The relationship between smoking and rosacea: A Mendelian randomization study.

Background: Rosacea can be seen in many patients nowadays, and the related causes are complex. Despite a certain association between smoking and rosacea being reported by several studies, the actual causality has not been established for the possible bias and confounders.

Methods: We used Mendelian randomization (MR) to evaluate a potential causal effect of smoking on rosacea risk. Statistics on smoking and rosacea were obtained from the FinnGen project and Neale Lab Consortium. The causal association was assessed by multiple methods including inverse variance weighted (IVW), MR Egger, weighted median, and weighted mode. Furthermore, sensitivity analyses were also conducted to address pleiotropy, along with the leave-one-out method.R version 4.2.3 was applied for the analyses.

Results: The IVW estimation revealed that previous smoking has a deleterious effect on rosacea (odds ratio [OR] = 6.7729, 95% confidence interval [CI] = 1.5691-29.2356, p = 0.0104). By contrast, there was no statistically relationship between current smokers and rosacea (OR = 0.6180, 95% CI = 0.0605-6.3094, p = 0.6847). Results were similar in the analysis based on the weighted median method (previous smoking: OR = 8.6297, 95% CI = 1.0131-73.5071, p = 0.0486; current smoking: OR = 0.2896, 95% CI = 0.0106-7.9132, p = 0.4627). The stability of the causal effect estimates was supported by several sensitivity analyses and the leave-one-out method.

Conclusion: Our MR study found support forrosacea risk and previous smoking. Although no evidence was found to increase the risk of rosacea in current smokers, to prevent various diseases associated with smoking, the public should be encouraged to avoid smoking at the very beginning.