Casual association between childhood body mass index and risk of psoriasis: A Mendelian randomization study

Observational studies have suggested that childhood body mass index (BMI) is associated with the risk of psoriasis. However, their causal relationship remains unclear. In this investigation, we aimed to determine whether an association exists between childhood BMI and psoriasis.

Using summary statistics for childhood BMI of European descent from publicly available GWAS meta-analyses (n = 39 620), we conducted Mendelian randomization (MR) research using the inverse variance weighting (IVW), weighted median, and MR-Egger regression techniques. The outcome was a genome-wide association studies (GWAS) for the self-reported non-cancer disease classification psoriasis in the UK Biobank population (total n = 337 159; case = 3871; control = 333 288).

We selected instrumental variables from 16 single-molecule polymorphisms that attained genome-wide significance in GWAS on childhood BMI. Using the IVW method, our findings supported a causal relationship between childhood BMI and psoriasis (beta = 0.003, standard error [SE] = 0.001, p = 0.006). Using MR-Egger regression analysis, we evaluated the potential for directional pleiotropy to bias our results (intercept = 0.00039, p-value = 0.247) and found no causal relationship between childhood BMI and psoriasis (beta = -0.002, SE = 0.004, p = 0.625). The weighted median method, however, provided proof of a causal relationship (beta = 0.003, SE = 0.001, p = 0.029). Cochran's Q test and the funnel plot revealed little proof of heterogeneity or asymmetry, indicating the lack of directional pleiotropy.

According to the findings of the MR analysis, an increased childhood BMI may be linked to a higher likelihood of psoriasis.