Associations between inadequate sleep and obesity in the US adult population: analysis of the national health interview survey (1977-2009)

Background: Epidemiologic studies show a curvilinear relationship between inadequate sleep (< 7 or > 8 hours) and obesity (Body Mass Index > 30 kg/m(2)), which have enormous public health impact. Methods: Using data from the National Health Interview Survey, an ongoing nationally representative cross-sectional study of non-institutionalized US adults (>= 18 years) (1977 through 2009), we examined the hypothesis that inadequate sleep is independently related to overweight/ obesity, with adjustment for socio-demographic, health risk, and medical factors. Self-reported data on health risks, physician-diagnosed medical conditions, sleep duration, and body weight and height were used. Results: Prevalence of overweight and obesity increased from 31.2% to 36.9% and 10.2% to 27.7%, respectively. Whereas prevalence of very short sleep (< 5 hours) and short sleep (5-6 hours) has increased from 1.7% to 2.4% and from 19.7% to 26.7%, it decreased from 11.6% to 7.8% for long sleep. According to multivariate-adjusted multinomial regression analyses, odds of overweight and obesity associated with very short sleep and short sleep increased significantly from 1977 to 2009. Odds of overweight and obesity conferred by long sleep did not show consistent and significant increases over the years. Analyses based on aggregated data showed very short sleepers had 30% greater odds of being overweight or were twice as likely to be obese, relative to 7-8 hour sleepers. Likewise, short sleepers had 20% greater odds of being overweight or 57% greater odds of being obese. Long sleepers had 20% greater odds of being obese, but no greater odds of being overweight. Conclusions: Our findings support the hypothesis that prevalence of very short and short sleep has gradually increased over the last 32 years. Inadequate sleep was associated with overweight and obesity for each available year.