STATISTICAL BRIEF #67
Chaya T. Merrill, M.P.H., Carol Stocks, R.N., M.H.S.A, Elizabeth Stranges, M.S.
From 1997 to 2006, the number of uninsured individuals in the United States increased by about 6 million people, to more than 50 million.1 While lack of health insurance impacts the low-income population disproportionately, more than 40 percent of uninsured hospital stays were among middle- and high-income individuals.1, 2
The average hospital bill for an uninsured stay in 2006 was $19,400. When there is no insurance coverage, hospitals bill patients directly. The resulting burden of payment for uninsured individuals and their families can be substantial. Likewise, the costs of uncompensated care may represent a burden to hospitals and, ultimately, contribute to increases in healthcare costs to society overall.
Trends in health insurance coverage can be driven by several factors including changes in employer-sponsored health benefits, the incomes of working families, the costs of health insurance premiums, and the accessibility of public insurance programs.3 Lack of health insurance has serious consequences on an individual and societal level. The uninsured may be more likely to delay or forego necessary medical care until hospitalization is inevitable.
This Statistical Brief presents data from the Healthcare Cost and Utilization Project (HCUP) on a ten-year trend in uninsured hospital stays from 1997 to 2006. Characteristics of uninsured hospitalizations, such as changes in utilization, cost, patient populations, and geographic locations, are compared to the overall picture of hospital care. All differences between estimates noted in the text are statistically significant at the 0.05 level or better.
Table 1 shows the ten-year trend in the number of uninsured hospitalizations from 1997 to 2006. In 1997, there were 1.7 million uninsured stays compared to more than 2.2 million uninsured stays in 2006—a 34 percent increase in 10 years (figure 1). As shown in figure 2, hospitalizations billed to Medicaid (the public insurance program for low-income individuals) increased by 36 percent, stays billed to Medicare (the public insurance program for the elderly and disabled) increased by 17 percent, and privately insured stays remained relatively stable. The overall growth in all hospital stays was about 14 percent.
Hospital charges reflect the amount the hospital billed for the admission. While these charges generally are discounted for insured patients, the uninsured population typically has been billed the full amount. From 1997 to 2006 hospital charges for the uninsured grew by 76 percent, from an average of $11,000 to $19,400 per stay (after adjusting for inflation).4 Meanwhile, the estimated hospital costs of providing care (i.e., the amount the hospital incurred to provide services) also increased for the uninsured, but at a slower rate of about 33 percent, from $5,100 to $6,800 per stay. Despite these increases in hospital charges and costs, the average length of time uninsured patients stayed at the hospital remained steady at about 4 days per stay.
Previous research has shown that increasing numbers of uninsured patients present to the emergency department (ED) possibly because of their lack of access to primary care.5 Over this ten-year period, the percentage of uninsured hospitalizations originating in the ED increased from about 51 percent of stays in 1997 to nearly 60 percent of stays in 2006. Meanwhile, the percentage of uninsured patients who died at the hospital remained at about 1.5 percent since 1997.
Comparison of uninsured stays to hospital stays overall, 2006
Table 2 provides more detailed information about uninsured hospital stays in 2006 relative to all hospital stays. Compared to all hospital stays, uninsured hospitalizations were, on average, shorter and less expensive. The mean cost to provide uninsured care was about $1,500 less expensive ($6,800 versus $8,400 per hospital stay) and shorter (3.9 versus 4.6 days).
Relative to all hospital stays, uninsured stays began in the ED much more frequently with nearly 60 percent of these stays originating in the ED compared to 44 percent of hospital stays overall. Compared to privately-insured stays, uninsured stays began in the ED nearly twice as often (data not shown). In terms of how uninsured patients were discharged from the hospital, uninsured patients were nearly 4 times more likely to leave against medical advice, but were 2.5 times less likely to be discharged to home healthcare and slightly less likely to die in the hospital.6
Uninsured hospitalization rates were higher among populations living in the poorest areas compared to those living in wealthier communities.7 The rate of uninsured stays was 1.9 times greater in the poorest communities compared to wealthier communities: 10.9 uninsured stays per 1,000 population living in the poorest areas versus 5.9 uninsured stays per 1,000 population living in wealthier communities. Among hospital stays overall, the rate of hospital stays in the poorest areas was 1.2 times greater than in wealthier communities.
