Engaging in high levels of physical activity throughout adulthood may reduce the risk of dementia and preserve cognitive health.
In a large US-based study involving participants from the Nurses’ Health Study (NHS) and the Health Professionals Follow-Up Study (HPFS) with up to 37 years of follow-up data, those in the highest quartile of total physical activity had a 28-percent lower risk of dementia (hazard ratio [HR], 0.72, 95 percent confidence interval [CI], 0.68–0.76; p<0.0001) and 23-percent reduced risk of subjective cognitive decline (relative risk [RR], 0.77, 95 percent CI, 0.73–0.80; p<0.0001). [Lancet Public Health 2026;11:E530-E542]
Similar protective benefits emerged for specific types of physical activity. Being in the high vs low tertile of walking or vigorous aerobic exercise was associated with reduced risks of dementia (HRs, 0.76 and 0.89, respectively; p<0.0001 for both) and subjective cognitive decline (RRs, 0.82 and 0.89, respectively; p<0.0001 for both). For weightlifting, more than 0.5 h per week of training was also associated with decreased dementia risk compared with no training (HR, 0.87; p<0.0001).
Additionally, higher levels of total physical activity helped preserve cognitive function. Compared with the lowest quartile, the highest quartile of total physical activity was associated with fewer years of age-related cognitive differences across global cognition (1.15 fewer years; p<0.0001), verbal memory (1.27 fewer years; p<0.0001), and Telephone Interview for Cognitive Status score (0.79 fewer years; p=0.016). Consistent associations were observed for vigorous aerobic exercise but not for walking.
To rule out the possibility of reverse causation, a 4-year lag period was incorporated into the primary analysis. Sensitivity analyses using longer lag windows yielded consistent results.
“To our knowledge, this study is the first to relate different types of long-term physical activity to multiple cognitive outcomes and to address reverse causation with lagged analyses,” the authors said. “Our findings add to the growing evidence that an active lifestyle supports long-term cognitive health.”
The authors discussed multiple mechanistic pathways that support the protective role of physical activity in cognitive health. “Physical activity promotes brain maintenance and plasticity through neurogenesis and angiogenesis,” they said.
“Exercise further promotes brain health by modulating growth factor signalling, enhancing the expression of brain-derived neurotrophic factor, and initiating a cascade of signalling pathways that support synaptic plasticity and cognitive performance. Additionally, higher activity might slow amyloid-related tau accumulation, thereby mediating slower cognitive and functional decline,” they added.
The authors highlighted the need for more studies to help guide activity-specific recommendations.
In the current study, the population comprised 63,596 NHS participants (followed up from 1990 to 2003) and 43,440 HPFS participants (followed up from 1990 to 2003) for the dementia endpoint, 13,647 NHS participants (followed up from 1995 to 2008) for the objective cognitive function, and 29,801 NHS participants (followed up in 2012 and 2014) and 17,162 HPFS participants (followed up in 2008, 2012, 2016, 2018, and 2020) for the subjective cognitive decline.
Physical activity was assessed every 2 to 4 years using self-report questionnaires, beginning in 1986 for both cohorts. Total physical activity, walking, and vigorous aerobic exercise were each expressed as the summed metabolic equivalent of task hours per week.
At the midpoint assessment, participants with higher levels of total physical activity were less likely to use antidepressants or have a history of hypertension, diabetes, or hypercholesterolaemia relative to those with lower levels of activity. Participants with higher levels of total physical activity also tended to have a lower BMI, higher alcohol intake, greater total energy intake, and to engage in more hours of sedentary behaviour per week.
The study was limited by its observational nature and a population consisting predominantly of White health professionals, which may restrict the generalizability of the findings.