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Most Frequent Conditions in U.S. Hospitals, 2010

Statistical Brief #148

, , MPH, and , RN, MHSA.

Published: .

Introduction

A patient can be admitted to the hospital with multiple conditions or diagnoses. The principal diagnosis is the condition that is primarily responsible for a patient’s hospitalization. This condition can affect other components of the patient’s hospital stay, including the length of stay, health care costs, and procedures performed.

This Statistical Brief presents data from the Healthcare Cost and Utilization Project (HCUP) on the most common principal diagnoses in 2010 for all hospital stays in the United States, as well as for stays by age and primary payer. Changes in the overall number of stays and the rate of hospitalization in the population are presented for the most common conditions in 1997 and 2010. All differences between estimates noted in the text are statistically significant at the .001 level or better.

Findings

Highlights

  • Liveborn (newborn infant) was the most common reason for hospitalization in 2010 (3.9 million stays) and accounted for about 10 percent of all hospital stays.
  • Pneumonia was the second most common diagnosis in 2010 and accounted for about 2.8 percent of all stays.
  • Acute renal failure was the most rapidly growing condition between 1997 and 2010, with an increase of 264 percent in the rate of hospitalization.
  • Mood disorders was the most common principal diagnosis among children ages 1–17.
  • Obstetrics-related trauma was the most common diagnosis among adults ages 18–44.
  • Osteoarthritis was the most common diagnosis among adults ages 45–64 and 65–84.
  • Among adults ages 18–44, the rate of hospitalization for normal pregnancy and/or delivery fell 56 percent between 1997 and 2010, but the rate of hospitalization for delivery following a Cesarean section increased 82 percent.
  • Four of the most common conditions for uninsured hospital stays increased by 50 percent or more from 1997 to 2010: skin and subcutaneous tissue infections, mood disorders, nonspecific chest pain, and alcohol-related disorders.

Most frequent principal diagnoses during hospital stays, 2010

Table 1 shows the most frequent principal diagnoses during hospital stays in 2010. In 2010, there were 39 million hospital stays in the U.S.—1,261 stays per 10,000 population. The 10 most frequent principal diagnoses accounted for 30 percent of all stays in 2010.

Table 1. Number of stays and stays per 10,000 population for the most frequent principal diagnoses for hospital stays, 2010.

Table 1

Number of stays and stays per 10,000 population for the most frequent principal diagnoses for hospital stays, 2010.

Liveborn (newborn infant) was the most common reason for hospitalization, accounting for more than 3.9 million stays in 2010 (10 percent of all stays).

Two respiratory illnesses—pneumonia and chronic obstructive pulmonary disease (COPD)—were among the 10 most frequent principal diagnoses in 2010. Pneumonia was the second most common reason for hospitalization in 2010 (2.8 percent of all stays).

Two circulatory conditions—congestive heart failure (CHF) and cardiac dysrhythmias—were also among the 10 most common principal diagnoses in 2010.

Principal diagnoses with the most rapid growth, 1997–2010

Although the rate of hospitalization overall remained stable between 1997 and 2010, the hospitalization rate for some principal diagnoses experienced rapid growth (table 2). Acute renal failure was the most rapidly growing condition between 1997 and 2010, with an increase of 264 percent in the hospitalization rate (from 3.6 to 13.1 stays per 10,000 population). The hospitalization rate for 5 conditions—prolonged pregnancy, pulmonary heart disease, osteoarthritis, anemia, and septicemia—also doubled during this time period.

Table 2. Number of stays, stays per 10,000 population, and percentage change in rate of selected principal diagnoses for hospital stays, 1997 and 2010.

Table 2

Number of stays, stays per 10,000 population, and percentage change in rate of selected principal diagnoses for hospital stays, 1997 and 2010.

Most frequent principal diagnoses by age during hospital stays, 2010

Table 3 highlights the 5 most frequent reasons for hospitalization for each age group in 2010 as well as the change in the rate of hospitalization for these diagnoses since 1997. Overall, the hospitalization rate increased with age—with the exception of infants, who had a high hospitalization rate (11,438 per 10,000 population) primarily because of newborn births, which accounted for 86 percent of stays for children younger than 1 year.

Table 3. Number of stays, stays per 10,000 population, and percentage change in rate of the most frequent principal diagnoses for hospital stays by age, 1997 and 2010.

Table 3

Number of stays, stays per 10,000 population, and percentage change in rate of the most frequent principal diagnoses for hospital stays by age, 1997 and 2010.

For children ages 1–17, the top 3 principal diagnoses in 2010—mood disorders, pneumonia, and asthma—each occurred in 17 stays per 10,000 population. The rate of hospitalization for asthma fell by 30 percent and doubled for skin and subcutaneous tissue infections between 1997 and 2010.

