The women whose sleep duration increased by two or more hours had a 15 per cent greater risk of developing type 2 diabetes.
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The new study adds to a growing body of information linking a lack of sleep to a range of ailments including obesity, metabolic syndrome, mood disorders, cognitive impairment and accidents.
“We controlled for many of these indicators of health status, including sleep apnea diagnosis, snoring, and depression, and we still saw a relationship between large increases in sleep duration and increased risk of diabetes”. The results showed that the first group who first slept for five hours a night had reduced sensitivity to insulin, which could trigger the onset of diabetes.
The team tested two groups of eight healthy men and women in their early 20s, all of whom were given both oral and intravenous tests in which they drank or were infused with a sugary liquid, after which their baseline insulin levels were tested. About 15 percent slept 6 hours or less a night, and another 15 percent slept 9 or more hours.
The reason why long or extended sleep duration might increase the risk of diabetes is not clear.
Wright said that our internal clock signals the release of melatonin levels in the body which enables us to feel sleepy at night.
“We have a clock in our brain which controls 24-hour patterns in our physiology and behavior”.
Women who were chronically short on sleep who then tried to catch up were the ones who fared the worst in the study. When people eat instead of going to sleep, however, it changes the way the body responds to food. In the end, it will damage insulin sensitivity, he said.
“Our bodies can adapt initially but over the long term they may not be able to sustain it”, Wright said.
Study co-authors included Research Associate Christopher Depner, former Research Associate Mark R. Smith and former graduate students Rachel Markwald and Andrew McHill of CU-Boulder, as well as first author Dr. Robert Eckel, Dr. Leigh Perreault and Associate Professors Janine Higgins and Edward Melanson of the University of Colorado Anschutz Medical Campus. She also noted that for now, it is unclear whether sleeping more or less could prevent type 2 diabetes, but further studies are investigating this.
“These were young and very healthy people we studied”, said Wright. “I think the next step is to test those at a higher risk of diabetes”.
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The study was funded by the National Institutes of Health and the Howard Hughes Medical Institute with the Biological Sciences Initiative/Undergraduate Research Opportunities Program at CU-Boulder and appeared online in the journal Current Biology.
