Skip Navigation Archive: U.S. Department of Health and Human Services
Archive: Agency for Healthcare Research Quality
Archive print banner

Half of All Hospital Patients Have Coexisting Diseases

This information is for reference purposes only. It was current when produced and may now be outdated. Archive material is no longer maintained, and some links may not work. Persons with disabilities having difficulty accessing this information should contact us at: Let us know the nature of the problem, the Web address of what you want, and your contact information.

Please go to for current information.

Press Release Date: November 17, 2000

According to the U.S. Agency for Healthcare Research and Quality (AHRQ), more than half of all hospital patients have "comorbidities"—co-existing diseases which are not the main reason they were hospitalized, but which can complicate treatment and lengthen their stays.

One in three hospital patients has two or more comorbidities. A fifth have hypertension, or high blood pressure, in addition to their principal diagnosis. Hypertension can complicate treatment of a principal diagnosis, for example, by increasing the risk of a complicating stroke or heart attack. The second most common comorbidity—present in roughly 14 percent of patients—are fluid and electrolyte disorders. These are, for example, abnormalities in a patient's potassium or sodium level, and they may indicate that the patient is significantly dehydrated. These disorders can complicate a hospital stay by increasing the risk of a complicating heart arrhythmia or unstable blood pressure.

Nearly 11 percent of hospital patients suffer from emphysema or chronic bronchitis—chronic lung diseases that can increase the risk of a complicating pneumonia during a hospital stay. Almost 10 percent have diabetes mellitus, and about 7 percent have an irregular heartbeat.

These statistics on comorbidities are derived from a comprehensive AHRQ report, Hospitalization in the United States, 1997, which is available free of charge from the AHRQ Publications Clearinghouse, P.O. Box 8547, Silver Spring, MD 20907.

Select to access a chart of the five most common comorbidities among hospital patients (PDF File, 8 KB; PDF Help).

For more information, please contact Robert Isquith, (301) 427-1539 or

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


AHRQ Advancing Excellence in Health Care