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Hospitalization in the United States, 2002

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Executive Summary

The United States (U.S.) spends approximately one-third of its health care dollar on hospital care, making hospitalizations the single most expensive component of the health care system. Information about hospitalizations is therefore essential for decisionmakers seeking to understand how well the system is working and to improve its efficiency and quality. Hospitalization in the United States, 2002 summarizes information from the Nationwide Inpatient Sample (NIS), an all-payer hospital database maintained by AHRQ. This report updates an earlier Fact Book that described hospital care in 1997. AHRQ has attempted to maintain the general content of the earlier document to allow for easy comparison between 1997 and 2002 hospital care information. A separate Fact Book (forthcoming) will compare use of procedures in U.S. hospitals between 1997 and 2002.

This fact book describes:

For the most part, the characteristics of hospitalizations remained consistent from 1997 to 2002. However, notable exceptions include significant increases in the percent of admissions that begin in the emergency department (ED), discharges with a comorbidity of hypertension, total charges for hospitalizations, and obesity-related procedures. These differences are highlighted and elaborated upon in this report.

In 2002, there were 37.8 million discharges from U.S. acute care hospitals, with aggregate charges of $650 billion. About 85 percent of discharges are from metropolitan hospitals and 45 percent are from teaching hospitals. Nearly three-quarters of discharges are from private not-for-profit hospitals, while 13 percent are from non-Federal government hospitals and 23 percent are from for-profit hospitals.

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Who Is Admitted to the Hospital?

Gender and Age Characteristics

Women are hospitalized more frequently than men. Of the 38 million hospital stays in the U.S., nearly 60 percent are for women. Women account for even more hospital care in the 18-44 age group, where nearly three times as many women than men are hospitalized. The primary reasons for the high rate of hospitalizations for women continue to be related to pregnancy and childbirth. These rates have remained essentially unchanged since 1997.

Rates of hospitalization also vary greatly by age group. The elderly account for a disproportionate share of hospitalizations. For example, while individuals age 65 and older comprise about 12 percent of the U.S. population,1 they account for approximately 35 percent of all hospital stays. The rates of hospitalization by gender are largely influenced by age. While younger women ages 18-44 are hospitalized at higher rates than men, older women are hospitalized at lower rates than their male counterparts. These figures closely resemble those from 1997.

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Why Are Patients Admitted to the Hospital?

Most Frequent Reasons for Hospitalization (Principal Diagnosesi)

Pregnancies and childbirth-related conditions account for nearly a quarter of hospitalizations. Twelve percent of hospital stays are related to pregnancy and childbirth (the mother's stay) and 11 percent are related to newborn infant births.

Generally, the reasons for hospitalizations did not vary greatly from 1997 to 2002. However, hospitalizations associated with stroke have fallen 12 percent, causing this category to drop from the 7th most frequent reason for admission to the 15th.

Most Common Reasons for Hospitalization by Age Groups

Reasons for hospitalization vary considerably by age group. The only top 10 condition that is common across each age group is an infection—pneumonia. For individuals 18-44, 9 of the top 10 reasons for hospitalization pertain to pregnancy and delivery. After these conditions are excluded, 3 of the top 10 conditions for this age group pertain to mental illness or substance abuse. However, alcohol-related conditions dropped 18 percent, from the 4th most common condition in 1997 among individuals 18-44 to the 11th in 2002. Depression is a top 10 condition for 3 different age groups: 1-17, 18-44, and 45-64.

Most Common Reasons for Hospital Stays by Body System

In 2002, diseases of the circulatory system continue to comprise the most frequent reason for hospitalization. These diseases account for 17 percent of all hospital stays. Conditions include coronary atherosclerosis, congestive heart failure, heart attack, and cardiac dysrhythmia. The next most common reasons for hospitalization continue to include pregnancy and childbirth (diagnoses received by women), followed by birth and other perinatal conditions (diagnoses received by babies). The top 10 conditions by body system (Major Diagnostic Category) are nearly identical to those identified in 1997 with one exception—diseases of the endocrine system now appear in the top 10. This shift is attributable to a 370-percent increase in one Diagnosis Related Group: surgical treatments for obesity.


