Thirty-year trends of physical activity in relation to age, calendar time and birth cohort in Finnish adults

Background: The aim of this article was to investigate time trends 1972-2002 in leisure time, occupational and commuting physical activity across birth cohorts in Finnish adults. Methods: The study population comprised 59 028 men and women aged 25-64 years who participated in the FINRISK Study. The first birth cohort was born in 1913 and the last in 1977. Prevalence of physical activity was reported across birth cohorts and study years and change in the prevalence was tested using log-linear regression analysis. Results: The prevalence of leisure-time physical activity increased between 1972 and 2002 from 66 to 77 in men and from 49 to 76 in women. In each study year, the younger people were more active than the older ones. However, within the birth cohorts, physical activity tended to increase with age. The prevalence of physically demanding work decreased from 60 to 38 in men and from 47 to 25 in women and the prevalence of daily commuting activity decreased from 30 to 10 in men and from 34 to 22 in women, in the same time period. In the 1970s and the 80s, the older people had more physically demanding work than the younger ones, but within the birth cohorts, occupational activity decreased with age. Conclusion: During the past 30 years, the prevalence of leisure-time physical activity has increased, while the prevalence of occupational and commuting physical activity has decreased. The cross-sectional association of age with different types of physical activity was different from that assessed within the birth cohorts.