute illness
(Appendix B), c) body mass index (BMI) between 19 and 30, d) absence of medications
with the potential to effect cardiovascular reactivity and kidney function (as defined by
the American Heart association: Cardiac Medications At-A-Glance, 2007) (Appendix B).
All participating subjects abstained from the use of tobacco products or cigarette
smoke areas for 12 hours preceding their involvement in the study. Participants abstained
from the consumption of caffeine and strenuous exercise for 12 hours prior to the testing
session. Participants also stopped eating 8.5 hours prior to testing and were allowed only
a limited amount of water based upon their body weight between 7.5 and 8.0 hours prior
to testing. All participants underwent two sessions: a pre-testing and a testing session.
During the testing session, eleven subjects were exposed to a psychological stressor and
nine subjects were not.
Physiological Measurements
Blood Pressure (BP). Systolic blood pressure (SBP), the pressure against the
walls of the vasculature when the left ventricle of the heart is contracting, and diastolic
blood pressure (DBP), the pressure against the vasculature when the left ventricle of the
heart is at rest, were measured by an automated Tango Blood Pressure Monitor. Blood
pressure measurements were performed on the participants’ non-dominant arm at specific
intervals during the testing session.
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Heart Rate (HR). Electrocardiograms (EKG) were measured using a three lead
method. Three bipolar silver-silver electrodes were used to assess the electrical activity
of the heart. To determine HR, an interbeat interval (IBI) calculation was performed by
the COP-WIN/HRV 6.10 software program (Bio-impedance Technology, Inc., Chapel
Hill, NC), operating on a Gateway computer (Gateway, 2005).
Cardiac Output (CO) and Stroke Volume (SV), and Pre-Ejection Period (PEP).
Cardiac output, stroke volume, and PEP were measured by an Impedance Cardiograph
modal HIC-3004/T (Bio- Impedance Technology, Inc., Chapel Hill, NC). The HIC3004/T was attached to three bipolar silver-silver electrodes and four cardiograph bands
in accordance with an established method (Sherwood, Allen, Fahrenberg, Kelsey,
Lovallo, & van Doornen, 1990; see procedure). This non-invasive method of impedance
cardiography measures aortic flow and relates it to changes in thoracic resistance (Miller
& Hovath, 1978). As mentioned above the COP-WIN/HRV 6.10 software calculated HR
from the EKG signals sent by the electrodes. In addition, this software also calculated
SV using the Kubicek formula (Kubicek, Karnegis, Patterson, Witsoe, & Mattson, 1966).
This allowed the software to calculate cardiac output (l/min), which is the product of
mean SV (ml) and HR (bpm) during each minute of recording (Kubicek et al., 1966).
Pre-Ejection period is a complex measure of time for the left ventricle to contract.
Reductions in contraction time are associated with SNS arousal.
Total Peripheral Resistance (TPR). The COP-WIN/HRV 6.10 software also
calculated TPR with a formula involving both CO and mean arterial blood pressure that
follows: TPR (dyne-seconds/cm-5) = (Mean Arterial Pressure/Cardiac Output) X 80.
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Height and Weight. Height and weight were measured using a Detecto medical
scale (Webb City, MO). Body mass index (BMI) was calculated using the equation
BMI= 703[weight (lb)/height (in2)].
Urinalysis. Four oz. McKesson Medi-Pak sterile specimen cups (McKesson
Corporation, San Francisco, CA) were used to collect subjects’ urine before the baseline
period and after the recovery period. A 100 mL graduated cylinder was used to measure
urine volume. A 15 cm hydrometer and its associated jar (CLIA waived, Inc., San Diego,
CA) were used to measure specific gravity within a range of 1.000 to 1.060 with a
precision of 0.001. The hydrometer is a long, narrow, glass, cylinder with a weighted end
to allow it float upright in a liquid. Each subjects’ urine was poured into the jar and then
the hydrometer was placed slowly into the jar, weighted end down. The cylinder contains
a scale to measure specific gravity. Wherever the urine surface met the scale of the
cylinder, was noted as the specific gravity of the urine. Specific gravity is a ratio of the
density of the measured liquid, in this case urine, to that of water. Therefore it has no
units. Only urine samples of 70 mL or more could be tested for specific gravity with this
method. Urine samples smaller than 70 mL had to be measured with test strips.
Also urinalysis test strips with 10 parameters (CLIA waived, Inc., San Diego, CA)
were used to assess specific gravity in the urine obtained from the pre-testing session and
the baseline and recovery periods of the testing session. The test strips have 10 sets of
chemical reagents on them, each testing a different aspect of the urine. Each reagent set
changes color in response to the urine composition. When testing the urine, the
experimenter submerged the strip in the urine held in the urine cup and immediately
removed the strip. The strip was then dabbed on a piece of paper to dry it. Afterwards, at
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specific time intervals, the experimenter matched the test strips’ colors to a chart that
defined what the color changes meant in relation to urine composition.
Manual Blood Pressure. Manual blood pressure measurements were taken with a
Littmann cardiology three stethoscope (St. Paul, MN) and a manual sphygmomanometer
complete with a mercury manometer and an inflatable cuff. All blood pressure
measurements were taken by a Vermont licensed emergency medical technicianintermediate.
Water Calculation. To calculate the standard amount of water given to individual
subjects, the following calculation was used: 8.0 mL of water * body weight (in Kg).
This amount was marked on a plastic cup for them to take home. For example, an
individual who weighs 50 Kg was assigned approximately 400 ml or the equivalent of 1.5
cups. The volume of water in mL was measured using a 100 mL graduated cylinder.
