Patients who slept for short or long durations experienced an increase in weight compared with those who slept for an average duration of 7 to 9 hours, according to the results of a longitudinal study reported in the April issue of Sleep.

"Individual and environmental factors that have an influence on energy balance are not fully understood," write Jean-Philippe Chaput, MSc, from Laval University in Quebec City, Quebec, Canada, and colleagues. "Current treatments for obesity have been largely unsuccessful in maintaining long-term weight loss, suggesting the need for new insight into the mechanisms that result in altered metabolism and behavior and may lead to obesity."

To determine the relationship between sleep duration and subsequent body weight and fat gain, the investigators evaluated body composition measurements and self-reported sleep duration in 276 adults aged 21 to 64 years who were enrolled in the Quebec Family Study, a 6-year longitudinal study in a community setting. More than half of the sample was drawn from families in which at least 1 parent and 1 offspring had a body mass index (BMI) of 32 kg/m² or higher. The investigators compared changes in adiposity indices among groups determined by sleep duration: short (5 - 6 hours), average (7 - 8 hours), and long (9 - 10 hours).

Compared with average-duration sleepers, short-duration sleepers gained 1.98 kg more in a 6-year period (95% confidence interval [CI], 1.16 - 2.82), and long-duration sleepers gained 1.58 kg more (95% CI, 1.02 - 2.56) after adjustment for age, sex, and baseline BMI. At 6 years, short-duration and long-duration sleepers were 35% and 25% more likely to experience a 5-kg weight gain, respectively, vs average-duration sleepers.

Compared with average-duration sleepers, short-duration sleepers had a 27% increased risk for the development of obesity, and long-duration sleepers had a 21% increase in risk. Adjustment for energy intake and physical activity participation did not affect these associations, which remained significant after inclusion of important covariates.

Limitations of the study include those inherent in questionnaire-based measurements; small sample size limiting statistical power and generalizability; heterogeneity in age; use of a nonrandom sample originally studied to explore the role of genetics in the cause of obesity; use of self-reported sleep durations; and possible confounding by unmeasured variables in the relationship between sleep time and adiposity, such as sleep-disordered breathing, insomnia, or depression.

"This study provides evidence that both short and long sleeping times predict an increased risk of future body weight and fat gain in adults," the study authors write. "Hence, these results emphasize the need to add sleep duration to the panel of determinants that contribute to weight gain and obesity."

This was not an industry-supported study. The Medical Research Councils of Canada and other agencies from the governments of Quebec and Canada have supported the Quebec Family Study. The study authors have disclosed various financial relationships with GlaxoSmithKline; sanofi-aventis; MSD; Novartis; Abbott Laboratories; AstraZeneca; Fournier Pharma Inc; Solvay Pharma; Pfizer Canada; Pharmacia; Dairy Farmers of Canada; Dairy Management Inc; Hôpital Laval Research Center; George A. Bray Chair in Nutrition; and the Canada Research Chair in Physical Activity, Nutrition, and Energy Balance.

Sleep. 2008;31:517-523.

Clinical Context

Parallel to increasing body weight in the US population has been a reduction in sleep times. For the past 4 decades, daily sleep duration has decreased by 1.5 to 2 hours, and the proportion of young adults sleeping less than 7 hours per night has more than doubled, from 15.6% in 1960 to 37.1% from 2001 to 2002.

Cross-sectional studies in adults and children have repeatedly shown that reduced sleep is associated with increased weight, most likely via an alteration of the neuroendocrine control of appetite characterized by a decrease in the levels of the anorexigenic hormone leptin and an increase in the levels of the orexigenic factor ghrelin. These neuroendocrine changes may favor a positive energy balance and weight gain with time, but studies to date cannot distinguish cause from effect. The present study looked at longitudinal associations between sleep duration and adiposity indices in the Quebec Family Study.

Study Highlights

• The goal of this study was to characterize longitudinal associations between sleep duration and adiposity indices (body weight and fat gain) in the Quebec Family Study.
• The hypothesis of this analysis was that short sleep duration predisposes to increased body weight and fat gain because of the combined effects of increased energy intake and reduced physical activity.
• Participants were 276 adults aged 21 to 64 years who were enrolled in the Quebec Family Study, a 6-year longitudinal study in a community setting.
• More than half of the sample came from families with at least 1 parent and 1 offspring who had a BMI of 32 kg/m² or higher.
• Exclusion criteria were diabetes, change in body weight of more than 2 kg during the 6 months before baseline testing, and missing data on 1 or more of the variables investigated.
• The number of hours of sleep was evaluated at baseline and year 6 through a question inserted in a self-administered questionnaire on physical activity participation.
• Covariates measured via self-reported questionnaires at baseline and year 6 included age, sex, smoking habits, employment status, highest educational level, total annual family income, menopausal status, shift-working history, alcohol intake, and coffee intake.
• The investigators compared changes in adiposity indices among 3 groups: short sleep duration (5 - 6 hours), average sleep duration (7 - 8 hours), and long sleep duration (9 - 10 hours).
• There were no significant differences among groups for energy intake and resting metabolic rate. However, short-duration sleepers reported greater participation in vigorous physical activity.
• Shift-working history, participation in vigorous physical activity, employment status, smoking habits, and coffee intake were the main independent predictors of sleep duration.
• In a 6-year period, short-duration sleepers gained 1.98 kg more (95% CI, 1.16 - 2.82) vs average-duration sleepers after adjustment for age, sex, and baseline BMI.
• After adjustment for covariates, the average weight gain of short-duration sleepers was 88% more than the weight gain of average-duration sleepers, and increase in waist circumference and percentage of body fat was 58% and 124% higher, respectively.
• During 6 years, short-duration sleepers were 35% more likely to experience a 5-kg weight gain vs average-duration sleepers.
• Compared with average-duration sleepers, short-duration sleepers had a 27% increased risk for obesity.
• Long-duration sleepers had higher BMIs at baseline, making it plausible that they would be more likely to gain weight during the follow-up period.
• Long-duration sleepers gained 1.58 kg more (95% CI, 1.02 - 2.56) during the 6-year study period, after adjustment.
• Long-duration sleepers also had a significantly higher increase in body weight (71%), waist circumference (47%), and percentage of body fat (94%) vs the increase seen in average-duration sleepers.
• During 6 years, long-duration sleepers were 25% more likely to experience a 5-kg weight gain vs average-duration sleepers.
• Compared with average-duration sleepers, long-duration sleepers had a 21% increase in risk for the development of obesity.
• Adjustment for energy intake and physical activity participation did not affect these associations, which remained significant after inclusion of important covariates.
• Based on these findings, the investigators concluded that both short and long sleeping times predict an increased risk for future body weight and fat gain in adults and that sleep duration should be added to the panel of determinants contributing to weight gain and obesity.

Pearls for Practice

• After adjustment for age, sex, and baseline BMI in a 6-year period, short-duration sleepers gained 88% more weight vs average-duration sleepers, on average, and increase in waist circumference and percentage of body fat was 58% and 124% higher, respectively. During 6 years, short-duration sleepers were 35% more likely to experience a 5-kg weight gain vs average-duration sleepers, and they had a 27% increased risk for obesity.
• After adjustment, long-duration sleepers also had a significantly higher increase in body weight (71%), waist circumference (47%), and percentage of body fat (94%) vs the increase seen in average-duration sleepers. During 6 years, long-duration sleepers were 25% more likely to experience a 5-kg weight gain vs average-duration sleepers, and they had a 21% increase in the risk for the development of obesity.