A case-control study on the association between rheumatoid arthritis and bladder pain syndrome/interstitial cystitis

AIM: While bladder pain syndrome/interstitial cystitis (BPS/IC) has been suggested by a number of studies to have autoimmune character, no population-based study to date has been conducted investigating its association with rheumatoid arthritis (RA). This study aimed to examine the association between IC/BPS and having previously been diagnosed with RA. METHODS: We conducted this study by using administrative claims data sourced from the Taiwan National Health Insurance Database. Our study included 9,269 cases with BPS/IC and 46,345 randomly selected controls. Conditional logistic regression was performed to calculate the odds ratio (OR) for the association between previously diagnosed RA and IC/BPS. RESULTS: RA was found among 202 (2.2%) cases and 504 (1.12%) controls. Conditional logistic regression analysis suggested that when compared with controls, the OR for prior RA among cases was 1.66 (95% CI = 1.47-1.87, P < 0.001) after adjusting for diabetes, hypertension, coronary heart disease, obesity, hyperlipidemia, chronic pelvic pain, irritable bowel syndrome, fibromyalgia, chronic fatigue syndrome, depression, panic disorder, migraine, sicca syndrome, allergy, endometriosis, asthma, overactive bladder, tobacco use disorder, and alcohol abuse. Additionally, BPS/IC was consistently and significantly associated with a previous diagnosis of RA regardless of prescription drug use; the OR for prior RA among groups prescribed ≤1 type of disease-modifying antirheumatic drug (DMARD), two types of DMARDs, and ≥3 types of DMARDs or TNF-alpha inhibitor when compared to controls were 1.49 (95% CI = 1.28-1.72), 1.91 (95% CI = 1.38-2.68), and 2.36 (95% CI = 1.77-3.17), respectively. CONCLUSIONS: There is an association between RA and BPS/IC after adjusting for socio-demographic characteristics and medical co-morbidities.