A strong inverse association between midlife cardiorespiratory fitness and stroke risk later in life has been confirmed, according to data published in Stroke.

Although low cardiorespiratory fitness is associated with increased risk of stroke, the extent to which this association is explained by the development of stroke risk factors has not been determined.  Therefore, researchers evaluated the relationship between midlife cardiorespiratory fitness and stroke risk in individuals over 65 years of age in an analysis independent of antecedent risk factor burden.

The study included 19 815 individuals who received Medicare coverage between 1999 and 2009. Researchers estimated cardiorespiratory fitness at baseline using Balke treadmill time and according to age- and sex-specific quintiles.

After 129 436 person-years of Medicare follow-up, researchers observed 808 stroke hospitalizations, more among men than in women. Higher midlife cardiorespiratory fitness 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 adjustment for hypertension, diabetes, and atrial fibrillation (HR: 0.63; 95% CI: 0.51-0.79; quintiles 4-5 vs 1).

One metabolic equivalent (MET) higher midlife cardiorespiratory fitness was associated with a 7% reduction in risk for stroke hospitalization (HR: 0.93; 95% CI: 0.98-0.97 per MET) in continuous analyses.

“Regular exercise has previously been associated with reduction in blood pressure, decreased insulin resistance, and lower heart rates,” the authors wrote. “Our study findings highlight the role of regular exercise and higher CRF [cardiorespiratory fitness] in midlife as a potential stroke prevention strategy. This protective effect of higher CRF seems to go beyond risk factors modification.”

Prior studies have suggested that exercise and higher cardiorespiratory fitness impact carotid artery distensibility and nitric oxide availability, improves endothelial dysfunction and as a result, affects conduit arteries and peripheral microcirculation. This heightened systemic endothelial function results in improvements in cerebrovascular function via increased cerebral blood follow and brain volume.

“These findings highlight the importance of increased exercise and physical activity in midlife as a potential strategy for stroke risk reduction in older age,” the authors concluded.

Additional studies are required to determine whether cardiorespiratory fitness among sedentary adults could reduce stroke risks in older adults instead of risk factor modification.

Reference

Pandey A, Patel M, Willis B, et al. Association between midlife cardiorespiratory fitness and risk of stroke. The Cooper Center Longitudinal Study. Stroke. 2016; doi: 10.1161/strokeaha.115.011532.