Methicillin-resistant Staphylococcus aureus colonization is associated with higher mortality in nursing home residents with impaired cognitive status.

OBJECTIVES: To assess the effect of methicillin-resistant Staphylococcus aureus (MRSA) colonization on morbidity and mortality of nursing home residents.
DESIGN: Three-year cohort study from 2000 to 2003.
SETTING: Twenty-three nursing homes of all types and regions in the northern part of Belgium (Flanders). PARTICIPANTS: Two thousand eight hundred fourteen nursing home residents. MEASUREMENTS: The consequences of MRSA colonization on mortality and hospitalization were studied, adjusting for potential confounders. Dates and cause of death and hospitalization were collected every 6 months during 3 years of follow-up.
RESULTS: After adjustment for age, sex, and Charlson comorbidity index, the risk for 36-month mortality remained significantly higher in MRSA carriers (hazard ratio (HR) = 1.4, 95% confidence interval (CI) = 1.1-1.8) than in noncarriers. The effect of MRSA on mortality was dependent on the degree of cognitive impairment, with the highest effect in patients with severe cognitive impairment (adjusted HR = 1.8, 95% CI = 1.1-2.8) and absence of effect in residents with good mental status (adjusted HR = 0.8, 95% CI = 0.43-1.62). Deaths were more frequently reported to be infection-related in MRSA carriers. No association was found between MRSA colonization and hospitalization for any reason, but during follow-up, MRSA carriers were twice as frequently hospitalized for respiratory tract infections.
CONCLUSION: Colonization of MRSA in Belgian nursing home residents was associated with higher mortality. This excess mortality was restricted to residents with impaired cognitive function, probably reflecting differences in therapeutic approaches, in delay of diagnosis of pneumonia and other acute disorders in these patients, or in both.