Longitudinal data from the U.K. Biobank showed that a daily total of 3,800 to 9,800 steps was tied to lower dementia risk:
"findings suggest that approximately 9800 steps per day may be optimal to lower the risk of dementia. We estimated the minimum dose at approximately 3800 steps per day, which was associated with 25% lower incident dementia. "
And here is the intensity part - " For peak 30-minute cadence, the optimal dose was 112 steps per minute"