Overview
- Nature Medicine published findings from the Harvard Aging Brain Study tracking about 296 cognitively unimpaired adults aged 50–90 for up to 14 years.
- Walking 3,000–5,000 steps a day was associated with an average three-year delay in decline, rising to about seven years for 5,000–7,500 steps.
- The link between activity and slower decline was largely explained by reduced accumulation of tau protein rather than changes in amyloid levels.
- Associations were strongest in participants with elevated baseline amyloid, while those with low amyloid showed little decline regardless of activity level.
- Researchers and outside experts cautioned that the study is observational with step counts measured only at baseline, and they plan mechanistic studies and trials to test causation and identify which activity features matter most.