Original Papers

Pneumonia and respiratory infections

Hospitalized community-acquired pneumonia in the elderly: an Australian case-cohort study

S. A. SKULL^a1a2a3 c1, R. M. ANDREWS^a2, G. B. BYRNES^a4, D. A. CAMPBELL^a5a6, H. A. KELLY^a6a7, G. V. BROWN^a8 and T. M. NOLAN^a3a6

^a1 Department of Paediatrics, University of Melbourne, Royal Children's Hospital, Parkville, Victoria, Australia

^a2 Menzies School of Health Research, Casuarina, Northern Territory, Australia

^a3 Murdoch Children's Research Institute, Parkville, Australia

^a4 Centre for Molecular, Environmental, Genetic and Analytic Epidemiology, School of Population Health, University of Melbourne, Victoria, Australia

^a5 Monash Institute of Health Services Research, Monash Medical Centre, Clayton, Victoria, Australia

^a6 School of Population Health, University of Melbourne, Victoria, Australia

^a7 Victorian Infectious Diseases Reference Laboratory, North Melbourne, Australia

^a8 Department of Medicine, The Nossal Institute for Global Health, and the Centre for Clinical Research Excellence in Infectious Diseases, University of Melbourne, Royal Melbourne Hospital, Parkville, Victoria, Australia

SUMMARY

This study describes the epidemiology of community-acquired pneumonia (CAP) in elderly Australians for the first time. Using a case-cohort design, cases with CAP were in-patients aged 65 years with ICD-10-AM codes J10-J18 admitted over 2 years to two tertiary hospitals. The cohort sample was randomly selected from all hospital discharges, frequency-matched to cases by month. Logistic regression was used to estimate risk ratios for factors predicting CAP or associated mortality. A total of 4772 in-patients were studied. There were 1952 cases with CAP that represented 4% of all elderly admissions: mean length of stay was 9·0 days and 30-day mortality was 18%. Excluding chest radiograph, 520/1864 (28%) cases had no investigations performed. The strongest predictors of CAP were previous pneumonia, history of other respiratory disease, and aspiration. Intensive-care-unit admission, renal disease and increasing age were the strongest predictors of mortality, while influenza vaccination conferred protection. Hospitalization with CAP in the elderly is common, frequently fatal and a considerable burden to the Australian community. Investigation is ad hoc and management empirical. Influenza vaccination is associated with reduced mortality. Patient characteristics can predict risk of CAP and subsequent mortality.

(Accepted May 01 2008)

(Online publication June 18 2008)

Correspondence:

^c1 Author for correspondence: Assoc. Professor S. A. Skull, Menzies School of Health Research, PO Box 41096, Casuarina, Northern Territory, Australia, 0810. (Email: saskull@unimelb.edu.au)