Insufficient Sleep Associated with Overweight and Obesity

January 2005 - Obese and overweight patients in a study group reported sleeping less than their peers with normal body mass indexes (BMIs), according to an article in the January 10 issue of Archives of Internal Medicine, one of the JAMA/Archives journals.

Insufficient sleep causes neurocognitive changes such as excessive daytime sleepiness, altered mood, and increased risk for work-related injury and automotive accidents, according to background information in the article. It has been reported that the average American is currently getting less sleep than they did a century ago. With these declining sleep times there has also been an increase in the number of both obese and severely obese people in the U.S.

Robert D. Vorona, M.D., from Eastern Virginia Medical School, Norfolk, and colleagues examined patients' total sleep time per 24 hours in relation to their body mass index (BMI; calculated as weight in kilograms divided by the square of height in meters). One thousand-one patients completed a questionnaire involving demographics, medical problems, sleep habits, and sleep disorders. The patients were classified as being of normal weight (BMI less than 25), overweight (BMI 25 29.9), obese (BMI 30 39.9), or severely obese (BMI 40 or greater). The average participant had a BMI of 30, and was 48 years old.

The researchers found that total sleep time decreased as BMI increased, except in the severely obese group. Men slept an average of 27 minutes less than women, and overweight and obese patients slept less than patients with normal BMIs. The difference in total sleep time between patients with a normal BMI and the other patients was 16 minutes per day, reaching 112 minutes, or 1.86 hours, over a week. In addition, night-shift work was associated with 42 minutes less total sleep time.

"Americans experience insufficient sleep and corpulent bodies. Clinicians are aware of the burden of obesity on patients," the authors write. "Our findings suggest that major extensions of sleep time may not be necessary, as an extra 20 minutes of sleep per night seems to be associated with a lower BMI. We caution that this study does not establish a cause-and-effect relationship between restricted sleep and obesity. Investigations demonstrating success in weight loss via extensions of sleep would help greatly to establish such a relationship."

This study was supported by the Division of Sleep Medicine of the Department of Internal Medicine and the Department of Family Practice of Eastern Virginia Medical School and by the office of Dr. Feldman (co-author).

Arch Intern Med. 2005; 165: 2530)

Source: Archives of Internal Medicine