IMPORTANCE

The updated 2018 Physical Activity Guidelines for Americans (PAG) reaffirmed key recommendations regarding aerobic activity in the 2008 edition and recently introduced health risks of sedentary behaviors and their association with physical activity.

OBJECTIVE

To examine the concurrent changing trends in adherence to the PAG for aerobic activity and time spent on sedentary behavior in US adults from 2007 to 2016.

DESIGN, SETTING, AND PARTICIPANTS: This study used data from a series of cross-sectional, nationally representative surveys on adults 18 years or older from the National Health and Nutrition Examination Surveys from 2007 to 2016. Data analysis was performed from September 1, 2018, to March 31, 2019.

MAIN OUTCOMES AND MEASURES

Duration, frequency, and intensity of leisure-time, work-related, and transportation-related aerobic activity were ascertained by a standardized questionnaire and summed as minutes per week. Adherence to the PAG for aerobic activity was defined as engaging in at least 150 minutes a week of moderate-intensity or 75 minutes a week of vigorous-intensity aerobic physical activity or an equivalent combination of moderate- and vigorous-intensity aerobic physical activity. Time spent on sedentary behavior was estimated by hours spent sitting on a typical day.

RESULTS

Among 27 343 participants 18 years or older (13 630 [52.0%] female; 14 628 [66.6%] non-Hispanic white), the weighted adherence rate to the PAG for aerobic activity was 65.2% (95% CI, 62.3%-68.2%) in 2015-2016, with no significant change from 2007-2008 (63.2%; 95% CI, 60.2%-66.1%) to 2015-2016 (P = .15 for trend). Time spent on sedentary behavior significantly increased over time from a weighted mean (SE) of 5.7 (0.3) hours per day in 2007-2008 to 6.4 (0.2) hours per day in 2015-2016 (P < .001 for trend). The weighted proportion of people not adhering to the PAG for aerobic activity and reporting long sedentary time (>6 hours per day) increased from 16.1% (95% CI, 14.4%-17.8%) in 2007-2008 to 18.8% (95% CI, 17.7%-20.0%) in 2015-2016.

CONCLUSIONS AND RELEVANCE

The findings suggest that the adherence rate to the PAG for aerobic activity in US adults has not improved since the release of the first edition in 2008 but that time spent on sedentary behavior has significantly increased over time. Further nationwide efforts appear to be warranted to not only promote physical activity but also reduce sedentary time in the United States.