Systemic Inflammation Is Associated with the Relationship between Benign Prostatic Hyperplasia and Rheumatoid Arthritis.

PURPOSE: Benign prostatic hyperplasia (BPH) and rheumatoid arthritis (RA) have both been associated with inflammatory processes; however, their association remains unclear. This study explored the prospective association between BPH and the subsequent risk of RA using data from the UK Biobank, and further evaluated whether the systemic immune-inflammation index (SII) and the neutrophil-to-lymphocyte ratio (NLR) are associated with this relationship. MATERIALS AND METHODS: A total of 222,891 males without RA or prostate cancer at baseline were included. BPH was identified through self-report, hospital ICD-10 codes (N40), and primary care records. Incident RA was defined using hospital ICD-10 codes (M05 to M06). Multivariable Cox proportional hazards models were applied to assess the association between BPH and risk of incident RA. Mediation analyses were used to explore the potential role of SII and NLR in this association. Sensitivity analyses, including subgroup analyses, multiple imputation, exclusion of early RA cases, and competing risk models, were performed to test robustness. RESULTS: During a median follow-up of 14 years, 2,252 incident RA cases were documented. After multivariable adjustment, BPH was associated with a higher risk of RA (hazard ratio=1.19, 95% confidence interval: 1.03 to 1.37). The association remained consistent across sensitivity analyses. Mediation analyses suggested that SII and NLR may partly account for the observed association between BPH and RA (4.28% and 7.25%, respectively). CONCLUSIONS: BPH was associated with an increased risk of RA, and systemic inflammatory markers were also associated with this relationship.