Physical activity, sedentary behaviour and sleep in Canadian children: parent-report versus direct measures and relative associations with health risk.

The accurate measurement of time devoted to physical activity, sedentary pursuits and sleep is difficult and varies considerably between surveys. This has implications for population surveillance and understanding how these variables relate to health.This sample of children (n = 878) was from the 2007 to 2009 Canadian Health Measures Survey. Moderate- to-vigorous physical activity (MVPA), sedentary behaviour and sleep duration were assessed using both a questionnaire and an accelerometer. This article compared parent-reported and directly measured physical activity, sedentary behaviour and sleep, and examined their associations, alone or in combination, with selected health markers in children aged 6 to 11.According to parent reports, the children in this study had an average of 105 minutes of MVPA, 2.5 hours of screen time and 9.7 hours of sleep per day; accelerometers recorded 63 minutes of MVPA, 7.6 hours of sedentary time and 10.1 hours of sleep per day. MVPA, measured by parent-report or accelerometry, was significantly associated with body mass index. In a regression model, directly measured MVPA and sleep were significantly associated with body mass index, and directly measured MVPA was significantly associated with waist circumference. Parent-reported screen time approached a significant association with body mass index.Time estimates and associations with health markers varied between parent-reported and directly measured physical activity, sedentary behaviour and sleep in children. These differences are important to understand before the two measurement techniques can be used interchangeably in research and health surveillance.