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Medicine & Science in Sports & Exercise:
doi: 10.1249/MSS.0b013e3182446c65
Epidemiology

A Prospective Study of Sedentary Behavior in a Large Cohort of Youth

MITCHELL, JONATHAN A.1; PATE, RUSSELL R.1; DOWDA, MARSHA1; MATTOCKS, CALUM2; RIDDOCH, CHRIS3; NESS, ANDY R.2; BLAIR, STEVEN N.1,4

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Abstract

Purpose: The study’s purpose was to describe longitudinal patterns of objectively measured sedentary behavior from age 12 to 16.

Methods: Children participating in the Avon Longitudinal Study of Parents and Children wore accelerometers for 1 wk at ages 12, 14, and 16. Participants included boys (n = 2591) and girls (n = 2845) living in a single geographic location in the United Kingdom (Bristol). Total minutes per day spent in sedentary behavior and time spent in blocks of sedentary behavior lasting 10–19, 20–29, and ≥30 min are described. Growth curve models were used to determine the rate of change in sedentary behavior from age 12 to 16.

Results: At age 12, the boys and girls, on average, were sedentary for 418.0 ± 67.7 and 436.6 ± 64.0 min·d−1, respectively, and sedentary behavior increased over time to 468.0 ± 74.3 and 495.6 ± 68.9 min·d−1 at age 14 and to 510.4 ± 76.6 and 525.4 ± 67.4 min·d−1 at age 16. Growth curve analyses found that total sedentary behavior increased at a rate of 19.5 ± 0.7 and 22.8 ± 0.7 min·d−1·yr−1 for the boys and girls, respectively. The absolute mean increase in total sedentary behavior (+92.4 and +88.8 min·d−1 for the boys and girls, respectively) closely matched the mean decrease in light physical activity (−82.2 and −82.9 min·d−1 for the boys and girls, respectively) from age 12 to 16. Time spent in continuous sedentary behavior lasting ≥30 min increased by 121% from age 12 to 16.

Conclusions: Sedentary behavior increased with age, at the expense of light physical activity. The increase in sedentary behavior lasting ≥30 min in duration contributed greatly to the increase in total sedentary behavior.

©2012The American College of Sports Medicine

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