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

Objectives: To study the association between community influenza activity a nd acute hospital admissions for pneumonia and influenza among elderly pers ons. Design: Multiple regression analysis of acute hospital admissions against c ommunity influenza activity, air temperature and seasonal and long-term tre nds. Setting: Three English health districts: 1987-95. Subjects: Persons aged greater than or equal to 65 years. Outcome measures: Acute hospital admissions for pneumonia and influenza (ICD9: 480-487); exc ess 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 comm unity influenza activity. However, most variation was explained by long-ter m and seasonal changes unrelated to influenza. In the large influenza epide mic of 1989/90 a typical health district (500000 total population) experien ced 56 excess admissions for pneumonia and influenza attributable to epidem ic influenza among persons aged greater than or equal to 65 years, requirin g 672 additional bed-days. However the figure varied widely between seasons and over the whole study period, the average winter excess was 17.5 admiss ions 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 a dmissions is modest, their impact on bed availability may be considerable b ecause of the duration of hospital stay in elderly persons.