Task Description
Paced Auditory Serial-Addition Task (PASAT). The PASAT is a mental
arithmetic task designed to measure rehabilitation from concussion (Gronwall, 1977)
(Appendix C). However, it has been modified to be used to induce psychological stress
in cardiovascular reactivity research (Willemson, Ring, Carroll, Evans, Clow, &
Hucklebridge, 1998; VanderKaay & Patterson, 2006; Rochette & Patterson, 2005). The
PASAT was presented from an audio CD which provided the participant with a list of
numbers varying from one to nine for six minutes. The task was divided into three two
minute periods, presenting the digits at varying speeds, with the first period presenting
the digits at one digit per 2.4 seconds, the second period at 2.0 seconds, and the third and
final period at 1.6 seconds. For every two digits presented the participant had to provide
22
their sum as a verbal response, without confusing the sum with the next digit provided by
the CD for addition with the most recent previous number.
The experimenter remained in the room in clear view of the participant to
document all incorrect verbalized answers. To better ensure the participant’s continued
effort during the six minute task and to further induce acute psychological stress, the
experimenter informed all subjects they should be able to answer 80% of the total
responses correctly. The participant was allowed a brief practice session of ten numbers,
repeated until the subject was comfortable with the concept, before the actual task began.
One study by Willemson, Ring, Carroll, Evans, Clow, and Hucklebridge (1998)
found that in a sample of 16 healthy subjects, the administration of the PASAT following
a period of rest induced increases in SBP, DBP, TPR, and HR but decreases in PEP. A
study of 42 healthy adult males by Mathias, Stanford, and Houston (2004) found
significantly higher HR and BP measurements during a six min PASAT condition as
opposed to a rest condition. In another study, performed by Rochette and Patterson
(2005) significant increases in BP, HR, SV, CO, and TPR were found in a sample of nonsmokers in response to a PASAT task.
Questionnaires
Smoker’s Screening Questionnaire (SSQ). This 10-item experimenter-designed
questionnaire assessed subjects’ eligibility for the study based on their circled choices
and written responses to questions about their smoking behavior to determine if they
were chippers or habitual cigarette smokers or neither (Appendix D). This questionnaire
was hosted by surveymonkey.com, where subjects, who responded to flyers advertising
23
the study, answered it online. The experimenter reviewed each subject’s answers with
the subject on the day of testing, if the subject was selected for participation.
Health Information Screening Sheet (HISS). The HISS was a 12-item self-report
questionnaire designed by the experimenter to screen potential participants for eligibility
into the study (Appendix B). It inquires about participants’ height, weight, age, medical
history, medication use, and health behaviors (i.e. exercise and caffeine intake).
Participants responded by circling choices for each item that most adequately represented
them and on occasion writing a further elaboration on their answer when necessary. This
questionnaire was also hosted by surveymonkey.com. The experimenter reviewed each
subject’s answers with the subject on the day of testing, if the subject was selected for
participation.
24-Hour Profile. The 24-hour profile is a 10 item, experimenter designed, selfreport questionnaire used to ensure compliance with established subject participation
guidelines about smoking, eating, and exercise behaviors during various time intervals
between the pre-testing and testing sessions (Appendix E). Subjects responded by first
listing all of the foods they had consumed in the last 24 hours and then answered yes or
no to further questions regarding specific behaviors during various time intervals between
the two testing sessions.
Visual Analog Scale (VAS). The VAS, a self report questionnaire, modified from
Monk’s (1989) Global Vigor and Affect (GVA) was used to assess participants affective
state directly following the baseline, PASAT, and recovery tasks (Appendix F). The
scale includes nine adjectives (happiness, boredom, anxiety, satisfaction, depression,
interest, anger, frustration, and irritation) and two questions about the difficulty and
24
challenge encountered during the tasks. Participants were instructed to visually represent
their affect by drawing a perpendicular line through each of the eleven 10.00 cm lines of
the VAS, with each line beginning at “not at all” and ending at “extremely.” It is
important that the participant report affect as soon as possible in regards to a task so as to
accurately represent their affect during a task; thus the VAS simplicity and efficiency is
valued for this purpose. It is ideal because its simplicity and efficiency helps prevent
against the questionnaire itself influencing subjects affect in repeated measures designs,
such as this study (Monk, 1989).
Procedure
Recruiting/Scheduling. The study was advertised by flyers around St. Michael’s
College campus (Appendix A). Potential participants who responded to the flyers were
emailed a copy of the HISS (Appendix B) and SSQ (Appendix D). All participants who
were eligible based on their responses to these two questionnaires were contacted. The
participants, who chose to take part in the study, came to two sessions: a pre-testing and a
testing session. During the testing session all participants were randomly assigned to take
part in either a stress condition (n=11) or non-stressed condition (n=9). Together these
two sessions took approximately 80 minutes to complete. All participants were paid
$20.00 dollars as compensation for their time and also had the option of viewing their
blood pressure and heart rate results upon completion of the study. This study was
performed with permission and in accordance with the standards imposed by the
Institutional Review Board at Saint Michael’s College.
Pre-Testing Session. Each participant was asked to report to the lab for an
evening pre-testing session, 12 hours prior to testing. Upon arrival, each participant was
25
first asked to complete a consent form (Appendix G). They were then given one copy of
the consent form for their records (Appendix H). While at the pre-testing session, the
participant’s, height, weight and three manually measured blood pressures were recorded
(Appendix I). Blood pressure was assessed manually in order to confirm participants did
not have an existing hypertension condition. Subjects were asked to provide a urine
sample at the pre-testing session to establish their kidneys were functioning normally.
They were given a sheet of instructions on how to collect the urine sample (Appendix J).
Immediately after the pre-testing session, the experimenter used urinalysis test strips to
test each participant’s urine sample for specific gravity and the presence or absence of
protein, along with eight other miscellaneous variables. The experimenter also measured
specific gravity with a hydrometer and its associated jar. All urinalysis measurements
were recorded (Appendix K).
Before leaving the pre-testing session, the subjects were instructed verbally to
conform to a few behavioral stipulations over the night to prepare for the testing session.
