Regular lack of sleep does more than make you tired. People who routinely slept fewer than 6 hours a night were almost five times more likely to develop impaired fasting glucose during an average 6 year follow-up, compared with people who got 6–8 hours a night, in a case-control study with 364 people.
This finding is consistent with prior-study results, which suggested that chronic short sleep was linked with an increased risk for other adverse health effects including obesity, hypertension, cardiovascular disease, and death, Lisa Rafalson, Ph.D., said at a conference on cardiovascular disease epidemiology and prevention sponsored by the American Heart Association.
“It's important for physicians to discuss short sleep with their patients because shortened sleep has a lot of associated ill-health effects, and it is a behavior that can be modified to some degree,” Dr. Rafalson said in an interview.
A physician-patient conversation about sleep “can take place throughout the life cycle.” Many physicians bring up sleep habits only with patients who have newborn or young children, said Dr. Rafalson, an epidemiologist in the department of social and preventive medicine at the State University of New York at Buffalo. The new finding and prior evidence highlight the importance of encouraging adequate sleep in adults of all ages.
Her study included some of the 1,455 people who were enrolled in the Western New York Health Study during 1996–2001 and were then reexamined in 2003–2004, an average of 6 years after their baseline exam. She identified 91 people who had a normal serum level of fasting glucose (defined as lower than 100 mg/dL) at their baseline exam, and who then developed impaired fasting glucose (defined as a serum level of 100 mg/dL or greater but less than 125 mg/dL) during follow-up. Her analysis compared the 91 cases with 273 control individuals who had normal fasting glucose levels at both baseline and follow-up. Each case was matched with three controls by sex, race/ethnicity, and year of enrollment in the study.
Cases and controls were divided into three categories based on their usual sleep habits during the work week (Sunday night through Thursday night): fewer than 6 hours a night (25 people), 6–8 hours a night (314 people), and more than 8 hours a night (24 people). Sleep data were not available for one person. These categories are standard for sleep research.
Short sleepers had a 4.7-fold increased risk for developing impaired fasting glucose during follow-up, compared with people who usually had 6–8 hours of sleep nightly, a statistically significant difference. The analysis showed no significant difference in the incidence of impaired fasting glucose between those who slept 6–8 hours nightly and those who routinely slept more than 8 hours. The analysis was adjusted for several baseline measures, including age, serum glucose level, blood pressure, smoking status, depression, family history of diabetes, and weight change during follow-up.
Dr. Rafalson acknowledged that impaired fasting glucose was not itself a disease state, but it's “a strong predictor of who will develop type 2 diabetes. It's a high-risk situation.” Her analysis did not examine differences in the rate of development of new-onset diabetes.
Other researchers have proposed several hypotheses on how chronic short-sleep duration could lead to adverse changes in health, such as increased blood pressure or elevated blood glucose.
Sleep deprivation is a stressor that produces sympathetic activation and release of stress hormones, such as cortisol. Elevated cortisol levels can lead to insulin resistance and impaired glucose tolerance that can result in obesity. Sleep deprivation has also been linked to adverse changes in satiety hormones, including increased levels of ghrelin, a hormone that signals a person to eat more, and reduced levels of leptin, a hormone that signals satiety and causes people to stop eating. These changes can lead to overeating and eventual obesity, followed by impaired fasting glucose, Dr. Rafalson said.