High amounts of sedentary behavior and low levels of physical activity are associated with increased risk of premature mortality and some chronic diseases.1 Engaging in high volumes of moderate- to vigorous-intensity physical activity may reduce the mortality risk associated with excessive sedentary behavior.1,2 Understanding the combined prevalence of these behaviors could help practitioners determine whether to prioritize interventions targeting sedentary time, physical activity, or both. We examined patterns in joint categories of sitting time and leisure-time physical activity among US adults.
We used data from the 2015-2016 National Health and Nutrition Examination Survey (NHANES), a nationally representative survey of the noninstitutionalized, civilian US population.3 NHANES collects health information through in-home interviews and physical examinations. The National Center for Health Statistics research ethics review board approved NHANES. Adult participants (aged ≥18 years) provided written consent. The overall 2015-2016 interview response rate was 61.3%, and there were 5992 adult respondents.
Sedentary behavior was measured as sitting time, defined as daily time spent “sitting at work, at home, getting to and from places, or with friends, including time spent sitting at a desk, traveling in a car or bus, reading, playing cards, watching television, or using a computer” and was assessed with the question “How much time do you usually spend sitting on a typical day?” Reported sitting time was categorized into quartiles of 0 to less than 4 hours, 4 to less than 6 hours, 6 to 8 hours, and more than 8 hours per day.2 Respondents also reported the frequency and duration of moderate- and vigorous-intensity leisure-time physical activity during a typical week. Total leisure-time physical activity was calculated as weekly minutes of moderate-intensity activity plus twice the reported minutes of vigorous-intensity activity and was categorized according to current guidelines as inactive (no moderate- or vigorous-intensity activity), insufficiently active (some activity but not enough to meet sufficiently active definition), sufficiently active (150-300 min/wk), or highly active (>300 min/wk).4
Categorical variables for sitting time and leisure-time physical activity were cross-tabulated to estimate the proportion of adults in each joint category. Estimates were stratified by sex and age category. Analyses were conducted in Stata version 13.1 (StataCorp) using survey commands to account for the sampling design, and full sample interview weights were applied.
We analyzed data from 5923 adults with complete data (98.8% of total). Overall, 25.7% (95% CI, 23.0%-28.5%) reported sitting for more than 8 hours per day and 44.6% (95% CI, 40.2%-49.0%) were inactive. Across joint categories, the greatest proportion of adults reported sitting for 6 to 8 hours per day and being inactive (13.9%; 95% CI, 12.1%-16.0%), followed by sitting for more than 8 hours per day and being inactive (11.4%; 95% CI, 10.5%-12.4%), and sitting for 4 to less than 6 hours per day and being inactive (11.2%; 95% CI, 9.6%-13.0%) (Figure). The smallest proportions reported sitting for less than 4 hours per day and being sufficiently active (2.6%; 95% CI, 2.1%-3.2%) or sitting for less than 4 hours per day and being insufficiently active (2.7%; 95% CI, 2.0%-3.6%). Patterns were similar by sex (Table). Some differences in the joint distribution of sitting time and leisure-time physical activity were observed between age categories. For example, the joint prevalence of sitting for more than 8 hours per day and being inactive increased with increasing age.
These data reveal a substantial prevalence of high sitting time and physical inactivity among US adults: about 1 in 4 sit for more than 8 hours a day, 4 in 10 are physically inactive, and 1 in 10 report both. The limitations of this study include possible bias inherent in self-reported data and that physical activity episodes shorter than 10 minutes may not have been captured.
Both high sedentary behavior and physical inactivity have negative health effects, and evidence suggests that the risk of premature mortality is particularly elevated when they occur together.1,2 Evidence-based strategies to reduce sitting time, increase physical activity, or both would potentially benefit most US adults, particularly older adults. Practitioners can support efforts to implement programs, practices, and policies where adults live, learn, work, and play to help them sit less and spend more time being physically active.1,5,6
Corresponding Author: Emily N. Ussery, PhD, National Center for Chronic Disease Prevention and Health Promotion, Division of Nutrition, Physical Activity, and Obesity, Centers for Disease Control and Prevention, 4770 Buford Hwy NE, Atlanta, GA 30341 (yzv4@cdc.gov).
Correction: This article was corrected for errors in the Figure on April 9, 2019.
Author Contributions: Dr Ussery had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.
Concept and design: Ussery, Fulton, Katzmarzyk, Carlson.
Acquisition, analysis, or interpretation of data: All authors.
Drafting of the manuscript: Ussery.
Critical revision of the manuscript for important intellectual content: All authors.
Statistical analysis: Ussery, Carlson.
Administrative, technical, or material support: Ussery, Fulton, Carlson.
Supervision: Fulton, Katzmarzyk, Carlson.
Conflict of Interest Disclosures: None reported.
Funding/Support: This research was funded by the Centers for Disease Control and Prevention.
Role of the Funder/Sponsor: The Centers for Disease Control and Prevention supported the staff responsible for the design and conduct of the study; the collection, analysis, and interpretation of the data; the preparation, review, and approval of the manuscript; and the decision to submit the manuscript for publication.
Disclaimer: The findings and conclusions in this report are those of the authors and do not necessarily represent the official position of the Centers for Disease Control and Prevention.
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