Objectives: To determine whether cardiorespiratory fitness at baseline is associated with maintenance of cognitive function over 6 years or with level of cognitive function on tests performed 6 years later in a longitudinal study of healthy older people.
Design: Prospective cohort.
Setting: Community-based study of noninstitutionalized adults aged 55 and older living in Sonoma, California.
Participants: Three hundred forty-nine cohort members without evidence of cardiovascular disease, musculoskeletal disability, or cognitive impairment at baseline.
Measurements: Cardiorespiratory fitness measures were based on a standard treadmill exercise test protocol and included peak oxygen consumption (peak VO2), treadmill exercise duration, and oxygen uptake efficiency slope (OUES). Cognitive function was evaluated at baseline with a modified Mini-Mental State Examination (mMMSE) and after 6 years of follow-up with a detailed cognitive test battery that included the full MMSE, three tests of attention/executive function, two measures of verbal memory, and two tests of verbal fluency.
Results: Participants with worse cardiorespiratory fitness at baseline experienced greater decline on the mMMSE over 6 years (mean mMMSE decline (95% confidence interval) by baseline peak VO2 tertile: lowest = -0.5 (-0.8 to -0.3), middle = -0.2 (-0.5-0.0), highest = 0.0 (-0.3-0.2), P =.002 for trend over tertiles). Participants with worse baseline cardiorespiratory fitness also performed worse on all cognitive tests conducted 6 years later. Results were similar for analyses based on peak VO2, treadmill exercise duration, and OUES. After adjustment for demographic and health-related covariates, measures of cardiorespiratory fitness were associated most strongly with measures of global cognitive function and attention/executive function.
Conclusion: Baseline measures of cardiorespiratory fitness are positively associated with preservation of cognitive function over a 6-year period and with levels of performance on cognitive tests conducted 6 years later in healthy older adults. High cardiorespiratory fitness may protect against cognitive dysfunction in older people.