To determine if smoking cessation improves flow-mediated dilation (FMD) of the brachial artery (BA).
The long-term effects of continued smoking and smoking cessation on endothelial function have not been described previously.
This was a one-year, prospective, double-blind, randomized, placebo-controlled clinical trial of the effects of 5 smoking cessation pharmacotherapies. FMD was measured by B-mode ultrasound before and 1-year after the target smoking cessation date. Cessation was verified by exhaled carbon monoxide levels. ΔFMD was compared among study arms and between subjects that successfully quit and those who continued to smoke. Predictors of baseline FMD and ΔFMD were identified by multivariable regression.
The 1,504 current smokers (58% female, 84% white) were mean (standard deviation): 44.7 (11.1) years old and smoked 21.4 (8.9) cigarettes/day. Baseline FMD was similar in each treatment arm (p=0.499) and was predicted by BA diameter (p<0.001), reactive hyperemia blood flow (p<0.001), high-density lipoprotein cholesterol (p=0.001), and carbon monoxide (p=0.012) levels. After one year, 36.2% quit smoking. FMD increased by 1% [6.2% (4.4%) to 7.2% (4.2%)] after 1 year (p=0.005) in those who quit, but did not change (p=0.643) in those who continued to smoke. Improved FMD among quitters remained significant (p=0.010) after controlling for changes in BA diameter, reactive hyperemia, low-density lipoprotein cholesterol, and presence of a home smoking ban.
Despite weight gain, smoking cessation leads to prolonged improvements in endothelial function, which may mediate part of the reduced cardiovascular disease risk observed after smoking cessation.