Physical activity trajectories from youth to midlife over 18 years in Australian women

Background: Women’s physical activity levels vary across their lifespans, and there may be different trajectories at young ages. In this study, we used 18 years of data from women born in 1973–78 to identify: (1) different physical activity trajectories in the transition from youth to midlife and (2) determinants of these physical activity trajectories.

Methods: Data were from the 1973–78 cohort of the Australian Longitudinal Study on Women’s Health (n = 8157). Surveys were mailed at three-year intervals from 2000 (age 22–27) to 2018 (age 40–45) to collect data on physical activity, sociodemographic factors, health indicators and health behaviours. Group-based trajectory modelling was used to identify trajectories of physical activity. Multinomial logistic regression models were used to examine the associations of sociodemographic factors, behavioural and health characteristics at age 22–27, with the different physical activity trajectories.

Results: Four trajectories were identified: Low (58.7% of participants), Declining (16.9%), Increasing (18.0%), and High (6.5%). The 18-year cumulative median of physical activity (MET.minutes/week) was 550 in the Low, 1225 in the Declining, 1288 in the Increasing, and 2134 in the High group. The most significant determinants of physical activity trajectories were cohabitation status, physical function and mental health.

Conclusions: Although physical activity levels in young women may temporarily decline due to major life events, the cumulative median of physical activity was above the lower levels of the current physical activity guidelines, even in the Low group. The data suggest that women in this group are characterised by living with a partner and/or children, and poor physical function and mental health.

Practical implications: Increasing opportunities for activity in low active women may increase population-level physical activity during young to mid-age.

Funding: The Australian Longitudinal Study on Women’s Health is funded by the Australian Government Department of Health.