Uninsured hospital stays, by patient gender and age, 1997-2006
There were some key differences in demographic characteristics of uninsured stays compared to all hospital stays (table 3). For the uninsured, stays were about equally divided between men (51.2 percent) and women (48.4 percent); whereas, women accounted for a larger percentage of all hospital stays (58.4 percent).
Throughout the ten-year period from 1997 to 2006, individuals ages 18 to 44 years comprised about 38 percent of the total U.S. population, but accounted for nearly half of all uninsured stays (figure 3). The mean age of uninsured patients was about 13 years younger than for the overall patient population (35 years versus 48 years, respectively). While children and adolescents comprised a similar percentage of uninsured stays compared to their portion of all hospital stays, this was not the case for 18–44 year olds. Nearly half of uninsured stays were among 18 to 44 year olds compared to about a quarter of overall hospital stays, as shown in table 3. Also, a third of uninsured stays were for 45 to 64 year olds compared to about 23 percent of all stays. In contrast, a small portion of uninsured stays, less than 3 percent, were for elderly patients (65+ years) while this elderly group accounted for 34.2 percent of all hospital care.
Uninsured elderly care should be rare given the availability of Medicare insurance coverage for the elderly. When elderly hospital stays were excluded, the mean age for uninsured patients was comparable to non-elderly patients overall (34 years compared to 32 years, respectively). When elderly patients were excluded, the age distribution for uninsured inpatients changed minimally. On the other hand, the age distribution of all hospital stays increased by more than 50 percent for each age group. This resulted in larger differences between the portion of uninsured versus insured hospital stays for children (ages less than 1 and 1–17 years) and smaller differences in the portion of uninsured versus insured stays among non-elderly adults (ages 18–44 years and 45–64 years).
Most common principal diagnoses associated with uninsured hospitalizations, 1997-2006
Table 4 shows that from 1997 to 2006 newborn birth remained the most common reason for uninsured hospitalizations, accounting for more than 250,000 uninsured stays in 2006 (11.2 percent of all uninsured stays). Newborn birth was also the most frequent reason for admission among all hospital stays (10.9 percent of all stays). Perineal trauma due to childbirth remained a common condition among uninsured stays and hospital stays overall (representing about 2 percent of hospitalizations).
One condition that showed a significant change in the uninsured population was the number of hospital admissions for skin infections, a potentially preventable event given early intervention. Uninsured hospitalizations for skin infections increased sharply from about 28,000 stays in 1997 to about 75,000 stays in 2006, representing nearly twice the portion of uninsured stays in 2006 (3.3 percent in 2006 compared to 1.7 percent in 1997). In 2006, skin infections were reported more than twice as frequently in uninsured stays compared to all stays.
Mental health and substance abuse conditions (mood-, alcohol-, and substance-related disorders) remained a common reason for uninsured hospital stays, collectively accounting for 182,900 stays in 2006 (8.2 percent of all uninsured stays). These conditions were more frequently cited as the main reason for hospitalization in uninsured stays compared to all hospital stays. In fact, in 2006, stays principally for alcohol and substance abuse were about 4 times more common in uninsured stays compared to all hospital stays.
Two of the other most common reasons for uninsured hospitals stays included cardiac conditions, nonspecific chest pain and hardening of the arteries, accounting for 122,800 uninsured stays (5.4 percent of all uninsured stays). While stays for nonspecific chest pain were more common among uninsured hospitalizations compared to overall hospital stays, hospitalizations for hardening of the arteries were less common in uninsured stays.
Stays for pneumonia and diabetes with complications were also commonly cited in uninsured hospital stays. The portion of uninsured stays for pneumonia decreased from 1997 to 2006 (by about 27 percent) and remained less common compared to overall hospital stays. The percentage of uninsured stays for diabetes with complications remained about the same over the ten-year period, but was about 77 percent higher relative to all hospital stays.
