Economic Burden of Irritable Bowel Syndrome with Constipation: A Retrospective Cohort Study in a Large Managed Care Population

Abstract

Purpose: The prevalence of irritable bowel syndrome with constipation (IBS-C) is approximately 5-10% in the U.S. However, the economic burden of IBS-C is not well understood. This study aimed to estimate the incremental costs of IBS-C in a managed care population. Methods: Patients aged ≥18 years continuously enrolled in 2010 were identified using claims from the HealthCore Integrated Research Database, which consists of 14 geographically-dispersed US health plans representing 45 million lives. IBS-C patients were defined as those with >1 medical claim of IBS (ICD-9-CM code 564.1x) and >2 medical claims for constipation (ICD-9-CM 564.0x) or >1 medical claim for constipation plus >1 pharmacy claim for a constipation-related prescription. Controls without IBS, constipation, abdominal pain, or bloating were randomly selected using 1:1 matching on age, gender, health plan region and insurance plan type. Patients with diagnoses or prescriptions suggesting mixed IBS, IBS with diarrhea, chronic diarrhea, or drug-induced constipation were excluded. All-cause medical services included inpatient visits, emergency room (ER) visits, physician office visits, and other outpatient services for any condition. Total healthcare costs consisted of costs from medical services and pharmacy costs. Generalized linear models with bootstrapping were used to assess the incremental costs attributable to IBS-C, after adjusting for a series of confounders including demographics, Elixhauser comorbidity index (ECI) score, and 15 general and gastrointestinal-related comorbidities not included in the ECI score (e.g., chronic pain, hyperlipidemia, gastro esophageal reflux disorder, hemorrhoids). Results: A total of 7,652 patients (n=3,826 for IBS-C) were identified. The mean (+SD) age was 48 (+17) years; 83.6% were female. IBS-C patients had significantly higher unadjusted all-cause healthcare costs compared to controls ($11,182 vs. $3,116, p<0.01). Over half (54.2%) of this difference was due to physician office visits and other outpatient services/diagnostics (13.2% and 41.0%, respectively). The remaining difference was attributable to hospitalizations (22.5%), prescriptions (16.9%) and ER visits (6.5%). After adjusting for demographic characteristics and comorbidities, the incremental total all-cause healthcare costs associated with IBS-C were $3,856 (in 2010 U.S. dollars), of which 21.8% were for pharmacy costs (see Table).Table: Adjusteda mean all-cause costs for IBS-C patients and controls in 2010Conclusion: IBS-C is associated with a substantial economic burden even after controlling for general and gastrointestinal-related comorbidities. The majority of incremental costs are attributable to medical services. Disclosure: Qian Cai, Abhishek Kavati, Hiangkiat Tan, and Judith Stephenson: employees of Healthcore, Inc., which is a consultancy whose activities related to the project are funded by Forest Laboratories, Inc., and Ironwood Pharmaceuticals; Robyn Carson and Jessica Buono: employees of Forest Laboratories, Inc. and own stock and/or stock options in Forest Laboratories, Inc.; Phil Sarocco and William Spalding: employees of Ironwood Pharmaceuticals, Inc. and own stock and/or stock options in Ironwood Pharmaceuticals. This research was supported by an industry grant from Forest Laboratories, Inc., and Ironwood Pharmaceuticals, Inc., were involved in the study design; collection, analysis and data interpretation; and decision to submit these data for presentation. Study was sponsored by Forest Laboratories, Inc., and Ironwood Pharmaceuticals, Inc.