Excess hospital admissions for pneumonia and influenza in persons > or = 65 years associated with influenza epidemics in three English health districts: 1987-95

OBJECTIVES: To study the association between community influenza activity and acute hospital admissions for pneumonia and influenza among elderly persons. DESIGN: Multiple regression analysis of acute hospital admissions against community influenza activity, air temperature and seasonal and long-term trends. SETTING: Three English health districts: 1987-95. SUBJECTS: Persons aged > or = 65 years. OUTCOME MEASURES: Acute hospital admissions for pneumonia and influenza (ICD9: 480-487); excess hospital admissions during epidemic periods. RESULTS: The final regression model explained 70% of the total variation in hospital admissions for pneumonia and influenza, including 14% due to community influenza activity. However, most variation was explained by long-term and seasonal changes unrelated to influenza. In the large influenza epidemic of 1989/90 a typical health district (500,000 total population) experienced 56 excess admissions for pneumonia and influenza attributable to epidemic influenza among persons aged > or = 65 years, requiring 672 additional bed-days. However the figure varied widely between seasons and over the whole study period, the average winter excess was 17.5 admissions per health district, requiring an additional 210 bed-days. CONCLUSIONS: Influenza epidemics exert a variable impact on acute hospital admissions for pneumonia and influenza among elderly persons, which in the past have been poorly quantified. Although the absolute numbers of excess admissions is modest, their impact on bed availability may be considerable because of the duration of hospital stay in elderly persons.