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. Author manuscript; available in PMC: 2014 Mar 3.
Published in final edited form as: J Am Coll Cardiol. 2013 Mar 12;61(10):1078–1088. doi: 10.1016/j.jacc.2012.11.057

National Trends in Heart Failure Hospitalization Rates, 2001–2009

Jersey Chen *,†, Kumar Dharmarajan †,‡, Yongfei Wang *,†, Harlan M Krumholz *,†,§
PMCID: PMC3939721  NIHMSID: NIHMS497495  PMID: 23473413

Abstract

Objective

This study sought to analyze recent trends over time in heart failure (HF) hospitalization rates, length of stay (LOS), and in-hospital mortality by age groups using a large national dataset of U.S. hospital discharges.

Background

HF hospitalization rates, LOS, and mortality have fallen over the past decade for older Medicare beneficiaries, but whether this holds true for younger adults is unknown.

Methods

From the National Inpatient Sample (NIS), we calculated HF hospitalization rates, LOS, and in-hospital mortality from 2001–2009 using survey data analysis techniques.

Results

1,686,089 hospitalizations with a primary discharge diagnosis of HF were identified from NIS data between 2001 and 2009. The overall national hospitalization rate decreased from 633 to 463 hospitalizations per 100,000 persons, (− 26.9%, p-for-trend<0.001). However, statistically significant declines (p<0.001) were only observed for patients age 55–64 years (−36.5%) 65–74 years (−37.4%), and ≥75 years (−28.3%), but not for patients age 18–44 years (−12.8%, p=0.57) or 45– 55 years (−16.2%, p=0.04). Statistically significant declines in LOS were only observed for patients age 65 years and older. Overall in-hospital mortality fell from 4.5% to 3.3%, a relative decline of 27.4%, (p-for-trend <0.001), but patients age 18 to 44 years did not exhibit a significant decline (−8.1%, p-for-trend=0.18). In secondary analyses significant declines in HF hospitalization rate over time were observed for white men, white women, and black women, but not for black men (−9.5%, p-for-trend=0.43).

Conclusions

Younger patients have not experienced comparable declines in HF hospitalization, LOS, and in-hospital mortality as older patients. Black men remain a vulnerable population for HF hospitalization.

Journal subject codes: congestive heart failure, epidemiology, hospitalization, mortality

Introduction

The heart failure (HF) hospitalization rate has dropped substantially over the past decade in the Medicare population (1) —nearly 30% from 1998 to 2008—implying some success in preventative efforts. However, the etiology of HF often differs between younger adults and older Medicare beneficiaries. Hypertension is the most common etiology of HF in the younger adults, (2) while coronary artery disease becomes a more common risk factor for HF among middle-aged and older patients. (3,4). In addition, as age increases, the prevalence of HF with preserved ejection fraction rises dramatically, in conjunction with comorbid risk factors such as hypertension, atrial fibrillation, diabetes mellitus, and renal insufficiency. (3,5,6) As such, declines in the HF hospitalization rate observed for older Medicare patients may not necessarily indicate a corresponding decrease for younger populations. Whether HF hospitalization rates differ across age groups in the U.S. population is unknown, and the focus of this study.

In addition, we have a limited understanding of how HF hospitalization rates have changed over time across race-sex groups. One study of the Medicare population found that HF hospitalization rates declined at a slower rate for black men compared with other groups. (1) However, black patients are more likely to develop HF at younger ages than white patients, (2) and whether this affects differences across race with respect to declines in HF hospitalizations is unknown. Furthermore, black patients represent a higher proportion of the uninsured and Medicaid enrollees, (7) which may potentially lead to differences in HF hospitalizations across race compared with studies examining Medicare data alone. As such, confirming whether black men had slower declines in HF hospitalization rate in the general population is important, as it may indicate that this group is a particularly vulnerable population that would benefit from targeted preventative efforts against HF risk factors. (8,9)

Accordingly, we analyzed data from the National Inpatient Sample (NIS), a large national dataset of acute care hospitalizations that includes all age groups and all types of health insurance coverage to examine changes across patient age categories in HF hospitalization rates, length of stay (LOS), and in-hospital mortality between 2001 and 2009. Secondary analyses examined trends in HF hospitalization by race-sex categories.

Methods

Data

The NIS, collected by the Agency for Healthcare Research and Quality’s Healthcare Cost and Utilization Project, is the largest all-payer inpatient database publicly available in the U.S. Consisting of discharge data from over 1,000 hospitals across 44 states, the NIS was designed to approximate a 20% stratified sample of U.S. community hospitals.(10) Statistical sampling weights provided by the NIS allows extrapolation to calculate expected hospitalization rates for the nation.(11) NIS data was collected on all patients regardless of health insurance provider. The following NIS fields were used for this analysis: patient age, sex, race, principal and secondary diagnosis codes, admission date, discharge date, in-hospital death, insurance status, and state of hospitalization. Secondary analyses stratified by race-sex categories were conducted in a subset of patients hospitalized in states that reported complete data on patient race across all years to the NIS.

Study Cohort

A total of 71,371,439 hospital discharges were reported to the NIS from 2001–2009 from 44 states reporting data to NIS. We excluded the following hospitalizations: discharges in which patient age was less than 18 years (n=12,091,363), those with missing data on patient age, sex, admission date, discharge date, or in-hospital death (n=252,617), discharges in which patients were admitted and discharged alive the same day as such events may not have truly represented hospitalizations for acute conditions (n=1,0373,079), and discharges from states that did not report data for each year of the study period (n=9,648,462). HF hospitalizations were classified as those with a principal discharge diagnosis of HF based on the following International Classification of Diseases, 9th revision, Clinical Modification (ICD-9-CM) codes: 402.01, 402.11, 402.91, 404.01, 404.03, 404.11, 404.13, 404.91, 404.93, and 428.xx.

