Published Online: October 19, 2010
Guijing Wang, PhD; Zefeng Zhang, MD, PhD; Carma Ayala, MPH, PhD; Hilary K. Wall, MPH; and Jing Fang, MD
Objective: To examine the costs of hospitalizations related to heart failure (HF) among patients aged 18 to 64 years by diagnosis status.
Background: There are few reports on HF-related hospitalization costs in patients aged 18 to 64 years, although this group has had increased HF hospitalization rates in recent decades.
Methods: Using the 2005 MarketScan Commercial Claims and Encounters inpatient data set, we identified 23,216 hospitalizations for which HF was the primary or secondary diagnosis among patients aged 18 to 64 years who had a noncapitated health insurance plan. We used multivariate regression to analyze the association between patient characteristics and both hospitalization costs and length of stay (LOS).
Results: For the entire population, the mean cost of hospitalization was $23,077; the cost was higher when HF was a secondary rather than the primary diagnosis ($25,325 vs $17,654; P <.001). After controlling for covariates, hospitalizations with HF as a secondary diagnosis resulted in $3944 higher costs than those with HF as the primary diagnosis (P <.001). Among those with HF as a secondary diagnosis, the cost of hospitalization with the primary diagnosis of ischemic heart disease was $14,989 higher than it was when the primary diagnosis was noncardiovascular disease and nonrespiratory conditions (P <.001). However, patients in the latter group had a longer LOS.
Conclusions: Information on the costs of HF-related hospitalizations can be used as inputs in economic evaluations such as cost-effectiveness analyses and as references for policy makers in making resource allocation decisions.
(Am J Manag Care. 2010;16(10):769-776)
The costs of 23,216 hospitalizations related to heart failure (HF) among patients aged 18 to 64 years were analyzed.
- The mean cost of HF-related hospitalizations was $23,077 and was higher when HF was a secondary rather than the primary diagnosis.
- For those with a secondary diagnosis of HF and the primary diagnosis of ischemic heart disease, the costs of hospitalizations were $14,989 higher than they were when the primary diagnosis was noncardiovascular disease and nonrespiratory conditions.
- Among all the categories of primary diagnoses, the primary diagnosis of noncardiovascular disease and nonrespiratory conditions resulted in the longest length of stay.
In the United States, rates of hospitalization for heart failure (HF) increased substantially in the past 3 decades, and HF has become an epidemic.1-3 Although HF affects adults 65 years or older more than those below age 65 years, the younger group had a higher relative increase in hospitalization rates for HF, regardless of sex, than did the older group.1 In addition, the percent increase was greater for hospitalizations with HF as a secondary diagnosis than it was for hospitalizations with HF as the primary diagnosis.1 Nationally, approximately 70% of HF-related hospitalizations listed HF as a secondary diagnosis.1 From a public health perspective, promoting prevention and improving medical management based on an understanding of the costs for HF-related hospitalizations in people aged 18 to 64 years could have a large payoff in terms of containing the ever-increasing healthcare costs.
For 2007, the medical cost of HF in the United States for those aged 65 years or older was estimated at $30.2 billion.4 The hospitalization cost for this age group was estimated at $20.1 billion in 2009.5 The average cost for an HF hospitalization more than doubled from about $7000 in the 1990s to $18,086 in recent years.6-8 On the national level, HF has an extraordinary impact, consuming 1% to 2% of the total healthcare resources in industrialized countries, including the United States, with this percentage likely to increase in the future.9-11 Moreover, HF is the fastest-growing cardiac disease entity in the United States, affecting 2% of the population, with nearly 1 million hospitalizations for acute decompensated congestive HF occurring annually.11
Although many researchers have investigated the medical costs related to HF, nearly all the cost studies have been for the population 65 years or older because of the high hospitalization rates for HF in this age group.4,6-9,12-18 Correspondingly, information is lacking on the costs of HF in adults under 65 years. Furthermore, although many previous studies had focused on hospitalization costs,8,18,19 the costs by detailed diagnosis codes and diagnosis status have not been well examined. Because the types of HF vary considerably and at least 70% of HF diagnoses are listed as a secondary diagnosis, it would be helpful to have cost analyses for this disease that consider these characteristics, especially as the information obtained could influence the cost-effectiveness of HF management programs. Thus, we investigated HF-related hospitalization costs among patients aged 18 to 64 years by diagnosis status.
We identified HF-related hospitalizations from the 2005 MarketScan Commercial Claims and Encounters inpatient data set, which in that year had data on more than 1 million inpatient hospitalizations for privately insured patients 64 years or younger. The data contain comprehensive, highquality coding of medical services.20 Researchers have previously used this database for medical cost analyses of cardiovascular diseases (CVDs).21-24
We used the primary diagnosis and 14 secondary diagnoses to identify hospitalizations for patients aged 18 to 64 years with a diagnosis of HF; our analysis was restricted to the International Classification of Diseases, Ninth Revision (ICD-9) codes listed in the American College of Cardiology/American Heart Association HF performance measures (Table 1). We identified 23,216 HF-related hospitalizations for patients with a noncapitated health insurance plan and with hospitalization costs between the 1st and 99th percentiles. We excluded the hospitalizations of patients with a capitated health insurance plan because their costs did not reflect the medical services they received; excluding hospitalizations with a cost below the 1st or above the 99th percentile reduced the influences of extreme values on the cost estimates. We further created 2 subsamples for the cost analyses: (1) HF as the primary diagnosis and (2) HF as a secondary diagnosis. Hospitalizations with both the primary diagnosis and a secondary diagnosis of HF were included in the first subsample.
