Shift Lag:
The time it takes to
adjust
Aims
To know the effects of shift work upon
EP’s and EZ’s
To know the key study of Czeisler (1982)
To understand the effects of a phase
delay system in shift work
To be able to explain the role of
melatonin on biological adjustment
To be able to evaluate research on
disruptions to biological rhythms
 SCN
disruption
 EP and EZ De-synchronisation
 12000 Lux artificial Light is best
 Individual differences (unhappy and happy)
 Czeisler’s research
 Accidents that justify research
 Influence of Day time Sleep
 Phototherapy
 Melatonin
Shift work
patterns involve
dividing the day
into three eight
hour shifts
12:00-8:00am
8:00am-4:00pm
4:00pm-12:00 am
 Shift
work patterns involve dividing the day into
three eight hour shifts
 12:00 - 8:00 am
 8:00 am - 4:00 pm
 4:00 pm -12:00 am
 Therefore leading to the disruption of the EP’s and
EZ’s.
 There is usually a shift change each week, and Jet
Lag studies show us that this is not long enough time
for resynchronisation to complete. Therefore
workers are in a chronic state of Jet Lag impairing
performance and increasing stress.
 When
we are working out of phase with our
biological clocks our performance is reduced,
we are less attentive and slower to respond.
 Disasters examples
 Two problems arise with shift work


The need to maintain a 24 hour that is out of
sync with the world and
The demands of a changing shift pattern
 Negative



effects
e.g. decreased attention
slowing of reasoning skills
impaired reaction could have serious
consequences on the ability to do work or drive
safely.
Possible
justification
for animal
research
Practical
application of
Psychology in
the real world
 Peter
Tripp
 Randy Gardner
 If
the question asks for disruption of biorhythms you can
discuss sleep deprivation, shift work, jet lag and SAD and
DSPS
 The specification states that you need to know about
disruption of biological rhythms… clearly suggesting more
than one. The two obvious ones suggested above are the
effects shift work and of jet lag. However, SAD is a
disrupted biorhythm that can be seen as either circadian
or infradian so can also be discussed in a question on
disruption of rhythms.
 However, a much richer vein of material would be a
discussion of the effects of sleep deprivation studies,
covered in the sleep section. Work by Dement, Jouvet,
Rechtschaffen, Huber-Weidman and the case studies of
Randy Gardner and Peter Tripp look at the effects of
disrupting the stages of sleep (ultradian) and the sleep-
The need to maintain a 24 hour that is out
of sync with the world
 People
who are working shifts are often sleep deprived
because they find it hard to sleep with there is light
outside and its noisy
 The
social constraints may tempt workers to stay
awake when they should be sleeping
 Found
that older shift workers had less total
sleep time because they woke up early.
 To
solve the problem of being woken by
daylight, shift workers are recommended to
use thick curtains or blackout blinds.
 Shifts
workers tend to be awake late evening and/or
early morning and sleep during the day. Unless
workers succeed in resetting their biological clocks
they experience sleepiness at work and insomnia at
home.
 This is more severe when shifts change often and
they move against the clock.
 After a shift change people take a week to adapt
to the new regime, during which they are less
productive as they are operating during their
body’s night clock and restless when they should
be sleeping.

Czeisler et al (1990) believes that shift work environments that are warm
and dimly lit are counter productive. So, they compared the rate of
adaptation of two groups of ppts to an imposed shift change by asking
them to report to the laboratory during the night and sleep at home during
the day.
The control group worked during the night in ordinary indoor lights of about 150
lux.
 The experimental group worked under bright illumination of 7000-12000 lux,
equivalent to early morning light.
 The experimental group were also asked to stay in complete darkness from
9am to 5pm, whilst the controls were given no specific instructions.


