Overview
- In a Harvard Aging Brain Study cohort of 296 cognitively healthy adults tracked for about nine years, higher daily step counts correlated with slower cognitive decline only among those with elevated amyloid.
- Walking 3,000–5,000 steps per day was associated with an estimated three-year delay in decline, while 5,000–7,500 steps corresponded to an estimated seven-year delay.
- Pedometer data and PET scans indicated no association between activity and amyloid levels or accumulation, with benefits instead linked to slower tau buildup in the inferior temporal cortex.
- A subset of 172 participants with repeated tau PET scans showed that reduced tau accumulation statistically accounted for the activity–cognition relationship.
- The largest gains appeared when sedentary individuals increased to low or moderate activity ranges, though authors caution the observational design limits causal claims and the mostly white, highly educated sample constrains generalizability.