Economic Burden in Direct Costs of Concomitant Chronic Obstructive Pulmonary Disease and Asthma in a Medicare Advantage Population

BACKGROUND: Chronic obstructive pulmonary disease (COPD) is a highly prevalent disease whose sufferers consume a large amount of resources. Among community-dwelling Medicare beneficiaries, 12% reported that they had COPD in 2002. For clinicians, differentiating COPD from asthma may be difficult, but among patients with COPD and asthma, approximately 20% have both conditions. The economic impact of concomitant asthma and COPD is potentially large but has not been studied. OBJECTIVES: To assess the cost burden of asthma in patients with COPD in a Medicare Advantage population. METHODS: We reviewed the database of a large health plan that contained information from more than 30 distinct plans covering approximately 25 million members. We identified Medicare beneficiaries aged 40 years or older with medical and pharmacy benefits and medical claims with International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) diagnosis codes for COPD or asthma over a 1-year identification period (calendar year 2004). We assigned patients to 2 cohorts based on diagnoses on medical claims (any diagnosis field) during 2004; the COPD cohort had at least 1 medical claim for COPD, and the COPD + asthma cohort had at least 1 claim for COPD and at least 1 claim for asthma. A patients index date was the first date during 2004 in which there was a medical claim with a diagnosis code for COPD or asthma. To confirm diagnosis, each patient was required to have at least 1 additional claim for COPD (COPD cohort) or at least 1 claim for COPD and at least 1 claim for asthma (COPD + asthma cohort) during the 24-month period from 12 months before through 12 months after the index date. We excluded patients who (1) were not continuously enrolled during the 12 months before and after the index date and (2) did not have at least 1 pharmacy claim for a drug of any type (to verify pharmacy benefits). Outcome measures included the use of emergency room (ER) and hospital services, and cost (net provider payment after subtraction of member cost share), categorized as all-cause, non-respiratory, and respiratory-related. ER use and inpatient hospital stays were identified using place-of-service codes. A minimum of 2 consecutive dates of service (length of stay [LOS] of at least 1 day) was required to indicate an inpatient hospitalization. An LOS of at least 1 day was required to distinguish inpatient services from other services (e.g., procedures or tests) reported on claims with an inpatient place of service. Multivariate analyses adjusted for age, gender, census region, and Charlson Comorbidity Index (CCI). Ordinary least squares regression was used to predict respiratory-related total health care costs, and logistic regression was used to predict the occurrence of at least 1 acute event, defined as use of either an ER or an inpatient hospital. All 2-way interactions were considered, and only those with significant results were included in the models. All reported P values were 2-sided with a 0.05 significance level. RESULTS: During 2004, 68,532 individuals within the database were enrolled in a Medicare Advantage plan. After application of the other inclusion criteria, we excluded approximately 11% of the patients who did not have 1 pharmacy claim of any type. There were 8,086 patients (11.8%) who had at least 1 medical claim with diagnosis codes for COPD and at least 1 other medical claim for either COPD or asthma and were continuously enrolled for at least 24 months. The COPD + asthma cohort numbered 1,843 patients (22.8%), and the COPD cohort numbered 6,243 patients (77.2%). Compared with COPD patients without asthma, patients with COPD + asthma were slightly younger, and a higher proportion was female. There were differences between the 2 cohorts in geographic distribution, and the COPD + asthma cohort had a higher disease severity with a mean CCI score of 2.6 