The impact and cost of influenza in the elderly

Background: Traditional methods of measuring the impact and cost of influenza virus have focused on epidemic years and morbidity and mortality due to pneumonia and influenza. Methods: Annualized age-sex-race adjusted rates of hospitalization for pneumonia and influenza and other diagnoses among elderly Medicare beneficiaries during the epidemic influenza season of 1989 to 1990 and the nonepidemic season of 1990 to 1991 were compared with an interim period in 1990 without influenza virus circulation. Results: The rates of hospitalization for pneumonia and influenza, acute bronchitis, chronic respiratory disease, and congestive heart failure were significantly greater during each influenza period compared with the interim period. The highest rates were found in the epidemic season of 1989 to 1990. The amount reimbursed by Medicare to hospitals for the treatment of excess hospitalizations during periods of influenza activity was more than 1 billion in 1989 to 1990 and almost 750 million in 1990 to 1991. Conclusions: Measures of the impact and cost of influenza in elderly Americans should include all of the diagnoses listed above and should recognize that the impact of influenza virus is significant even in nonepidemic years. There are great opportunities for cost savings if effective control programs are implemented. (Arch Intern Med. 1993;153: 2105-2111)