Time trends in physical activity in leisure time in the Danish population from 1987 to 2005

Aims: To examine time trends in leisure-time physical activity in the Danish population from 1987 to 2005. Methods: Analyses were based on four national representative population surveys of 4752 respondents in 1987, 4667 in 1994, 16,688 in 2000, and 14,566 in 2005. Associations between leisure-time physical activity (dichotomised into high versus low) and temporal changes according to year of birth, age, and calendar-year were estimated in an age-period-cohort logistic regression model. Time trends in socioeconomic differences in physical activity were analysed by testing interaction terms. Results: The odds ratio (OR) of being highly physically active in leisure time in 2005 compared to 1987 was 1.6 (95% CI: 1.3-1.9) among men and 1.8 (95% CI: 1.5-2.2) among women. The age-and calendar-year-adjusted probability of being highly physically active increased with year of birth. The OR of being highly physically active among men and women with 13 or more years of education were 2.1 (95% CI: 1.8-2.3) and 2.0 (95% CI: 1.7-2.2), respectively, compared to individuals with less than 10 years of education. There was no significant interaction between educational level and year of interview (p>0.05). Conclusions: During the past 20 years, physical activity in leisure time has increased. Younger generations seem to be more physically active in leisure time than older generations. Due to the stable socioeconomic inequality gap in physical activity, future intervention strategies should target these inequalities.