Large, Prospective Analysis Links Lack of Sleep to Weight Gain

Emma Hitt, PhD

June 19, 2006

June 19, 2006 — Lack of sleep is significantly associated with weight gain, according to the largest analysis of this issue to date.

The findings represent a prospective analysis of 68,183 women, followed over 16 years, from the Nurses Health Study and were presented Monday at the Associated Professional Sleep Societies annual meeting, held in Salt Lake City, Utah.

"Two prior longitudinal studies have assessed this issue, but both were small and had conflicting results," noted lead author Sanjay R. Patel, MD, with the Case Western Reserve University, in Cleveland, Ohio. "Our study is therefore the largest to prospectively investigate whether sleep duration predicts future weight gain," he told Medscape.

Women in the Nurses Health Study filled out a questionnaire about their sleeping habits starting in 1986 and again every 2 years thereafter. Calculations were adjusted for body mass index (BMI) and age.

Over 16 years, women who had 5 or fewer hours of sleep per night gained, on average, 1.04 kg (95% confidence interval [CI], 0.39-1.69) more than those getting at least 7 hours, and women sleeping only 6 hours gained 0.68 kg (95% CI, 0.39-0.97) more than those who slept 7 or more hours per night.

In addition, women sleeping 5 or fewer hours per night had a 32% increased risk of gaining 15 kg (relative risk [RR], 1.32; 95% CI, 1.19-1.47) and those sleeping for 6 hours had a 12% increased risk (RR, 1.12; 95% CI, 1.06-1.19) relative to those who slept 7 hours per night.

Likewise, the overall risk of developing obesity was increased. The relative risks for developing obesity, defined as BMI > 30 kg/m2, were 1.15 (95% CI [1.04-1.26]) and 1.06 (95% CI [1.01-1.11]) for those who slept a maximum of 5 or 6 hours per night, respectively.

"These associations remained significant after inclusion of important covariates and were not affected by adjustment for physical activity or dietary consumption," the authors noted in their abstract.

According to Dr. Patel, women who slept less actually had a lower caloric intake than women who slept more. "Thus our results suggest that women who sleep less must have a reduced expenditure of calories," he said. "We also found that women who slept less burned less energy in exercise, but the differences were not large enough to explain the weight findings."

One explanation for the findings, noted Dr. Patel, is that reduced sleep may slow a person's basal metabolic rate. Another is that "very small activities that we did not assess, such as the time spent standing instead of sitting or fidgeting while seated may be reduced in short sleepers."

According to Dr. Patel, obtaining an adequate amount of sleep should be considered an integral part of a healthy lifestyle, just as much as eating healthy and exercising regularly. "Physicians should ask about their patients' sleep and help their patients improve their sleep habits."

"This is the first study that I am aware of that has shown statistically significant results for weight gain," noted James Gangwisch, PhD, with the Columbia University Medical Center, in New York, New York. Dr. Gangwisch and his team recently analyzed data from the first National Health and Nutrition Examination Study (NHANES I) and found similar results with regard to sleep and weight gain.

"Unfortunately self-reported dietary consumption data are notoriously inaccurate, so it is hard to say for sure whether there were differences in food consumption based on hours slept," Dr. Gangwisch told Medscape. "However, sleep deprivation has been shown to compromise insulin sensitivity which can facilitate fat deposition," he added.

APSS 2006 Annual Meeting: Abstract 349. Presented June 19, 2006.

Reviewed by Marni Kelman, MSc


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