Seasonal Variation in Children's Physical Activity and Sedentary Time
Medicine and Science in Sports and Exercise 2015
Purpose: Understanding seasonal variation in physical activity is important for informing public health surveillance and intervention design. The aim of the current study was to describe seasonal variation in children's objectively measured physical activity and sedentary time. Methods: Data are from the UK Millennium Cohort Study. Participants were invited to wear an accelerometer for seven days on five occasions between November 2008 and January 2010. Outcome variables were sedentary time (2241 counts per min; min/day). Season was characterised using a categorical variable (spring, summer, autumn, winter) and a continuous function of day of year. Cross-classified linear regression models were used to estimate the association of each of these constructs with the outcome variables. Modification of the seasonal variation by sex, weight status, urban/rural location, parental income and day of the week (week/weekend) was examined using interaction terms in regression models. Results: At least 1 wave of valid accelerometer data was obtained from 704 participants (47% male; baseline age 7.6(0.3) years). MVPA was lower in autumn and winter relative to spring, with the magnitude of this difference varying by week/weekend day, sex, weight status, urban/rural location and family income (p for interaction Conclusion: Lower levels of MVPA and elevated sedentary time support the implementation of intervention programmes during autumn and winter. Evidence of greater seasonal variation in weekend behaviour and amongst certain socio-demographic subgroups highlights targets for tailored intervention programmes.