Methodological Tests of
Sweating Activity
Measurement for
Research
Barbara J. Holtzclaw, PhD, RN, FAAN
Associate Dean, College of Nursing
D.W. Reynolds Center for Geriatric Nursing Excellence
James W. Mold, MD, MPH
College of Medicine, Dept. of Family and Preventive Medicine
MEDICINE
Let talk about sweat!
Types of sweat glands:
• Eccrine (thermoregulatory, cover most
of body)
• Apocrine (non-thermoregulatory,
emotion responsive, in specific regions)
• Apoeccrine (newly identified, function
not known).
• Epithelial cells lining the coiled portion of
the sweat gland produce a precursor
secretion containing concentrations of
sodium = 142 mEq/L and chloride = 104
mEq/L.
• Cholinergic sympathetic nerve fibers
supplying glandular cells evoke
secretion.
• Electrolytes flow through ductal portion of
sweat gland to be reabsorbed at a rate
dependent on sweat rate.
• Light SNS stimulation of sweat gland lets
precursor fluid flow through duct slowly
allowing reabsorption and concentration of
most of the Na+ and Cl+ ions. Low osmotic
pressure of sweat reduces reabsorption of
water and urea; lactate and K+ remain
concentrated.
• Strong SNS stimulation of sweat gland by
exercise produces large amounts of
precursor secretion, little reabsorption of
ions, and dilute sweat (50-60 mEq/L). Rapid
tubular transit of sweat prevents low
reabsorption.
Physiological Mechanisms
• Thermoregulatory
•
•
•
•
•
•
•
Increased heat generation
External heat exposure (hot room)
Reduced heat dissipation (e.g. blankets)
Elevation of set point/thermo-neutral zone (e.g. fever)
Reduced sweat threshold (e.g. night time*)
Early phase of acclimatization
Circadian rhythm disturbances (e.g. depression)
• Non-thermoregulatory
• Autonomic non-thermoregulatory responses
• Direct sweat gland stimulation
• Osmotic mechanisms
Sweat measurement appears as a study
variable in a variety of investigations.
Measurement requirements depend on
need to determine:
• Body distribution of sweat
• Amount of sweat production
• Consistency and contents of sweat
• Circadianicity of perceptible sweating
Sweat as a study variable
• Fever
• Exercise
• Night sweats
• Hot flashes
• Heat stress
• Mental stress
Sweat as a diagnostic biomarker
• Cystic Fibrosis
• Hyper- or Hypohidrosis
• Metabolic disorders
• C-fiber dysfunction
• Complex pain disorders
Questions & Measurements:
Typical sweating-related research questions:
• When does it occur? = time it occurs
• Thermal causal factors = thermometry
• How much water loss? = change in weight
• What is being secreted? = sweat analysis
Questions & Measurements:
Questions related to cause and mechanisms:
• Sudomotor function? = ability of sweat
glands to release chloride ions
• Sudomotor activity = what stimulates sweat
glands?
• Autonomic activity = general distribution
[ANS contribution is complex]
Critical factors dictating selection of
measurement methods:
• Mechanisms underlying sweat
production and secretion
• Relationship of sweat to the research
question
Precision and accuracy of sudomotor
components are important when inferential
questions or correlates are proposed.
Research situation: Interdisciplinary researchers
planning clinical research to study factors
related to night sweats in adult men and women
from unknown cause.
• Prevalence estimates range from 10% - 41%
• Commonly under-reported
Underlying question:
• Are night sweats associated with adverse
health outcomes
Autonomic, non-thermoregulatory mechanisms
that Induce Sweating
• Increased sympathetic activity, central
• Disturbed sleep stages
• Vagal stimulation (gustatory, gastrointestinal
distention or cardiac pain)
• Autonomic nervous system
dysfunction/instability
• Medullary and spinal cord abnormalities
• Anxiety states
Methodological aims of this pilot study were
to:
1. determine an accurate, feasible strategy
to measure sweat frequency and intensity
in adults
2. test feasibility, ease of measurement, and
seek potential predictive correlates
associated with sweat activity for a future
study of idiopathic night sweats
Methods:
Systematic search of existing or historically
documented sweat measurement techniques:
• Search included data from scientific
literature, instrument vendors, and
reports.
• Preliminary categorization done to
describe/compare/contrast capabilities
of extant techniques to measure
sweating activity.
Results from Search:
• Measurements included sweating intensity,
amount, ion concentrations, and excitation
frequency were found.
• Over a dozen methods in historical reviews
included galvanic responses; electrodermal
conductance measurements, and sweat
distribution by starch-iodine compounds.
Results from Search:
• Newer investigators found that electrode
configuration, type of electrodes, excitation
frequency and signal extraction, influenced
other factors that could dominate the
measurement of sweating activity.
• Skin conductance levels did not directly
correlate with sweat production or evaporation
from skin, but instead with the filling of the
sweat ducts and the reabsorption process.