Subjects were given a sheet to remind them of the stipulations (Appendix L). Each
participant was assigned a standard amount of water based on his or her weight. The
experimenter instructed each subject to consume the allotted amount of water between
1.0 and 0.5 hours before the time of testing. This request was made in an attempt to
standardize the amount of water in participants’ bodies and to ensure participants could
provide a baseline urine sample upon arrival at the lab for the testing session. With the
exception of the standardized amount of water, all subjects were instructed not to eat or
drink for 8.5 hours prior to the testing session. It was hoped that by restricting eating 8.5
hours prior to testing that subjects would be similar in sodium levels prior to testing,
26
although this couldn’t be completely standardized. This experiment attempted to
standardize participants’ sodium and water levels because this experiment measured
changes in urine concentration, which is influenced by participants’ baseline sodium and
water levels. The experimenter also asked participants to not drink any caffeine or
exercise anytime 12 hours before the testing session because this too could possibly alter
the balance of sodium and water in the body as well as possibly affect the cardiovascular
reactivity measurements obtained during the testing session.
Testing Session. All subjects were tested between 8 am and 12 pm Monday
though Friday, approximately 12 hours following the pre-testing session. The testing
session lasted between 80 and 90 minutes. Upon arrival for the testing session, subjects
were asked to provide a baseline urine sample. A sheet of directions on how to provide
the sample was given to them (Appendix J). After participants returned with the sample
they were asked to fill out the 24 Hour Profile (Appendix E). Whilst a participant
worked on filling out the questionnaire, the experimenter placed the urine sample in a
container in a separate room for analysis immediately following the testing session.
When the urine was tested, all measurements were recorded (Appendix K). Upon
completion of the 24 hour food profile the subject’s height, weight, and 3 manual BPs
were measured and recorded (Appendix I).
Next participants were prepped for impedance cardiography. To do so, two
electrode bands were applied to each participant’s neck and two were applied to each
participant’s chest. Then 3 EKG (silver-silver chloride bipolar) electrodes were placed on
the participant, with one EKG electrode placed directly below each collar bone and the
remaining EKG electrode was placed on the left side of the rib cage on the sixth inter-
27
coastal space. Prior to the placement of the three EKG electrodes, the skin where the
electrodes would be placed was cleaned with a benzalkonium chloride towelette. One
wire, with a metal clamp, was attached to each of the four electrode bands and to each of
the three EKG electrodes. These wires connected the participants to the Impedance
Cardiograph modal HIC-3004/T (Bio- Impedance Technology, Inc., Chapel Hill, NC). In
addition, an automatic, inflatable, BP cuff, connected to the Tango blood pressure
monitor was applied to the non-dominant arm of all participants. Then each subject,
while seated, underwent three tasks: a baseline period, a stress task, and a recovery
period.
To establish each subject’s baseline cardiovascular reactivity, subjects rested in a
dimly lit room in a sitting position for ten minutes while listening to calm music. This
allowed participants to acclimate to the study session and the surroundings of the
experimental room. Impedance cardiography (HR, SV, CO, PEP) was measured
continuously from minute seven until minute ten. In addition, blood pressure (SBP,
DBP) and TPR were obtained at minutes eight, nine, and ten. Immediately following the
baseline period, the subject completed the baseline VAS (Appendix F).
After the baseline period, if the participant was assigned to the stressor condition,
the participant engaged in the six minute mental arithmetic task, the PASAT (Appendix
C), with the lights turned fully on. If the subject was assigned to the condition with no
stressor, then they simply read numbers from a list, which were the same numbers
provided as answers by the subjects in the stressed condition. During the PASAT, in the
case of participants in the stressed condition, or the reading of the numbers, for the
participants in the non-stressed condition, impedance cardiography, BP and TPR were
28
measured continuously. Directly after the PASAT, the subject completed a second VAS
in response to the PASAT (Appendix F).
Following the completion of the second VAS, a subject’s cardiovascular
reactivity was assessed again while he or she rested in a sitting position listening to calm
music for 16 minutes in a dimly lit room. During this recovery period, impedance
cardiography was assessed continuously during the recovery period and BP and TPR
were measured every other minute. Afterwards the subject was asked to complete a third
VAS pertaining to the recovery period (Appendix F).
At the end of the recovery period, the cardiovascular reactivity equipment was
removed. Afterwards, a second urine sample was obtained and again the urine was put
aside in a container in a separate room for analysis following the completion of the
testing session. The participant was then compensated $20.00, debriefed (appendix M),
and any questions were answered. A complete overview of the tasks is provided in time
table format in appendix N.
Research Design, Data Reduction, and Statistical Analyses
Data Reduction. During baseline the impedance cardiography 55s ensemble
averages for HR, CO, SV, PEP, and TPR as well SBP and DBP measurements were
averaged over the last 3 minutes, to yield one value for each subject at baseline. All of
these measurements were averaged across the entire time period for each subject during
the PASAT task.
Data Analyses.
29
A series of repeated measures ANOVAs were conducted to test hypotheses 1, 2,
and 3. The within-subjects factors were baseline and PASAT and the between-subjects
factor was condition (stress, non-stressed).
Results
Sample Characteristics
The final sample consisted of 20 participants (11 stressed, 9 non-stressed). All
participants complied with the protocol and all subjects were retained in the study. In
addition to the final sample, there were seven subjects excluded due to difficulties with
the impedance cardiography equipment. There was no impedance cardiograph data (HR,
SV, CO, PEP, TPR) for three subjects but their SBP and DBP data and urine data were
still used. There was only one subject with no SBP or DBP data but their cardiograph
data was still useful.
The following are general characteristics of the final sample (n=20): Age
(M=20.75 years, SD= .97 years, range 19-22 years), BMI (M=22.39, SD=2.26). daily
caffeine consumption (M= 1.25 cups, SD= .99 cups), weekly exercise (M= 3.63 hours,
SD= 4.85). The study included 10 males and 10 females. In terms of medication use, 4
female participants were on birth control and 2 participants were on allergy medications.
Cardiovascular Reactivity
Main Effects. There were significant main effects for task for all cardiovascular
variables (HR, SV, CO, PEP, SBP, DBP, MAP, & TPR) (all p’s < .05), such that during
the PASAT, HR, CO,SBP, DBP, MAP, and TPR were significantly increased and PEP
and SV were significantly decreased as compared to the baseline task. There were no
main effects found for condition.