Statistical analyses

We conducted a pre-specified analysis calculating population-based HF hospitalization rates per 100,000 persons for each calendar year, with the numerator representing the number of HF hospitalizations and the denominator representing the population age 18 years and older from U.S. Census estimates for each state.(12) Survey analysis methods were employed that used hospital-level discharge weights provided by the NIS to estimate the number of HF hospitalizations on a national level.(13) HF hospitalization rates were calculated for the overall cohort and for subgroups of age (18–45, 45–54, 55–64, 65–74, and ≥75 years), sex, and, insurance status (Medicare, Medicaid, private insurance [including health maintenance organizations], self-pay, no charge, and other). Because a denominator population of individuals specifying particular types of health insurance could not be constructed for each year, differences in HF hospitalization rate by insurance status were not estimated. Differences in LOS and in-hospital mortality rates were able to be evaluated by insurance status as calculation of these rates used the hospitalization as the unit of analysis. Comorbidities were identified from ICD-9-CM secondary diagnosis codes and were classified according to hierarchical condition categories, similar to those used by the Centers for Medicare and Medicaid Services for calculating their 30-day HF mortality measure.(14) To evaluate whether HF hospitalization rates declined faster than the overall hospitalization rate any cause, we calculated the hospitalization rate per 100,000 persons for all principal diagnoses over the study period.

In-hospital survival curves were constructed that assumed that the discharge date recorded in NIS was the date of death, where the denominator represented the number of patients still hospitalized on a given hospital day, and the numerator represented the number of patients who were not recorded as having an in-hospital death on that hospital day. Survival curves were generated for three-year periods (2001–2003, 2004–2006, and 2007–2009) to examine how aggregate in-hospital mortality changed over the study period.

Statistical significance of the annual changes in HF hospitalization rate and in-hospital mortality were assessed using Poisson regression that included a variable representing the linear trend from the baseline year of 2001; a similar analysis was conducted for LOS using linear regression. All p-values were two-sided with a significance threshold of p<0.001. Statistical analyses were performed using SAS 9.2 (SAS Institute, Cary, North Carolina).

Results

Our analytic cohort consisted of 48,305,918 hospitalizations for any principal discharge diagnosis across 29 states that reported data for each year between 2001 to 2009, of which 1,686,089 hospitalizations were for a principal discharge diagnosis of HF. After applying sampling weights to calculate the number of national discharges for HF from the NIS sample, this represents an estimated 8,249,759 HF hospitalizations in the U.S. from 2001–2009. HF patients were predominantly elderly with slightly more than half of the cohort aged 75 years and older. (Table 1) In 2001 there were slightly more women than men (55.0% v 45.0%) which diminished by 2009 (50.6% v 49.4%). White patients comprised the majority of patients; the proportion of patients with unknown race decreased from 27.7% to 10.7% as more states reported race data to NIS over the study period.

Table 1.