The resetting of the biological clocks were monitored by measuring
body temperature, which varies rhythmically.
After 6 days the experimental group had all shifted the low point of the circadian
temperature rhythm by 10 hours,
 the controls 1 hour.
 Bright lighting in the work place seems to be key to helping workers to adapt
to new shifts so that they are alert at work and sleep well during the day.
Even in this situation adaptation can take up to 4 days, so workers who change
shift every week would spend most of their time desynchronised .

Shift work
Conclusions
Artificial light can help us
adapt our bio rhythms to
suit the environment,
however, brighter light is
even more effective.
Clearly, this useful in the
workplace to help shift
workers to adapt to
changing sleep-wake
cycles.
Boivin et al (1996) put 31 male
participants on an inverted sleep pattern (so
they were awake at night and slept during the
day) for three days. Each day when they woke
they were sat in front of dim lights for 5 hours
and then placed in one of four conditions: Very
bright light, Bright light ,Ordinary room light ,
Continued dim light. Core body temperature
was recorded and used as a measure of how
well they were adapting to the new rhythm.
After three days: Group 1 had advanced by
five hours (they were adapting to the new
pattern best) Group 2 had advanced by three
hours. Group 3 had advanced by one hour.
Group 4 had drifted backwards by one hour
(were failing to show any signs of adapting).
Other individual differences: ………………………….
……………………………………………………………………………………
……………………………………………………………………………………
……………………………………………………………………………………
……………………………………………………………………………………
…………………
 Insomnia
 Temptations
 Less
quality and quantity
 Tiredness
 Social
isolation
 Divorce
Causality?






Describe the findings and significance of the MooreEde (1993) research. ($77Billion, accidents, medical expense)
Describe the shift work patterns as suggested by
Monk and Folkard (1983). (RapidCircadian maintained, Slow)
What has been suggested as a method of rapidly
resetting biological rhythms? (Bright light substitute)
Explain the findings of Dawson and Campbell’s (1991)
research. (bright light 4 hours helped ppts to work better)
Describe Czeisler’s (1982) suggestions.
Evaluate research into disrupting biological rhythms.
 Czeisler
et al (1982) carried out a study in a
Utah chemical plant, where there was a high
incidence of health, sleep and stress
problems reported by staff who were on short
rotation shifts.
 Czeisler persuaded the company to change to
a phase delay system (moving a shift forward
each time) and to increase shift rotation
from 7 to 21 days, allowing for more
adjustment. Consequently, 9 months later
worker satisfaction and factory output both
increased.
A
significant strength of this research is the
consistent evidence that disrupting biological
rhythms has a negative impact upon
cognitive and emotional well being. Leading
at times to serious consequences.
 For example, Czeisler et al (1982) found out
that there was a high incidence of health, sleep
and stress problems reported by staff who were
on short rotation shifts.
A
Further strength of this research area is
that the evidence is generated from field
studies that have high validity.
 However, an unavoidable limitation is the
inability to control for confounding variables,
such as personality and individual
differences.
 Therefore, it proves to be more difficult to
reach complete conclusions about the causal
influences in any resulting behaviour.
 This
area of study has huge application in the
real world. Although many of these studies
show the negative consequences of
disrupting biological rhythms, many people
who carry out shift work do not suffer from
cognitive impairment, (lack of attention or
concentration ) or any negative effects on
their emotional well being.
 This demonstrates clearly the remarkable
ability of our biological rhythms to adapt to
changing environmental circumstances.
Different Recommendations
Less fluctuations (non-fluctuating shifts)
cause less disruption to the SCN
 It
might help if shift workers reset their
biological clocks as quickly as possible.
Bright lights as a substitute to daylight
has proven effective in resetting the
biological clock.
 Dawson and Campbell exposed workers
to a 4 hour pulse of very bright light
which appeared to help them work
better.
Different Recommendations
 Monk
and Folkard (1983) identified two
major types of shiftwork:


