Resumen de A Prospective Study of Sedentary Behavior in a Large Cohort of Youth.

Jonathan A. Mitchell, Russell R. Pate, Steven N. Blair, Marsha Dowda, Andy Ness, Calum Mattocks, Chris Riddoch

• 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[middle dot]d-1, respectively, and sedentary behavior increased over time to 468.0 +/- 74.3 and 495.6 +/- 68.9 min[middle dot]d-1 at age 14 and to 510.4 +/- 76.6 and 525.4 +/- 67.4 min[middle dot]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[middle dot]d-1[middle dot]yr-1 for the boys and girls, respectively. The absolute mean increase in total sedentary behavior (+92.4 and +88.8 min[middle dot]d-1 for the boys and girls, respectively) closely matched the mean decrease in light physical activity (-82.2 and -82.9 min[middle dot]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. (C)2012The American College of Sports Medicine