It seems obvious to anyone that humans greatly differ in the sleeping and waking cycles, or circadian rhythms. Some people are "larks," at their most chipper and alert in the mornings, while others are "owls," only coming alive after the sun goes down and wide awake far into the night. Not surprisingly, these variations are largely genetically determined, with the first so-called "clock genes" being discovered about a decade ago.
Research into these particular genes has been slow because of the difficulty in isolating them from body cells, but in a new study published in the August 23, 2010 edition of the journal Proceedings of the National Academy of Sciences, scientists successfully used human hair to investigate the relationship between clock genes and the human sleep cycle.
Clock Genes and Circadian Rhythms
The genes responsible for regulating humans' sleep cycles work as other genes do: by transcribing their DNA into RNA, which then makes proteins that carry out the genes' instructions, in this case determining when people sleep and when they are at peak wakefulness. The genes' activity rises and falls throughout the day and night, causing the genes' owners to feel awake and alert, or sleepy and sluggish.
Studies of Human Hair
By plucking head or beard hair from several subjects, researchers at Yamaguchi University in Japan were able to isolate three different clock genes from the cells clumped at the hair follicles. From these samples, they were able to determine that the points in the day when the clock genes were most active corresponded to the points in the day or night when the subjects reported feeling the most wakeful and alert.
Shift Work and Jet Lag
Another component of the study involved tracking the clock genes of subjects who worked and slept on unusual cycles, or who alternated between differing work/sleep shifts, such as working from 6 a.m. to 3 p.m. one week, then switching to 3 p.m. to midnight for the next.
Researchers found that even after a significant amount of time spent "adjusting" to unusual schedules, subjects’ clock genes failed to completely reset themselves to the new rhythms, sometimes significantly so. Even when work and sleep schedules were adjusted or alternated by four to seven hours, subjects' body clocks shifted by only about two hours, leaving the workers feeling listless and permanently "jet-lagged."
Further research in this area will definitely be of value to patients suffering from various sleep disorders or unbalanced circadian rhythms. This study and other recent research like it already suggests that shift workers whose schedules don't correspond to their genetically regulated circadian rhythms might be at a higher risk for strokes and heart attacks.
Sources:
Akashi, Makoto et al. "Noninvasive method for assessing the human circadian clock using hair follicle cells". Proceedings of the National Academy of Sciences. August 23, 2010
Pappas, Stephanie. "Sleep Secrets Revealed in Human Hair". LiveScience. August 23, 2010
Jenny Ashford - Jenny Ashford is a writer and graphic artist from central Florida. Her main area of interest in her Suite 101 articles is science, with a ...
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