Uninsured hospital stays, by region, 1997-2006
Trends in the percentage of hospital stays that were uninsured within each region varied substantially (figure 4). From 1997 to 2006, the proportion of uninsured hospitalizations grew in the South and the Northeast, by 39.3 percent and 25.6 percent, respectively. The South had the highest proportion of uninsured stays during this ten-year period, ranging from 5.6 percent of all hospital stays in 1997 to nearly 8 percent in 2006. The rates of uninsured stays were lower in the Northeast: 4.3 percent of all hospitalizations in 1997 and 5.4 percent in 2006.
In contrast, the percentage of uninsured stays decreased by nearly 20 percent in the Midwest from 4.7 percent to 3.8 percent and remained relatively stable at about 4 percent in the West (after dropping to 2.8 percent in 2002).
The estimates in this Statistical Brief are based upon data from the HCUP 1997 to 2006 Nationwide Inpatient Sample (NIS). Most statistics were generated from HCUPnet, a free, online query system that provides users with immediate access to the largest set of publicly available, all-payer national, regional, and State-level hospital care databases from HCUP.
Supplemental sources included data from the U.S. Census Bureau, Population Division (National Population Estimates—Characteristics), the Bureau of Labor Statistics (Consumer Price Index Tables), and the HCUP Cost-to-Charge Ratio files.
Diagnoses, ICD-9-CM, and Clinical Classifications Software (CCS)
The principal diagnosis is that condition established after study to be chiefly responsible for the patient’s admission to the hospital. Secondary diagnoses are concomitant conditions that coexist at the time of admission or that develop during the stay.
ICD-9-CM is the International Classification of Diseases, Ninth Revision, Clinical Modification, which assigns numeric codes to diagnoses. There are about 13,600 ICD-9-CM diagnosis codes.
CCS categorizes ICD-9-CM diagnoses into a manageable number of clinically meaningful categories.8 This "clinical grouper" makes it easier to quickly understand patterns of diagnoses and procedures.
Types of hospitals included in HCUP
HCUP is based on data from community hospitals, defined as short-term, non-Federal, general and other hospitals, excluding hospital units of other institutions (e.g., prisons). HCUP data include OB-GYN, ENT, orthopedic, cancer, pediatric, public, and academic medical hospitals. They exclude long-term care, rehabilitation, psychiatric, and alcoholism and chemical dependency hospitals, but these types of discharges are included if they are from community hospitals.
Unit of analysis
The unit of analysis is the hospital discharge (i.e., the hospital stay), not a person or patient. This means that a person who is admitted to the hospital multiple times in one year will be counted each time as a separate "discharge" from the hospital.
Costs and charges
Total hospital charges were converted to costs using HCUP Cost-to-Charge Ratios based on hospital accounting reports from the Centers for Medicare and Medicaid Services (CMS).9 Costs will tend to reflect the actual costs of production, while charges represent what the hospital billed for the case. For each hospital, a hospital-wide cost-to-charge ratio is used because detailed charges are not available across all HCUP States. Hospital charges reflect the amount the hospital charged for the entire hospital stay and does not include professional (physician) fees. For the purposes of this Statistical Brief, costs are reported to the nearest hundreds.
For the purposes of this Statistical Brief, all charge and cost data have been presented in 2006 dollars using the Bureau of Labor Statistics Consumer Price Index All Urban Consumers (CPI-U) U.S. city average and reported to the nearest hundred. (Note: Costs for the 1998 data are imputed from the 1997 CCR file.)
Payer is the expected primary payer for the hospital stay. To make coding uniform across all HCUP data sources, payer combines detailed categories into more general groups:
– Medicare includes fee-for-service and managed care Medicare patients.
– Medicaid includes fee-for-service and managed care Medicaid patients. Patients covered by the State Children's Health Insurance Program (SCHIP) may be included here. Because most state data do not identify SCHIP patients specifically, it is not possible to present this information separately.
– Private insurance includes Blue Cross, commercial carriers, and private HMOs and PPOs.
– Other includes Worker's Compensation, TRICARE/CHAMPUS, CHAMPVA, Title V, and other government programs.
– Uninsured includes an insurance status of "self-pay" and "no charge."