For hospitalizations with a secondary diagnosis of HF, we identified the primary diagnoses of (1) ischemic heart disease (IHD) (ICD-9 codes 410-414); (2) other diseases of the heart (ICD-9 codes 392-398, 402, 404, 415, 416, 420-427, and 429); (3) other CVDs (ICD-9 codes 390-459, excluding the codes for IHD and other diseases of the heart); (4) respiratory disease (ICD-9 codes 460-519), including pneumonia and chronic obstructive pulmonary disease; and (5) non-CVD and nonrespiratory conditions.
Outcome Measures and Other Control Variables
The main outcome for this analysis, hospitalization costs (total payments to providers, not charges), represented the total costs per hospitalization, which included the costs for physician services, all diagnostic tests, therapeutics, supplies, and room fees during the stay. We excluded the hospitalizations with a cost below $1060 (cutoff point of the 1st percentile) and above $208,507 (cutoff point of the 99th percentile).
Length of stay (LOS) was a second outcome measure. Because LOS is a major factor influencing the cost, reducing it might have important implications for managing HF and for cost containment.19,25,26 The LOS was categorized as 1 for hospital stays of fewer than 7 days and as 2 for hospital stays of 7 or more days. We used 7 days as the cutoff point because the average number of days for an HF-related hospitalization in the United States is about 6 to 8 days.11,19 In our data, the average was 6.3 days.
We included age, sex, urbanization, and the Charlson Comorbidity Index as control variables. We used the Charlson Comorbidity Index, which measures the likelihood of death or serious disability in the subsequent year by diagnosis codes for up to 18 different diseases,27 to control for the effects of disease severity and comorbidities on the costs.16
Statistical analyses were performed using SAS version 9.2 (SAS Institute Inc, Cary, NC). Significance was assumed when the 2-tailed probability value was less than .001. For cost comparisons between hospitalizations with the primary diagnosis of HF and those with a secondary diagnosis of HF, the Wilcoxon 2-sample test was used. We used regression models to conduct multivariate analysis of the costs and LOS. Medical cost data were usually skewed and not normally distributed; thus, many researchers have used log-transformation in cost analyses. Many other studies, however, did not use the transformation because of the difficulties in interpreting the results.28-30 We excluded hospitalizations with total costs below the 1st or above the 99th percentile to avoid the effects of outliers, and our large sample sizes also made the analysis relatively robust to the violations of normality. Therefore, we did not transform the costs in our analysis. Because the study samples consisted of hospitalizations rather than patients, some patients might have had multiple hospitalizations during the year. To account for the possibility of the repeated measures in the analysis, we used the PROC MIXED procedure to estimate the impact of patient characteristics and other covariates on hospitalization costs, and we used the PROC GENMOD procedure to estimate the impact of these variables on LOS.
For all 23,216 HF-related hospitalizations, the mean cost was $23,077; for the 6806 hospitalizations (29%) with HF listed as the primary diagnosis, the mean cost was $17,654, and for the 16,410 hospitalizations (71%) with HF listed as a secondary diagnosis, the mean cost was $25,325 (Table 2). Hospitalized men incurred higher costs than hospitalized women, and among the 6 groups formed by combining sex and diagnosis status, men with HF as a secondary diagnosis had the highest cost ($27,277), whereas women with HF as a primary diagnosis had the lowest cost ($16,058). The costs across age groups varied slightly regardless of diagnosis status.
The regression results indicated that sex significantly influenced costs, but age did not (Table 3). In the entire sample, hospitalized men incurred costs that were $4317 (P <.001) higher than those of hospitalized women. Regional variations in the hospitalization costs were significant, with the highest cost in the West. Hospitalized patients with a LOS of 7 days or more incurred significantly higher costs than those with a LOS of less than 7 days. Hospitalized patients with a secondary diagnosis of HF incurred costs that were $3944 (P <.001) higher than hospitalized patients with the primary diagnosis of HF.
Among patients with a secondary diagnosis of HF, 17% had a primary diagnosis of IHD; 14%, other diseases of the heart; 7%, other CVDs; 18%, respiratory diseases; and 44%, non-CVD and nonrespiratory conditions. Among these groups, hospitalized patients with IHD had the highest costs per hospitalization ($36,442). After controlling for other covariates and using hospitalizations with the primary diagnosis of non-CVD and nonrespiratory conditions as the reference, hospitalized patients with IHD incurred costs that were $14,989 higher (P <.001); those with other diseases of the heart had costs that were $9480 higher (P <.001) (Table 3).
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