30
Task by Condition Comparisons. In order to assess the effects of acute
psychological stress on cardiovascular reactivity within the participants, a series of
repeated measures ANOVA’s were performed. Separate analyses were conducted for
each cardiovascular variable (HR, SV, CO, PEP, SBP, DBP, & TPR) using Task
(baseline, PASAT) as the within-subjects factor and Condition (stressed, non-stressed) as
the between-subjects factor.
There were significant Task x Condition interactions found for HR, F(1, 15)=
19.75, p< 0.0001, PEP, F(1, 14)= 9.76, p< 0.01, SBP, F(1, 17)= 18.61, p< 0.0001, DBP,
F(1, 17)= 6.09, p< 0.03, and MAP, F(1, 17)= 207.68, p<0.003. Independent samples ttests were conducted for all of these interactions with these cardiovascular variables’
change scores (PASAT values minus baseline values). In the stressed condition, the
participants had significantly greater increases in HR, t(15)= 2.33, p< .04, SBP, t(15)=
4.31, p< 0.0001, DBP, t(15)= 2.47, p< .03, and MAP, t(15)=2.33, p< .003, than
participants in the non-stressed condition (see Figures 1, 2, 3, & 4). In addition, the
participants in the stressed condition had a significantly greater reduction in PEP, t(14)=
3.12, p< .01 as compared to the participants in the non-stressed condition (see Figure 5).
No other Task x Condition interactions were demonstrated.
31
Non-stressed
95
Stressed
┌──────── * ─────────┐
90
85
HR (BPM)
80
75
70
65
60
55
50
baseline
PASAT
Figure 1. Heart rate (HR) reactivity for stressed and non-stressed
participants by task, * p<0.04
Non-stressed
Systolic Blood Pressure (mmHg)
135
Stressed
┌──────── * ─────────┐
130
125
120
115
110
105
100
baseline
PASAT
Figure 2. Systolic blood pressure (SBP) reactivity for stressed and nonstressed participants by task, * p < .0001
32
88
Non-stressed
86
Stressed
┌──────── * ─────────┐
Diastolic Blood Pressure (mmHg)
84
82
80
78
76
74
72
70
baseline
PASAT
Figure 3. Diastolic blood pressure (DBP) reactivity for stressed and nonstressed participants by task, * p < .03
105
Non-stressed
Stressed
Mean Arteriole Pressure (mmHg)
┌──────── * ─────────┐
100
95
90
85
80
baseline
PASAT
Figure 4. Mean Arterial Pressure (MAP) reactivity for stressed and
non-stressed participants by task, *p < .003
* p<0.003
33
165
Non-stressed
┌──────── * ─────────┐
160
Pre-Ejection-Period (ms)
Stressed
155
150
145
140
135
130
baseline
PASAT
Figure 5. Pre-ejection period (PEP) for stressed and non-stressed
participants by task, * p< .01
Renal Excretion Reactivity
Main effects. There were no significant main effects for task or condition for the
urine measures, specific gravity and volume (all p’s> .05).
Task by Condition Comparisons. In order to assess the effects of acute
psychological stress on renal excretion reactivity within the participants, a series of
repeated measures ANOVA’s were performed. Separate analyses were conducted for the
participants’ urine samples’ mean volume values and for their mean values of specific
gravity, as measured by test strips. The specific gravity values measured by the
hydrometer and its associated flask were not utilized for data analysis because much of
the data collected by this method was incomplete. The analyses used Task (baseline,
PASAT) as the within-subjects factor and Condition (stressed, non-stressed) as the
between-subjects factor. No significant Task by Condition interactions were found (see
figures 6 and 7).
34
Urine Volume (mL)
Non-stressed
Stressed
250
225
200
175
150
125
100
75
50
baseline
PASAT
Figure 6. Urine volume reactivity for stressed and non-stressed
participants, p > .05
Non-stressed
Stressed
Specific Gravity of Urine
1.016
1.014
1.012
1.01
1.008
1.006
baseline
PASAT
Figure 7. Urine Specific gravity (SG) reactivity for stressed and nonstressed participants, p >0.05
35
Discussion
The present study was performed to better understand the role the kidneys and
cardiovascular system play in making psychological stress a risk factor for CVD and
kidney disease. These are deadly diseases which are prevalent in the U.S. and the
treatment necessary for patients afflicted by them is often times very costly. Thus, it is
important to understand the risks factors for these two diseases so preventative care can
be improved. Therefore, the specific aim of this study was to investigate the effects of
acute psychological stress on non-smokers’ cardiovascular reactivity and renal excretion
reactivity.
As hypothesized, participants exposed to an acute psychological stressor
following a baseline period did respond with greater cardiovascular reactivity as
compared to participants not exposed to an acute psychological stressor. The participants
exposed to the stressor experienced greater increases in HR, SBP, DBP, MAP, and TPR
and a greater reduction in PEP than participants not exposed to the stressor. All of these
cardiovascular responses are indicative of SNS arousal (Sherwood & Turner, 1995;
Schächinger, Weinbacher, Kiss, Ritz, & Langewitz, 2001).
Although the stressor proved to be effective in stimulating the SNS, as indicated
by the cardiovascular response, renal excretion reactivity was not indicative of SNS
stimulation. The study found no difference between the stress and non-stressed
conditions in urine volume excreted and the specific gravity of the urine excreted. This
suggests that the acute psychological stressor did not activate the RAAS via SNS
stimulation, to cause the retention of water and sodium. It is possible that psychological
36
stress has no effect on the RAAS, and therefore no effect on the kidney. However, these
two measures are indirect measures. Therefore, they can not truly depict the stimulation
of the RAAS, which is the system that affects renal reactivity to psychological stress.
A more direct indication of the RAAS functioning would be to take blood
samples before and after the acute psychological stressor and measure any one of the
hormones in the RAAS biochemical pathway. Other studies have shown psychological
stress activates the RAAS by measuring PRA, as a direct measure of RAAS reactivity to
stress (Clamage, Vander, & Mouw, 1977; Syvalahti, Lammintausta, & Pekkarinen, 1976;
Baumann, Ziprian, Godicke, Hartrodt, Naumann, & Lauter, 1973). Without such
measures, this study is unable to definitively state whether or not the RAAS reacted
differently to the stress as compared to baseline.
