Research into the human circadian rhythms has shown that a polymorphism in the PER2 gene causes irregular sleeping patterns. There are two terms used to describe irregular sleeping patterns an “owl” which is a person that sleeps and goes to bed late (known as delayed sleep-phase syndrome) and a “lark” that wakes up and goes to bed early (known as advanced sleep-phase syndrome). It is not your lifestyle as people have thought that influences your sleeping patterns but your genes. If people are forced into alternative wake and sleep patterns it can cause insomnia, sleepiness, metabolic syndrome, psychiatric problems and cancer. In 2006 a 5 year study, EUCLOCK, was started to understand how the circadian clock synchronises with environmental cycles.
The daily cycles of light and dark influence biochemistry, physiology and behaviour of an organism. The suprachiasmatic nucleus (SCN), found in the brain’s hypothalamus, directs many of the cycles including gene expression in the brain and body through neural signaling and hormones. Genes responsible for time-keeping, CLOCK, BMALI, PER and CRY, have a 24 hour expression cycle and mutations in these genes cause divergence from this having longer, shorter or no fixed cycle, suggesting that these are master genes. These genes direct peripheral clocks in the body, such as kidney cells, gastrointestinal tract, etc, which all have their own cycle lengths and the SCN acts as a reference point keeping them in sync. It is suggested that health problems such as depression are caused through a mismatch between the central and peripheral time-keeping centers. Researchers have found that resetting the body clocks of larks was easier than owls. Using pharmaceutical products to treat sleep pattern disorders may not be desirable as the drugs may affect other body systems. Intense light therapy has been used successfully to reset body clocks.
Article: Phillips, Melissa Lee. (2009) Circadian rhythms: Of owls, larks and alarm clocks (Vol 458) [Online] Available: http://www.nature.com/news/2009/090311/full/458142a.html [20 March 2009]
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By Eloise Shaw (s42025656)
