April 15, 2013

The Science Bit

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The following information is provided by Dr Debra Skene, Black Tonic‘s Scientific Collaborator:

Broken body clocks and sleep problems

Debra J. Skene, Scientific Collaborator

Centre for Chronobiology | Faculty of Health and Medical Sciences |University of Surrey | Guildford, UK

Within our brain is a clock which provides information about “the time of day” to our bodily functions enabling us, for example, to be awake during the day and sleep at night. This clock is synchronised to the 24 h light/dark cycle by environmental light that enters the eyes. In totally blind people (such as Jo) light transmission is impaired and is unable to synchronise the body clock thus the desynchronised clock “free runs” at its own pace. As Jo says: “I have a tick, but no light to reset my tock”. In most people a desynchronised clock free-runs at a period length of greater than 24 h. While in a desynchronised state, symptoms akin to jet lag are experienced (daytime sleepiness, poor night sleep, reduced alertness and performance during waking). This is a lifelong condition for totally blind people.

Body clocks can also be disturbed by rapid shifts in time as experienced following travel across time zones or by rotating shift workers. Steve and Anna have flown across time zones; Helen and Lena are shift workers. Symptoms of disrupted clocks are poor night sleep, daytime napping, reduced alertness, fatigue, and reduced ability to perform during waking hours that may predispose a person to accidents and risk. The long term consequences of repeated clock disruptions are just beginning to be studied with epidemiological studies showing increased cardiovascular and cancer risk in night shift workers.

How to treat and correct disturbed clocks is an important research area. Currently there are two recognised treatments, melatonin tablets and light exposure (especially light enriched with the colour blue). These treatments can directly speed up or slow down the body clock so that it more quickly becomes synchronised to the new time zone or the new work shift schedule. Appropriately timed melatonin and light (and avoidance of light at some times) can be used to alleviate the symptoms of jetlag or shift work. For example, Anna’s “jet lag pack” includes melatonin pills, a Lightbox, an eye mask, sunglasses and a chart showing when to use these for maximum effect. Melatonin is also currently the treatment of choice for cyclic sleep/wake disorder experienced by totally blind people. Melatonin has been shown to correct the underlying clock problem in the blind as well as improve night sleep and reduce daytime napping.

Further reading

Arendt, J. and Skene, D.J. Melatonin as a chronobiotic. Sleep Medicine Reviews (2005) 9, 25-39.

Skene, D.J. and Arendt, J. Circadian rhythm sleep disorders in the blind and their treatment with melatonin. Sleep Medicine (2007) 8, 651-655.

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