Disruption of biological rhythms

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• Night workers often experience a circadian 'trough' of decreased alertness during their shifts. This occurs between midnight, when cortisol levels are lowest, and 4.00 am, when core body temperature is at its lowest

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• Daytime sleep is typically between 1 and 2 hours shorter than a nocturnal sleep period. REM is particularly affected. This is because of interruptions such as noises outside

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• Found that individuals who worked shifts for more than 15 years were 3 times more likely to develop heart disease than non-shift workers

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• Linked shift work to kidney disease. This may be due to the direct effects of desynchronisation or indirect effects such as sleep disruption

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• Divorce rates can be as high as 60% among all night-shift workers

1. Gold et al. (1992)

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   • Research indicates that more problems occur when people have to do rotating shifts 

1. Bambra et al. (2008)

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   • Follow the logical order of the day (phase delay) and it may be easier on the body and less damaging to health

1. Gronfier et al. (2007)

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   • Were able to entrain circadian rhythms to longer than 24 hours just by using bright light pulses

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• Analysed US baseball results over a 3 year period. Teams that travelled east-west won on average 44% of their games, whereas when travelling west-east the percentage dropped to 37%

1. Herxheimer and Petrie (2001)

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   • Reviewed 10 studies and found that where melatonin was taken near to bed-time, it was remarkably effective

1. Fuller et al. (2008)

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   • When travelling, it helps to eat at the right time and got to sleep when the clock says it's time to go to sleep. This research suggests that a period of fasting followed by eating on the new time schedule should help entrain biological rhythms