Midlife Cardiorespiratory Fitness Associated With Stroke Risk in Later Life

A strong, inverse association exists between midlife cardiorespiratory fitness (CRF) and stroke risk in later life independent of baseline and antecedent burden of risk factors, such as hypertension, diabetes mellitus (DM), and atrial fibrillation (AF), according to a new study.

“Several previous studies have demonstrated an inverse relationship between CRF and both fatal and nonfatal stroke,” the researchers said. “However, the mechanism by which higher levels of CRF might lower stroke risk have not been well established, and it remains uncertain to what extent there may be a direct effect of CRF on stroke risk, independent of established stroke risk factors such as hypertension, DM, and AF.”
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Linking participant data from the Cooper Center Longitudinal Study with Medicare claims files, the researchers studied 19,815 individuals who survived to receive Medicare coverage from 1999 to 2009. CRF estimated at baseline by Balke treadmill time was analyzed as a continuous variable (in metabolic equivalents) and according to age- and sex-specific quintiles (Q1=low CRF).

They assessed associations between midlife CRF and stroke hospitalization after age 65 by applying a proportional hazards recurrent events model to the failure time data with hypertension, DM, and AF as time-dependent covariates.

After 129,436 person-years of Medicare follow-up, the investigators observed 808 stroke hospitalizations. After adjustment for baseline risk factors, higher midlife CRF was associated with a lower risk of stroke hospitalization (hazard ratio [HR], 0.61; 95% confidence interval [CI], 0.49-0.76; quintiles 4-5 vs 1]. This association remained unchanged after additional adjustment for burden of Medicare-identified stroke risk factors (hypertension, DM, and AF; HR, 0.63; 95% CI, 0.51-0.79; quintiles 4-5 vs 1).

“Additional studies are needed to determine whether improvement in CRF among sedentary adults may reduce the risk of stroke in older age above and beyond risk factor modification,” the researchers concluded.

—Mike Bederka

Reference:

Pandey A, Patel MR, Willis B, et al. Association between midlife cardiorespiratory fitness and risk of stroke: the Cooper Center Longitudinal Study [published online June 9, 2016]. Stroke. doi:10.1161/STROKEAHA.115.011532.