What are some of the issues with disrupting biological rhythms? And evaluate.

Shift Work can disrupt biological rhythms. Night workers sleep during the day so they are alert when they got to work, which is the reverse of our natural rhythm and therefore is not influenced by cues from zeitgebers. During shifts, they experience periods of decreased alertness between midnight and 4.00am when cortisol levels are lowest. Often experience sleep problems as during the day, there are other distractions, daylight reduces sleep quality and daytime sleep typically a couple of hours shorter than nocturnal sleep. This combined with the circadian trough, makes it difficult for shift workers to stay awake during shifts. Shift workers have also been reported to be more likely to develop organ disease, which may either be due to effects of desynchronsisation or subsequent sleep deprivation.

Understanding the consequences of shift work has useful applications, since society requires individuals to work at such times e.g. lorry drivers, nurses, pilots etc. It is therefore important to ensure such individuals are not in poor health and that this does not have a knock on effect on others through accidents being caused, such as the Three-Mile nuclear power station disaster, occurring at 4.00am.

 However, the nature of the disruption will have an impact on the effects. Bambra et al. (2008) reviewed research and found that forward rotating shifts (phase delay), may be easier on the body and less damaging on worker health. An example would be a week of morning shifts, followed by a week of afternoon shift, followed by a week of afternoon shifts. Quicker rotations (every few days as opposed to each week) is also better for health and work-life balance. This suggests that the potentially negative effects of sleep disruption can be reduced.

Additional research suggests that the harmful effects can again be minimised. Boivin et al (1996) found that when 31 males were put an inverted sleep-wake cycle, those exposed to the brightest lights had advanced 5 hours compared with an hour delay for those exposed to dim light. This shows how biological clocks can be reset to a certain extent due to artificial light, and therefore one may be able to adjust to a disrupted rhythm.

As evident in this research, lab experiments are often used to assess the impact of disrupting biological rhythms. A strength of these methods is that they are highly controlled, for example, the amount of light participants are exposed to and how they are woken up, increasing internal validity, increasing our understanding of the effect that purely disruption has on behaviour. 

One problem with the cause of disruption and the consequences observed, is that it is difficult to determine whether the negative effects of shift work are caused by disruption to circadian rhythm or even subsequent sleep deprivation. It may be the case that other variables are responsible for the effects, for example, the social disruption that results from shift work.  

Jet lag also disrupts the circadian rhythm of the sleep-wake cycle. Most travellers report less difficulty in adjusting to phase delay, when they are flying west (New York to London). This is because do not need to get up when in circadian trough but when body feels awake. Symptoms include loss of appetite, nausea, fatigue, disorientation, mild depression and insomnia. Recht et al. (1995) analysed US baseball teams over a three-year period and found that teams that travelled west won 44% if their games, whereas teams travelling east won just 37% of games. 

Such negative effects, may, however, be addressed fairly simply. Herxheimer and Petrie (2001) reviewed 10 studies and found that melatonin was a remarkably effective cure for jet lag/shift work when taken near to bed-time, but not when taken at the wrong time of day, when may actually delay adjustment. This suggests that if used appropriately, it possible to significantly reduce the effects of jet lag.

Furth research has identified ways to minimise the effects of disruption. Coren (1996) documented a number of techniques to reduce jet lag such as immediately adjusting to local zeitgebers by sleeping when it is dark and remaining awake when light. Again, this suggests that if we adopt certain practices, we can prevent the experience of negative effects of disruption. 

Similarly to shift-work, it is difficult to determine whether the experience of jet lag is indeed caused by disruption of the circadian rhythm or instead caused by other variables such as anxiety regarding travel, time consuming travel, consumption of caffeine/alcohol etc. 

One could argue that research into the consequences of biological rhythm disruption is reductionist, as it does not account for individual differences. It may be the case that personality can influence the effects of disruption, for example, anxious individuals finding it more difficulty to adjust to the disruption. Equally, some individuals have more stable circadian rhythms than others, which may mean they cope better.

Much of the research documented above suggesst that the effects of disrupting biological rhythms are not entirely determined and that individuals can make choices to limit the negative effects of disruption, by using artificial lights, taking medication and exposing oneself to external zeitgebers. This is encouraging, as whilst it is possible that shift work or jet lag may cause a host of problems, we have some choice regarding taking measures to alleviate the symptoms.