Inflammatory bowel disease and rosacea: causal association analysis using bi-directional Mendelian randomization

Background: The association between rosacea and inflammatory bowel disease (IBD) has been studied in previous observational studies. It is unclear, however, whether the association is causal or not. Methods: : Independent genetic variants for IBD were chosen as instruments from published GWAS studies involving 38155 cases with an IBD diagnosis and 48485 controls in order to investigate the causal effect of IBD on rosacea. Summarized data for rosacea were gathered from various GWAS studies that included 1195 cases and 211139 controls without rosacea. Reverse-direction MR analysis was done to investigate the relationship between genetically proxied rosacea and IBD. With the use of the inverse variance-weighted (IVW), MR-Egger, and weighted median approaches, a 2-sample Mendelian randomization study was carried out. Analysis of heterogeneity and sensitivity was performed to examine the pleiotropy and robustness of effect estimates. Results: : The forward-direction of the MR study was to reveal that genetic predisposition to IBD (OR: 1.1291; 95% CI: 1.0444 to 1.2206), UC (OR: 1.2030; 95% CI: 1.0867 to 1.3318) and CD (OR: 1.1291; 95% CI: 1.0444 to 1.2206; p=0.0023) was associated with an increased risk of rosacea. The reverse-direction MR analyses did not demonstrate that a genetic predisposition to rosacea was not associated with total IBD (OR: 0.9683; 95% CI: 0.9112 to 1.0291), UC (OR: 0.9714; 95% CI: 0.8949 to 1.0545) and CD (WM: OR: 0.9751; 95% CI: 0.8971 to 1.0598; p =0.5525). Conclusion: Our findings provided evidence for a causal impact of IBD, UC, and CD on rosacea, but not vice versa. The elevated incidence of rosacea in patients with IBD should be recognized by doctors to make an early diagnosis and initiate specialized therapy.