Characteristics of patients hospitalized for heart failure

Description 2001 2002 2003 2004 2005 2006 2007 2008 2009 p-for-trend
N (HF hospitalizations) 999801 948849 946043 970085 965377 931124 882364 803318 802796 <0.001
Age (years)
  18 to <45 3.7% 4.0% 4.0% 4.2% 4.2% 4.4% 4.5% 4.3% 4.1% 0.048
  45 to <55 7.2% 7.9% 7.8% 8.2% 8.1% 8.8% 8.9% 8.5% 8.6% 0.004
  55 to <65 13.0% 13.5% 14.1% 14.1% 13.7% 14.1% 14.4% 14.3% 14.3% 0.005
  65 to <75 22.9% 22.7% 22.0% 21.5% 21.0% 20.4% 20.4% 20.0% 20.3% <0.001
  >=75 53.2% 52.0% 52.1% 52.0% 53.0% 52.2% 51.9% 52.9% 52.7% 0.942
Gender
  Male 45.0% 45.6% 46.1% 47.1% 48.3% 48.7% 48.9% 49.3% 49.4% <0.001
  Female 55.0% 54.4% 53.9% 52.9% 51.7% 51.3% 51.1% 50.7% 50.6% <0.001
Race
  White 51.6% 51.3% 49.3% 51.3% 53.3% 50.1% 50.3% 54.6% 58.9% 0.080
  Black 12.2% 14.1% 13.7% 15.0% 12.0% 14.9% 15.7% 15.3% 17.2% 0.019
  Hispanic 5.9% 6.3% 8.3% 6.6% 6.4% 7.7% 6.9% 6.9% 8.2% 0.167
  Other 2.6% 3.1% 2.9% 3.0% 2.7% 2.9% 3.5% 4.5% 5.0% 0.008
  Unknown 27.7% 25.2% 25.8% 24.1% 25.5% 24.3% 23.6% 18.8% 10.7% 0.009
Primary Insurance
  Medicare 75.6% 76.0% 76.4% 75.2% 76.5% 75.4% 74.0% 73.8% 73.8% 0.014
  Medicaid 6.6% 6.9% 7.4% 7.5% 7.3% 7.7% 7.6% 7.5% 8.0% 0.003
  Private including HMO 13.7% 12.8% 11.9% 12.4% 11.5% 11.6% 12.7% 13.5% 12.5% 0.780
  Self Pay 2.5% 2.5% 2.3% 3.0% 3.1% 3.2% 3.3% 3.1% 3.8% 0.001
  No charge 0.2% 0.2% 0.3% 0.4% 0.3% 0.4% 0.5% 0.4% 0.4% 0.003
  Other 1.4% 1.5% 1.6% 1.6% 1.2% 1.7% 1.8% 1.7% 1.5% 0.241
Census Region
  New England 4.6% 5.3% 5.0% 6.6% 6.1% 6.4% 6.9% 5.6% 5.6% 0.161
  Mid Atlantic 10.9% 11.7% 13.0% 15.3% 15.8% 17.4% 16.1% 12.2% 14.0% 0.215
  South Atlantic 24.2% 26.1% 26.4% 25.3% 24.9% 24.4% 25.0% 26.5% 26.7% 0.340
  West South Central 17.8% 13.1% 11.9% 11.3% 10.8% 10.7% 12.1% 13.0% 12.1% 0.174
  East South Central 6.6% 7.1% 8.2% 7.4% 7.5% 7.4% 5.5% 6.4% 5.8% 0.122
  West North Central 10.8% 10.5% 10.5% 9.8% 9.4% 10.4% 9.4% 10.3% 9.9% 0.133
  East North Central 10.5% 9.4% 9.7% 9.9% 10.5% 8.5% 9.7% 9.3% 9.5% 0.243
  Mountain 1.3% 1.7% 1.5% 1.6% 1.4% 1.4% 1.6% 2.0% 1.6% 0.157
  Pacific 13.1% 15.1% 13.9% 12.8% 13.5% 13.3% 13.8% 14.8% 14.7% 0.395
Cardiovascular
  PCI 4.3% 4.5% 4.6% 4.8% 5.4% 5.9% 6.4% 7.2% 7.2% <0.001
  CABG 13.7% 13.5% 13.1% 13.3% 13.5% 13.8% 13.6% 14.0% 13.9% 0.111
  Acute Myocardial Infarction 2.4% 2.4% 2.5% 2.4% 2.5% 2.2% 2.3% 2.3% 2.4% 0.244
  Unstable Angina 4.0% 3.8% 3.5% 3.3% 3.1% 2.9% 2.7% 2.7% 2.5% <0.001
  Chronic atherosclerosis 47.9% 48.1% 48.8% 49.4% 50.1% 49.8% 50.8% 52.0% 52.4% <0.001
  Cardio-respiratory failure and shock 7.2% 7.4% 7.6% 7.8% 7.2% 9.0% 11.4% 12.3% 15.7% 9.002
  Valvular or Rheumatic Heart Disease 17.7% 18.4% 19.2% 19.7% 20.8% 21.2% 21.6% 21.0% 21.9% <0.001
Comorbidity
  Hypertension 39.7% 42.3% 43.4% 43.9% 43.5% 43.6% 54.3% 57.1% 59.0% <0.001
  Stroke 0.5% 0.5% 0.5% 0.5% 0.5% 0.5% 0.4% 0.5% 0.5% 0.031
  Renal Failure 11.7% 13.2% 14.9% 16.8% 21.8% 32.7% 37.6% 40.8% 44.4% <0.001
  COPD 29.1% 30.1% 30.5% 31.2% 31.7% 31.5% 32.1% 30.5% 31.1% 0.064
  Pneumonia 7.2% 7.7% 8.1% 8.3% 9.7% 11.8% 12.9% 14.0% 14.6% <0.001
  Diabetes and Complications 39.8% 40.5% 40.7% 40.5% 40.3% 40.5% 41.8% 42.2% 42.8% 0.002
  Protein-Calorie Malnutrition 1.6% 1.5% 1.6% 1.9% 2.0% 1.9% 2.3% 2.8% 3.4% <0.001
  Dementia and Senility 5.9% 6.2% 6.3% 6.5% 6.8% 7.2% 7.7% 8.4% 8.6% <0.001
  Hemiplegia, Paralysis, Functional Disability 3.1% 3.2% 3.0% 3.0% 2.9% 2.9% 3.1% 3.6% 3.6% 0.132
  Vascular or Circulatory Disease 8.9% 9.2% 9.0% 9.5% 9.8% 10.0% 10.9% 11.7% 11.7% <0.001
  Metastatic Cancer and Acute Leukemia 1.4% 1.4% 1.4% 1.4% 1.4% 1.4% 1.5% 1.6% 1.6% 0.003
  Trauma 2.2% 2.5% 1.4% 1.5% 1.5% 1.5% 1.7% 1.9% 1.9% 0.415
  Major Psychological Disorders 1.8% 1.8% 1.8% 1.9% 1.8% 2.0% 2.1% 2.5% 2.5% 0.002
  Liver and Biliary Disease 1.3% 1.5% 1.5% 1.7% 1.6% 1.9% 1.9% 1.9% 2.1% <0.001
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Abbreviations: CABG, coronary artery bypass surgery; COPD, chronic obstructive pulmonary disease; HMO, health maintenance organization; HF, heart failure; PCI, percutaneous coronary intervention

Approximately three-quarters of the patients hospitalized with HF had Medicare insurance coverage. The majority (90.9%) of HF patients age 65 years and older were insured by Medicare; the majority of HF patients younger than 65 were covered by insurance other than Medicare (69.6%) including private health insurance (30.4%) and Medicaid (23.5%). (Figure 1)

Figure 1.

