Americans are very tired. The National Sleep Foundation recommends that adults sleep 7 to 9 hours per day, yet the percentage of U.S. adults securing at least 8 hours of sleep on weeknights has fallen from 38% to 27% since 2001. Sleep promotion is a recognized national health agenda with a Healthy People 2020 objective to increase the proportion of adults who get sufficient sleep to 71%.
CDC released a report last month on the prevalence of short sleep duration among U.S. workers. Short sleep duration (average ≤ 6 hours per 24-hour period) was reported by 30% of employed U.S. adults (approximately 40.6 million workers). The prevalence of short sleep duration was especially high among night shift workers in the transportation and warehousing (70%) and healthcare and social assistance (52%) industries. Sleep deprivation has been linked to adverse health consequences, such as obesity. But how does sleep deprivation lead to obesity?
Dr. Nathaniel Watson from the University of Washington and colleagues recently published a population-based twin-study evaluating the link between sleep duration and BMI (Sleep. 2012 May 1;35(5):597-603) that begins to unlock the sleep-BMI mystery. Investigators analyzed data from a twin registry involving 1,088 complete twin pairs. Normal sleep duration was considered 7 to 8.9 hours. Findings from this study suggest that restricting sleep provides a permissive environment for the expression of genes promoting obesity. The flipside is that extending sleep suppresses the expression of obesity genes.
The study adds to extant data suggesting that people who sleep six or fewer hours are at greater risk for obesity. Other published data suggest that too much sleep may increase the risk for cardiovascular disease, insulin resistance, and mortality. One may find it helpful to think of the relationship between nightly sleep duration and BMI as a U-shaped curve – both short and long sleepers weigh more than those in the sweet spot around 7 to 9 hours.
This study does not inform us about whether an intervention aimed at increasing sleep will result in clinically significant weight loss. But it does suggest that behavioral measures to lose weight may be more effective when genetic drivers of body weight are ratcheted down through sleep extension.
This knowledge may prove useful to our patients who are trying to get a handle on their body weight and literally feel tired doing so. Evidence is now mounting that a component of obesity treatment may be to tell our patients to get some sleep.
Jon O. Ebbert, M.D. is a professor of medicine and a primary care clinician at the Mayo Clinic in Rochester, MN. The opinions expressed are solely those of the author. Contact him at ebbert.jon@mayo.edu.