Sleep Loss Worsens Diabetes

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Type 2 Diabetes and Sleep

Patients with type 2 diabetes who routinely suffer from poor-quality sleep or short sleep of about six hours a night have poorer blood-sugar control than those who sleep longer, according to a new study.

Previous studies looking at non-diabetics have suggested that poor or short sleep interferes with the body's ability to properly regulate blood-glucose levels. The studies have also suggested chronically sleep-deprived people are at higher risk for developing type 2 diabetes, a condition characterized by high blood-glucose levels that result from the body's inability to use insulin. The disease most often occurs in overweight people age 45 and older. (Type 1 diabetes, usually diagnosed in childhood, is caused by the body's inability to produce insulin.)

Now, researchers at the University of Chicago and Northwestern University looked at 161 African-American patients with type 2 diabetes. Overall, they found that most patients reported sleeping for an average of six hours a night. Only 6% of patients reported getting eight hours of sleep on weeknights and 22% reported getting seven hours.

The findings are being published in this week's Archives of Internal Medicine as part of a theme issue devoted to sleep.

Researchers said patients reporting less sleep had higher A1C levels than those reporting more sleep. The average level was 8.2%. Researchers said a normal A1C level is between 4% and 6%. They also said they excluded patients with painful complications from diabetes from the study as pain commonly interferes with sleep. A1C measures blood-glucose levels over an average of two to three months.

However, researchers said more study is needed to determine whether lack of sleep makes diabetes worse or whether the disease itself contributes to poor sleep.

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One of the study's authors, Eve Van Cauter, a professor at the University of Chicago's medicine department, said one way to find out would be to study whether increasing sleep duration would improve glucose control in diabetics.

Previous studies, including work by Van Cauter, have shown that less sleep interferes with the body's ability to regulate glucose as well as hormones involved with appetite regulation.

In an interview, Van Cauter said she believes chronic sleep deprivation increases the risk of developing diabetes, weight gain and other medical problems.

"Slowly but surely there will be a sea-change in the way people view sleep," she said. "People will see increasing sleep as a good behavior."

In a separate study, also published in this week's Archives of Internal Medicine, researchers at the Universities of Iowa and Wisconsin found a link between short sleep duration and higher body-mass index, adding to other evidence that chronically sleep-deprived people are more likely to be overweight. BMI is a body-fat measure that uses height and weight.

They looked at people participating in an ongoing study of 990 people in southeastern Iowa who are part of a broader study looking at the environmental, occupational and general health of people living in a rural population. People who reported sleeping less than six hours a night had an average BMI of 30.24, while those reporting sleeping eight to nine hours had an average BMI of 29.27. Those who reported sleeping nine or more hours had an average BMI of 28.25. People with a body mass index of 30 or higher are considered obese while those with a BMI ranging from 25 to 29.9 are considered overweight.

Both studies were funded by units of the National Institutes of Health. The diabetes study also included funding from the MacArthur Foundation and the American Diabetes Association.

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