Figure 1

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Distribution health insurance status, by age≥65y and age<65y

Several comorbidities were more prevalent over the study period, including renal failure (from 11.7% to 44.4%, p-for-trend<0.001), hypertension (39.7% to 59.0%, p-for-trend<0.001), and cardio-respiratory failure or shock (7.2% to 15.7%, p-for-trend=0.002).

HF hospitalization rate

The national HF hospitalization rate declined from 633 to 463 hospitalizations per 100,000 persons from 2001 to 2009, a relative 26.9% decrease (p-for-trend<0.001). (Table 2) The aggregate hospitalization rate for any principal diagnosis also fell (from 17,087 to 14,183 per 100,000 persons, p-for-trend<0.001), a relative 17.0% decrease that was not statistically different than the HF hospitalization rate (p=0.002). Statistically significant declines in the HF hospitalization rate were observed for patients aged 55–64 years (from 704 to 447 per 100,000 persons, −36.5%, p-for-trend<0.001), 65–74 years (from 1709 to 1070 per 100,000 persons, −37.4%, p-for-trend <0.001) and ≥75 years (from 4272 to 3064 per 100,000 persons, −28.3%, p-for-trend<0.001). No statistically significant changes in HF hospitalization rates were observed for ages 18–44 (from 44 to 38 per 100,000 persons, −12.8%, p-for-trend =0.57) or 45–54 years (from 247 to 207 per 100,000 persons, −16.2%, p-for-trend=0.04). (Figure 2) The HF hospitalization rate declined for women (from 676 to 457 per 100,000 persons, −32.3%, p-for-trend <0.0001, while also declined for men but did not reach statistical significance (from 588 to 469 per 100,000 persons, −20.2%, p-for-trend=0.003). Statistically significant declines in the HF hospitalization rate were observed in five of the nine U.S. census regions.

Table 2.

Heart failure hospitalization rate per 100,000

Description 2001 2002 2003 2004 2005 2006 2007 2008 2009 relative
change		 p-for-trend
(2001–2009)
Overall 633 594 586 593 584 556 521 469 463 −26.9% <0.001
Age Categories
  18 to <45 44 45 45 48 48 49 47 41 38 −12.8% 0.570
  45 to <55 247 254 245 259 248 257 241 207 207 −16.2% 0.036
  55 to <65 704 653 649 640 593 563 526 462 447 −36.5% <0.001
  65 to <75 1709 1608 1552 1541 1487 1372 1266 1089 1070 −37.4% <0.001
  >=75 4272 3894 3827 3868 3861 3624 3373 3102 3064 −28.3% <0.001
Gender
  Male 588 558 557 575 580 557 523 474 469 −20.2% 0.003
  Female 676 627 613 611 588 556 520 464 457 −32.3% <0.001
Census Region
  New England 521 567 528 721 660 664 672 492 490 −5.9% 0.551
  Mid Atlantic 526 530 583 700 716 757 663 452 518 −1.5% 0.804
  South Atlantic 723 728 724 698 670 623 594 567 563 −22.1% <0.001
  West South Central 861 597 537 517 491 465 497 482 450 −47.8% <0.001
  East South Central 891 901 1024 939 942 884 606 640 578 −35.1% <0.001
  West North Central 810 738 730 695 660 695 589 581 555 −31.5% <0.001
  East North Central 687 569 577 597 619 472 499 424 424 −38.2% <0.001
  Mountain 277 329 284 308 263 249 253 289 226 −18.3% 0.011
  Pacific 395 427 385 359 374 353 342 330 322 −18.5% 0.003
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Figure 2.

Figure 2

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Heart failure hospitalization rate by age category, per 100,000 (2001–2009)

Sensitivity analyses that examined age categories in 5-year intervals and found that patients aged 55 years and older had statistically significant declines in the HF hospitalization rate (p<0.001) with marginal statistical significance for patients aged 45–49 and 50–54 years (p=0.07 and 0.01, respectively); no statistically significant declines in HF hospitalization rates were found for patients in 5-year age categories <45 years (all p>0.54).

In secondary analyses of 36,229,163 patients hospitalized in the 20 states that reported complete data on patient race, the overall decline in HF hospitalization rate was 24.7%, (p-for-trend <0.001) comparable to the primary analysis examining all states. Statistically significant declines were observed for white and black women (white women, −33.5%; black women −30.9%). White men had a non-statistically significant decrease in HF hospitalization rate (− 24.7%, p-for-trend=0.003), while black men did not have a statistically significant change in HF hospitalization rate (− 9.5%, p-for-trend=0.43) over the study period. Among patients age 75 years or older, there was no significant difference (p=0.59) between the change in HF hospitalization rate over time between black men (−29.8%, p-for-trend <0.001) and white men (−26.0%, p-for-trend <0.001). (Supplemental Table) While changes in HF hospitalization rate over time were not statistically significant for either black or white men younger than 55 years, there was essentially no change in the point estimates of relative change of HF hospitalization rate for black men 18–44 years (−2.7%, p-for-trend=0.70) or 45–54 years (+3.7%, p-for-trend=0.02) in contrast to white men 18–44 years (−21.0%, p-for-trend=0.55) or 45–54 years (− 17.6%, p-for-trend=0.08).

