Lack of Sleep, Circadian Disruption Increase Risk of Diabetes

According to a study (abstract) recently published in Science Translational Medicine, a chronic lack of sleep combined with disrupted circadian rhythms, as is frequently experienced by individuals who perform shift work, can increase the risk of developing type 2 diabetes.

The authors of the study, dubbed "Adverse Metabolic Consequences in Humans of Prolonged Sleep Restriction Combined With Circadian Disruption," note that epidemiological studies have linked short sleep duration and circadian disruption with a higher risk for metabolic syndrome and diabetes. Therefore, they sought to test the dual hypotheses that "prolonged sleep restriction with concurrent circadian disruption, as can occur in people performing shift work, impairs glucose regulation and metabolism."

Endogenous circadian rhythms are controlled by the central circadian pacemaker in the hypothalamus and help synchronize molecular circadian "clocks" in peripheral cells and tissues, the authors note. These clocks, in turn, optimize physiological functions to match daily patterns of behavior. Misalignment of these endogenous rhythms and daily behaviors occurs in shift workers, and this disruption "may contribute to the known adverse health consequences of shift work, including fatigue and poor sleep, gastrointestinal complaints, detrimental metabolic changes, and increased risks of developing obesity and diabetes."

In the study, 21 healthy, nonobese adults spent more than five weeks setting an initial "optimal sleep" baseline under controlled laboratory conditions. Study subjects then spent three weeks exposed to circadian disruption induced by imposing 28-hour fasting/feeding and sleep/wake cycles (with dim lighting during wakeful periods) in conjunction with sleep restriction of 6.5 hours in bed (the equivalent of 5.6 hours per 24-hour period). Finally, participants underwent nine days of recovery sleep, with stable circadian re-entrainment.

The researchers found that both fasting and postprandial peak plasma glucose levels increased after exposure to the three-week sleep restriction/circadian disruption protocol compared with responses to the same meal at baseline. In some cases, the postprandial glucose response reached prediabetic levels as the pancreas stopped secreting enough insulin to handle the intake load. At the same time, the resting metabolic rate dropped an average 8 percent from baseline among study participants. These effects largely normalized after the period of recovery sleep and circadian re-entrainment.

"Our results suggest that efforts to reduce the health impact and risk of diabetes in shift workers should focus on improving sleep duration and circadian realignment strategies to minimize circadian disruption and desynchrony of central and peripheral circadian oscillators," say the authors.