The main reason for a hospitalization is recorded as the principal diagnosis on a patient's medical record. However, patients may also have secondary diagnoses, some of which are comorbidities—coexisting medical conditions that originated prior to the stay. Comorbidities can increase the costs and complications of hospital stays. Nearly 60 percent of all hospitalizations have at least one comorbidity and over a third of hospitalizations have two or more. This represents an increase from 1997, when 54 percent of all hospitalizations reported at least one comorbidity.

Most Common Comorbidities

Hypertension is the most common comorbidity, seen in about 30 percent of all records—an increase of 50 percent from 1997. Other common comorbidities include depression (seen in 5 percent of stays) and obesity (4 percent of stays), neither of which was among the top 10 comorbidities in 1997.

Variations in Comorbidities by Age Group

Comorbidities vary by age group. Fluid and electrolyte disorders are the most common comorbidities for patients under age 18 and they are the second most common comorbidity for the very old (80+ years of age). However, hypertension is, by far, the most common comorbidity for all adults. Drug abuse continues to be a top 10 comorbidity for children and adolescents up to age 17 (seen in 2 percent of all stays) and adults up to age 44 (seen in 5 percent of all stays), while alcohol abuse is a top 10 comorbidity for adults ages 18-64 (seen in 4 to 5 percent of all stays).

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How Are Patients Admitted to the Hospital?

Admission Status

Approximately half of hospitalizations continue to be routine—patients enter the hospital directly. The second most common source of admission is through the emergency department (ED), comprising 43 percent of all admissions. The remaining 7 percent of hospital admissions are from another hospital, another health care facility, or of unknown origin.

Admissions Through the Emergency Department

Admissions through the ED tend to be more expensive and serious. Since 1997 admissions through the ED rose by 18 percent. The highest rate of admission through the ED is seen among the uninsured—61 percent of uninsured hospitalizations begin in the ED. The mean charge for stays that originated in the ED is $19,000, which is 12 percent greater than the average charge for hospital stays overall.

The top 10 reasons for hospitalization (principal diagnosis) among patients admitted through the ED reveal serious, often life-threatening conditions. Six of the top 10 conditions for patients admitted through the ED relate to the circulatory system: congestive heart failure, chest pain, coronary atherosclerosis, heart attack, stroke, and irregular heartbeat. A new top 10 condition for patients admitted through the ED is affective disorders (primarily depression).

Pneumonia is the only top 10 infection-related condition for admission through the ED—this finding differs from 1997, when both pneumonia and septicemia were primary reasons for hospital admission through the ED. Septicemia dropped from the 10th to the 16th most frequent condition for admission through the ED. Asthma is also no longer in the top 10 conditions admitted through the ED—in 1997, asthma ranked 9th and in 2002, 13th.

Variations in ED Admissions by Age Group and Gender

The percentage of people admitted to the hospital through the ED increased for all age groups, and the increases are largest for elderly patients. For patients ages 1-17 years, there was a 10-percent increase in admissions through the ED—45 percent were admitted through the ED in 2002, as compared with 41 percent in 1997. For patients over age 45, the proportion admitted through the ED increased the most. For example, for patients 80+, 55 percent were admitted through the ED in 1997, as compared with 64 percent in 2002; this finding represents a 19-percent increase over the 5-year period.

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How Much Do Hospitals Charge?

Hospital charges are defined as the amount the hospital bills for the entire stay (excluding most physician fees). Charges may not reflect the actual cost of hospital care or how much is reimbursed. The average charge for a hospital stay is more than $17,300 (2002 dollars). This amount represents a 24-percent increase from 1997, when the average charge for a hospital stay was about $13,900 (adjusted for inflation). Over the same time period, the average cost for a hospital stay remained essentially the same—$7,500.

