Time Trends in Physical Activity and Sedentary Time from 2005 to 2011 in Norwegian 9- and 15-year olds

Aim: The aim of this study was to assess time trends in objectively assessed physical activity in a population based sample of children and adolescents living in Norway.

Methods: The sample population (n=4766) consists of two independent samples of 9- and 15-year-old children recruited within the PANCS project in 2005-06 and 2011. Physical activity was assessed by using ActiGraph accelerometers. Analysis of covariance was used to assess changes in physical activity level.

Results: Among 9-year-olds, there was no change in mean physical activity level from 2005-06 to 2011. However, the 9-year-olds in 2011 had a lower mean physical activity level during week days and a higher mean physical activity level during weekends compared to the 9-year-olds in 2005-06. Also, 9-year-olds in 2011 spent more time being sedentary (p<0.001) and spent less time in activities of light and moderate-to-vigorous intensities than their peers in 2005-06 (p=0.001). Among 15-year-old girls and boys, there was no change in mean physical activity level. However, 15-year-olds in 2011 had more sedentary minutes (p<0.001) and spent less time in activities of light intensities than their peers in 2005-06 (p<0.001).

Conclusions: There was no change in mean physical activity level over the six year period. However, participants in 2011 had more sedentary time and fewer minutes in activities of light intensity than in 2005-06. As sedentary time might be detrimental for health, the trend of more sedentary time is of concern.