Failing to sleep deeply for just three nights running has the same negative effect on the body's ability to manage insulin as gaining 20 to 30 pounds, diabetes researchers report.
In fact, young adults who do not get enough deep sleep may be increasing their risk for type 2 diabetes, according to the study.
Researchers reported that three nights of interrupted sleep effectively gave people in their 20s the glucose (blood sugar) and insulin (the hormone that controls glucose uptake) responses of people three times their age.
Previous studies have demonstrated that not getting enough hours of sleep affects the body's ability to manage blood sugar levels and appetite, increasing the risk of obesity and diabetes. This current study provides the first evidence linking poor sleep quality—specifically the loss of deep or slow-wave sleep-to increased diabetes risk, said the University of Chicago Medical Center research team.
The researchers recruited five men and four women, all lean and healthy, who were between the ages of 20 and 31. They first observed the participants for two nights of uninterrupted sleep, during which they slept for 85 hours, to establish their normal sleep patterns.
Then they observed the same participants over a three-night study period, during which the researchers deliberately disturbed their sleep when their brain waves indicated the beginning of slow-wave sleep.
The sounds used to interrupt the sleep patterns were loud enough to move the participants to a different level of sleep but not loud enough to fully wake them. According to the researchers, the participants could recall hearing between three and 15 noises at night, although they were interrupted on average 250 to 300 times. The interruptions increased in number each night, as the participants' need for deep sleep increased.
"This decrease in slow-wave sleep resembles the changes in sleep patterns caused by 40 years of aging," said lead author Esra Tasali, MD, assistant professor of medicine at the University of Chicago Medical Center. Young adults spend 80 minutes to 100 minutes per night in slow-wave sleep, while people over age 60 generally have less than 20 minutes. "In this experiment," she said, "we gave people in their 20s the sleep of those in their 60s."
At the end of each study, the researchers gave intravenous glucose (a sugar solution) to each subject, and then took periodic blood samples to measure the levels of glucose and insulin.
Participants were nearly 25% less sensitive to insulin after nights of interrupted sleep. As their insulin sensitivity declined, they needed to make more insulin to process the same amount of glucose, or blood sugar. However, in all but one subject, their bodies did not make more insulin. As a result, they had 23% more blood glucose, the equivalent of glucose levels in an adult over 60 with impaired glucose tolerance.
The researchers also found that the participants who typically had the least amount of slow-wave sleep during the nights they were not interrupted experienced the greatest decline in insulin sensitivity during the study.
"These findings demonstrate a clear role for slow-wave sleep in maintaining normal glucose control, according to Dr. Tasali. "A profound decrease in slow-wave sleep had an immediate and significant adverse effect on insulin sensitivity and glucose tolerance."
The researchers suggested that improving the quality of sleep, especially for people as they age or if they are obese, could be an important step in preventing the onset of type 2 diabetes.