Hypothesis / aims of study
Interstitial Cystitis/Bladder Pain Syndrome (IC/BPS) is a condition defined by pain pressure or discomfort perceived to be associated with the bladder for a minimum of six weeks and not explainable by infection or other cause. Definitive diagnosis of this condition often can go unmade for as many as 4 - 5 years. The reported prevalence of IC/BPS in women ranges from 2.7 - 6.5% depending on the definition of severity applied when surveying patients. In males, the disorder is more rare, with prevalence ranging from 1.9 - 4.2%. Patients are reported to have a variety of related comorbid conditions, resulting in multiple caregivers, healthcare encounters and attendant costs for care. In this study, we aimed to characterize the comorbidity burden and Healthcare Resource Use (HRU) in this population.
Study design, materials and methods
We conducted a descriptive, non-interventional, retrospective cohort study using Merative Marketscan® Commercial and Medicare Supplemental database from January 1, 2008, to June 30, 2021. Patients included in the study had at least one IC/BPS diagnosis defined as a claim with ICD-9 diagnosis code 595.1 or ICD-10 diagnosis code N30.1. The index date was defined as the date of first diagnosis. Patients were required to have at least 12 months of continuous enrollment prior to and after the index date. We evaluated demographic factors such as age, sex, region, as well as comorbidity prevalence (e.g., mental health disorders, substance use disorders, chronic pain, etc.) over the study period relative to the date of IC/BPS diagnosis. HRU (inpatient, emergency department, and outpatient visits) was assessed over a period spanning from 1 year prior to the index date to 3 years post index. We compared frequencies of comorbidities with reported rates in the literature by US based health institutions and in peer reviewed sources (e.g., Centers for Disease Control (CDC), National Heart Lung and Blood Association (NHLBI), National Institutes of Mental Health (NIMH)). We reported on comorbidities that occurred at rates exceeding 20% within our cohort except for diabetes, chronic liver disease, and Substance Use Disorders (SUD).
Results
Patients with IC/BPS (N=74,942) included in the study were mid-life (mean age of 48 years) and mostly female (90%). Mean pre-index and follow-up time for observation of comorbidities was 1,249 days (3.4 years) and 1,362 days (3.7 years), respectively.
Out of the 49 total comorbidities observed the most common comorbidities in this patient population included pain related conditions consisting of, chronic pain (93%), back pain (64%), chronic pelvic pain (59%), headaches (43%), and fibromyalgia (26%). Urinary tract infection was identified in 75% of patients. Disorders associated with immunity, including allergic rhinitis (43%), autoimmune disease (40%), and asthma (23%) were also common. Mental health disorders including, anxiety (46%), depression (40%) and SUD (10%) were prevalent. More than half (53%) of IC/BPS patients with any SUD were non-nicotine and non-cannabis dependent. Patients with SUD predominantly reported nicotine dependency (52%) and opioid use disorder (33%). Additional comorbidities of interest or observed among > 20% of patients, included sleep disorders (36%), hyperlipidemia (50%), hypertension (48%), COPD (38%), dyspepsia (28%), diabetes (19%) and chronic liver disease (18%). (Figure 1.)
The multimorbidity observed in this patient cohort likewise was high. Nearly 70% of patients presented with 5 or more comorbidities, while additional 11% of patients presented with 4 comorbidities. (Figure 2.)
Nearly all the patients (>99%) had at least one healthcare encounter within each year of follow-up mostly occurring in the outpatient setting and ranged between 20 to 22 visits per patient per year. In comparison, for both inpatient (IP) and emergency department (ED) settings we observed less than 1 visit per patient per year.
Interpretation of results
Our results are supportive of observations from previous reports which note a high prevalence of back, pelvic and complex pain disorders as well as a high frequency of mental illness, autoimmune disease and sleep disorders.(1,2) Several of these comorbidities were noted to occur at a higher prevalence than in previous reports. Of interest, our results revealed significant comorbidities not previously reported in the IC/BPS population and at a prevalence higher than current population estimates for adults. Notable among these observations are chronic liver disease, sleep disorders, respiratory illnesses, hyperlipidemia and substance use disorders.
Chronic liver disease was observed in our IC/BPS cohort at a rate of 18% compared with a 2018 CDC National Health Interview Survey which reported a 2% prevalence in adults. Among the patients within the IC/BPS cohort with chronic liver disease, only 4.5% of these patients were observed having a sole diagnosis of fatty liver disease. This suggests that most (>90%) IC/BPS patients who had chronic liver disease within this cohort presented with serious hepatic diseases (e.g., cirrhosis, hepatitis, etc.) possibly in addition to fatty liver disease. Our investigation also observed a 36% prevalence of sleep disorders within our cohort compared with 2022 reports from the NHLBI reporting up to 21%. Within our study, 98% of IC/BPS patients with a sleep disorder diagnosis were in relation to sleep deprivation (i.e., excluding hypersomnia, narcolepsy or cataplexy). Respiratory disorders, asthma and COPD, were observed at a prevalence of 23% and 38%. This is higher than current CDC estimates (7.9% and 6.4%). Hyperlipidemia was observed at a prevalence of 50% which is higher than 2022 CDC estimates for adults 20 years and over (28%). Our investigation also captured IC/BPS patients with substance use disorder (SUD). Opioid related SUDs were observed at a rate of 33% of patients diagnosed with an SUD (3.2% overall), which is higher than was reported by the NIH in 2016 detailing data from their 2012-2013 survey of the US adult population (2.1%). Most patients with SUD had some form of nicotine dependence (52%) alone or in combination with other SUDs. However, overall, we observed a lower rate of nicotine use than in CDC reports on smoking among US adults (12.5%).
In addition to the high comorbidity burden, we also report high outpatient HRU ranging from 20 to 22 visits per patient per year compared to an average of 3.2 annual encounters among US adults as reported by CDC from the NCHS 2019 National Ambulatory Medical Care Survey. This reflects observations by investigators in Hsieh et al. who reported more outpatient visits among IC/BPS patients than matched controls. (3)
Concluding message
Our study reveals that patients with IC/BPS have a high burden of comorbidities, with chronic pain, chronic liver disease, respiratory illness, mental health disorders, cardio-vascular disease, sleeping disorders, and autoimmune disease being most notable. This is unsurprisingly, coupled with increased utilization of the healthcare system in the form of high numbers of outpatient visits. The high prevalence of comorbidity and multimorbidity in this patient population should be considered in the context of clinical decision making to optimize disease management and improve overall health outcomes.