The effect of smoking on endothelial vasodilatory function evaluated by local infusion of metacholine in the forearm is dependent on the duration of smoking

The objective of the study was to evaluate if endothelial vasodilatory function in the human forearm is impaired by regular cigarette smoking. The setting was a tertiary university hospital. Subjects were 56 apparently healthy subjects from a population screening (mean age 50) and 52 young healthy volunteers (mean age 25) who were investigated regarding endothelial-dependent (EDV) and endothelial-independent vasodilation (EIDV) by means of local infusion of metacholine (MCh; 2 and 4 mg/min) and sodium nitroprusside (SNP; 5 and 10 mg/min) in the forearm. Forearm blood flow (FBF) was measured by venous occlusion plethysmography. The MCh to SNP FBF ratio was denoted the endothelial function index. In the young subjects, no differences between smokers (n = 12) and non-smokers regarding EDV or EIDV were seen. In the population sample, however, the smokers (n = 8) showed an attenuated endothelial function index when compared with non-smokers (1.0 +/- 0.1 vs. 1.3 +/- 0.3, p = .02). The EDV showed a significant inverse relationship to the duration of smoking (r = -0.52, p < .05), independent of age, when the smokers in both groups were analyzed together. A similar, although not significant, relation was found between the endothelial function index and the duration of smoking (p = -.44). The present study showed that endothelial vasodilatory function was impaired in middle-aged, but not young, smokers, suggesting that the duration of smoking is of major importance for the deleterious effects of smoking on endothelial vasodilatory function.