Length of stay

Observed mean LOS for HF hospitalization fell from 5.6 days to 5.3 days, a relative 6.4% decline (p-for-trend <0.001) (Table 3). Median LOS was 3.7 days in 2001 (25th to 75th percentile 2.1 to 6.3 days) which declined to 3.5 days (25th to 75th percentile 2.0 to 5.9 days) by 2009, (p-for-trend <0.001). Examined across patient age, statistically significant declines in LOS were only observed for those 75 years and older (− 8.5%, p-for-trend<0.001). Statistically significant declines in LOS for HF hospitalizations were observed for Medicare patients ( −7.1%, p-for-trend<0.001), while those with other insurance coverage was not associated with significant changes over time. The Mid Atlantic census region had the largest decline in LOS (−13.1%, p-for-trend <0.001). Secondary analyses were performed examining with renal failure or cardio-respiratory failure/shock, two comorbidities with large increases in prevalence over time. Patients with renal failure or cardio-respiratory failure/shock had significantly longer LOS (p<0.001) compared with patients without renal failure or cardio-respiratory failure/shock. Declines in LOS were steeper for patients with renal failure or cardio-respiratory failure/shock, compared with patients without renal failure or cardio-respiratory failure/shock.

Table 3.

Length of stay for heart failure hospitalization

Description 2001 2002 2003 2004 2005 2006 2007 2008 2009 relative
change		 p-for-
trend
(2001–2009)
ALL 5.6 5.6 5.6 5.6 5.5 5.4 5.4 5.3 5.3 −6.4% <0.001
Age Categories
  18 to <45 5.1 5.1 5.1 5.0 5.0 4.9 5.0 5.3 5.0 −2.0% 0.559
  45 to <55 5.2 5.2 5.2 5.2 5.1 5.0 5.0 5.1 5.1 −1.8% 0.553
  55 to <65 5.6 5.6 5.5 5.6 5.3 5.3 5.4 5.4 5.5 −2.7% 0.061
  65 to <75 5.7 5.7 5.6 5.6 5.5 5.5 5.4 5.4 5.4 −5.0% 0.007
  >=75 5.7 5.7 5.6 5.7 5.6 5.5 5.4 5.3 5.3 −8.5% <0.001
Gender
  Male 5.6 5.5 5.5 5.5 5.4 5.3 5.3 5.3 5.2 −5.5% 0.003
  Female 5.7 5.7 5.6 5.7 5.6 5.5 5.4 5.4 5.3 −6.9% <0.001
Insurance status
  Medicare 5.7 5.7 5.6 5.6 5.5 5.5 5.4 5.4 5.3 −7.1% <0.001
  Medicaid 6.1 5.9 6.0 5.9 5.8 5.6 5.9 5.7 5.6 −7.3% 0.074
  Private including HMO 5.3 5.1 5.1 5.2 5.1 5.0 4.9 5.1 5.2 −2.6% 0.090
  Self Pay 4.8 4.9 4.7 5.0 4.6 4.8 4.8 4.6 4.8 −1.5% 0.268
  No charge 5.0 5.4 4.7 5.1 5.2 4.7 5.5 5.3 5.0 1.1% 0.349
  Other 5.0 5.4 5.4 4.9 4.9 4.9 5.1 4.9 4.9 −2.1% 0.396
Census Region
  New England 5.6 5.3 5.2 5.4 5.4 5.2 5.4 5.6 5.1 −8.4% 0.787
  Mid Atlantic 7.3 7.2 6.7 7.0 6.7 6.5 6.4 6.3 6.3 −13.1% <0.001
  South Atlantic 5.4 5.4 5.5 5.3 5.2 5.2 5.2 5.2 5.2 −4.1% 0.131
  West South Central 5.3 5.3 5.3 5.3 5.1 5.0 5.0 5.2 4.9 −6.2% 0.093
  East South Central 5.5 5.7 5.5 5.5 5.4 5.3 5.2 5.2 5.1 −6.7% 0.436
  West North Central 5.4 5.4 5.2 5.3 5.2 4.9 5.0 5.0 4.8 −9.8% 0.058
  East North Central 6.0 5.9 5.9 5.7 5.6 5.4 5.4 5.4 5.5 −8.5% 0.056
  Mountain 5.2 4.9 5.0 4.8 4.6 4.7 4.9 5.1 4.8 −8.5% 0.133
  Pacific 5.3 5.2 5.2 5.1 5.1 5.1 5.0 5.2 5.1 −3.8% 0.635
Selected comorbidities
  Renal Failure
  No 5.3 5.2 5.1 5.1 4.9 4.7 4.7 4.6 4.6 −13.7% <0.001
  Yes 8.5 8.5 8.2 8.1 7.4 6.7 6.5 6.4 6.2 −26.6% <0.001
  Cardio-respiratory failure and shock
  No 5.3 5.2 5.2 5.2 5.1 5.1 5.0 5.0 4.8 −8.6% <0.001
  Yes 10.1 10.3 10.1 10.1 9.8 8.7 8.2 8.1 7.7 −24.3% <0.001
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In secondary analyses among patients hospitalized states that reported complete race data, the overall decline in LOS was 7.9%, (p-for-trend <0.001). Statistically significant reductions in LOS were observed for white men (−7.1%), white women (−8.8%) and black women (−8.6%). LOS fell over time for black men (−7.8%, p-for-trend=0.18) but did not reach statistical significance.