Among adults ages 18–44, 4 of the top 5 conditions were related to pregnancy and childbirth: trauma to the perineum and vulva due to childbirth, maternal stay with a previous Cesarean section, prolonged pregnancy, and hypertension complicating pregnancy and childbirth. The rate of hospitalization for delivery following a Cesarean section increased 82 percent; however, the rate of hospitalization for normal pregnancy and/or delivery fell 56 percent between 1997 and 2010 (data not shown).

In 2010, osteoarthritis was the most common principal diagnosis among adults ages 45–64 and 65–84. The rate of hospitalization for this condition increased 164 percent and 60 percent, respectively, among these age groups between 1997 and 2010. Cardiovascular conditions were also common among adults age 45 and older. The rate of hospitalization for nonspecific chest pain and coronary atherosclerosis for adults ages 45–64 decreased 16 percent and 64 percent, respectively, between 1997 and 2010.

Congestive heart failure (CHF), pneumonia, septicemia, and cardiac dysrhythmias accounted for 4 of the top 5 conditions among adults ages 65–84 and age 85 and older. Hospitalization rates for CHF, pneumonia, and septicemia were higher by a factor of 2 or more for adults age 85 and older, compared to rates among adults ages 65–84. From 1997 to 2010, the hospitalization rate for CHF and pneumonia decreased among adults age 65 and older. In contrast, hospitalization rates for septicemia increased by 80 percent among adults ages 65–84 and by 56 percent among adults age 85 and older.

Bipolar disorders and depressive disorders among children ages 1–17, 1997 and 2010

One age-related finding of particular interest warranted further analysis—mood disorders, the fourth-ranked principal diagnosis among children ages 117 in 1997, was the most frequent principal diagnosis in 2010. Table 4 shows the number of stays and rate of hospitalization for the two specific diagnoses that constitute mood disorders—bipolar disorders and depressive disorders—by age within the 117 age group.

Table 4. Number of stays, stays per 10,000 population, and percentage change in rate of principal bipolar disorders and depressive disorders among children ages 1–17, 1997 and 2010.

Table 4

Number of stays, stays per 10,000 population, and percentage change in rate of principal bipolar disorders and depressive disorders among children ages 1–17, 1997 and 2010.

Overall, depressive disorders comprised the largest share of mood disorders, with the rate of hospitalization highest among children ages 1517 (29 stays per 10,000 population in 2010). The rate of hospitalization for depressive disorders among children remained relatively stable between 1997 and 2010. In contrast, there was more than a four-fold increase in the rate of hospitalization for bipolar disorders among children ages 117 between 1997 and 2010. This increase occurred for all ages (where data were available), with the highest rates among children ages 1014 and 1517 (11 and 21 stays per 10,000 population, respectively, in 2010). Bipolar disorders accounted for an increasing share of hospital stays for mood disorders among children ages 117 in 2010 (48 percent) versus 1997 (16 percent).

Most frequent principal diagnoses by payer during hospital stays, 2010

Table 5 shows the top 5 principal diagnoses for hospital stays by primary payer. The principal diagnoses for hospitalizations by primary payer generally varied, although some conditions were common across all payer types.

Table 5. Number of stays, percentage distribution, and percentage change in stays of the most frequent principal diagnoses for hospital stays by payer, 1997 and 2010.

Table 5

Number of stays, percentage distribution, and percentage change in stays of the most frequent principal diagnoses for hospital stays by payer, 1997 and 2010.

There were 14.5 million stays with Medicare as the primary payer in 2010. CHF was the most common principal diagnosis, accounting for 5 percent of all Medicare stays. The number of stays for pneumonia decreased slightly between 1997 and 2010 (12 percent), but there was an increase in the number of stays billed to Medicare for septicemia (122 percent), osteoarthritis (87 percent), and cardiac dysrhythmias (32 percent).

Medicaid was the primary payer for 8.3 million stays in 2010—an increase of 47 percent from 1997. Three pregnancy- and childbirth-related conditions accounted for nearly 30 percent of all Medicaid stays in 2010: newborn birth, trauma to the perineum and vulva caused by childbirth, and previous Cesarean section. The number of stays for newborn birth and previous Cesarean section both grew from 1997 to 2010 (48 percent and 169 percent, respectively). Mood disorders was the third most common condition with Medicaid as the primary payer, increasing 78 percent from 1997 to 2010.

Private insurance was the primary payer for 12.5 million stays in 2010. Newborn birth was the most common reason for stays billed to private insurance, accounting for 15 percent of stays. Osteoarthritis was the second most common principal diagnosis among private insurance stays and more than tripled between 1997 and 2010.

