Editor's Note: This article is based on Kim MH, Johnston SS, Chu B, et al. Estimation of Total Incremental Health Care Costs in Patients With Atrial Fibrillation in the United States. Circ Cardiovasc Qual Outcomes. 2011;4:313-320.

Introduction

These investigators provide an estimate of the cost of atrial fibrillation (AF) management in the United States by conducting a retrospective observational cohort study from Medicare and commercial databases. This is an important issue for several reasons. First, the incidence and prevalence of AF appears to be increasing and as the population ages, the number of patients with AF is expected to rise. Prior studies are limited to relatively small or regionally localized groups of patients with AF. The purpose of this study was to more accurately assess the costs of AF management by using large national databases that reflect more recent changes in AF management. Finally, the authors try to quantitatively estimate the increment in costs due to AF.

Methods

Patient selection was based on being ≥20 years of age at the time of diagnosis and having one or more inpatient or two or more outpatient diagnoses of AF between 2005 and 2006, and 12 or more months enrollment before selection. The AF patients were propensity score-matched with a 1:1 ratio to patients without a diagnosis of AF. Propensity score matching is a statistical technique used in observational studies to minimize selection bias. In this study, propensity scoring was performed using a logistic regression model that made AF the dependent variable, and the independent variables included baseline patient demographics, and cardiovascular co-morbidities. The discriminative power of the propensity score model was measured using the area under the receiver operating curve, or C statistic. Direct costs were measured in dollars at 2008 values for all inpatient and outpatient medical services, as well as pharmacy costs over 12 months from patient identification. Health care expenditures included covered costs from the insurance plans, patient co-payments, deductibles, co-insurance payments, and coordination of benefits. The medical costs in US dollars were further analyzed and divided into all costs, AF costs, cardiovascular costs and non-cardiovascular costs over 1 year after the index.

A total of 98,290 patients were identified of which 89,066 AF patients were successfully matched. The C statistic was 0.93. The mean age of the study population was 71 years, with a male female ratio of 55%/45%. The two cohorts were well balanced with respect to age, sex and co-morbidities. In the patient cohort, 19.5% had newly diagnosed AF and 80.5% had preexisting AF. Five percent of patients also had atrial flutter. Rate control therapy was received by 73.5%, rhythm control therapy by 22% and 57% of the AF patients were taking warfarin. Common baseline illnesses included hypertension (in 82% of AF patients), coronary artery disease (in 28.6% of patients), congestive heart failure (in 19.5% of patients), diabetes (in 22% of patients), pulmonary disease (in 14.9% of patients), peripheral vascular disease (in 5.4% of patients), mitral valve disease (in 12% of patients), cardiomyopathy (in 5.1% of patients), thyroid disease (in 4.5% of patients) and ischemic stroke (in 8.8% of patients).

Results

The total direct costs per patient over 12 months were a mean of $20,670 in the AF group and $11,965 in the control group, a net incremental cost of $8705 per patient. The principal cause of this cost difference was inpatient services. One of the most important findings is that of the increment in inpatient costs, other cardiovascular diagnoses, excluding AF and non-cardiovascular diagnoses make up 90% of the inpatient hospital costs for patients with AF. Over one year, 37.5% of AF patients compared to 17.5% of patients were hospitalized for any cause and 2.1% compared to 0.1% died during hospitalization. AF patients were 4 times more likely to undergo cardiovascular hospitalizations compared to control patients. Three times as many AF patients as control subjects had multiple hospitalizations. Outpatient medical costs were higher in AF patients compared to the matched controls ($9225 versus $5629), but surprisingly not outpatient medical costs ($3605 versus $3714). Costs were higher among patients younger than 65 years, particularly among men.

The national incremental cost of AF was calculated by extrapolating the above findings to an estimated 3.5 million cases of AF in 2010 based on US Census Bureau projections of the age and sex distribution of the US population to be an incremental cost of $26 billion over 12 months. This breaks out to incremental costs due to AF: $6 billion, other cardiovascular costs: $9.9 billion; non-cardiovascular costs: $10.1 billion). Cardiovascular costs were based on AF as the primary diagnosis and may be underestimates.

One limitation of this study is that it does not allow us to analyze in detail the components of the cardiovascular (heart failure) and other costs (stroke, under or over anticoagulation with warfarin).

Summary

AF is responsible for an incremental cost to the United States health care system of between $6 and $26 billion. This may be an underestimate as it only includes costs due to patients with AF identified as a primary diagnosis. The other interesting observation is the striking decrease in the incremental cost of AF treatment in the elderly. It is interesting to speculate that this may reflect a lower degree of symptom burden and a greater reliance on rate control. Another observation made was the lack of variation in the incremental cost of AF treatment for women over the age range studied. One potential interpretation of this finding is that women with AF receive a more conservative management approach. In summary, it appears that therapies that decrease inpatient costs in patients with AF and decrease cost of care while improving outcomes and quality of life are much needed for this disease.

Keywords: Atrial Fibrillation, Cohort Studies, Cost of Illness, Disease Management, United States, Medicare, Quality of Life

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