In-hospital mortality

Observed in-hospital mortality for HF patients fell from 4.5% to 3.3%, a relative decline of 27.4%, (p-for-trend <0.001). There was increasingly higher survival during the HF hospitalization across the first, middle, and last thirds of the study period. (Figure 3) Statistically significant reductions in in-hospital mortality were observed for patients age 45 to 54 years (−21.7%), 55 to 64 years (−35.7%), 65 to 74 years (−29.0%) and 75 years or older (−25.4%); however patients age 18 to 44 years did not exhibit a significant decline in in-hospital mortality (−8.1%, p=0.18). (Table 4) Patients with Medicare, Medicaid, private insurance, and self pay coverage had significant declines in in-hospital mortality. Improvements in in-hospital mortality were observed across all census regions, except for the New England and Mountain regions. Similar to LOS, patients with renal failure or shock had significantly higher in-hospital mortality compared with patients without renal failure or shock, and faster rates of decline over the study period.

Figure 3.

Figure 3

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In-hospital survival for HF hospitalization, by hospital day

Table 4.

In-hospital mortality for heart failure hospitalization, per 100

Description 2001 2002 2003 2004 2005 2006 2007 2008 2009 relative change p-for-
trend
(2001−2009)
ALL 4.5 4.3 4.2 4.0 3.8 3.6 3.3 3.3 3.3 −27.4% <0.001
Age Categories
  18 to <45 1.7 1.6 1.6 1.7 1.2 1.4 1.4 1.4 1.5 −8.1% 0.181
  45 to <55 1.6 1.7 1.7 1.7 1.6 1.3 1.3 1.3 1.3 −21.7% <0.001
  55 to <65 2.7 2.4 2.3 2.4 1.9 1.9 1.7 1.6 1.7 −35.7% <0.001
  65 to <75 3.6 3.5 3.3 3.2 2.9 2.8 2.5 2.5 2.5 −29.0% <0.001
  >=75 6.0 5.8 5.6 5.4 5.2 4.9 4.6 4.5 4.5 −25.4% <0.001
Gender
  Male 4.7 4.5 4.2 4.1 3.8 3.5 3.2 3.3 3.3 −30.5% <0.001
  Female 4.4 4.1 4.1 3.9 3.8 3.6 3.4 3.4 3.3 −24.8% <0.001
Insurance status
  Medicare 4.9 4.7 4.5 4.3 4.1 3.9 3.6 3.6 3.6 −27.4% <0.001
  Medicaid 2.6 2.5 2.6 2.3 1.8 1.8 1.8 1.8 1.7 −32.5% <0.001
  Private including HMO 3.8 3.1 3.3 3.3 3.2 3.0 3.1 2.9 3.0 −21.0% 0.009
  Self Pay 2.3 2.1 1.9 2.6 2.1 1.7 1.7 1.6 1.1 −52.1% <0.001
  No charge 1.7 0.8 1.1 2.3 1.4 1.2 1.8 0.6 2.3 33.2% 0.757
  Other 4.6 5.2 6.5 5.1 4.7 3.7 3.8 4.8 6.0 31.2% 0.660
Census Region
New England 5.0 4.6 4.1 4.1 3.9 4.0 3.4 3.7 3.8 −23.3% 0.001
Mid Atlantic 5.4 5.5 4.6 4.8 4.7 4.1 3.9 4.0 3.8 −29.9% <0.001
South Atlantic 4.3 3.8 3.9 3.7 3.2 3.1 2.9 2.8 3.1 −28.8% <0.001
West South Central 3.9 3.5 3.9 3.5 3.3 3.3 2.9 2.8 3.0 −23.7% <0.001
East South Central 4.5 4.7 4.6 4.5 4.1 3.6 3.6 3.7 3.4 −23.5% <0.001
West North Central 4.8 4.5 3.9 4.0 4.1 3.7 3.5 3.6 3.6 −25.0% <0.001
East North Central 4.8 4.4 4.2 3.8 3.5 3.4 3.1 2.9 2.9 −39.5% <0.001
Mountain 4.1 4.1 3.9 3.9 2.8 3.5 3.6 3.5 2.9 −29.4% 0.006
Pacific 4.6 4.3 4.4 4.0 3.9 3.7 3.6 3.8 3.3 −27.9% <0.001
Selected comorbidities
  Renal Failure
  No 3.6 3.3 3.2 3.0 2.8 2.6 2.3 2.5 2.3 −36.8% <0.001
  Yes 11.3 10.5 9.7 9.0 7.2 5.5 4.9 4.6 4.5 −60.0% <0.001
  Cardio-respiratory failure and shock
  No 3.0 2.7 2.6 2.5 2.4 2.2 2.0 2.0 1.8 −39.6% <0.001
  Yes 24.7 23.8 22.7 22.4 21.6 16.7 13.1 12.9 11.3 −54.2% <0.001
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Abbreviations: HMO, health maintenance organization

In secondary analysis, the overall decline in in-hospital mortality restricted to states reporting complete patient race data was statistically significant (−29.1%, p-for-trend=<0.001) and similar to the primary analysis. All race-sex groups exhibited statistically significant declines in-hospital mortality: white men (−27.7%), white women (−24.6%), black men (−39.2%), and black women (−31.7%) (p-for-trend <0.001).

