Physical activity level and future risk of mild cognitive impairment or dementia: a critically appraised topic.

Background: The relationships between physical activity, cognition, and development of neurodegenerative diseases represent an area of intense research interest. Meta-analyses and prospective cohort studies show that greater levels of physical activity are associated with lower dementia risk. Most studies, however, depend on self-report data that are subject to recall and other biases. Obtaining objective and quantitative physical activity data could strengthen observational study validity. Objective: To examine the association between objectively measured daytime activity and mild cognitive impairment (MCI) or Alzheimer disease (AD). Methods: The objective was addressed through the development of a structured, critically appraised topic. We incorporated a clinical scenario, background information, a structured question, literature search strategy, critical appraisal, results, evidence summary, commentary, and bottom line conclusions. Participants included consultant and resident neurologists, clinical epidemiologists, a medical librarian, and behavioral neurology and neuropsychiatry content experts. Results: We selected a prospective, single-center cohort study of 716 cognitively normal elderly participants followed for 3.5 years. Greater levels of physical activity, as measured using wrist actigraphy, were associated with a lower risk of incident MCI or AD (hazard ratio, 0.477; 95% confidence interval, 0.273-0.832). Conclusions: Objective measurement confirms that greater levels of physical activity are associated with decreased risk of a future diagnosis of MCI or AD. Further studies are needed to confirm the temporal association of exercise and future cognitive health and understand the relevant underlying biological mechanisms.