The indirect measures used can not control for the other feedback systems in the
body that help maintain fluid and electrolyte balance, like the release of anti-diuretic
hormone, for example, which causes the retention of water, or for diuretic hormone,
which causes an increased excretion of water. Future studies should make use of other,
more direct measures. Although it is possible, that with a larger sample size this indirect
measure may have indicated a difference in renal reactivity to the stress, as mediated by
the RAAS, but again the confidence in such a finding would be low given its indirect
nature.
Overall, some of this study’s findings indicate that acute psychological stress can
increase cardiovascular reactivity, reinforcing the findings of similar studies (Sloan,
Shapiro, Baciella, Bigger, Low, & Gorman, 1996; Patterson, Marsland, Manuck,
Kameneva, & Muldoon, 1998). Although the findings are not novel, they do add upon
37
the literature, supporting psychological stress as a risk factor for CVD. Future studies
should continue to focus on the detrimental effects of psychological stress on the human
body. Moreover, more research is needed to clarify the cardiovascular and renal systems’
responses to psychological stress and how these responses contribute to disease of the
cardiovascular and renal systems.
38
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43
Appendices
Appendix A
$$ Research Study $$
Check it out!
Are you…
18-35
Not Overweight
A non-smoker
If you are, you might qualify for a research study.
In return for participation, you will be given blood pressure
and heart activity measurements. Also you will be paid
TWENTY DOLLARS for your participation.
Research Study
Matt (207)592-0306
mscanlin@smcvt.edu
Research Study
Matt (207)592-0306
mscanlin@smcvt.edu
Research Study
Matt (207)592-0306
mscanlin@smcvt.edu
Research Study
Matt (207)592-0306
mscanlin@smcvt.edu
Research Study
Matt (207)592-0306
mscanlin@smcvt.edu
Research Study
Matt (207)592-0306
mscanlin@smcvt.edu
Research Study
Matt (207)592-0306
mscanlin@smcvt.edu
For more information, please contact Matthew Scanlin at
(207) 592-0306
or email at mscanlin@smcvt.edu
44
Age:_______
Appendix B
Health Information Screening Sheet
Height:__________ Weight_________ Sex: ________
Do you have any permanent or chronic health problems: (e.g. High BP, Asthma, Allergies,
Heart Condition, Ulcer, Arthritis, Diabetes, Cancer, kidney disease, hyper/hypo
aldosterone...): YES NO
If yes, specify:_____________________________________________
Have you been diagnosed or have symptoms of a urinary tract infection (UTI) within the last
THREE months? YES
NO
Do you have any physical disabilities that effect general activity levels: YES
If yes, specify:_____________________________________________
NO
Has your health changed in the last 6 months: YES NO
If yes, how:_________________________________________________
Are you or do you think that you may be pregnant: YES
NO
Do you take any prescription drugs: YES
NO
If yes, which:_______________________________________________
For what health problems:____________________________________
Do you take any of the following drugs (if so circle the medication):
Anticoagulants
Antiplatelet Agents
Beta Blockers
Angiotensin-Converting Enzyme (ACE) Inhibitors
Calcium Channel Blockers
Angiotensin II Receptor Blockers (or Inhibitors)
Diuretics
Vasodilators
Other:________________
Statins
Digitalis Preparations
Are you taking any hormones: YES NO
TYPE: ________________________
Do you take any non-prescription pills (i.e. aspirin) regularly?: YES NO
If yes, what and how often:__________________________________
For what health problem:_____________________________________
Do you drink coffee, tea, or caffeinated beverages such as soda: YES
If yes, how much a day:________________
Do you exercise regularly: YES
NO
If yes, how many hours a week:__________
NO
45
Appendix C
PASAT Script
* PASAT CD should be inserted into the CD player by the lab assistant/researcher who
collected the VAS – Baseline sheet. The volume to the CD player and the lighting should
also be increased.
[Enter room with clipboard containing PASAT #’s sheet, blue highlighter, and clipboard
containing a pen and VAS – Cognitive task sheet. Place the Clipboard containing the pen
and VAS on the couch and hold onto the clipboard containing the PASAT #’s sheet]
[Lab assistant/researcher stands in front of participant] “We are
now going to begin the cognitive task that was mentioned to you in
the consent form. The cognitive task that you will be engaging in
is a math task. The task will not be written, instead you will hear a
long list of single-digit numbers presented to you from a CD. The
numbers will range from 1-9 and there are no zeros. You will be
required to listen to these numbers and add together the two most
recent numbers that you hear from the CD and give a response
aloud. For example, you may hear the numbers 4 and 5 from the
CD and you would need to say the number 9 aloud – 4 plus 5
equals 9. If the third number that you hear is 2, then your
response should be 7 – remember that you must add together the
two most recent numbers from the CD and that includes the recent
number 2 and the number 5 which was incorporated into the
previous example. You will now perform a practice trial with 10
numbers to make sure that you understand. This is a practice trial
and not the actual task”
[Lab assistant/researcher moves to the CD player and PRESSES PLAY]
[Lab assistant/researcher] “You
may begin the practice trial when the CD
begins. Remember to say your responses aloud clearly”.
[Lab assistant/researcher PRESSES PLAY on the CD and listens to the practice trial and
assists the participant if it is warranted. PRESS PAUSE on the CD player when the trial
is completed. This procedure may be repeated if the participant is having difficulty
understanding the task. It is permitted to continue to the actual task when the participant
answers the majority of the calculations correctly.]
46
[After the practice trial has been completed successfully. Lab assistant/researcher]
“We are now going to begin the actual task. This task will last for
6 minutes. Remember, you must say your numerical responses
aloud and except for the first number that you hear, you should
give a response after each number. It is also imperative that you
remain perfectly still throughout the task. Do not cross your legs,
close your eyes, or fidget at any time. Do you have any questions
at this time?
