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Objective - Accelerometer

64. Association Between Objectively-Measured Physical Activity and Sleep, NHANES 2005-2006

Research Article
Paul D. Loprinzi et al
August 2011

Commentary by Rona Macniven, Cluster for Physical Activity and Health (CPAH), University of Sydney


This study used accelerometers to provide objective measures of physical activity to compare various aspects of sleep variables in a large, nationally-representative sample of US adults. Findings included that people who were meeting physical activity recommendations were less likely to feel overly sleepy during the day, have leg cramps while sleeping, and have difficulty concentrating when tired. Previous studies have found physical activity to be associated with sleep quality but this is the first study to objectively measure physical activity, thus providing greater validity to the findings.

Data came from the National Health and Nutrition Examination Survey (NHANES) 2005-2006 which included 3,081 adults aged 18-85 years who wore an ActiGraph accelerometer for 7 days. At the start of this time period, they were asked 20 questions on sleep such as frequency of trouble falling asleep, waking up at night and being unable to get back to sleep, feeling too tired during the day, having leg jerks or cramps and struggling to concentrate. They were also asked demographic and other questions about age, race, marital status, smoking status, general health and depression.

Statistical tests, after accounting for age, body mass index (BMI), health status, smoking status, and depression, found that the relative risk of often (compared to never) feeling overly sleepy during the day decreased by a factor of 0.65 (95% CI: 0.44-0.97) for participants meeting physical activity guidelines compared to those not meeting guidelines. Statistically significant results were also found for having leg cramps while sleeping (sometimes compared to never 0.68 (95% CI: 0.49-0.95) and having difficulty concentrating when tired (yes, moderate-to-extreme difficulty compared to no difficulty p=0.11). Those who were more active also fell asleep quicker.

This study provides higher quality evidence than has been achieved before of the benefits of physical activity in relation to sleep. Experimental studies of physical activity interventions which include measures of sleep would be an interesting next step to develop this area of physical activity research.