Jaemyung Kim, John M. Schuna Jr.

Oregon State University, Corvallis, OR

The 2011-2012 and 2013-2014 cycles of the National Health and Nutrition Examination Survey (NHANES) implemented a wrist-worn accelerometer protocol to objectively assess physical activity among Americans. Unfortunately, there remains few validated approaches for translating wrist-worn accelerometer data into meaningful estimates of physical behavior which has limited opportunities to describe Americans’ physical activity and sedentary behavior using 2011-2014 NHANES accelerometer data. One previously validated method for assessing sedentary time (ST) via wrist-worn accelerometry is known as the Sedentary Sphere (SS) method. The SS method has yet to be used to describe ST in US adults. PURPOSE: To describe ST in US adults (age ≥ 18 y) using the SS method. METHODS: US adults (N = 9,298) who completed a wrist-worn accelerometer protocol during the 2011-2014 NHANES were included in analyses. ST was quantified using the SS method whereby participant posture is estimated from derived arm elevation and movement intensity. Wear-time adjusted means and standard errors of average daily ST were calculated and compared using survey regression procedures across groupings of sex (male vs. female), age (18-29y, 30-44y, 45-59y, 60+y), and quartiles of total physical activity (< 10,425.7, 10,425.7 – 12,874.6, 12,874.7 – 15,563.5, > 15,563.5 MIMS/day). Survey procedures were used for all analyses to account for the complex, multi-stage design of NHANES. RESULTS: Mean daily ST among American adults was 489 ± 1.5 min/day. ST was higher among males than females (510 ± 1.6 vs. 470 ± 1.8 min/day, p < 0.001). ST was positively associated with age. Those Americans 60+y had the highest ST while those 18-29y had the lowest values (511 ± 2.3 vs. 459 ± 2.1 min/day, p < 0.001). ST was inversely associated with total physical activity. ST in the most active grouping (> 15,563.5 MIMS/day: 422 ± 2.3 min/day) was dramatically lower than ST in the least active grouping (< 10,425.7 MIMS/day: 556 ± 3.3 min/day, p < 0.001). CONCLUSION: ST calculated by the SS method significantly varied across groupings of sex, age, and total physical activity among American adults. Future research should focus on examining associations between ST calculated by the SS method and health outcomes of interest.

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