Conditions with the Highest Charges and Longest Length of Stay

The average length of a hospital stay is 5 days—a decrease of 6 percent since 1997. The most expensive condition is infant respiratory distress, for which the average charge is $90,000. Four of the top 10 most expensive conditions relate to the care of infants: respiratory distress, prematurity and low birthweight, heart defects, and intrauterine hypoxia/birth asphyxia (lack of oxygen during childbirth). Two of these conditions, respiratory distress and prematurity, also have the longest mean length of stay of all hospitalizations—24 days.

The most expensive conditions and those with the longest length of stay are relatively uncommon. The 10 most expensive conditions combined represent less than 2 percent of all discharges; the 10 conditions with the longest stays represent slightly more than 2 percent of all discharges.

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Who Is Billed for Hospital Care?

Payers of Hospital Care

HCUP data capture information on patients regardless of who pays for their care. Government (Medicare and Medicaid) is billed for 56 percent of all hospital stays; private insurance is billed for 36 percent of stays; and 5 percent of stays are uninsured. Other payer sourcesii are billed for approximately 3 percent of all hospital stays in U.S. community hospitals.

Hospital data provide information on charges—the amount billed—not on what was actually paid for care.iii Examining charges over time can provide insight into the relative growth in various areas.


Medicare, the federally sponsored health care program for the elderly and disabled, serves approximately 39 million individuals, most of whom are 65 years of age and older.2 Similar to 1997, Medicare continues to be billed for approximately 44 percent of the national hospital bill, while only 34 percent of hospital stays are for Medicare patients and only 12 percent of the U.S. population is 65 or older. The most common reason for hospitalizations among stays billed to Medicare is congestive heart failure, followed by pneumonia and coronary atherosclerosis.


Medicaid, the Federal- and State-government-sponsored health care program for low-income people, serves about 33 million individuals.2 Approximately 12 percent of the U.S. population is covered by Medicaid, and this program is billed for 18 percent of the national hospital bill.

Women and children continue to comprise a large portion of Medicaid enrollment, which results in Medicaid being billed for a larger share of certain conditions. Nearly 40 percent of newborn stays, 40 percent of stays for fetal distress, and nearly 50 percent of all stays for normal pregnancies are billed to Medicaid. This government program is also billed for a large portion of mental health conditions, including over one-third of all stays for depression and over half of all stays for schizophrenia.

Private Insurers

More than 200 million individuals have private health insurance through commercial insurance plans.2 These plans include employer-sponsored health plans and self-purchased plans. Commercial health plans are billed for approximately 31 percent of the national hospital bill. The most common conditions for hospitalizations under commercial plans are pregnancy and childbirth, but heart-related conditions, back problems, pneumonia, and affective disorders (primarily depression) are also frequent.


About 44 million individuals, more than 15 percent of the population, have no health insurance.2 However, only 5 percent of hospitalized patients are uninsured at the time of discharge from the hospital, and uninsured stays comprise about 4 percent of the national hospital bill. Two of the top 10 conditions for hospitalization of the uninsured are for alcohol abuse disorders or mental health conditions.

Infections are also a concern for this population. For instance, uninsured hospitalizations for tuberculosis rose by 56 percent: 25 percent of hospital admissions for this infection are for the uninsured in 2002, compared to 16 percent in 1997. Approximately 20 percent of hospital stays for alcohol-related mental disorders and 8 percent of stays for depression are uninsured.

Aggregate Charges by Payer

The aggregate total billed to Medicare is $283 billion, which represents a 29-percent increase since 1997 (adjusted for inflation). The aggregate bill to Medicaid is $119 billion, a 47-percent increase. The aggregate bill to private insurers is $203 billion, a 31-percent increase. And the aggregate hospital bill for the uninsured is $25 billion, a 39-percent increase over 5 years. The largest increase in charges was seen for Medicaid and the uninsured.

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How Are Patients Discharged from the Hospital?

Discharges from the Hospital

Over three-fourths of hospital discharges continue to be routine—patients are typically discharged to their home. About 11 percent of patients leaving the hospital are discharged to long-term care facilities, including skilled nursing facilities, intermediate care, or nursing homes. Another 2 percent are discharged to another hospital and 2 percent die during their hospital stay. Less than 1 percent of admissions result in patients leaving the hospital against medical advice. These figures have remained stable since 1997.

