Causal effect of body mass index on herpes zoster and postherpetic neuralgia: A Mendelian randomization study

Although observational studies have reported the relationship between body mass index (BMI), herpes zoster (HZ), and postherpetic neuralgia (PHN), the impacts of BMI on the incidence of HZ and PHN are still controversial. Our study aimed to explore the causal effect of BMI on HZ and PHN by a 2-sample Mendelian randomization (MR) approach. Genome-wide association studies data on BMI, HZ, and PHN were derived from publicly available genetic summary datasets. A total of 28 phenotypic single-nucleotide polymorphisms were selected as instrumental variables for BMI. Inverse-variance weighted (IVW) method was conducted as the primary MR analysis method to explore the causal effect of BMI on HZ and PHN. Several sensitivity analyses were performed to test the robustness of the MR results. Our study found no strong evidence for an effect of BMI on HZ incidence (IVW: OR = 1.018, 95% CI = 0.964-1.075, P = .524). However, it demonstrated that increased BMI was related to a higher risk of PHN (IVW: OR = 1.234, 95% CI = 1.002-1.520, P = .048). Besides, no significant heterogeneity or horizontal pleiotropy was observed in our study, and sensitivity analysis was consistent with the results. There is no causal effect of BMI on HZ risk, but it may be causally associated with a risk of PHN.