Breaks in Sedentary Time during Childhood and Adolescence: Iowa Bone Development Study

KWON, SOYANG1; BURNS, TRUDY L.2,3; LEVY, STEVEN M.2,4; JANZ, KATHLEEN F.2,5

Medicine & Science in Sports & Exercise: June 2012 - Volume 44 - Issue 6 - p 1075–1080
doi: 10.1249/MSS.0b013e318245ca20
Epidemiology

Purpose: The frequency of interruptions in sedentary time (sedentary breaks) is an aspect of sedentary behaviors that may be associated with metabolic health outcomes. The aim of this study was to describe the change in the frequency of sedentary breaks during a 10-yr period from ages 5 to 15 yr.

Methods: The longitudinal Iowa Bone Development Study has collected accelerometry data at approximately 5, 8, 11, 13, and 15 yr. Data from participants who wore an accelerometer at least 10 h·d−1 and 3 d per data collection episode were used (423 children at age 5 yr, 550 children at age 8 yr, 520 children at age 11 yr, 454 children at age 13 yr, and 344 children at age 15 yr). The frequency of sedentary breaks was determined based on accelerometry data and compared by weekday/weekend, period during the day, gender, and data collection episode.

Results: The frequency of sedentary breaks decreased by >200 times per day during a 10-yr period from ages 5 to 15 yr. Linear regression models estimated a 1.84-times-per-hour decrease per year for boys and a 2.04-times-per-hour decrease per year for girls (P values < 0.0001). Both boys and girls showed significantly fewer breaks on weekdays from morning to 3:00 p.m. than on weekends from morning to 3:00 p.m. (P values < 0.0001). The frequency of sedentary breaks was slightly higher among boys than among girls (gender difference ≤2 times per hour; P values < 0.01 at ages 11, 13, and 15 yr).

Conclusions: Breaks in sedentary time notably decrease during childhood and adolescence. During school hours, boys and girls have fewer breaks in sedentary time than during any other period of weekday or weekend day.

1Consortium to Lower Obesity in Chicago Children, Children’s Memorial Hospital, Chicago, IL; 2Department of Epidemiology, University of Iowa, Iowa City, IA; 3Department of Pediatrics, University of Iowa, Iowa City, IA; 4Department of Preventive and Community Dentistry, University of Iowa, Iowa City, IA; and 5Health and Human Physiology, University of Iowa, Iowa City, IA

Address for correspondence: Soyang Kwon, PhD, 2300 Children’s Plaza Box no. 157, Chicago, IL 60614; E-mail: skwon@childrensmemorial.org.

Submitted for publication October 2011.

Accepted for publication December 2011.

©2012The American College of Sports Medicine