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Influenza Most Deadly for the Very Elderly

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AHRQ News and Numbers

Release date: November 7, 2006

Nearly 8 percent of patients age 85 years and older that are hospitalized for influenza do not survive the disease, a death rate more than twice the 3 percent for hospitalized patients ages 65 to 84, according to a new report by the Department of Health and Human Services' Agency for Healthcare Research and Quality (AHRQ).

Influenza, or flu, is a contagious respiratory illness caused by viruses. Flu kills more than 36,000 Americans each year and afflicts between 5 and 20 percent of the U.S. population, according to Federal estimates. Experts endorse vaccinations through November and December since most flu activity occurs during January or subsequent months of most years.

The new Federal study by AHRQ concluded that:

  • More than 21,000 people were hospitalized specifically for influenza in 2004. In 16,000 more cases, hospital patients had influenza in addition to the illness for which they were admitted.
  • Elderly patients were the most likely to be hospitalized for influenza. Among those 65 years or older, there were 28 hospitalizations per 100,000 population—a rate more than 3 times greater than that of children younger than 18 years, which experienced 8 hospitalizations per 100,000 population.
  • Among younger adults (18 to 44 years and 45 to 64 years), there were 2 to 4 hospitalizations, respectively, per 100,000 population.
  • Among those elderly patients who were hospitalized for influenza or had influenza in addition to other illnesses, about 75 percent were admitted through hospital emergency departments.
  • Midwesterners had the highest chance of being hospitalized for influenza (11 per every 100,000 persons), while westerners had the lowest chance (3 per every 100,000 persons.
  • Patients hospitalized for influenza stayed an average of 5.3 days, slightly longer than the 4.6 average days for other illnesses.

These statistics are from the Nationwide Inpatient Sample, a database of hospital inpatient stays that is nationally representative of all short-term, non-Federal hospitals. The data are drawn from hospitals that comprise 90 percent of all discharges in the United States and include all patients, regardless of insurance type, as well as the uninsured. For more data, see Hospital Stays for Influenza, 2004, HCUP Statistical Brief No. 16 (PDF Help).

To speak with an AHRQ data expert, or for information from previous AHRQ News and Numbers summaries, contact Bob Isquith at or call (301) 427-1539.

Current as of November 2006


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