Endothelium-dependent vasodilation is associated with exercise capacity in smokers and non-smokers

Smoking is an established cardiovascular risk factor that impairs endothelial function and reduces exercise capacity. Peripheral vascular endothelial function correlates with exercise capacity, but whether this association prevails in smokers is unknown. The purpose of this investigation was to examine the association between endothelial function and exercise capacity in chronic smokers and non-smoking controls. Brachial artery flow-mediated dilation (FMD, endothelium-dependent) following 5 minutes of upper arm occlusion was compared in 26 smokers (age 58 +/- 2 years; 15 female; BMI (body mass index) = 28 +/- 1) and 39 non-smokers (age 58 +/- 2 years; 24 female; BMI = 28 +/- 1) using ultrasound. Exercise treadmill time (ETT) was recorded from a standard Bruce protocol during symptom limited stress testing. There was found to be a significant positive association between FMD and ETT in smokers (r = 0.60, p < 0.05) and non-smokers (r = 0.28, p < 0.05). FMD was significantly lower in smokers versus non-smokers (8.9 +/- 0.9 vs 12.6 +/- 0.7%, p < 0.05). ETT was significantly lower in smokers (425 +/- 35 seconds) versus non-smokers (522 +/- 25 seconds, p < 0.05). After adjusting for FMD, there were no longer group differences in ETT. When patients were matched according to FMD, there were no differences in ETT between smokers and non-smokers. In conclusion, peripheral endothelial dysfunction is a correlate of low exercise capacity in smokers and non-smokers alike. Future research is needed to examine if improving endothelial function will lead to concomitant increases in exercise capacity in chronic smokers.