CHICAGO Deep, restful sleep may be important for keeping type 2 diabetes at bay, U.S. researchers said on Monday.
They said slim, healthy young adults who were deprived of the deepest stage of sleep known as slow-wave sleep developed insulin resistance -- a trait linked to type 2 diabetes -- after just three nights.
The effect was comparable to gaining 20 to 30 pounds.
"It demonstrates the importance of deep sleep not only for the brain, but for the rest of the body," said Eve Van Cauter, a professor of medicine at the University of Chicago.
Earlier studies have shown deep sleep is important for memory and other brain functions, she said in a telephone interview.
"It turns out deep sleep also has implications for glucose metabolism and diabetes risk," said Van Cauter, whose study appears in the Proceedings of the National Academy of Sciences.
Type 2 diabetes is associated with excess body weight, a rich diet and a sedentary lifestyle. And poor sleep quality has been linked with changes in appetite and metabolism.
Van Cauter's team wanted to see if a disruption in deep sleep could increase the risk for type 2 diabetes.
Her team studied nine adults between the ages of 20 and 31, who spent two consecutive nights in a sleep lab where they slept undisturbed for 8.5 hours each night.
Then, for three nights, the researchers disrupted their sleep with noise just as brain wave activity indicated they were drifting off into deep sleep. The sounds were loud enough to disturb deep sleep, but subtle enough not to wake the study participants.
The effect was to reduce slow-wave deep sleep by about 90 percent without altering total sleep time.
At the end of each study, the researchers injected a sugar or glucose solution into each subject and measured their blood sugar and response to insulin, the hormone that regulates the glucose.
After three nights of disturbed sleep, eight of the nine volunteers had become less sensitive to insulin, without increasing the production of insulin.
Since insulin tells the body it has consumed energy, this deficiency can lead to weight gain and diabetes.
Reduced sleep often results from obesity and age. While most young adults spend 80 to 100 minutes per night in slow-wave sleep, this decreases to just 20 minutes for adults over 60.
"Any condition that involves a decrease in deep sleep is linked to an increase in diabetes risk. That is the case for aging and sleep apnea. This study really demonstrates a causal link," Van Cauter said.
At least 194 million people worldwide have diabetes, and the World Health Organization expects the number to rise to more than 300 million by 2025.
Most have type 2 diabetes, formerly called adult-onset diabetes, in which insulin production decreases or the body is becomes less able to use it.
(Editing by Todd Eastham)