Physical Inactivity Isn't Associated with Excess Risk for Dementia

Prior studies that linked physical inactivity and dementia have been limited by short follow-up durations (i.e., <10 years), resulting in possible reverse-causation bias; that is, physical activity might have been measured during the prodromal phase of dementia — the time when physical activity typically declines. In this meta-analysis of individual patient data from 405,000 people (mean age, 46; without dementia at baseline) in 19 cohort studies, researchers determined whether baseline physical inactivity — assessed longer than 10 years before dementia onset — was associated with excess risks for developing dementia, diabetes, coronary heart disease, and stroke.

After mean follow-up of 14.9 years, 2044 cases of dementia had occurred. When f…