Prospective cohort study using 5,925 community-dwelling women aged ≥65 from the Study of Osteoporotic Fractures (4 US clinical centers, 1986–1988 baseline, 6–8 year follow-up) to test whether physical activity predicts cognitive decline. Women with higher baseline physical activity were significantly less likely to develop cognitive decline over follow-up. The association was robust to adjustment for baseline health, functional status, and multiple confounders, and was consistent across age, education, and comorbidity subgroups. Published in Archives of Internal Medicine 161:1703–1708.
"Women with higher levels of baseline physical activity were less likely to develop cognitive decline. This association was not explained by differences in baseline function or health status."
"For every 10 blocks walked per day (approximately 1.6 km [1 mile]), women had a 13% lower odds of cognitive decline."
A methodologically solid paper that addresses the main alternative explanation (reverse causality) directly: if cognitive impairment were causing reduced activity, then baseline walking speed — which captures physical capacity — should predict cognitive decline, but it does not. The limitation is that physical activity is self-reported and the sample is predominantly white women from a fracture-risk cohort, limiting generalizability. For the wiki, the relevance is primarily as evidence for a behavioral mechanism through which the trend toward compression of morbidity can be sustained or reversed — physical activity is one of the few modifiable factors that appears to delay functional and cognitive decline in old age, which matters for projections of disability prevalence and long-term care demand.