Background Maintaining physical activity during later life is associated with optimal health; however, research on the long-term trajectories of physical activity into old age and their predictors has been limited. This study aimed to identify distinct 20 year trajectories of physical activity spanning from midlife to old age and predictors of physical activity trajectories.

Methods Participants were men drawn from the British Regional Heart Study, a prospective cohort study, involving 7735 men recruited from Primary Care Practices in 1978–80. Men were followed up after 12, 16 and 20 years, reporting physical activity levels (walking, cycling, recreational activity and sport/exercise), health status and socio-demographic characteristics. Group-based trajectory modelling was applied to identify distinct trajectories of physical activity and to examine the effects of predictor variables on trajectories. Predictors of trajectory group membership were examined using multinomial logistic regression. The effects of developing cardiovascular disease and changing employment status on trajectories were estimated for each trajectory group.

Results 7658 men (mean baseline age 50.2±5.8 years) providing valid questionnaire and physical activity data (of which 78% provided activity data at ≥2 surveys) were included in analyses. Three distinct trajectories of physical activity emerged: low decreasing (34.1%), low stable (45.8%) and moderate increasing (20.1%). Membership of the moderate increasing trajectory group was predicted by being married, having children, drinking alcohol and eating breakfast. Men with manual occupations, men residing in regions other than the South, men who were overweight/obese, men with doctor-diagnosed health conditions and men who smoked were less likely to be in the moderate increasing trajectory group. Being employed was associated with an increase in physical activity in the low decreasing group (β 0.43, p<0.001) but a decrease in the low stable (β −0.22, p<0.001) and moderate increasing groups (β −0.84, p<0.001). Development of cardiovascular-related conditions was associated with a decline in physical activity in the low decreasing (β −0.42, p<0.001) and low stable groups (β −0.13, p<0.05) but was not associated with any change in the moderate increasing group (β −0.06, p=0.34).

Conclusion This study highlights the heterogeneity in physical activity levels over time in older adults and that activity levels in midlife are likely to dictate trajectories into old age. Efforts to promote physical activity in later life may need to focus attention earlier in the lifecourse. The effects of retirement and cardiovascular disease on physical activity may depend on prior activity trajectories. Thus, different strategies may be needed in these groups.