Staphylococcus aureus bloodstream infections: the association between age and mortality and functional status.

OBJECTIVES To assess the association between Staphylococcus aureus (S. aureus) blood stream infections (BSIs) and morbidity and mortality in older adults. DESIGN Retrospective review. SETTING Veterans Affairs Ann Arbor Healthcare System. PARTICIPANTS All patients with S. aureus BSI during 2004/05. MEASUREMENTS Outcomes included in-hospital and 6-month mortality, as well as need for subacute care. RESULTS Sixty-eight patients with S. aureus BSI were identified (mean age 63.5+/-13.0). Outcomes of interest included in-hospital mortality (19.1%), 6-month mortality (33.8%), and need for subacute care (65.4%). Univariate analysis identified several predictors of death, including older age, chronic renal insufficiency, catheter-related infection, Charlson weighted index of comorbidity score, and infection with methicillin-resistant S. aureus (MRSA). Multivariable analysis demonstrated that older age (odds ratio (OR)=1.1, P<.01), chronic renal insufficiency (OR=16.6, P=.01), and MRSA infection (OR=5.1, P=.03) were independently associated with 6-month mortality. These results suggest that, for every decade increase in age, the odds of death within 6 months of S. aureus BSI doubles (OR=1.1). Chronic renal insufficiency was also independently associated with in-hospital mortality. Of the previously community-dwelling patients (n=50), 41 survived hospitalization, of whom 22 (53.7%) required subacute care after discharge. CONCLUSION Better understanding of the epidemiology of S. aureus BSI in older patients and validation of risk factors for poor functional outcomes and death should be the focus of future prospective studies.