Discharges to Other Institutions

Hospitalizations that result in discharges to other institutions tend to be those in which the patient has lost functional status, often after stroke, hip fracture, or heart attack. Older patients are more often discharged to other institutions than are younger patients. While 3 to 8 percent of patients in the 18-44 and 45-64 age groups are discharged to long-term care and other institutions, 21 percent of patients 65-84 and 41 percent of patients 85+ are discharged to long-term care and other facilities.

Conditions with the Highest In-hospital Mortality

Some patients are admitted to the hospital for end-of-life care; therefore, mortality for some conditions is expected to be high. As noted above, approximately 2 percent of hospital stays end in death. Cancer-related conditions continue to be among the top conditions that account for in-hospital mortality, that is, the largest percentage of cases who die in the hospital. As in 1997, 4 of the 10 most frequent conditions with the highest rates of in-hospital death are cancer without specification of site, cancer of the liver and intrahepatic bile duct, leukemia, and cancer of bronchus or lung. The two conditions with the largest numbers of deaths are infection-related: pneumonia and septicemia. The two conditions with the highest percentage of in-hospital mortality are cardiac arrest and shock.More than 50 percent of all admissions for these conditions result in death at the hospital.

Conditions with the Highest In-hospital Mortality by Age Group

For all age groups, cardiac arrest/ventricular fibrillation is the condition with the highest percentage of in-hospital deaths. In the youngest age category—less than 1 year—the largest number of in-hospital deaths is associated with prematurity and low birthweight. Among the elderly (65+), the largest numbers of in-hospital deaths are associated with pneumonia, heart attack, septicemia, stroke, and congestive heart failure, accounting for nearly a quarter million deaths in the hospital in 2002. Brain injury is the leading cause of death among hospitalized children (1-17 years) and young adults (18-44 years), in terms of the number of people affected.

Patients Leaving Against Medical Advice

As noted above, fewer than 1 percent of patients leave against medical advice. More than 17 percent of all discharges in which patients leave against medical advice are for substance abuse- or alcohol-related mental disorders. Other common conditions among patients leaving against medical advice include medical problems, such as pneumonia or diabetes, rather than surgical problems.

i Go to the Appendix for the complete listing of all principal diagnoses.
ii Other payer sources include Workers' Compensation, Civilian Health and Medical Program of the Uniformed Services (CHAMPUS), Civilian Health and Medical Program of the Department of Veterans Affairs (CHAMPVA), Title V, and other government programs.
iii For information on health expenditures, go to

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The mission of the Agency for Healthcare Research and Quality (AHRQ) is to improve the quality, safety, efficiency, and effectiveness of health care for all Americans. To help fulfill this mission, AHRQ develops a number of databases, including those of the powerful Healthcare Cost and Utilization Project (HCUP). HCUP is a Federal-State-Industry partnership designed to build a standardized, multi-State health data system; HCUP features databases, software tools, and statistical reports to inform policymakers, health system leaders, and researchers.

For data to be useful, they must be disseminated in a timely, accessible way. To meet this objective, AHRQ launched HCUPnet, an interactive, Internet-based tool for identifying, tracking, analyzing, and comparing statistics on hospital utilization, outcomes, and charges ( Menu-driven HCUPnet guides users in tailoring specific queries about hospital care online; with a click of a button, users receive answers within seconds.

In addition, AHRQ produces the HCUP Fact Books to highlight statistics about hospital care in the U.S. in an easy-to-use, readily accessible format. Each Fact Book provides information about specific aspects of hospital care—the single largest component of our health care dollar. These national estimates are benchmarks against which States and others can compare their own data.

This Fact Book provides critical information about hospitalization facts and trends for policymakers and researchers interested in improving the quality and efficiency of the U.S. health care system. It is an update to the first HCUP Fact Book, which presented characteristics of hospital care in 1997. It provides insight for individuals interested in gaining a better understanding of trends in hospitalizations during 2002 and how these compare with data from 1997. Efforts have been made to maintain the general content of the initial Hospitalization in the United States, 1997 Fact Book to allow for easy comparison of 1997 to 2002 data.

