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Midlife fitness predicts less burden of chronic disease in later life.

OBJECTIVE
To investigate the relationship between midlife fitness in healthy adults and the development of nonfatal chronic conditions (CCs) in older age.


DESIGN
Cohort study.


SETTING
Data on participants were drawn from the Cooper Center Longitudinal Study and linked with US Medicare claims made in the years 1999 through 2009.


PARTICIPANTS
The cohort included 18 670 participants (median age, 49 years; 21% women) who had received a comprehensive clinical examination between 1970 and 2009 at the Cooper Center, were ≥65 years of age and covered by Medicare between 1999 and 2009, and who reported no baseline history of CCs such as cardiovascular disease, diabetes, and cancer. The participants tended to be from upper educational and socioeconomic strata.


ASSESSMENT OF RISK FACTORS
Fitness was assessed by maximal treadmill effort using the modified Balke protocol. The participants' treadmill times were classified into age- and sex-specific quintiles (Q) of fitness (Q1, least fit) and converted into metabolic equivalents (MET). Clinical and anthropometric variables and physical activity were measured.


MAIN OUTCOME MEASURES
The main outcome measure was the association between level of fitness in midlife (ie, at study entry) and the development of chronic conditions (specifically, congestive heart failure, ischemic heart disease, stroke, diabetes mellitus, chronic obstructive pulmonary disease, chronic kidney disease, Alzheimer's disease, and colon or lung cancer), recorded by Medicare. The conditions were each assigned a value of 1, and those present were summed for survivors at ages 70, 75, 80, and 85 years. Death was an additional outcome. Total follow-up was 120 780 person-years.


MAIN RESULTS
At study entry the participants had, overall, low levels of traditional risk factors for CCs, with the less fit having somewhat less healthy risk factor profiles. The highest level of midlife fitness (Q5) was associated with developing fewer CCs compared with low midlife fitness (Q1) in men (15.6; 95% confidence interval [CI], 15.0-16.2 vs 28.2; 95% CI, 27.4-29.0 per 100 person-years) and women (11.4; 95% CI, 10.5-12.3 vs 20.1; 95% CI, 18.7-21.6 per 100 person-years). After multivariate adjustment, higher fitness remained associated with a lower risk of developing CCs (men: hazard ratio [HR], 0.95; 95% CI, 0.94-0.96 per MET; and women: HR, 0.94; 95% CI, 0.91-0.96 per MET). Level of fitness was similarly associated with the development of CCs in younger and older participants. Among the 2406 participants who died during the study period, the number of CCs among the more fit persons was significantly lower than that among the less fit; thus, in their final 5 years of life, 58.3% of fitness Q4 and Q5 versus 43.5% of Q1 had ≤1 CC and 9.5% of Q4 and Q5 versus 18.3% of Q1 had ≥4 CCs.


CONCLUSIONS
Healthy, fit, middle-aged adults developed fewer chronic conditions in later life than unfit persons and had a lesser burden of chronic disease before death.