Relationship between neighborhood poverty rate and bloodstream infections in the critically ill.

BACKGROUND: Poverty is associated with increased risk of chronic illness, but its contribution to bloodstream infections is not well-defined.
METHODS: We performed a multicenter observational study of 14,657 patients, aged 18 yrs or older, who received critical care and had blood cultures drawn between 1997 and 2007 in two hospitals in Boston, Massachusetts. Data sources included 1990 U.S. Census and hospital administrative data. Census tracts were used as the geographic units of analysis. The exposure of interest was neighborhood poverty rate categorized as <5%, 5%-10%, 10%-20%, 20%-40%, and >40%. Neighborhood poverty rate is the percentage of residents with income below the federal poverty line. The primary end point was bloodstream infection occurring 48 hrs before critical care initiation to 48 hrs after. Associations between neighborhood poverty rate and bloodstream infection were estimated by logistic regression models. Adjusted odds ratios were estimated by multivariable logistic regression models.
RESULTS: Two thousand four-hundred thirty-five patients had bloodstream infections. Neighborhood poverty rate was a strong predictor of risk of bloodstream infection, with a significant risk gradient across neighborhood poverty rate quintiles. After multivariable analysis, neighborhood poverty rate in the highest quintiles (20%-40% and >40%) were associated with a 26% and 49% increase in bloodstream infection risk, respectively, relative to patients with neighborhood poverty rate of <5%.
CONCLUSIONS: Within the limitations of our study design, increased neighborhood poverty rate, a proxy for decreased socioeconomic status, appears to be associated with risk of bloodstream infection among patients who receive critical care.