Differential Effects of Tobacco Cigarettes and Electronic Cigarettes on Endothelial Function in Healthy Young People.

Tobacco cigarette(TC) smoking has never been lower in the US, but EC vaping has reached epidemic proportions amongst our youth. Endothelial dysfunction, as measured by flow mediated vasodilation(FMD) is a predictor of future atherosclerosis and adverse cardiovascular events, and is impaired in TC smokers, but whether FMD is also reduced in EC vapers is uncertain. The aim of this study in otherwise healthy young people was to compare the effects of acute and chronic TC smoking and EC vaping on FMD. FMD was compared in 47 non-smokers(NS), 49 chronic EC-vapers and 40 chronic TC-smokers at baseline, and then after EC-vapers(n=31) and non-smokers(n= 47) acutely used an EC-with-nicotine(ECN), EC-without-nicotine(EC0), and nicotine inhaler(NI) at ~4week intervals, and after TC-smokers(n=33) acutely smoked a TC, compared to sham-control. Baseline FMD was not different among the groups (NS:7.7±4.5%∆ vs EC:6.6±3.6%∆ vs TC:7.9±3.7%∆, p=0.35), even when compared by group and sex. Acute TC smoking vs control impaired FMD(FMD pre/post smoking: -2.52±0.92%∆ vs 0.65±0.93%∆, p=0.02). Although the increase in plasma nicotine was similar, acute EC vaping did not impair FMD. In otherwise healthy young people who regularly smoke TCs or ECs, impaired FMD was not present. However, FMD was significantly impaired after smoking one TC, but not after vaping an equivalent "dose"(estimated plasma nicotine) of an EC, consistent with the notion that non-nicotine constituents in TC smoke mediate the impairment. Although it is reassuring that acute EC-vaping did not acutely impair FMD, it would be dangerous and premature to conclude that ECs do not lead to atherosclerosis.