The direct costs of untreated comorbid insomnia in a managed care population with major depressive disorder

Abstract

Objectives: Previous research has shown that untreated insomnia has significant direct and indirect burden. Despite the high comorbidity of insomnia and Major Depressive Disorder (MDD), no studies have attempted to determine the economic costs among patients diagnosed with MDD and insomnia. The purpose of this study was to estimate the economic burden of comorbid untreated insomnia within an adult and elderly population with MDD.

Design: A retrospective, observational study comparing direct health care costs in insomnia patients with MDD to a matched non-insomniacs group with MDD that had MDD and no insomnia. Data was from taken from managed care claims database in the United States.

Measurements and results: A large managed care claims database was used to identify MDD subjects (aged >or=18 years) anytime between 01/01/1998 to 11/30/2007 using MDD-specific ICD-9-CM diagnoses. Insomniacs with MDD (n = 38,213) were selected from this cohort using insomnia-specific ICD-9-CM codes or hypnotic use. Costs were calculated for the twelve months prior to initiating insomnia treatment/diagnosis. Direct costs were compared with 1:1 matched non-insomniacs with MDD. Total direct costs included inpatient, outpatient, emergency room (ER) and drug costs. Cost outcomes were analyzed using a generalized linear model with gamma distribution and log link, and GEE estimation. Insomniacs with MDD had statistically greater (p < 0.01) total outpatient visits 8.34 (SE = 0.04) vs non-insomniacs with MDD 7.26 (SE = 0.04); MDD-related visits 3.9 (SE = 0.04) vs non-insomniacs with MDD 2.1 (SE = 0.02); and antidepressant prescriptions 5.0 (SE = 0.03) vs non-insomniacs with MDD 4.2 (SE = 0.03). Overall direct costs for insomniacs with MDD were significantly (p < 0.001) higher than non-insomniacs with MDD ($4858 vs $4007). Similar direct cost differences ($1007) were found in a sample of elderly (aged >or=65 years) patients (n = 2756) mean age = 75.6 yrs.

Conclusions: Untreated insomnia within an adult and elderly comorbid MDD population is associated with higher MDD-related and overall direct costs compared to MDD without insomnia. Key limitations associated with this study make it likely that the direct costs and appearance of comorbidities may have been underestimated. These include that: the non-insomnia with MDD group may have untreated/undiagnosed insomnia; some identified cases were likely treated with over-the-counter or behavioral treatment; and that other drugs may have been used for insomnia were not considered for this study and may have been taken for another condition. Future research needs to determine whether treating comorbid insomnia within a MDD population is cost-effective.