Socioeconomic and Racial/Ethnic Disparities in the Incidence of Bacteremic Pneumonia Among US Adults

Objectives. We examined associations between the socioeconomic characteristics of census tracts and racial/ethnic disparities in the incidence of bacteremic community-acquired pneumonia among US adults.Methods. We analyzed data on 4870 adults aged 18 years or older with community-acquired bacteremic pneumonia identified through active, population-based surveillance in 9 states and geocoded to census tract of residence. We used data from the 2000 US Census to calculate incidence by age, race/ethnicity, and census tract characteristics and Poisson regression to estimate rate ratios (RRs) and 95% confidence intervals (CIs).Results. During 2003 to 2004, the average annual incidence of bacteremic pneumonia was 24.2 episodes per 100 000 Black adults versus 10.1 per 100 000 White adults (RR = 2.40; 95% CI = 2.24, 2.57). Incidence among Black residents of census tracts with 20% or more of persons in poverty (most impoverished) was 4.4 times the incidence among White residents of census tracts with less than 5% of persons in poverty (least impoverished). Racial disparities in incidence were reduced but remained significant in models that controlled for age, census tract poverty level, and state.Conclusions. Adults living in impoverished census tracts are at increased risk of bacteremic pneumonia and should be targeted for prevention efforts.Bacterial pneumonia is an important cause of morbidity and mortality in adults¹ and is a potentially serious complication of influenza infection.^2,3 Racial/ethnic disparities in the incidence of bacterial pneumonia are a public health problem. Among US adults, rates of bacteremic pneumonia caused by Streptococcus pneumoniae (pneumococcus), the leading cause of community-acquired pneumonia, are higher among Blacks than among Whites.⁴ Vaccination against pneumococcal disease is recommended for persons aged 65 years and older, for cigarette smokers, and for persons with certain chronic conditions.⁵ Vaccination coverage with 23-valent pneumococcal polysaccharide vaccine is lower, however, among Hispanic and non-Hispanic Black adults with indications for vaccination than among non-Hispanic White adults.^6,7 The introduction of pneumococcal conjugate vaccination for children in 2000 led to lower pneumococcal disease incidence in all age groups^8,9 and narrowed the difference between incidence in Black and White children, although disparities persist among adults.^10,11 Less is known about the factors influencing racial/ethnic disparities in the incidence of bacteremic pneumonia caused by other common pathogens. A better understanding of the underlying factors that sustain disparities in bacterial disease would help to direct prevention efforts.Several previous studies examined the contributions of socioeconomic inequalities to racial/ethnic disparities in invasive pneumococcal disease.^12–15 Between 1960 and 1970, a series of population-based studies in US communities identified socioeconomic measures, including average income and education, as strongly associated with both race/ethnicity and bacterial meningitis incidence.^16–18 However, socioeconomic data have not routinely been collected in US surveillance systems for invasive bacterial disease. With geocoding software, individual cases can be mapped to census tract of residence.¹⁵ Census tract–level socioeconomic measures can then be included in analyses of health outcomes to better understand racial/ethnic disparities in disease incidence.¹⁹ We used a large population-based surveillance system for invasive bacterial infections to examine associations between the socioeconomic characteristics of census tracts and racial/ethnic disparities in the incidence of bacteremic community-acquired pneumonia among US adults. We sought to identify a single, publicly available census tract characteristic that could be used to target interventions to geographic areas likely to have high incidences of bacteremic pneumonia and to monitor inequalities in disease burden.