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We are all familiar with the negative consequences of getting too little sleep, but they may be more serious than just feeling a bit groggy. A new study published in the journal Science Translational Medicine has shown that sleep restriction, along with a disruption of one’s internal body clock, can raise the risk of obesity and type 2 diabetes . This could explain the increased rates of these conditions in shift workers and others who work at night.
Researchers at Harvard disrupted the study subjects’ circadian rhythms by adjusting their sleep/wake cycles and feeding schedules to 28 hour “days” in lieu of 24 hour ones. Subjects were kept in a dimly lighted room so their internal clocks did not adjust to external light and dark cues, but rather maintained their normal 24 hour cycles. In addition to this circadian disruption, subjects were permitted only 5.6 hours of sleep per 24 hours for three weeks. Twenty-one subjects completed the study.
When undergoing this regimen, study participants had a reduced resting metabolic rate and increased plasma glucose concentrations after eating. The latter effect is because their pancreas’ were not secreting enough insulin to clear the glucose out of the blood. Levels of ghrelin -– the hormone that makes you hungry — were higher during sleep restriction, while levels of leptin –- the hormone that makes you feel full -– were lower. These effects were independent of gender and of age, which ran counter to the researchers’ expectations since older people often experience dramatic changes in both sleep patterns and circadian rhythms. After nine days of recovery sleep, the levels of these parameters reverted back to normal.
The authors note that their results accord with a number of studies showing that sleep deficiency impairs glucose metabolism by decreasing insulin sensitivity. They go on to say that the number of hours we sleep each night, as well as the length of days or weeks we are subjected to inadequate sleep, probably both contribute to increasing our risk of diabetes. Circadian disruption, such as that occurring during jet lag or shift work, also adversely affects glucose metabolism.
These results were highlighted in The New York Times, along with those from an unrelated study claiming that children with attention deficit hyperactivity disorder (ADHD) symptoms may in fact be sleep deprived [2-3]. So in these busy times, it is as important as ever for everyone, young and old, to carve out the time for a decent night’s sleep.
- Buxton et al. Adverse metabolic consequences in humans of prolonged sleep restriction combined with circadian disruption. Sci Transl Med. 2012 Apr 11;4(129):129ra43.
- http://www.nytimes.com/2012/04/17/health/research/curtailed-sleep-raises-risk-of-obesity-and-diabetes.html”>Risks: More Signs of Rest’s Regulatory Powers NYTimes. 2012 Apr 16.
- Attention Problems May Be Sleep-Related. Well Blog – NYTimes.com. 2012 Apr 16.