Too much or too little shut-eye can increase risk of developing the disease
Middle-aged and older women who regularly sleep six hours or less a night, or who increase their average sleep time by two hours or more over a period of several years, are at an increased risk of developing type 2 diabetes, a new study from Harvard T.H. Chan School of Public Health found.
Earlier research has linked too much and too little sleep with increased diabetes risk, with those who sleep seven to eight hours a night having the lowest risk. But most previous studies were smaller and measured sleep duration only once. The new study is one of the first, and the largest, to look at long-term sleep habits—including changes over time—and how those habits affect diabetes risk.
The researchers analyzed nearly 60,000 women aged 55 to 83 between 1986 and 2000, measuring their diet quality, physical activity and weight, to see whether these factors explained the connection between sleep duration to later risk of diabetes.
They did find a link between consistently short sleep duration and type 2 diabetes. They also found that, among women who increased their sleep by two hours or more over time, diabetes risk increased by 15 percent. This change was not fully explained by weight, diet or physical activity, suggesting that, in those whose sleep duration increases over time, some other mechanism is at play involving sleep times and metabolic health.
“Our results support the message that long-term maintenance of healthy sleep duration is a pillar of health and chronic disease prevention,” said Elizabeth Cespedes, lead author of the study. “However, simply increasing sleep duration after previous years of short sleep may not be a panacea.”