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The Association Between Midlife Cardiorespiratory Fitness Levels and Later-Life Dementia: A Cohort Study
Study Questions:
Is there evidence that midlife cardiorespiratory fitness levels prevent or delay the onset of dementia?
Methods:
A prospective observational cohort study was conducted in a preventive medicine clinic setting in 19,458 community-dwelling, nonelderly adults who had a baseline fitness examination. Fitness levels were assessed using the modified Balke treadmill protocol between 1971 and 2009, and incident all-cause dementia using Medicare Parts A and B claims data from 1999 to 2009.
Results:
Over 80% of participants were male, average age was 50 years, 15% were smokers, mean value cardiovascular risk factors were low risk, and mean (standard deviation) cardiorespiratory fitness was 10.6 (2.4) METs. A total of 1,659 cases of incident all-cause dementia occurred during 125,700 person-years of Medicare follow-up (median follow-up, 25 years [interquartile range, 19-30 years]). After multivariable adjustment, participants in the highest quintile of fitness level had lower hazard of all-cause dementia than those in the lowest quintile (hazard ratio [HR], 0.64; 95% confidence interval [CI], 0.54-0.77). Higher fitness levels were associated with lower hazard of all-cause dementia with previous stroke (HR, 0.74; 95% CI, 0.53-1.04) or without previous stroke (HR, 0.74; 95% CI, 0.61-0.90).
Conclusions:
Higher midlife fitness levels seem to be associated with lower hazards of developing all-cause dementia later in life. The magnitude and direction of the association were similar with or without previous stroke, suggesting that higher fitness levels earlier in life may lower risk for dementia later in life, independent of cerebrovascular disease.
Perspective:
The study was conducted in a healthy and highly educated cohort from the mid-upper socioeconomic strata, who sought further assessment in the Cooper Clinic, a pioneer in prevention. Whether it is fitness in mid-life (examples: regular physical activity from leisure time exercise, fireman, brick layer, mailperson) or other unmeasured variables is not clear from this study. Nevertheless, the message is that regular physical activity reduces cardiovascular risk, helps control hypertension and diabetes, and that mid-life fitness reduces dementia even in persons who have a stroke.
Keywords: Stroke, Dementia, Leisure Activities, Cardiovascular Diseases, Motor Activity, Risk Factors, Medicare, Hypertension, Diabetes Mellitus, United States
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