Chronic Tonsillitis and IgA Nephropathy: Findings From a Nationwide Japanese Cohort Study

Rationale & ObjectiveLittle is known regarding the association between chronic tonsillitis and the onset of IgA nephropathy (IgAN). In the present study, we examined the potential relationship between chronic tonsillitis and a subsequent risk of developing IgAN.Study DesignObservational cohort study.Setting& Participants: 4,311,393 individuals without a history of IgAN identified between January 2005 to May 2022 within a Japanese nationwide epidemiological database, the JMDC Claims Database, representing health claims to over 60 insurers.ExposureComorbid chronic tonsillitis based on diagnosis codes.OutcomeIgAN occurrence.Analytical ApproachCause-specific Cox proportional hazards analysis adjusting for potential confounding factors were employed to estimate hazard ratios (HRs).ResultsComorbid chronic tonsillitis was identified in 12,842 individuals, constituting 0.3% of the cohort. The cohort had a median age of 44 years (interquartile range: 36-53), and males accounted for 57.9%, with a follow-up of 1,089 days (interquartile range: 532-1,797), during which 2,653 cases of IgAN developed. Cumulative incidence curve showed a higher cumulative incidence of IgAN in individuals with chronic tonsillitis compared to their counterparts without this condition. Multivariable cause-specific analysis further demonstrated that individuals with chronic tonsillitis had an elevated risk of developing IgAN, with a HR of 2.72 (95% confidence interval: 1.79-4.14).LimitationsPotential residual confounders, and lack of consideration for ethnic distinctions.ConclusionsUsing a largescale epidemiological dataset, these findings suggest a relationship between chronic tonsillitis and an elevated risk of IgAN development in the general Japanese population.