Overview
- Harvard Aging Brain Study researchers in the United States, Canada and Australia tracked 296 cognitively normal adults aged 50–90 with waist‑worn pedometers, annual cognitive tests over a mean 9.3 years and PET imaging.
- Walking 3,000–5,000 steps per day was associated with about a three‑year delay in functional and cognitive decline, rising to roughly seven years at 5,000–7,500 steps.
- No additional cognitive benefit was observed beyond about 7,500 daily steps, and those logging fewer than 3,000 steps with elevated beta‑amyloid declined faster.
- Higher step counts correlated with slower accumulation of tau in Alzheimer’s‑affected brain regions, while no link was found with beta‑amyloid levels.
- The findings, published in Nature Medicine, position habitual moderate activity as a potential resilience factor and motivate randomized trials to test causality and refine exercise targets.