Economic burden of irritable bowel syndrome with constipation: a retrospective analysis of health care costs in a commercially insured population.

BACKGROUND: The prevalence of irritable bowel syndrome with constipation (IBS-C) is estimated to be between 4.3% and 5.2% among adults in the United States. Little is known about the health care resource utilization and costs associated with IBS-C.
OBJECTIVES: To (a) evaluate the annual total all-cause, gastrointestinal (GI)-related, and IBS-C-related health care costs among IBS-C patients seeking medical care in a commercially insured population and (b) estimate the incremental all-cause health care costs among IBS-C patients relative to matched controls.
METHODS: Patients aged ≥ 18 years with continuous medical and pharmacy benefit eligibility in 2010 were identified from the HealthCore Integrated Research Database, which consists of administrative claims from 14 geographically dispersed U.S. health plans representing 45 million lives. IBS-C patients were defined as those with ≥ 1 medical claim with an ICD-9-CM diagnosis code in any position for IBS (ICD-9-CM 564.1x) and either ≥ 2 medical claims for constipation (ICD-9-CM 564.0x) on different service dates or ≥ 1 medical claim for constipation plus ≥ 1 pharmacy claim for a constipation-related prescription on different dates of service during the study period. Controls were defined as patients without any medical claims for IBS, constipation, abdominal pain, or bloating or pharmacy claims for constipation-related prescriptions. Controls were randomly selected and matched with IBS-C patients in a 1:1 ratio based on age (± 4 years), gender, health plan region, and health plan type. Patients with diagnoses or prescriptions suggesting mixed IBS, IBS with diarrhea, chronic diarrhea, or drug-induced constipation were excluded. Total health care costs in 2010 U.S. dollars were defined as the sum of health plan and patient paid costs for prescriptions and medical services, including inpatient visits, emergency room (ER) visits, physician office visits, and other outpatient services. The total cost approach was used to assess total all-cause or disease-specific health care costs for patients with IBS-C, while the incremental cost approach was used to examine the excess all-cause costs of IBS-C by comparing IBS-C patients with matched controls. Generalized linear models with bootstrapping were used to assess the incremental all-cause costs attributable solely to IBS-C after adjusting for demographics, Elixhauser Comorbidity Index (ECI) score, and other general and GI-related comorbidities not included in the ECI score.
RESULTS: A total of 7,652 patients (n = 3,826 each in the IBS-C and control cohorts) were included in the analysis. The mean (± SD) age was 48 (± 17) years, and 83.6% were female. The mean annual all-cause health care costs for IBS-C patients were $11,182, with over half (53.7%) of the costs attributable to outpatient services, including physician office visits and other outpatient services (13.1% and 40.6%, respectively). Remaining total all-cause costs were attributable to hospitalizations (21.8%), prescriptions (19.1%), and ER visits (5.4%). GI-related costs ($4,456) comprised 39.8% of total all-cause costs, while IBS-C-related costs ($1,335) accounted for 11.9% and were primarily driven by costs of other outpatient services (50.3%). After adjusting for demographics and comorbidities, the incremental annual all-cause health care costs associated with IBS-C were $3,856 ($8,621 for IBS-C patients vs. $4,765 for controls, P less than 0.01) per patient per year, of which 78.1% of the incremental costs were due to medical services, and 21.9% were due to prescription fills.
CONCLUSIONS: IBS-C imposes a substantial economic burden in terms of direct health care costs in a commercially insured population. Compared with matched controls, IBS-C patients incurred significantly higher total annual all-cause health care costs even after controlling for general and GI-related comorbidities. Incremental all-cause costs associated with IBS-C were mainly driven by costs related to more frequent use of medical services as opposed to prescriptions.