The uninsured accounted for 2.3 million stays in 2010—a 40-percent increase since 1997. Newborn births accounted for 7 percent of all uninsured stays in 2010. Four of the most common conditions for uninsured hospital stays increased by more than 50 percent from 1997 to 2010: alcohol-related disorders and nonspecific chest pain grew by 52 percent and 68 percent, respectively; stays for mood disorders nearly doubled; and skin and subcutaneous tissue infections nearly tripled.

Data Source

The estimates in this Statistical Brief are based upon data from the HCUP 2010 NIS. Historical data were drawn from the 1997 NIS. Supplemental sources included data on national population estimates from “Intercensal Estimates of the Resident Population by Single Year of Age, Sex, Race, and Hispanic Origin for the United States: April 1, 2000 to July 1, 2010,” Population Division, U.S. Census Bureau, Release date: September 2011. Available at (http://www.census.gov/popest/data/intercensal/national/nat2010.html). (Accessed January 7, 2013).

Supplemental sources also included data on national population estimates from “Intercensal Estimates of the United States Resident Population by Age and Sex, 1990–2000: Selected Months,” Population Division, U.S. Census Bureau, Release date: August 2004. Available at (http://www.census.gov/popest/data/intercensal/national/index.html). (Accessed January 7, 2013).

Many hypothesis tests were conducted for this Statistical Brief. Thus, to decrease the number of false-positive results, we reduced the significance level to .001 for individual tests.

Definitions

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 14,000 ICD-9-CM diagnosis codes.

CCS categorizes ICD-9-CM diagnoses into a manageable number of clinically meaningful categories.1 This “clinical grouper” makes it easier to quickly understand patterns of diagnoses. CCS categories identified as “Other” are typically not reported; these categories include miscellaneous, otherwise unclassifiable diagnoses that may be difficult to interpret as a group.

The single-level diagnosis CCS aggregates illnesses and conditions into 285 mutually exclusive categories. The multi-level CCS groups single-level CCS categories into broader categories (e.g., “Diseases of the Circulatory System”, “Mental Disorders”, and “Injury”) and also splits single-level CCS categories to provide more detail about particular groupings of codes.

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 obstetrics and gynecology, otolaryngology, orthopedic, cancer, pediatric, public, and academic medical hospitals. Excluded are long-term care, rehabilitation, psychiatric, and alcoholism and chemical dependency hospitals. However, if a patient received long-term care, rehabilitation, or treatment for psychiatric or chemical dependency conditions in a community hospital, the discharge record for that stay will be included in the NIS.

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.

Payer

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.

For More Information

For more information about HCUP, visit http://www.hcup-us.ahrq.gov/.

For additional HCUP statistics, visit HCUPnet, our interactive query system, at http://hcupnet.ahrq.gov/.

For information on other hospitalizations in the United States, download HCUP Facts and Figures: Statistics on Hospital-Based Care in the United States in 2009, 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:

Introduction to the HCUP Nationwide Inpatient Sample, 2010. Online. May 2012. U.S. Agency for Healthcare Research and Quality. Available at http://hcup-us.ahrq.gov/db/nation/nis/NISIntroduction2010.pdf. (Accessed January 7, 2013).

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. Available at http://www.hcup-us.ahrq.gov/reports/CalculatingNISVariances200106092005.pdf. (Accessed January 7, 2013).

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. Available at http://www.hcup-us.ahrq.gov/reports/methods/2006_05_NISTrendsReport_1988-2004.pdf. (Accessed January 7, 2013).

Footnotes

1

HCUP Clinical Classifications Software (CCS). Healthcare Cost and Utilization Project (HCUP). U.S. Agency for Healthcare Research and Quality, Rockville, MD. Available at http://www​.hcup-us.ahrq​.gov/toolssoftware/ccs/ccs.jsp. Updated March 2012. (Accessed January 7, 2013).

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, nonrehabilitation 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 more than 95 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.

About HCUPnet: HCUPnet is an online query system that offers instant access to the largest set of all-payer health care databases 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 United States. HCUPnet generates statistics using data from HCUP’s Nationwide Inpatient Sample (NIS), the Kids’ Inpatient Database (KID), the Nationwide Emergency Department Sample (NEDS), the State Inpatient Databases (SID), and the State Emergency Department Databases (SEDD).

Suggested Citation: Pfuntner, A (Truven Health Analytics), Wier, LM (Truven Health Analytics), Stocks, C (AHRQ). Most Frequent Conditions in U.S. Hospitals, 2010. HCUP Statistical Brief #148. January 2013. Agency for Healthcare Research and Quality, Rockville, MD. Available at http://www​.hcup-us.ahrq​.gov/reports/statbriefs/sb148.pdf.

Acknowledgments: The authors would like to acknowledge the contributions of Eva Witt of Truven Health Analytics.

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