Overview
- The Harvard Aging Brain Study followed 296 adults aged 50–90 without cognitive impairment for a median of about nine years, tracking daily steps alongside PET measures of amyloid and tau.
- Walking roughly 5,000 to 7,500 steps per day was associated with delaying the onset of cognitive symptoms by up to about seven years versus sedentary participants, while 3,000 to 5,000 steps linked to a delay of about three years.
- Compared with inactivity, higher activity levels were associated with markedly smaller declines, with reported reductions of about 40–54% in cognitive decline and 34–51% in functional decline across activity strata.
- Dose–response analyses indicated the largest incremental gains among the most sedentary participants, with benefits stabilizing around 7,500 steps per day, below the commonly cited 10,000-step benchmark.
- Authors emphasize the findings are associative rather than causal and propose vascular and anti-inflammatory pathways as plausible mechanisms, calling for mechanistic and interventional studies to test causality.