AHRQ welcomes questions and comments from readers of this report who are interested in obtaining more information about hospitalization in the U.S. We also invite you to tell us how you are using this Fact Book and other HCUP data and tools and to share suggestions on how HCUP products might be enhanced to further meet your needs. Please E-mail us at or send a letter to the address below:

Irene Fraser, Ph.D.
Center for Delivery, Organization, and Markets
Agency for Healthcare Research and Quality
540 Gaither Road
Rockville, MD 20850

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Without the following State Partner Organizations, the Healthcare Cost and Utilization Project (HCUP) and the 2002 Nationwide Inpatient Sample (NIS) would not be possible:

  • Arizona Department of Health Services.
  • California Office of Statewide Health Planning & Development.
  • Colorado Health & Hospital Association.
  • Connecticut Chime, Inc..
  • Florida Agency for Health Care Administration.
  • Georgia GHA: An Association of Hospitals & Health Systems.
  • Hawaii Health Information Corporation.
  • Illinois Department of Public Health.
  • Iowa Hospital Association.
  • Kansas Hospital Association.
  • Kentucky Department for Public Health.
  • Maine Health Data Organization.
  • Maryland Health Services Cost Review Commission.
  • Massachusetts Division of Health Care Finance and Policy.
  • Michigan Health & Hospital Association.
  • Minnesota Hospital Association.
  • Missouri Hospital Industry Data Institute.
  • Nebraska Hospital Association.
  • Nevada Department of Human Resources.
  • New Jersey Department of Health and Senior Services.
  • New York State Department of Health.
  • North Carolina Department of Health and Human Services.
  • Ohio Hospital Association.
  • Oregon Association of Hospitals & Health Systems.
  • Rhode Island Department of Health.
  • Pennsylvania Health Care Cost Containment Council.
  • South Carolina State Budget & Control Board.
  • South Dakota Association of Healthcare Organizations.
  • Tennessee Hospital Association.
  • Texas Department of State Health Services.
  • Utah Department of Health.
  • Vermont Association of Hospitals and Health Systems.
  • Virginia Health Information.
  • Washington State Department of Health.
  • West Virginia Health Care Authority.
  • Wisconsin Department of Health and Family Services.

Acknowledgments: Thanks to the following individuals for their assistance with this Fact Book: David Ross (Medstat) for statistical programming, Barry Friedman (AHRQ) for his contribution of cost information, David Adamson (Medstat) for developmental editing, Gail Eisen (Medstat) and DonnaRae Castillo for copy editing, and The Madison Design Group for design and layout.

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In 1999, AHRQ launched an initiative to provide timely data regarding hospital care in the U.S. by producing a series of easily accessible Fact Books that summarize several aspects of hospitalizations. The first published Fact Book, Hospitalization in the United States, 1997, provided a general overview of hospitalizations, addressing such issues as:

  • What types of conditions are treated?
  • Who is admitted to the hospital conditions treated in the hospital?
  • Who is billed for hospital care?

Hospitalization in the United States, 2002 updates the first Fact Book. Similar to the 1997 version, this report draws from the Nationwide Inpatient Sample (NIS), a database maintained by AHRQ, to provide comprehensive information about hospitalizations. This report answers the following questions:

  • Who is admitted to the hospital?
  • Why are patients admitted to the hospital?
  • How are patients admitted to the hospital?
  • How much do hospitals charge?
  • Who is billed for hospital care?
  • How are patients discharged from the hospital?

Findings from this report indicate that many aspects of hospitalizations have remained stable since 1997, but there are key exceptions.

The following pages provide a rich depiction of hospital care in 2002. Information on data sources and methods is available at the end of this document. An appendix provides descriptive information about hospital discharges for specific diagnoses by several characteristics: number of discharges, mean length of stay, mean charges, and number of admissions from the ED.

A complete medical dictionary with terms used in this Fact Book is available at

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The information on this page is archived and provided for reference purposes only.


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