A 5-yr change in Norwegian 9-yr-olds' objectively assessed physical activity level.

Purpose: To describe changes in objectively assessed physical activity by socioeconomic status (SES) between 1999-2000 and 2005 in 9-yr-old children living in Oslo, Norway.

Methods: Two cross-sectional studies were conducted in 1999-2000 and 2005. The participation rate was 70.9% in 1999-2000 and 91.4% in 2005. Participants were identified by SES based on whether the school they attended was in an area designated as high, middle, or low mean income. Physical activity was assessed objectively by accelerometers. A total of 718 children (1999-2000, n = 340; 2005, n = 378) provided valid physical activity assessments that met all inclusion criteria. General linear models were used to assess the changes in physical activity between 1999-2000 and 2005.

Results: A significant increase in mean physical activity level and physical activity during weekends was observed between the two study periods (P = 0.02 and <0.001, respectively), with the patterns being similar for girls and boys. Interactions were found between change in physical activity and SES. Although the mean physical activity level and moderate-to-vigorous physical activity (MVPA) among children from low-SES groups showed no change over time, an increase was seen among children from middle-SES groups. Moreover, in high-SES groups, an increase was observed for mean physical activity level (girls only) between study periods, whereas no change was seen for MVPA participation.

Conclusions: Nine-year-old children living in Oslo, Norway, have increased both their mean and weekend physical activity level between 1999-2000 and 2005. However, because these opportunities are not equal across SES groups, interventions are required to focus on the needs of children from low-SES groups.