Lack of Sleep May Raise Risk of Diabetes
The combination of not enough sleep and circadian rhythm disruption caused a marked decrease in insulin secretion in response to the meal, the researchers reported.
Specifically, fasting plasma insulin, postprandial peak insulin, and integrated plasma insulin concentrations were significantly reduced, by 12% (P=0.0064), 27% (P<0.0001), and 27% (P<0.0001), respectively.
That, in turn, led to significant increases in both fasting and postprandial peak plasma glucose concentrations compared with response to the same meal at baseline.
Overall, fasting concentrations increased 8% (P=0.0019) on average, postprandial concentrations rose 14% (P=0.0004), and the integrated postprandial response over 90 minutes increased 15% (P<0.0001).
The resting metabolic rate fell by 8% on average - enough to translate into a yearly weight gain of about 10 pounds a year if diet and activity levels did not change, the researchers reported.
Americans used to sleep more. Between 1959 and 2002, the percentage of people sleeping fewer than seven hours a night on a regular basis more than doubled. Meanwhile, the number of people with type 2 diabetes has soared. Could there be a connection? At the very least there’s an association between lack of sleep and diabetes, but it’s still not clear whether the former helps cause the latter and, if so, how.
The first real clue that sleep deprivation could lead to type 2 diabetes came from a 1999 study published in The Lancet. Healthy young people without any hint of diabetes came to live in a lab for a week. Their sleep was restricted to just four hours for six nights in a row. By the end of the experiment, their bodies’ ability to use glucose had radically shifted. “After a week of short sleep, their glucose metabolism looked like that of old men,” says Kristen Knutson, PhD, an assistant professor of medicine at the University of Chicago who studies the role of sleep in disease. “For a long time, people thought sleep was for the brain and only for the brain. This study showed that it was for the body, too.”
Since this landmark study, similar experiments have been conducted to explore the relationship between sleep and diabetes in more detail. A 2008 study in the Proceedings of the National Academy of Sciences sought to uncover the influence of deep sleep on the risk for diabetes. During sleep, the body cycles between rapid eye movement (REM) sleep and four stages of non-REM sleep, the deepest of which is called slow-wave sleep. While volunteers in the study got a normal amount of total and REM sleep, the researchers restricted their slow-wave time. The result? Metabolic changes that increase the risk of diabetes. According to Knutson, this study showed that “it’s not just how much sleep that matters, but you need good-quality sleep.”
These short-term experiments show that sleep can affect metabolism, but they can’t prove that inadequate sleep causes diabetes. For starters, it isn’t clear whether or not the body would eventually adjust to the sleep deficiency and normalize its metabolism over time. However, evidence that sleep and diabetes are connected has been established by assessing the health and sleep habits of groups of people. A 2010 study in Diabetes Care found that people with sleep problems - difficulty falling or staying asleep, sleeping fewer than five to six hours a night or more than eight to nine hours - are more likely to develop type 2 diabetes than sound sleepers.
Most of the changes reverted to baseline or near-baseline levels after the recovery phase of the experiment.
Buxton and colleagues cautioned that the study was too short to tease out the actual mechanisms behind the changes they observed.
Previous preclinical research has shown that resistance to infection is weakened depending on the 24-hour light-dark cycle of an immune protein known as toll-like receptor 9 (TLR9). And some research also has suggested that moving the clocks ahead for daylight saving time has a negative effect on circadian rhythms.
The study had support from the National Institute on Aging, the National Heart, Lung and Blood Institute, the National Center for Research Resources, the Center for Clinical Investigation of the Harvard Clinical and Translational Science Center, the Joslin Diabetes and Endocrinology Research Center Service Specialized Assay Core, the National Space Biomedical Research Institute, and the Natural Sciences and Engineering Research Council of Canada.
Buxton reported being a consultant and expert witness in a lawsuit involving sleep, circadian rhythms, and diabetes in railroad workers.
Primary source: Science Translational Medicine
Source reference: Buxton OM, et al “Adverse metabolic consequences in humans of prolonged sleep restriction combined with circadian disruption” Sci Transl Med 2012; (4)129ra43.