There seems to be a much better way:
https://publichealth.jhu.edu/2025/small-amounts-of-moderate-...
"The researchers found that engaging in as little as 35 minutes of moderate to vigorous physical activity per week, compared to zero minutes per week, was associated with a 41% lower risk of developing dementia over an average four-year follow-up period. Even for frail older adults—those at elevated risk of adverse health outcomes—greater activity was associated with lower dementia risks.
The researchers found dementia risk decreased with higher amounts of physical activity. Dementia risks were 60% lower in participants in the 35 to 69.9 minutes of physical activity/week category; 63% lower in the 70 to 139.9 minutes/week category; and 69% lower in the 140 and over minutes/week category."