Rapidly rotating the shifts (weekly)
Slowly rotating the shifts (monthly)
 There
are problems with both shift work
systems. However rapidly rotating may be
more beneficial. They allow the workers to
maintain a fairly consistent circadian
rhythm. Whereas, slowly rotating shifts can
cause harmful effects by causing major
changes to individuals circadian rhythms.
Fast rotation = less disruption and less social isolation; more consistent Circadian activity

On the other hand, research has found that it
takes people about a week before their circadian
rhythms have adjusted to a new sleep/wake
cycle, so one might expect slow rotation would
be better. Rapid rotation means that your
rhythms are always disrupted.
Different Recommendations
Different Recommendations
Jet Lag
Shift Work
12:00-8:00. 8:00-4,:00 4:00-12:00
Jet Lag
Shift Work
Imagine you are an
occupational psychologist
and have been asked to
work with a flight crew to
help them deal with Jet
Lag. After reading your
notes on this topic and the
information on page
175/176 in Eysenck and 8/9
in the complete companion
What recommendations
would you make?
Imagine you are an
occupational psychologist
and have been asked to
work with nurses to help
them deal with the effects
of shift work. After reading
your notes on this topic and
the information on page
176 in Eysenck and 8/9 in
the complete companion
What recommendations
would you make?
.
Melatonin
.
Melatonin helps Jet/Shift lag because it
binds to neurone receptor sites on the
SCN, altering their activity, resetting the
biological clock.
Takahashi (2002) found that Melatonin
speeds up the resynchronisation process
after an 11 hour flight.
Sharkey (2001) Melatonin speeds up
biological adjustment to shift patterns,
and increased sleep time during non-work
periods.
Herxheimer and Petrie (2001) reviewed 10
studies and found that where melatonin was
taken near to bedtime, it was remarkably
effective. However, if taken at the wrong time of
day it may actually delay adaptation
 If
you take 0.5mg of melatonin you will fall asleep
earlier and wake earlier (phase advance). This is
called phase advance because we advance the sleep
phase (sooner).
 If we are exposed to bright light in the evening, the
opposite occurs: we sleep and wake later – phase
delay.


Phase advance – early bird – Older people
Phase delay – owl – Teenagers/young adults
AO2/3: Individual differences
 Biological
rhythms play an important role in
our sleep and wake cycle, as well as our
cognitive and emotional preoccupations
 Pineal gland, and suprachiasmatic nucleus
relate endogenous pacemakers to exogenous
zeitgebers
 Disruption of biological rhythms bear
catastrophic consequences
This is the
consequence of
Disrupting
Circadian
Rhythms
SCN disruption
15 years of Shift
Work increases
risk of heart and
Organ disease
Czeilser 82
Less REM
Less DEEP sleep
(SWS4)
1- 2 hour less
sleep; REM
reduction
Bright
light/artificial
light
Shift
Lag
Cause 1: sleep deprivation
Causality can
Not be
established
The brighter the light
The greater the adaptation
Divorce rate,
Sleep deprivation
Insomnia,
cancers, heart
diseases
Cause 2: Circadian
Rhythm/SCN disruption
Czeilser 1990
Recommendations
Boivin
10,000 lux
Black out blinds
Melatonin
The brighter the light
The greater the Circadian shift
 Describe
and evaluate research and or
theories into biological rhythms (24 marks)
 Write
up a report discussing research into
circadian rhythms (8m).
 Describe the human endogenous pacemaker
(biological clock) in control of the sleep
wake cycle (6m).
 What application to the real world has
biological rhythm research got? (4m)
 Explain individual difference effects on
Circadian Rhythm research (8m)
 Discuss research and explanations of the
disruption to Circadian rhythms (16m)
AO2/3 Evaluation/commentary
 Jet
lag example
 SCN disruption
 Jet lag research
 Individual differences
 Shift work example
 Czeilser Utah
 Czeilser 1990
 Melatonin treatments (x3)
 Justification of animal research
 Animal research
 Real world application