P4392A systematic review and meta-analysis of the cardiovascular effects of e-cigarette

Abstract Background Electronic cigarette (EC) is marketed as a safe alternative to tobacco smoking, but EC cardiovascular effects remains largely unknown. Purpose To systematically review and meta-analyse published literature to investigate the cardiovascular effects and associated risk from EC use. Methods We searched PubMed from January 2000 until November 2017 for published studies assessing the cardiovascular effects of EC. For each eligible study we used the mean difference (MD) with 95% confidence intervals (CIs) for SBP, DBP and HR. The pooled MDs for each outcome of interest were calculated by using a fixed effects model. The presence of heterogeneity among studies was evaluated by the I2 statistic. Results We report conflicting evidence on the effects of EC on heart rate and blood pressure, which is mainly based on non-randomized clinical studies of moderate quality. In a meta-analysis of 14 studies (n=441 participants), that despite the negative effects of EC on heart rate (pooled MD=2.27, 95% CI: 1.64 to 2.89, p<0.001), diastolic (DBP, pooled MD=2.01mmHg, 95% CI: 0.62 to 3.39, p=0.004) and systolic blood pressure (SBP, pooled MD=2.02mmHg, 95% CI: 0.07 to 3.97, p=0.042), benefits may be observed in terms of blood pressure regulation when switching from tobacco smoking to EC (SBP pooled MD=−7.00, 95% CI: −9.63 to −4.37, p<0.001; DBP pooled MD=−3.65, 95% CI: −5.71 to −1.59, p=0.001). Evidence suggests that EC negatively affects endothelial function, arterial stiffness and the long-term risk for coronary events, but these findings are derived from single study reports and have not been confirmed in additional studies. Conclusions We report adverse effects of EC use on heart rate and blood pressure. Unless supported by stronger evidence, EC should not be labelled as cardiovascular safe products. Future studies should delineate whether EC use is less hazardous to cardiovascular health than conventional cigarette smoking.