Causal effect between chronic periodontitis and IgA nephropathy: Insights from a 2-sample bidirectional Mendelian randomization study.

Epidemiological evidence suggests an association between chronic periodontitis and immunoglobulin A nephropathy (IgAN), although this association remains controversial. This study aimed to investigate the causal effect between chronic periodontitis and IgAN using a 2-sample bidirectional Mendelian randomization (MR) analysis, using single nucleotide polymorphisms as genetic instrumental variables obtained from publicly available genome-wide association study data. The main MR analysis employed the inverse variance weighted method, complemented by supplementary analyses utilizing MR-Egger and weighted median methods. Heterogeneity was analyzed using the Cochran Q test, and pleiotropy was evaluated using the MR-Egger intercept test. A leave-one-out analysis was used to identify potentially influential single nucleotide polymorphisms, and the MR-pleiotropy residual sum and outlier method method was used to identify outliers. The inverse variance weighted results indicated that there was no genetic evidence for a strong causal effect of chronic periodontitis on IgAN in the genetic prediction (odds ratio = 1.02, 95% confidence interval = 0.97-1.07, P = .42). There was no genetic evidence for a strong causal effect of IgAN on chronic periodontitis (odds ratio = 1.19, 95% confidence interval: 0.92-1.53, P = .18). This MR study found no genetic evidence for a strong causal effect between chronic periodontitis and IgAN in the European population.