Background: Few studies have examined the relation between lung function and ischemic stroke incidence; none have studied African Americans.
Methods: We followed 13,842 middle-aged adults initially free of stroke and coronary heart disease and observed 472 incident ischemic strokes over 13 years. Quartiles of FEV(1) as a percentage of predicted value (FEV(1)PP) and FVC as a percentage of a predicted value (FVCPP) were used as the indicators of lung function.
Results: In the age-, race-, gender-, and education-adjusted models, both lung function measures were significantly inversely related to ischemic stroke incidence (linear trend for FEV(1)PP, p < 0.01; linear trend for FVCPP, p < 0.01), but adjustment for possible confounders attenuated these relations. For white subjects, a significant inverse relation remained even after full adjustment (relative hazards [RH] across FEV(1)PP quartiles (lowest to highest) were 1.59, 1.52, 1.26, and 1.00; and for FVCPP quartiles were 1.56, 1.80, 1.09, and 1.00 [trend for both, p < 0.05]). There was no association for African Americans (RH across FEV(1)PP and FVCPP quartiles were 0.74, 0.89, 0.73, 1.00 [linear trend, p = 0.27] and 0.81, 1.07, 0.61, 1.00 [linear trend, p = 0.75], respectively). An inverse relation between lung function and ischemic stroke was also observed among white subjects who never smoked (FEV(1)PP) or had no respiratory symptoms (both FEV(1)PP and FVCPP) but not among their African-American counterparts.
Conclusions: Among white subjects, participants with impaired lung function have a modestly higher risk of ischemic stroke even if they have never smoked nor had respiratory symptoms.