Age and time effects on children's lifestyle and overweight in Sweden

Background: High physical activity, low sedentary behavior and low consumption of sugar-sweetened beverages can be markers of a healthy lifestyle. We aim to observe longitudinal changes and secular trends in these lifestyle variables as well as in the prevalence of overweight and obesity in 7-to-9-year-old schoolchildren related to gender and socioeconomic position. Methods: Three cross-sectional surveys were carried out on schoolchildren in grades 1 and 2 (7-to-9-year-olds) in 2008 (n = 833), 2010 (n = 1085), and 2013 (n = 1135). Information on children's level of physical activity, sedentary behavior, diet, and parent's education level was collected through parental questionnaires. Children's height and weight were also measured. Longitudinal measurements were carried out on a subsample (n = 678) which was included both in 2008 (7-to-9-year-olds) and 2010 (9-to-11-year-olds). BMI was used to classify children into overweight (including obese) and obese based on the International Obesity Task Force reference. Questionnaire reported maternal education level was used as a proxy for socioeconomic position (SEP). Results: Longitudinally, consumption of sugar-sweetened beverages >= 4 days/week increased from 7% to 16% in children with low SEP. Overall, sedentary behavior >4 hours/day doubled from 14% to 31% (p < 0.001) and sport participation >= 3 days/week increased from 17% to 37% (p < 0.001). No longitudinal changes in overweight or obesity were detected. In the repeated cross-sectional observations sedentary behavior increased (p = 0.001) both in high and low SEP groups, and overweight increased from 13.8% to 20.9% in girls (p < 0.05). Overall, children with high SEP were less-often overweight (p < 0.001) and more physically active (p < 0.001) than children with low SEP. Conclusions: Children's lifestyles changed longitudinally in a relatively short period of two years. Secular trends were also observed, indicating that 7-9-year-olds could be susceptible to actions that promote a healthy lifestyle. Socioeconomic differences were consistent and even increasing when it came to sugar-sweetened beverage consumption. Decreasing the socioeconomic gap in weight status and related lifestyle variables should be prioritized. Primary school is an arena where most children could be reached and where their lifestyle could be influenced by health promoting activities.