Overview
- Researchers followed nearly 300 cognitively unimpaired adults aged 50–90 in the Harvard Aging Brain Study using pedometers, PET imaging and annual cognitive testing for up to 14 years.
- Walking 3,000–5,000 steps per day was associated with about a three-year delay in cognitive decline, rising to roughly seven years at 5,000–7,500 steps per day.
- Higher step counts correlated with slower buildup of tau, the protein most closely tied to symptoms, while sedentary participants showed faster tau accumulation and functional decline.
- Associations were strongest in people with elevated amyloid at baseline; those with low amyloid showed little decline and no significant link between activity and outcomes.
- Investigators and independent experts stressed the study is observational and outlined next studies to probe activity intensity, long-term patterns and mechanisms to inform randomized trials.