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Discuss research into the disruption of biological rhythms (eg shift work, jet lag).
(8 marks + 16 marks)
Rhythms such as the circadian sleep/wake cycle can be disrupted when people work shift patterns or
experience jet lag. The impact of the desynchronisation of internal chemical cycles, controlled by the
endogenous pacemakers, such as the SCN, and exogenous zeitgebers, such as light, can be far
Shift workers who are sleeping in the day and working at night are working against their natural
circadian cycle and have difficulties entraining their rhythms to fit with the environmental demands
because they usually suffer from sleep deprivation.
Research by Tilley and Wilson found that workers who have night shifts experience sleep during the
day which is on average 2 hours shorter with less REM sleep. Poor daytime sleep then makes it even
more difficult for shift workers to stay awake though the night, thus leading to other complications
such as higher stress levels and a weaker state because the body can't restore itself during the REM
sleep it misses.
To exemplify the effect that shift work has upon biological rhythms, Knutsson et al found a
relationship between shift work and organ disease. It was found that individuals who worked night
shifts for more than 15years were three times more likely to develop heart disease than non-shift
workers, suggesting that the disruption of biological rhythms can lead to various health implications.
There is much evidence to support the idea that shift work produces a range of negative effects on
the body, meaning that the findings of research into the impact of health and functioning are reliable.
However, the methodology of studies investigating the long term effect of shift work is flawed
because correlational methods are used which makes it difficult to establish whether the negative
effects of shift work are due to disrupting biological rhythms (a biological explanation), or an indirect
effect of the disruption of social routines and activities (psychological explanation) making cause &
effect hard to establish.
For instance, Solomon (1993) found that high divorce rates in shift workers might be due to the strain
of missing family events & deprived sleep, thus the resulting stress might have an impact on health
Another effect of shift working is decreased alertness shift workers often experience a circadian
trough of decreased alertness during their shifts; Boivin et al suggested it occurs between midnight
when cortisol levels are lowest and 4:00am when the body temperature is highest.
Research into the disruption is highly valuable as it has applications for reducing errors caused by
decreased alertness (such as the Chernobyl disaster); for example the use of artificial lighting to
re-set rhythms of shift workers. Boivin (1996) exposed participants to different intensities of lights
and was able to shift circadian rhythms by posing as exogenous zeitgebers, therefore light
intensities can be used in night-shift workers' work to increase alertness and health.
Alternatively, travelling across time zones can result in needing to sleep when the body is
experiencing the chemical cycles required for being awake (low melatonin) and vice versa.
Those experiencing the effects of jet lag are likely to find that their sleep/wake cycle is disrupted
and that other circadian cycles are desynchronised from the outside world.
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However, jet lag may be caused by other factors than the disruption of biological rhythms alone. An
individual may have slept badly the night before, especially due to worry of travelling (psychological
factors). Traveling itself is tiring and many holidays involve lengthy journeys which don't allow for
naps. Drinking coffee, constant noise, low-oxygen cabins and large crowds are all
psychological/social factors which help explain jet lag, making research to highlight only biological
explanations reductionist.…read more