Roles of BMI in mediating the causal effect of obstructive sleep apnea on psoriasis: a two-step mendelian randomization study

Observational studies have reported an association between obstructive sleep apnea (OSA) and psoriasis. Nonetheless, the presence of a causal relationship within this observed association remains to be confirmed. Consequently, we utilized the Mendelian Randomization (MR) method to assess the causal effects between OSA on psoriasis. Single-nucleotide polymorphisms associated with OSA were extracted from the FinnGen study. statistics for psoriasis were obtained from the publicly available IEU GWAS database. Inverse-variance weighted (IVW) method was chosen as the primary analysis, combined with several sensitivity analyses to evaluate the robustness of results. The study design included two-sample MR and two-step MR. Our primary MR analysis revealed that genetically predicted OSA was positively linked to psoriasis (OR = 1.26, 95% confidence interval [CI]: 1.12-1.42, p < 0.001), while no significant causal relationships were observed between psoriasis and OSA (p > 0.05). The two-step MR suggests that BMI might act as a mediating factor in the effect of OSA on psoriasis, with a mediated portion estimated at 23%. Our findings provide support for a causal relationship between genetically predicted OSA and psoriasis. Furthermore, our results suggest that BMI may play a role in mediating the influence of OSA on psoriasis.