AIMS: Previous studies indicated a possible association between bladder pain syndrome/interstitial cystitis (BPS/IC) and sleep disorders including sleep abnormalities with delayed onset of sleep, waking up before needed, and snoring. Nevertheless, no previous study has reported the association between obstructive sleep apnea (OSA) and BPS/IC. In this retrospective cohort study, we examined the risk of BPS/IC among subjects with OSA during a 3-year follow-up in Taiwan using a population-based dataset. METHODS: This study comprised 2,940 study subjects with OSA, and 29,400 randomly selected comparison subjects. We individually followed-up each sampled subject (n = 32,340) for a 3-year period to identify those subjects who subsequently received a diagnosis of BPS/IC. A Cox proportional hazards regression model was constructed to estimate the risk of subsequent BPS/IC following a diagnosis of OSA. RESULTS: Incidences of BPS/IC during the 3-year follow-up period were 13.61 (95% confidence interval [CI] = 7.37-23.13) and 3.60 (95% CI = 2.06-4.39) for subjects with and those without OSA, respectively. After adjusting for diabetes, hypertension, coronary heart disease, obesity, hyperlipidemia, chronic pelvic pain, irritable bowel syndrome, fibromyalgia, chronic fatigue syndrome, depression, panic disorder, migraines, sicca syndrome, allergies, endometriosis, asthma, tobacco use disorder, and alcohol abuse, the stratified Cox proportional hazards regressions revealed that the hazard ratio for BPS/IC among subjects with OSA was 3.71 (95% CI = 1.81-7.62, P < 0.001) that of comparison subjects. CONCLUSIONS: This study provides epidemiological evidence of a link between OSA and a subsequent BPS/IC diagnosis. We suggest that clinical practitioners treating subjects with OSA be alert to urinary complaints in this population.