[Answer questions if need be, if no questions, proceed]
“I would like to inform you that someone in
your age cohort should be able to answer at least 80% of their
responses correctly. Since you did not encounter any difficulty
during the practice trial, you should have no problem with
answering 80% of your responses correctly. If you find that you
do make a mistake, pause, collect yourself, listen for the next two
numbers and proceed. I will be remaining in the room with you
and marking each error that you make. We will now begin the
task. Remember to remain still. You may begin when you hear
the first two numbers.”
[Lab assistant/researcher]
[Lab assistant/researcher moves to the CD player, PRESSES PLAY, moves and stands
directly in front of the participant, holds clipboard up and marks any errors as they occur.
The lab assistant/researcher should not talk to the participant for any reason except under
the following conditions: participant is moving - instruct him/her to remain still,
participant is bending his/her arm during BP measurement- instruct him/her to not bend
the arm and remain still, and participant is “giving up” on the task - inform him/her to
continue with the task. If the participant makes any comments, IGNORE them, with
ONE EXCEPTION – the participant indicates that he/she would like to withdraw from
the study.]
[Lab assistant/researcher who is controlling the computer should inform the lab
assistant/researcher who is administering the PASAT when the 6 minutes have passed
and PRESS STOP on the CD player. The lights should be dimmed, the VAS – Cognitive
task administered to the participant via the clipboard already inside the testing room, and
the relaxation CD should be inserted and played.]
47
Appendix D
Cigarette Smoking Characteristics Questionnaire (CSCQ)
Name:_____________________
Phone Number: ____________
Best day and time of day for someone to reach you by phone: ________________
Age: ______
Gender: _______
Height: ________
Weight: _________
Do you smoke cigarettes?
YES
NO (please circle one)
If yes, how long have you been a cigarette smoker? __________
How many cigarettes do you typically smoke per day? _______
How many days per week do you smoke? _______
How long have you been smoking this amount of cigarettes? _________
At what age did you smoke your first cigarette or try cigarette smoking? (Even if
your first cigarette was just a puff off of someone else’s, please indicate that age)
__________
At what age did you begin smoking cigarettes regularly? __________
What brand of cigarettes do you typically smoke?
(e.g. Camel Ultra Lights Hard Pack) _______________________
Are you currently in the process of quitting? _________________
Do you use other types of tobacco products such as snuff, dip, chew, cigars, pipes etc.?
YES
NO (please circle one)
IF YOU ARE SELECTED TO PARTICIPATE IN THIS STUDY, THE EXPERIMENTER
WILL CONTACT YOU BY TELEPHONE TO GIVE YOU FURTHER INFORMATION.
BY PROVIDING INFORMATION ON THIS QUESTIONNAIRE YOU GIVE THE
EXPERIMENTER PERMISSION TO CONTACT YOU.
48
Appendix E
24-Hour Profile
1. What and when have you eaten in the last 24 hours?
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
2. Have you eaten within the last 8.5 hours? Yes___ No___
3. Did you drink anything in the last 8.5 hours other than the assigned amount of
water?
Yes___ No___ If yes, what was it and how much? _________
4. Did you drink the assigned amount of water between 1 and 0.5 hours before the
testing session Yes___ No___
5. Have you drank any caffeinated beverages (i.e., coffee, tea, soda) or eaten
anything containing caffeine (i.e., chocolate) in the past 12 hours?
Yes___ No___
6. Have you drunk any alcohol in the past 24 hours?
Yes___ No___ If yes, what was it and how much? _____________
7. Have you taken any prescription or non-prescription drugs in the past 24 hours?
Yes___ No___ If yes, what? ________________
8. Did you exercise at all in the last 12 hrs?
Yes___ No___ If yes, what did you do for exercise and for how long
____________?
9. When did you last smoke a cigarette? ______________
10. Have you avoided all areas with cigarette smoke in the past 12 hours?
Yes_____ No____
49
Appendix F
Visual Analog Scale
Instructions: Below are words which describe the feelings people have. Please read each
one carefully and rate how much you have had that feeling during the resting (or math) task,
including now. You may mark anywhere on each line with a perpendicular line. Be sure to
mark each line and only once.
Happy
Not at all
Extremely
________________________________________________
Bored
________________________________________________
Anxious
________________________________________________
Satisfied
________________________________________________
Depressed
________________________________________________
Interested
________________________________________________
Angry
________________________________________________
Frustrated
________________________________________________
Irritated
________________________________________________
How challenging did you find the task?
Not at all
Extremely
________________________________________________
How difficult did you find the task?
Not at all
Extremely
________________________________________________
50
Appendix G
Human Subjects Consent Form – Non-Smokers
Consent to Act as a Subject in a Research Study
Title: The Effects of a Cognitive Task on Cardiovascular Reactivity and Renal Excretion
in a Sample of Non-Smokers
Investigator: Matthew C. Scanlin
Undergraduate Student
St. Michael’s College
(207) 592-0306
Research Supervisor:
Melissa M. VanderKaay, PhD
Assistant Professor of Psychology
St. Michael’s College
(802) 654-2921 Office
(802) 735-5230 Work cell
Description:
The goal of this study is to assess the physiological effects that occur during a
cognitive task in non-smokers. I have been asked to participate because I’m between the
ages of 18 and 35 years and both physically and mentally healthy. I acknowledge that
I’m not pregnant and that to my knowledge I lack any medical conditions in relation to
the cardiovascular system or kidney. I understand that I will participate in a pre-testing
session lasting no longer than 30 minutes and one laboratory testing session lasting
approximately 90 minutes. I will be asked to refrain from drinking any fluids or eating
any food for 8 hours prior to testing, with the exception of a standard amount of water
assigned for me to drink after 7:30 am and before 8:30 am, the day of testing. I will be
asked to not exercise at anytime 12 hours prior to the testing. I will be asked to drink
multiple standard amounts of water during the testing session and to provide two urine
samples. I will be provided complete privacy when providing the urine sample and it will
not be tested for any illegal drug usage. I’m aware that physiological factors such as
blood pressure and heart activity as well as urine concentration and volume will be
measured. I will be asked to complete multiple questionnaires pertaining to my medical
history, smoking behavior, and other behaviors. I’m aware that during the testing session
I will be asked to perform a 6 minute cognitive task.
