Physical activity and injurious falls in older Australian women: adjusted associations and modification by physical function limitation and frailty in the Australian Longitudinal Study on Women's Health

Objectives To investigate associations between leisure-time physical activity (LPA) and injurious falls in older women and explore modification of associations by physical function and frailty. Methods Women born during 1946-51 from the Australian Longitudinal Study on Women's Health, injurious falls (self-reported fall with injury and/or medical attention) and self-reported weekly LPA (duration and type). We undertook cross-sectional and prospective analyses using data from 2016 [n = 8,171, mean (SD) age 68 (1)] and 2019 surveys (n = 7,057). Associations were quantified using directed acyclic graph-informed logistic regression and effect modification examined using product terms. Results Participation in LPA as recommended by World Health Organization (150-300 min/week) was associated with lower odds of injurious falls in cross-sectional (adjusted Odds Ratio (OR) 0.74, 95% CI 0.61-0.90) and prospective analyses (OR 0.75, 95% CI 0.60-0.94). Compared with those who reported no LPA, cross-sectionally, odds of injurious falls were lower in those who reported brisk walking (OR 0.77, 95% CI 0.67-0.89) and vigorous LPA (OR 0.86, 95% CI 0.75-1.00). No significant association was found between different types of LPA and injurious falls prospectively. Only cross-sectionally, physical function limitation and frailty modified the association between LPA and injurious falls, with tendencies for more injurious falls with more activity in those with physical limitation or frailty, and fewer injurious falls with more activity among those without physical function limitation or frailty. Conclusion Participation in recommended levels of LPA was associated with lower odds of injurious falls. Caution is required when promoting general physical activity among people with physical limitation or frailty.