When more than one payer is listed for a hospital discharge, the first-listed payer is used.
Region is one of the four regions defined by the U.S. Census Bureau:
– Northeast: Maine, New Hampshire, Vermont, Massachusetts, Rhode Island, Connecticut, New York, New Jersey, and Pennsylvania
– Midwest: Ohio, Indiana, Illinois, Michigan, Wisconsin, Minnesota, Iowa, Missouri, North Dakota, South Dakota, Nebraska, and Kansas
– South: Delaware, Maryland, District of Columbia, Virginia, West Virginia, North Carolina, South Carolina, Georgia, Florida, Kentucky, Tennessee, Alabama, Mississippi, Arkansas, Louisiana, Oklahoma, and Texas
– West: Montana, Idaho, Wyoming, Colorado, New Mexico, Arizona, Utah, Nevada, Washington, Oregon, California, Alaska, and Hawaii
Admission source indicates where the patient was located prior to admission to the hospital. Emergency admission indicates the patient was admitted to the hospital through the emergency department. Admission from another hospital indicates the patient was admitted to this hospital from another short-term, acute-care hospital. This usually signifies that the patient required the transfer in order to obtain more specialized services that the originating hospital could not provide. Admission from long-term care facility indicates the patient was admitted from a long-term facility such as a nursing home.
Discharge status indicates the disposition of the patient at discharge from the hospital, and includes the following six categories: routine (to home), transfer to another short-term hospital, other transfers (including skilled nursing facility, intermediate care, and another type of facility such as a nursing home), home healthcare, against medical advice (AMA), or died in the hospital.
HCUP is a family of powerful healthcare databases, software tools, and products for advancing research. Sponsored by the Agency for Healthcare Research and Quality (AHRQ), HCUP includes the largest all-payer encounter-level collection of longitudinal healthcare data (inpatient, ambulatory surgery, and emergency department) in the United States, beginning in 1988. HCUP is a Federal-State-Industry Partnership that brings together the data collection efforts of many organizations—such as State data organizations, hospital associations, private data organizations, and the Federal government—to create a national information resource.
HCUP would not be possible without the contributions of the following data collection Partners from across the United States:
Arizona Department of Health Services
Arkansas Department of Health
California Office of Statewide Health Planning & Development
Colorado Hospital Association
Connecticut Hospital Association
Florida Agency for Health Care Administration
Georgia Hospital Association
Hawaii Health Information Corporation
Illinois Department of Public Health
Indiana Health Association
Iowa Hospital Association
Kansas Hospital Association
Kentucky Cabinet for Health and Family Services
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 Health and Human Services
New Hampshire Department of Health & Human Services
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
Oklahoma State Department of Health
Oregon Association of Hospitals and Health Systems
Rhode Island Department of Health
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
Wyoming Hospital Association
About the NIS
The HCUP Nationwide Inpatient Sample (NIS) is a nationwide database of hospital inpatient stays. The NIS is nationally representative of all community hospitals (i.e., short-term, non-Federal, non-rehabilitation hospitals). The NIS is a sample of hospitals and includes all patients from each hospital, regardless of payer. It is drawn from a sampling frame that contains hospitals comprising about 90 percent of all discharges in the United States. The vast size of the NIS allows the study of topics at both the national and regional levels for specific subgroups of patients. In addition, NIS data are standardized across years to facilitate ease of use.
HCUPnet is an online query system that offers instant access to the largest set of all-payer healthcare databases that are publicly available. HCUPnet has an easy step-by-step query system, allowing for tables and graphs to be generated on national and regional statistics, as well as trends for community hospitals in the U.S. HCUPnet generates statistics using data from HCUP's Nationwide Inpatient Sample (NIS), the Kids' Inpatient Database (KID), the State Inpatient Databases (SID) and the State Emergency Department Databases (SEDD).
For More Information
For more information about HCUP, visit www.hcup-us.ahrq.gov.
For additional HCUP statistics, visit HCUPnet, our interactive query system, at www.hcup.ahrq.gov.