Date: _________________
Signature: ___________________________
51
Order of Events
Pre-laboratory Session:
-Obtain written consent
- Measure height, weight, and blood pressure
-Provide urine sample
-Complete questionnaires
-Assignment of standardized water amount to be drank between 7:30 am
and 8:30 am the day of the testing session
- Reminder of testing session date and time
Laboratory Session:
- Provide urine sample
- Complete questionnaires
-Distribute standard amount of water
-Manually measure blood pressure
-Attach electrodes for cardiovascular measurement
-10 minute resting cardiovascular measurement
- 6 minute cognitive task with cardiovascular measurement
- 16 minute recovery period with cardiovascular measurement
- Provide Second Urine sample
- Remove electrodes
- Debriefing and Compensation
At any point during the study I have the ability to express questions, comments, or
concerns to the experimenter.
Risks and Benefits:
The electrodes used for cardiovascular measurement may cause slight discomfort
when removed and result in some redness for an hour. This study will be looking at the
physiological reactivity of the cardiovascular and renal systems in response to a cognitive
task. To the author’s knowledge no other study similar to this one has been performed.
So your participation will be helping to advance science and in addition you will be
assisting in research for an undergraduate research project. I will also receive my blood
pressure and heart rate measurements upon request.
If you experience any side effects call the investigator, Matthew C. Scanlin at (207)5920306, or the Research Supervisor, Professor Melissa M. VanderKaay at (802)735-5230.
Costs and Payments:
I may potentially receive extra credit in my course work for my participation if I
qualify. Otherwise I will be paid twenty dollars for my participation. I also understand
that I won’t be penalized for opting to leave the experiment at any point.
52
Confidentiality:
I understand that all information gathered from me during this experiment will be
kept confidential. Personally identifiable information will be kept in a locked laboratory
and only the investigator and research supervisor will have access. I am aware that my
information may be subpoenaed by a court order. I’m also aware that in any publication
or use of this data my identity won’t be revealed and thus I consent to the data collected
to be used in any form of publication.
Right to Withdraw:
I am aware that if at any point in the study I no longer wish to participate, I can
withdraw from the study and this decision will result in no adverse affect on me.
Voluntary Consent:
I acknowledge that I’ve fully read and understand the above statements. I am
aware of the risks participation in the study poses and that no compensation will be
granted by St. Michael’s College, its employees, or the experimenter for an injury
occurring because of my participation. I certify I am at least 18 years of age. I assert that
any questions I have in terms of the study have been answered by Matthew C. Scanlin or
Dr. Melissa M. VanderKaay. A copy of the consent form will be given to me upon my
signing it, indicating that I of my own free will agree to participate in the study.
Signature: ______________________
Date: ______________________
I certify that I have explained to the person, who signed above, the purpose, risks, and
benefits of the outlined study and that I have answered all questions asked. I assert that I
witnessed the above signature.
Date: ______________________
______________________
Investigator:
53
Appendix H
Human Subjects Consent Form – Non-Smokers (Participant Copy)
Consent to Act as a Subject in a Research Study
Title: The Effects of a Cognitive Task on Cardiovascular Reactivity and Renal Excretion
in a Sample of Non-Smokers
Investigator: Matthew C. Scanlin
Undergraduate Student
St. Michael’s College
(207) 592-0306
Research Supervisor:
Melissa M. VanderKaay, PhD
Assistant Professor of Psychology
St. Michael’s College
(802) 654-2921 Office
(802) 735-5230 Work cell
Description:
The goal of this study is to assess the physiological effects that occur during a
cognitive task in non-smokers. I have been asked to participate because I’m between the
ages of 18 and 35 years and both physically and mentally healthy. I acknowledge that
I’m not pregnant and that to my knowledge I lack any medical conditions in relation to
the cardiovascular system or kidney. I understand that I will participate in a pre-testing
session lasting no longer than 30 minutes and one laboratory testing session lasting
approximately 90 minutes. I will be asked to refrain from drinking any fluids or eating
any food for 8 hours prior to testing, with the exception of a standard amount of water
assigned for me to drink after 7:30 am and before 8:30 am, the day of testing. I will be
asked to not exercise at anytime 12 hours prior to the testing. I will be asked to drink
multiple standard amounts of water during the testing session and to provide two urine
samples. I will be provided complete privacy when providing the urine sample and it will
not be tested for any illegal drug usage. I’m aware that physiological factors such as
blood pressure and heart activity as well as urine concentration and volume will be
measured. I will be asked to complete multiple questionnaires pertaining to my medical
history, smoking behavior, and other behaviors. I’m aware that during the testing session
I will be asked to perform a 6 minute cognitive task.
Order of Events
Pre-laboratory Session:
-Obtain written consent
- Measure height, weight, and blood pressure
-Provide urine sample
-Complete questionnaires
-Assignment of standardized water amount to be drank between 7:30 am
and 8:30 am the day of the testing session
- Reminder of testing session date and time
54
Laboratory Session:
- Provide urine sample
- Complete questionnaires
-Distribute standard amount of water
-Manually measure blood pressure
-Attach electrodes for cardiovascular measurement
-10 minute resting cardiovascular measurement
- 6 minute cognitive task with cardiovascular measurement
- 16 minute recovery period with cardiovascular measurement
- Provide Second Urine sample
- Remove electrodes
- Debriefing and Compensation
At any point during the study I have the ability to express questions, comments, or
concerns to the experimenter.
Risks and Benefits:
The electrodes used for cardiovascular measurement may cause slight discomfort
when removed and result in some redness for an hour. This study will be looking at the
physiological reactivity of the cardiovascular and renal systems in response to a cognitive
task. To the author’s knowledge no other study similar to this one has been performed.
