Consequences of disruption of biological rhythms are seen in jet lag and shift work. Normally exogenous zeitgebers allow our bodies to adjust gradually. But, rapid changes can cause them to become desynchronised. Symptoms of desynchronisation include decreased alertness and performance, fatigue and nausea.
Shift work may involve working during the night when our internal body clocks are normally set to induce sleep, causing a breakdown between exogenous zeitgebers and endogenous pacemakers. In low light conditions melatonin is released to induce sleep. Therefore if awake during darkness hours this can cause decreased alertness. This also contributes to lower quality daytime sleep as melatonin levels are low. This can lead to sleep deprivation and a permanent state of dysychronisation. This can also increase stress levels which long term can have detrimental effects on health.
Jet lag is a physiological effect of a disrupted circadian rhythm which occurs through travelling through time zones quickly meaning our internal body clock does not match external zeitgebers. Biological clocks cannot cope with large shifts with the SCN taking several cycles to resynchronise. It is suggested to aid resynchronisation, and is most beneficial to, follow exogenous zeitgebers e.g. meals and sleep times and following the biological clock can cause synchronisation to take longer.
Recht et al studies US baseball teams who travelled coast to coast to play games. Results found teams travelling east to west, experiencing a phase delay, won 44% of games opposed to west to east teams, experiencing a phase advance, won only 37%. This difference may be explained through a disrupted rhythm therefore may provide support that disruption can lead to decreased performance. However, results were drawn based on correlation evidence therefore other confounding variables such as east coast teams being better at baseball and referee bias may have affected results. Therefore the study lacks internal validity. Also the difference in results between east and west coast teams was only 7% which may not be a high enough statistical difference to drawn conclusive results as to the affects that a disrupted biological rhythm has on performance.
As shift work and jet lag are unavoidable most research has focuses on how to reduce its harmful effects.
Boivin et al found artificial bright lights was effective in resetting biological rhythms. Four groups were exposed to varying light levels with the group exposed to the brightest light being the most responsive to having circadian rhythms rest. This suggests even artificial light can aid in helping reset disrupted rhythms. This has positive real world application as, if bright lights can be used in the workplace to aid in readjusting biological rhythms . This could help increase alertness during the night which may help to reduce the risk of work place disasters such as the Chernobyl disaster occurring.
However, this was a laboratory experiment therefore may lack external validity and findings may not be indicative of real life. Also participants were volunteers therefore may have been motivated to find a solution to their possible sleep problems therefore showed demand characteristics subconsciously. Therefore findings may apply to a real workforce and they may be less motivated and less likely to notice their rhythms change. Further issues arise within this study as it only focuses on the role light plays influencing biological rhythms despite temperature and social cues being found to have a strong influence. Therefore this study is reductionist and only focuses on a simplified understanding of exogenous zeitgebers.
Recht and Boivin's studies suggest that disruption occurs within everyone therefore needs to be treatable. However, such studies may be euro-centric as there is evidence of people coping in daylight year round e.g. Inuits. Therefore studies may be targeted at one specific culture and not generalisable to all. Therefore from research it is evident disrupted rhythms can cause problems, but the same factors do not cause disruption for all. Therefore the best method of treatment will also likely be subjective to the individual.
No comments:
Post a Comment