Lack of sleep unlikely to impact weight over time

NEW YORK (Reuters Health) - Regularly getting 5 hours or less of shut eye a night does not appear to have a considerable influence body weight or waist size over time, according to findings from a long-term study of British workers.

While some past research has identified a relationship between obesity and a lack of sleep, this research could not affirm which came first -- the lack of sleep or the weight problem.

To clarify whether lack of sleep over time might be related to obesity, Francesco P. Cappuccio and colleagues analyzed information from more than 10,000 white-collar British civil servants participating in a long term forward-looking study called the Whitehall II study.

The men and women were first had their health assessed between 1985 and 1988 when they were between 35 and 55 years old. They were subsequently assessed every two years thereafter.

Cappuccio, of the University of Warwick Medical School, in Coventry, England, and colleagues analyzed nightly sleep duration and indicators of obesity among 5,021 of the study participants during the 1997 to 1999 assessment.

In this assessment, the investigators identified a 65 percent increased risk of obesity among people sleeping less than 5 hours a night compared with those sleeping 7 hours nightly.

But when they looked at measures of body weight and waist circumference again between 2003 and 2004 among 3,786 of these men and women who were not obese during the earlier assessment, they found no significant association between sleep duration and future changes in body weight or waist circumference.

Taken together, these findings suggest that short duration of sleep might represent a risk marker as opposed to a causative factor for obesity, the researchers conclude in the latest issue of the American Journal of Epidemiology.

SOURCE: American Journal of Epidemiology, February 2008