So your participation will be helping to advance science and in addition you will be
assisting in research for an undergraduate research project. I will also receive my blood
pressure and heart rate measurements upon request.
If you experience any side effects call the investigator, Matthew C. Scanlin at (207)5920306, or the Research Supervisor, Professor Melissa M. VanderKaay at (802)735-5230.
Costs and Payments:
I may potentially receive extra credit in my course work for my participation if I
qualify. Otherwise I will be paid twenty dollars for my participation. I also understand
that I won’t be penalized for opting to leave the experiment at any point.
Confidentiality:
I understand that all information gathered from me during this experiment will be
kept confidential. Personally identifiable information will be kept in a locked laboratory
and only the investigator and research supervisor will have access. I am aware that my
information may be subpoenaed by a court order. I’m also aware that in any publication
or use of this data my identity won’t be revealed and thus I consent to the data collected
to be used in any form of publication.
Right to Withdraw:
I am aware that if at any point in the study I no longer wish to participate, I can
withdraw from the study and this decision will result in no adverse affect on me.
55
Appendix I
Pre-testing Session Participant Stats
Subject #:_________
Age: __________
Sex: __________
Height: __________inches
Weight: __________ lbs
Standard Amount of Water Assigned: __________
Manual Blood Pressure Measurements:
1_______/_______
2_______/_______
3_______/_______
Calculated BMI using the equation: __________
Testing Session Participant Stats
Height: __________ inches
Weight: __________ lbs
Manual Blood Pressure Measurements:
1_______/_______
2_______/_______
3_______/_______
Calculated BMI using the equation:___________
56
Appendix J
Urine Collection Procedure
Females
1. Use soap and water to wash hands for thirty seconds.
2. After washing the labia with the provided sterile wipe, spread the labia with 1 hand and
keep it apart for the duration of collection.
3. Void into toilet for a couple of seconds, just long enough so the urine makes initial
contact with the toilet water, and then place the cup into the stream of urine. Try to avoid
stopping urine flow when moving the container into place.
4. Cap the container while being careful to avoid touching the inside of it.
5. You will be given multiple cups because there is a chance you’ll need more than one,
if so please do your best to not loose any of the urine in the process of switching to a
another cup. Urine volume is being measured in this experiment so it is important to be
as accurate as possible.
Males
1. Use soap and water to wash hands for thirty seconds.
2. Pull back foreskin if necessary and wash the site with the sterile wipe provided.
3. Void into toilet for a couple of seconds, just long enough so the urine makes initial
contact with the toilet water, and then place the cup into the stream of urine.
Try to avoid stopping urine flow when moving the container into place.
4. Cap the container while being careful to avoid touching the inside of it.
5. You will be given multiple cups because there is a chance you’ll need more than one,
if so please do your best to not loose any of the urine in the process of switching to a
another cup. Urine volume is being measured in this experiment so it is important to be
as accurate as possible.
57
Appendix K
Urine Sample Measurements
Test Strip
Leukocytes
Negative
Trace Small Moderate
Large
Nitrite
Negative
Urobilinogen
0.2
1
3.2
16
Positive
2
32
4
64
8
128
Negative
Trace 30
100
300
>2000
5.0
6.5
7.5
8.0
8.5
Protein
PH
6.0
7.0
Blood
Negative
Non-hemolyzed
Hemolyzed
small Moderate
Specific Gravity
1.000 1.005 1.010 1.015 1.020 1.025 1.030
Ketone
Negative
Bilirubin
Negative
Glucose
Negative
Trace Small Moderate
Small Moderate
Large
100
5
1000
60
250
15
500
30
Large Large
>2000
11
Urinometer
Specific Gravity ____________
Volume
_________ mL
Large
58
Appendix L
Testing Session Reminder and Information Sheet for Smokers
Thank you for participating in this research study!
Your testing session is scheduled for _____________________.
You’ve been recruited because you qualify as a non-smoker. So please do not smoke or
surround yourself with second hand smoke.
Please do not eat or drink any time after___________________. However, anytime
between ____________________ before your testing session you must consume the
standard amount of water you were assigned which is_______________mL.
Please don’t drink any caffeine anytime after the pre-testing session tonight.
Please do not perform any strenuous exercise at anytime after the pre-testing session
tonight.
You may want to wear a t-shirt to the testing session so that electrodes can be attached
easily to you.
59
Appendix M
Debriefing Statement
First and foremost thanks for your participation in my study. This study was
concerned with the physiological responses of the cardiovascular system and kidney
function after a cognitive task. The cognitive task was the math test and was meant to be
challenging in order to induce stress not to assess true mathematical ability. All of your
results will be kept confidential.
You may experience some side effects. The skin exposed to electrode bands may
turn red but it will only last a few hours. If you have any comments, concerns, or
questions concerning the study please let me know at this time or feel free to call me at
(207) 592-0306 if something were to come up later. You can also email me at
mscanlin@smcvt.edu.
Sincerely,
Matthew Scanlin
Undergraduate Student
St. Michael’s College
60
Appendix N
Time Table for experiment
TASKS
BASELINE (10 min)
7-9:55
TIME
0 minutes
HR
SBP
DBP
Urine Collection
Urine collected
before cardio
equipment was put
on
Cop-Win
1 minutes
2 minutes
3 minutes
4 minutes
5 minutes
6 minutes
7 minutes
1
8 minutes
2
PASAT (6 min)
(Mental arithmetic task)
9 minutes
3
0-5:55
0 minutes
4
1 minute
5
2 minutes
6
3 minutes
7
4 minutes
8
5 minutes
9
PASAT RECOVERY
(16 min)
0 minutes
10
0-15:55
1 minute
11
2 minutes
12
61
3 minutes
13
4 minutes
14
5 minutes
15
6 minutes
16
7 minutes
17
8 minutes
18
9 minutes
19
10 minutes
20
11 minutes
21
12 minutes
22
13 minutes
23
14 minutes
24
15 minutes
Urine collected after
cardio equipment
was taken off
25