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O2‐05‐06: Is Physical Activity in Midlife Good for the Brain? Findings From 33 Years of Prospective Follow‐up
Author(s) -
Gross Alden L.,
Lu Haidong,
Meoni Lucy,
Schrack Jennifer,
Gallo Joe,
Sharrett A Richey
Publication year - 2016
Publication title -
alzheimer's and dementia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.713
H-Index - 118
eISSN - 1552-5279
pISSN - 1552-5260
DOI - 10.1016/j.jalz.2016.06.423
Subject(s) - hazard ratio , dementia , medicine , proportional hazards model , confidence interval , prospective cohort study , gerontology , cohort study , cohort , physical activity , demography , physical therapy , disease , sociology
Background:The causal link between physical activity and dementia in later life is widely considered self-evident, however most evidence is based on cross-sectional data or studies with unsatisfactory follow-up. Available data on the prospective relationship between physical activity in midlife and dementia is lacking. We leveraged over three decades of follow-up from a large, established cohort to determine whether physical activity and exercise in midlife are associated with dementia onset in later life. Methods:We used data from the Johns Hopkins Precursors study, a study of medical school graduates enrolled between 1948 and 1964. Questions about physical activity, exercise, and IADL limitations were asked via identical mailed surveys in 1978, 1986, 1989, 1993, 1997, and 2000. Dementia status was adjudicated through 2011 by a consensus committeeusingmedical records.WeusedCoxproportional hazards models to regress time to dementia on physical activity variables measured in 10-year age intervals from age 30.We excluded exposure data measured within 10 years of dementia onset. Models adjusted for age, BMI, and sex. Results: Of 676 participants aged 30 to 75 at study entry and contributing 23,310 person-years (mean 34.5 years), 31 (5%) developed dementia. Engaging in regular exercise at least once weekly during one’s 40’s (hazard ratio, HR: 0.69, 95% confidence interval, CI: 0.22,2.20), 50’s (HR: 1.53, 95% CI: 0.51,4.57), or 60’s (HR: 0.64, 95% CI: 0.28,1.51) were not associated with the hazard, or risk, of developing dementia when measured more than 10 years before dementia onset. Similarly, we found null associations between dementia onset and self-reported hours per week spent doing vigorous activity (e.g., strenuous sports, jogging), moderate activity (e.g., housework, walking, painting), light activity (e.g., sitting, driving, eating), and sleeping at any age from one’s thirties through the seventies (all p>0.1). Number of blocks walked per day and stairs climbed per day were not associated with hazard of dementia. Conclusions: The often reported relationship between physical activity and cognitive status in later life may be an artifact of reverse causation. Our results based on physical activity measured in midlife may explain null findings from randomized trials of physical activity to improve cognitive outcomes.