Discussion

Using a national all-payer database of hospital discharges in the U.S., we found that the overall national HF hospitalization rate fell by a relative 26.9% from 2001 to 2009. This decline is similar in magnitude to the 29.5% decrease in HF hospitalization rates observed in the Medicare population from 1998 to 2008.(1) However, our study adds to prior work by demonstrating the HF hospitalization rate did not decrease significantly for patients age 18–44 years and 45–55 years, indicating that trends for HF hospitalization rate observed for older Medicare patients do not necessarily apply to younger populations. An Australian study of HF hospitalization trends (15) also found that reductions in the HF hospitalization rate was predominately limited to older populations: from 1990–1993 to 2002–2005 the HF hospitalization rate fell by 44% for men and by 46.5% for women age 65–74 years, but the decline in HF hospitalization rate was much slower for women <65 years (−11.5%), and in fact increased slightly over time for men (+1.7%).

While the overall reduction in the HF hospitalization rate represents a success, our findings illustrate that challenges remain for ensuring comparable improvements for younger patients. One possible explanation for the lack of decline in HF hospitalization for younger patients is that HF risk factor control may have improved more in older patients. For example, hypertension is an important cause of diastolic HF, (16) but hypertension awareness and treatment is considerably lower for younger patients < 40 years compared with those ≥40 years. (17,18) Coronary artery disease is another major cause of HF that is more prevalent with older age, and the declines in ischemic heart disease events over the past decade in observed older patients (19) may have been less dramatic for younger patients. Other causes of heart failure, such as such as infectious etiologies and peripartum cardiomyopathy commonly manifest at younger ages,(20) and the incidence of these conditions may not have declined as rapidly as HF etiologies found more frequently in older patients.

Our overall findings of substantial decreases in HF hospitalization rates over time are consistent with reports from several countries. In Sweden (1988 to 2000),(21) the Netherlands (1980 to 1999), (22) New Zealand study (1988 to 2008),(23) and Scotland (1986 to 1999)(24) the HF hospitalizations rates peaked in the 1990s, and with significant declines afterwards. Two studies outside of the U.S. have evaluated HF hospitalization trends since 2000. In Canada (25) the overall age-standardized HF rate (including hospitalizations, outpatient clinic and emergency department visits) decreased by 25.1% from 1999 to 2007 (25); faster declines in HF hospitalization rate alone were observed. In New Zealand (23) the HF hospitalization rate peaked in 1998–1999 and decreased by 28.6% for men and 31.2% for women until 2008. Thus, the decline in the HF hospitalization rate over the most recent decade appears in line with observations from other developed nations.

Reasons for the decline in HF hospitalization rate are likely multi-factorial. One possibility is that control of risk factors leading to HF have improved over time. For example, hypertension control in the U.S. has increased from 27.3% from 1988–1994 to 50.1% in 2007–2008.(17) Incidence of ischemic heart disease has decreased dramatically over the past decade, (19,26) with parallel increases in the use of angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, beta-blockers, and statins in the U.S. (19) Another contributor to the decline in HF hospitalization rate may be due to shifting of location of HF care from hospitals to emergency department or outpatient settings. The Canadian study found a greater proportion of HF cases diagnosed in outpatient clinics and emergency department over time, with HF incidence rates declining faster for hospitals compared with other clinical settings; (25) nevertheless, the overall HF incidence rate from all locations fell over time suggesting that there has been some overall reduction in HF incidence as well in Canada. A U.S. study examining Medicare hospital and outpatient billing claims found a modest decline in overall HF incidence from 1994 to 2003, decreasing from 32 to 29 per 1000 person-years. (27)

Our study found that trends in LOS also diverged according to patient age. While patients of typical Medicare age (≥65 years) had statistically significant reductions in LOS over the study period, this was not the case for patients younger than 65 years. Understanding the reasons for the lack of decline in LOS in younger patients will ultimately require clinical data, but we speculate that it may be related in some part to differences in comorbidity burden. Older patients typically have multiple comorbidities, and thereby perhaps more opportunities to reduce LOS through more intensive use of skilled nursing facilities or increased referral to hospice, both of which have increased in the Medicare population over the past decade. (28)

Our study also noted divergence across age groups for in-hospital mortality, with no significant change for patients aged 18–44 years, but significant decreases for older patients. This may be due to differences in HF etiology or severity of illness in younger adults compared with older adults. Differences in discharge disposition may again play a role. While in-hospital mortality has decreased over the past decade among Medicare patients, 30-day mortality has decreased at a slower rate due to a greater proportion of deaths that occur after discharge from HF hospitalization. (28) As with LOS, the lack of improvement in in-hospital mortality may potentially be explained if a greater number of older patients were discharged to or died in non-hospital-based facilities, while younger patients were more likely to remain hospitalized until they died. Because the NIS does not track individual patients after hospital discharge, this hypothesis will need to be verified using other sources of data.

The prevalence of comorbidities of patients hospitalized for HF increased over time in our study sample. This is consistent with a study of the U.S. Veterans Administration population (29) demonstrating an increase in the comorbidity of hospitalized HF patients. Other countries have also documented increasing comorbidities. For example, in Western Australia the proportion of HF patients with renal failure increased from 6.3% to 17.3% and with diabetes mellitus increased from 18.5% to 26.9%; (15) in Scotland, the proportion of male HF patients with renal failure increased from 4.1% to 18.5%, and diabetes mellitus increased from 7.6% to 19.4%. (24) These findings either represent a true clinical increase in the burden of comorbidity, or are explained by the additional coding of secondary diagnoses over time. NHANES reports that the prevalence of several comorbidities has increased over time in HF patients—renal disease increased by 11.2 percentage points from 1988 to 2008, diabetes increased by 13.6 percentage points, and obesity increased by 14.0 percentage points. (30) This data, based on patient interviews and examination of subjects, strongly suggest that the comorbidity profile of HF patients has worsened over time. While it is possible that hospitals may have been more aggressive in coding secondary diagnoses over time for reimbursement purposes, such “upcoding” (31) seems unlikely to fully explain the increase in comorbidities seen in cohorts in Australia, Scotland and the U.S. Veterans Administration, given that these are government-run health care systems with little incentive to upcode for added reimbursement. Furthermore, substantial upcoding would alter the relationship between comorbidity and outcomes (such as mortality) as more patients with less severe comorbidities were included. However, this does not appear to be the case, at least in the Medicare population, as the coefficients of the CMS HF mortality model have remained stable from 2005 to 2008.(32,33)

