Trends in Self-Reported Sitting Time by Physical Activity Levels Among US Adults, NHANES 2007/2008-2017/2018.

Background: High levels of sedentary behavior and physical inactivity increase the risk of premature mortality and several chronic diseases. Monitoring national trends and correlates of sedentary behavior and physical inactivity can help identify patterns of risk in the population over time.

Methods: The authors used self-reported data from the National Health and Nutrition Examination Surveys (2007/2008-2017/2018) to estimate trends in US adults' mean daily sitting time, overall, and stratified by levels of leisure-time and multidomain physical activity, and in the joint prevalence of high sitting time (>8 h/d) and physical inactivity. Trends were tested using orthogonal polynomial contrasts.

Results: Overall, mean daily sitting time increased by 19 minutes from 2007/2008 (332 min/d) to 2017/2018 (351 min/d) (Plinear < .05; Pquadratic < .05). The highest point estimate occurred in 2013/2014 (426 min/d), with a decreasing trend observed after this point (Plinear < .05). Similar trends were observed across physical activity levels and domains, with one exception: an overall linear increase was not observed among sufficiently active adults. The mean daily sitting time was lowest among highly active adults compared with less active adults when using the multidomain physical activity measure.

Conclusions: Sitting time among adults increased over the study period but decreased in recent years.