Is electronic cigarette use a risk factor for stroke? A systematic review and meta-analysis

INTRODUCTION: Stroke, as a common cerebrovascular disease, has a high mortality and disability rate. Although many studies have reported that using e-cigarettes was associated with occurrence of stroke, some studies have concluded that e-cigarettes may help smokers stop using combustible cigarettes and reduce the risk of stroke. Therefore, we aimed to validate the hypothesis that e-cigarette use might be an independent risk factor for stroke occurrence by performing a systematic review and meta-analysis of clinical epidemiology studies. METHODS: The pooled effect was calculated by the random effects model. I(2) was used to test for heterogeneity. Sensitivity analysis was performed to evaluate the stability of the overall results. Funnel plot symmetry or Egger’s regression was used to evaluate publication bias. All p values were two-sided with significance level at 0.05. RESULTS: Six cross-sectional studies with high quality were finally included in the meta-analysis, which included a total of 1134896 participants. Analysis with random effects model showed that the total pooled odds ratio (OR) of stroke occurrence in e-cigarette users was 1.25 (95% CI: 1.01–1.55) (I(2)=96.6%, p<0.001). A stable result was revealed by sensitivity analysis. There was no publication bias. Due to high heterogeneity, we performed subgroup analysis. Compared to neither e-cigarette nor combustible cigarette users, pooled OR of stroke occurrence in e-cigarette only users was 1.13 (95% CI: 0.99–1.29) (I(2)=45.9%, p=0.116). Compared to combustible cigarette only users, pooled OR of stroke occurrence in both of e-cigarette and combustible cigarette users was 1.39 (95% CI: 1.19–1.64) (I(2)=5.6%, p=0.303). In addition, pooled OR in currently e-cigarette only users who were formerly combustible cigarette only users was 1.59 (95% CI: 1.22–2.07) (I(2)=0.0%, p=0.989). CONCLUSIONS: The role of e-cigarette use in the development of stroke is inconclusive, due to the strong effect of prior tobacco use as a risk factor for stroke in the included studies.