Measurements include sweat rates, amount, content, excitation frequency
Results from Search:
• Despite, the number of methods and analyses
of electrodermal measurements, no established
unit relating electrical measurements to sweat
activity has been fully validated.
• We selected a newly developed instrument
measuring parameters from skin conductance
curves, calibrated to measure quantity of sweat
production in perceptible sweating.
Tronstad, C., Gjein, G.E., Grimnes, S., Martinsen, O.G., Krogstad, A.-L.,
& Fosse, E. (2008). Electrical measurement of sweat activity.
Physiological Measurement, 29(6), S407-415.
Tronstad, C., Gjein, G.E., Grimnes, S., Martinsen, O.G., Krogstad, A.-L., &
Fosse, E. (2008). Electrical measurement of sweat activity.
Physiological Measurement, 29(6), S407-415.
Instrumentation Methods:
• 7 adults underwent polysomnography (PSG) in
a sleep lab.
• We selected a newly developed instrument
measuring parameters from skin conductance
curves, calibrated to measure quantity of sweat
production in perceptible sweating by electrical
impedance (Sudlogger).
• Variables included history of night sweats
severity/frequency, sleep-related symptoms.=
Instrumentation Methods:
• PSG readings tracked with biological signals:
core temperatures (VitalSense, ingested
disposable temperature probe), skin
temperatures (chest thermistor), and sweating
frequency and amplitude from forehead, chest,
arm, and palm (Sudologger).
36.45
36.40
36.35
Core Temp
36.30
36.25
36.20
36.15
36.10
1
6
11
16
21
26
31
36
41
46
51
56
61
66
71
76
81
86
91
96
101
106
111
116
121
126
131
136
141
146
151
36.00
35.50
35.00
Surface Temp
34.50
34.00
33.50
33.00
1
6
11
16
21
26
31
36
41
46
51
56
61
66
71
76
81
86
91
96
101 106
111 116 121
1
6
11
16
21
26
31
36
41
46
51
56
61
66
71
76
81
86
91
96
101
106
111
91
96
101
106
111
126 131
136 141
146 151
2600
2100
Sweat Volume
1600
1100
600
100
116
121
126
131
136
141
146
151
20
18
16
Sweat “Freq”
14
12
10
8
6
4
2
0
1
6
11
16
21
26
31
36
41
46
51
56
61
66
71
76
81
86
116
121
126
131
136
141
146
151
1
6
11
16
21
26
31
36
41
46
51
56
61
66
71
76
81
86
91
96
101
106
111
116
121
126
131
136
141
146
151
1
6
11
16
21
26
31
36
41
46
51
56
61
66
71
76
81
86
91
96
101
106
111
116
121
126
131
136
141
146
151
1
6
11
16
21
26
31
36
41
46
51
56
61
66
71
76
81
86
91
96
101
106
111
116
121
126
131
136
141
146
151
91
96
101 106 111 116 121 126 131 136 141 146 151
2.5
2
Sleep Stage
1.5
1
0.5
0
1.2
1
0.8
Arousals
0.6
0.4
0.2
0
1.2
1
PLMs
0.8
0.6
0.4
0.2
0
1.2
1
Apnea/Hypop
0.8
0.6
0.4
0.2
0
1
6
11
16
21
26
31
36
41
46
51
56
61
66
71
76
81
86
Results:
• Sweating (frequency, amplitude, and area
under the curve) was defined as > 1,000
impulses per 30 minute interval.
• Two subjects reported prior night sweats but
only 1 actually sweated during study.
• Two had sweating during the study but were
unaware of it.
Results [continued]:
• Subjective reports of night time sweating did
not predict objective sweating during the sleep
studies, and there were no other reliable
predictors.
• Sweating episodes were associated with higher
body temperature, earlier sleep stage and
periodic limb movements, but not with skin
temperature, apeneic/hypopneic episodes, or
brief spontaneous arousals.
Conclusions:
• No associations were found between subjective
and objective evidence of night sweats, nor
obstructive sleep apnea.
• Plans are to specifically enroll patients who
complain of severe and frequent night sweats
and to add measurements of heart rate
variability to our set of variables.
• The newly developed Sudologger was selected
to meet upcoming study needs.
References:
Mold, J. W., Mathew, M. K., Belgore, S., & DeHaven, M. (2002).
Prevalence of night sweats in primary care patients: an
OKPRN and TAFP-Net collaborative study. J Fam Pract,
51(5), 452-456.
Ohhashi, T., Sakaguchi, M., & Tsuda, T. (1998). Human
perspiration measurement. Physiological Measurement,
19(4), 449-461.
Provitera, V., Nolano, M., Caporaso, G., Stancanelli, A., Santoro,
L., & Kennedy, W. R. (2010). Evaluation of sudomotor
function in diabetes using the dynamic sweat test.
Neurology, 74(1), 50-56.
Tronstad, C., Gjein, G. E., Grimnes, S., Martinsen, O. G.,
Krogstad, A.-L., & Fosse, E. (2008). Electrical measurement
of sweat activity. Physiological Measurement, 29(6), S407415.