For information on other hospitalizations in the U.S., download HCUP Facts and Figures: Statistics on Hospital-based Care in the United States in 2006, located at http://www.hcup-us.ahrq.gov/reports.jsp.
For a detailed description of HCUP, more information on the design of the NIS, and methods to calculate estimates, please refer to the following publications:
Steiner, C., Elixhauser, A., Schnaier, J. The Healthcare Cost and Utilization Project: An Overview. Effective Clinical Practice 5(3):143–51, 2002.
Introduction to the HCUP Nationwide Inpatient Sample, 2006. Online. May 14, 2008. U.S. Agency for http://www.hcup-us.ahrq.gov/db/nation/nis/2006NIS_INTRODUCTION.pdf
Houchens, R., Elixhauser, A. Final Report on Calculating Nationwide Inpatient Sample (NIS) Variances, 2001. HCUP Methods Series Report #2003-2. Online. June 2005 (revised June 6, 2005). U.S. Agency for Healthcare Research and Quality. http://www.hcup-us.ahrq.gov/reports/methods/2003_02.pdf
Houchens RL, Elixhauser A. Using the HCUP Nationwide Inpatient Sample to Estimate Trends. (Updated for 1988–2004). HCUP Methods Series Report #2006-05 Online. August 18, 2006. U.S. Agency for Healthcare Research and Quality. http://www.hcup-us.ahrq.gov/reports/methods/2006_05_NISTrendsReport_1988-2004.pdf
Merrill, C.T. (Thomson Reuters), Stranges, E. (Thomson Reuters), and Stocks, C. (AHRQ). Trends in Uninsured Hospital Stays, 1997-2006. HCUP Statistical Brief #67. February 2009. Agency for Healthcare Research and Quality, Rockville, MD. http://www.hcup-us.ahrq.gov/reports/statbriefs/sb67.pdf
***AHRQ welcomes questions and comments from readers of this publication who are interested in obtaining more information about access, cost, use, financing, and quality of healthcare in the United States. We also invite you to tell us how you are using this Statistical Brief 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 email@example.com or send a letter to the address below:
Irene Fraser, Ph.D., Director
Center for Delivery, Organization, and Markets
Agency for Healthcare Research and Quality
540 Gaither Road
Rockville, MD 20850
1Medical Expenditure Panel Survey (MEPS), 2006. Agency for Healthcare Research and Quality (AHRQ).
2Definition of income levels were 200% to less than 400% of the federal poverty line for middle-income, and greater than or equal to 400% of the federal poverty line for high-income.
3The Kaiser Family Foundation. Health Coverage & the Uninsured: Trends in Health Coverage. Original source is no longer available on the Web; for related information, refer to: http://kff.org/uninsured/fact-sheet/key-facts-about-the-uninsured-population/ (accessed November 4, 2013).
4U.S. Department of Labor, Bureau of Labor Statistics. Consumer Price Index All Urban Consumers (CPI-U), U.S. city average. Retrieved from: http://www.bls.gov/cpi/home.htm (Accessed November 7, 2008).
5Newton, M.F., Keirns, C.C., Cunningham, R., Hayward, R.A., Stanley, R. Uninsured adults presenting to U.S. emergency departments. JAMA. 2008;300(16):1914-1924.
6Note: These figures do not control for differences in severity of illness at discharge.
7Poorest areas defined as ZIP codes with median household incomes in the lowest quartile (less than $38,000 per year).
