Longitudinal patterns of physical activity and mortality in mid-aged Australian women: A causal inference analysis

Background: The health outcomes of long-term patterns of meeting physical activity (PA) guidelines in women have seldom been explored.

Purpose: To examine the associations between longitudinal patterns of PA over 15 years and all-cause and cause-specific mortality in a cohort of mid-aged Australian women.

Methods: We analysed data collected at 3-year intervals from 11,336 participants in the Australian Longitudinal Study on Women’s Health (ALSWH; 1946-51 cohort). Mortality outcomes (all-cause, cardiovascular disease, cancer) were derived from Australian death registries. We analysed associations between meeting the WHO PA guidelines (150 min/week of moderate-to-vigorous PA) in 2001-2016 and outcomes in 2019. Using causal inference modelling, we emulated a target trial testing two interventions: 1) meeting the guidelines throughout the ‘exposure period’ (2001-2016) and 2) not meeting the guidelines at the beginning of the exposure period, but starting to first meet the guidelines at age 55, 60, and 65. Both were compared to the control of not meeting the guidelines throughout the exposure period. Analyses were adjusted for sociodemographic and health variables using marginal structural models.

Results: Consistent adherence to PA guidelines throughout the exposure period was significantly associated with a ~5% lower risk of all-cause mortality (incidence risk: 5.2% [95% CI: 3.3%, 7.2%]) than the control (10.4% [5.4%, 15.4%]). No significant associations were found for cause-specific mortality. Starting to meet guidelines at age 55, 60 and 65 were not significantly associated with all-cause/cause-specific mortality, compared with control.

Conclusions: Mid-aged women should maintain PA for health benefits.

Practical implications: An important public health message is that women can gain important health benefits from staying active in mid-age.

Funding: The ALSWH is funded by the Australian Government Department of Health. GIM: National Health and Medical Research Council (NHMRC) Investigator Grant (APP2008702). DD: NHMRC Emerging Leader Fellowship (2009254); NSW Cardiovascular Research Capacity Program EMCR Grant.