To systematically examine the amount and type of physical exercise that might reduce the future risk of dementia in community-living older people.
Six-year observational study.
All the Elderly Health Centers (EHCs) of the Department of Health in Hong Kong.
A total of 15,589 community-living Chinese aged 65 years and older with no history of stroke, clinical dementia, or Parkinson disease when they completed health assessment at the EHCs in the first 6 months of 2005.
Self-reported habitual physical exercise patterns, including the frequency, duration, and type of exercise, at baseline and Year 3 were analyzed. The study outcome was incident dementia in 6 years. Dementia was defined by presence of clinical dementia in accordance with the 10th revision of the International Statistical Classification of Diseases and Related Health Problems or Clinical Dementia Rating of 1 to 3.
Both the cognitively stable and incident groups reported exercising a median of 7 days per week and 45 minutes per day at baseline and Year 3. The former practiced aerobic and mind-body exercises more at baseline and Year 3, whereas the latter practiced stretching and toning exercises more. The odds ratio for dementia remained significant for aerobic (0.81; 95% confidence interval 0.68-0.95; P = .01) and mind-body exercises (0.76; 0.63-0.92; P = .004) after excluding participants who developed dementia within 3 years after baseline and adjusting for important potential confounders, such as age, gender, educational level, and physical and psychiatric comorbidities.
Although physical exercise is widely promoted as a nonpharmacological intervention for dementia prevention, not all types of exercise appear to be useful in reducing risk of dementia in older people. Our findings suggest that daily participation in aerobic and mind-body but not stretching and toning exercises might protect community-living older adults from developing dementia.