8HCUP CCS. Healthcare Cost and Utilization Project (HCUP). May 2008. U.S. Agency for Healthcare Research and Quality, Rockville, MD. www.hcup-us.ahrq.gov/toolssoftware/ccs/ccs.jsp
9HCUP Cost-to-Charge Ratio Files (CCR). Healthcare Cost and Utilization Project (HCUP). 2001-2005. U.S. Agency for Healthcare Research and Quality, Rockville, MD. www.hcup-us.ahrq.gov/db/state/costtocharge.jsp
|Table 1. Characteristics of uninsured hospital stays, 1997–2006|
|Number of hospital stays (percentage of all hospital stays)||1,676,300||1,759,800||1,766,700||1,777,000||1,779,100||1,847,900||1,757,100||2,081,000||2,096,000||2,243,900|
|Mean length of stay, days||3.9||3.9||3.9||3.9||3.9||4.0||3.8||3.9||3.9||3.9|
|Mean charge per stay, dollars*||$11,000||$11,100||$11,700||$12,200||$13,100||$15,400||$18,400||$18,500||$18,800||$19,400|
|Mean cost per stay, dollars*||$5,100||$5,100||$5,700||$5,500||$6,000||$6,700||$6,800||$7,100||$7,100||$6,800|
|Percentage of hospital stays that were admitted from the ED||50.5%||51.3%||52.1%||53.7%||54.9%||60.4%||59.8%||60.4%||59.1%||59.4%|
|Percentage of hospital stays in which the patient died in the hospital||1.5%||1.5%||1.5%||1.4%||1.4%||1.4%||1.3%||1.5%||1.4%||1.3%|
|*1997–2005 hospital charges and costs have been adjusted for inflation and are noted in 2006 dollars|
Source: AHRQ, Center for Delivery, Organization, and Markets, Healthcare Cost and Utilization Project, Nationwide Inpatient Sample, 1997–2006
|Table 2. Characteristics of uninsured hospital stays compared to all hospital stays, 2006|
|Uninsured stays||All hospital stays|
|Number of hospital stays
(percent of all stays)
|Total growth in number of stays, 1997-2006||33.9%||14.0%|
|Mean length of stay, days||3.9||4.6|
|Hospital charges and costs|
|Mean charge per stay, dollars||$19,400||$24,000|
|Aggregate charges (national bill), dollars||$43.5 billion||$943.4 billion|
|Mean cost per stay, dollars||$6,800||$8,400|
|Aggregate costs, dollars||$ 15.4 billion||$ 329.2 billion|
|Admission source and discharge status|
|Admitted from the ED||59.4%||43.8%|
|Left against medical advice||3.9%||1.0%|
|Discharged to home healthcare||2.6%||9.1%|
|Died in the hospital||1.3%||2.0%|
|Source: AHRQ, Center for Delivery, Organization, and Markets, Healthcare Cost and Utilization Project, Nationwide Inpatient Sample, 2006|
|Table 3. Characteristics of the uninsured patient population compared to the overall patient population, 2006|
|Uninsured hospital stays||All hospital stays|
|Number of hospital stays (percent of all stays)||2,243,900
|Age characteristics - stays for all patients|
|Mean patient age||35 years||48 years|
|Age characteristics - stays for non-elderly patients*|
|Mean patient age||34 years||32 years|
|Median community-level income** - Rate per 1,000 population|
|Low income (under $38,000)||10.9||149.9|
|Not low income ($38,000 and above)||5.9||122.3|
|*Age characteristics are presented for the non-elderly population because the majority of elderly patients (age 65+) qualify for Medicare coverage |
** Note: About 5% of median community-level income data were missing for uninsured hospital stays and about 2.5% missing for all hospital stays
Source: AHRQ, Center for Delivery, Organization, and Markets, Healthcare Cost and Utilization Project, Nationwide Inpatient Sample, 2006
|Table 4. Top 10 reasons for hospital stays among the uninsured, 1997 and 2006|
|Number of stays (percent of stays)|
|Uninsured hospital stays||All hospital stays|
|Nonspecific chest pain||39,300
|Diabetes mellitus with complications||31,000
|Hardening of the arteries||40,400
|Perineal trauma due to childbirth||30,000
|* Statistics based on estimates with a relative standard error (standard error/weighted estimate) greater than 0.30 or with standard error = 0 in the nationwide statistics (NIS and KID) are not reliable. These statistics are suppressed and are designated with an asterisk (*).|
Source: AHRQ, Center for Delivery, Organization, and Markets, Healthcare Cost and Utilization Project, Nationwide Inpatient Sample, 1997 and 2006
|Internet Citation: Statistical Brief #67. Healthcare Cost and Utilization Project (HCUP). May 2016. Agency for Healthcare Research and Quality, Rockville, MD. www.hcup-us.ahrq.gov/reports/statbriefs/sb67.jsp.|
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