E-cigarette (EC) use is increasing exponentially worldwide. The early cardiovascular effects of switching from tobacco cigarettes (TC) to EC in chronic smokers is unknown. Meta-analysis of flow-mediated dilation (FMD) studies indicate 13% lower pooled, adjusted relative risks of cardiovascular events with every 1% improvement in FMD.
This study sought to determine the early vascular impact of switching from TC to EC in chronic smokers.
The authors conducted a prospective, randomized control trial with a parallel nonrandomized preference cohort and blinded endpoint of smokers ≥18 years of age who had smoked ≥15 cigarettes/day for ≥2 years and were free from established cardiovascular disease. Participants were randomized to EC with nicotine or EC without nicotine for 1 month. Those unwilling to quit continued with TC in a parallel preference arm. A propensity score analysis was done to adjust for differences between the randomized and preference arms. Vascular function was assessed by FMD and pulse wave velocity. Compliance with EC was measured by carbon monoxide levels.
Within 1 month of switching from TC to EC, there was a significant improvement in endothelial function (linear trend β = 0.73%; 95% confidence interval [CI]: 0.41 to 1.05; p < 0.0001; TC vs. EC combined: 1.49%; 95% CI: 0.93 to 2.04; p < 0.0001) and vascular stiffness (−0.529 m/s; 95% CI: −0.946 to −0.112; p = 0.014). Females benefited from switching more than males did in every between-group comparison. Those who complied best with EC switch demonstrated the largest improvement. There was no difference in vascular effects between EC with and without nicotine within the study time frame.
TC smokers, particularly females, demonstrate significant improvement in vascular health within 1 month of switching from TC to EC. Switching from TC to EC may be considered a harms reduction measure.