Our secondary analyses of patients with renal failure or cardio-respiratory failure/shock confirm that patients with these comorbidities were indeed more complex, with higher LOS and in-hospital mortality than patients without these comorbidities. While the steeper decline over time in LOS and in-hospital mortality for patients with renal failure or cardio-respiratory failure/shock may potentially indicate that additional patients with less severe comorbidity were coded over time, this would also occur if patients with renal failure or cardio-respiratory failure/shock were more likely to be discharged to skilled nursing facilities or hospice over the study period. Ultimately, studies using clinical data will be required to determine whether the increase in comorbidities reflect a higher threshold for HF hospitalization, differences in coding of secondary diagnoses, or more intensive utilization of post-discharge facilities over time.

Secondary analyses also confirm that the HF hospitalization rate fell more slowly for black men compared with other race-sex groups. A prior study of Medicare beneficiaries(1) also reported that reductions in HF hospitalization rate lagged for black men, but until this time no large scale study had verified in a general non-Medicare population. A small study that analyzed hospital discharge data from Tennessee over 1997–2006, and reported that black men had 28.2% increase in age-adjusted HF hospitalization rate, (34) higher compared with other race-sex groups (range 4.0% to 11.7%). Taken together, these studies strongly suggest that black men represent a particularly vulnerable population for HF hospitalization.

We speculate that black men had a slower rate of decline in HF hospitalizations in part due to differences in risk factor management. The Multi-Ethnic Study of Atherosclerosis and the Coronary Artery Risk Development in Young Adults study suggested that the excess risk of developing HF among black patients was primarily due to higher rates of hypertension, obesity, and diabetes mellitus.(2,35) Prevalence of obesity and diabetes mellitus have increased faster in black men compared with other race-sex groups. (36,37) Hypertension has increased over the past two decades for men and black subjects, (17) yet black men have lower rates of blood pressure screening, awareness, treatment, and control of hypertension compared with other race-sex groups. (38,39) It was reassuring, however, to observe that the decline in in-patient mortality for black men hospitalized for HF was comparable to other race-sex groups. Of note, in-hospital mortality rates for black patients were lower than white patients, a finding also observed in other studies; (40,41) the reason for this phenomenon is not well understood as black HF patients have been found to receive comparable quality of HF care, as assessed by use of angiotensin-converting enzyme inhibitors and angiotensin receptor blockers; (41) the lower in-hospital mortality rate among black patients may represent differences in HF etiology, disease progression, or severity of HF among hospitalized patients.

Limitations

Our study was limited by the fact that HF hospitalizations were identified through ICD-9-codes and not clinically confirmed. ICD-9-CM codes have high specificity (~95%) and positive predictive value for HF (~95%), (42–49) but our findings would only be affected if HF coding patterns changed over time. Second, we were unable to examine subcategories of HF, i.e. systolic versus diastolic HF, and ischemic versus non-ischemic HF, nor were we able to assess severity of HF hospitalization such as use of care in the intensive care unit. Third, the NIS does not track individual patients over time, and as such we were unable to determine whether changes in HF hospitalization rates represented declines in unique individuals hospitalized or declines in readmission after index HF hospitalizations. Similarly we were unable to assess whether the decline in HF hospitalizations presented a decrease in incident or prevalent cases; however, studies of Medicare patients suggest that the decline in HF hospitalization rate was almost entirely due to new cases.(1) Lastly, we were only able to examine in-hospital outcomes and were not able to assess whether declines in inpatient mortality which may reflect shorter LOS; we were unable to examine whether post-discharge mortality increased to offset improved inpatient outcomes.

Conclusion

Using a large, all-payer population of U.S. adults, we observed a 26.9% decrease in the overall adjusted HF hospitalization rate from 2000 to 2009, but younger patients have not experienced comparable declines in HF hospitalization, LOS, and in-hospital mortality as older patients. Black men remain a vulnerable group with no significant decline in HF hospitalization rate over the past decade.

Supplementary Material

01

Acknowledgments

Acknowledgments and Funding Sources:

This work was supported by an Agency for Healthcare Research and Quality (AHRQ) Career Development Award (1K08HS018781-01) for Dr. Chen. Drs. Krumholz, Chen and Wang are supported by grant U01 HL105270-02 (Center for Cardiovascular Outcomes Research at Yale University) from the National Heart, Lung, and Blood Institute. Dr. Dharmarajan is supported by an NIH T32 training grant in cardiovascular disease (2T32HL007854-16A1) from Columbia University.

Footnotes

Disclosures:

Dr. Krumholz reports that he chairs a cardiac scientific advisory board for UnitedHealth and is the recipient of a research grant from Medtronic, Inc. through Yale University.

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