Infection rate and acute organ dysfunction risk as explanations for racial differences in severe sepsis

Abstract

Context: Severe sepsis, defined as infection complicated by acute organ dysfunction, occurs more frequently and leads to more deaths in black than in white individuals. The optimal approach to minimize these disparities is unclear.

Objective: To determine the extent to which higher severe sepsis rates in black than in white patients are due to higher infection rates or to a higher risk of acute organ dysfunction.

Design, setting, and participants: Analysis of infection-related hospitalizations from the 2005 hospital discharge data of 7 US states and infection-related emergency department visits from the 2003-2007 National Hospital Ambulatory Care Survey.

Main outcome measure: Age- and sex-standardized severe sepsis and infection hospitalization rates and the risk of acute organ dysfunction.

Results: Of 8,661,227 non-childbirth-related discharges, 2,261,857 were associated with an infection, and of these, 381,787 (16.8%) had severe sepsis. Black patients had a 67% higher age- and sex-standardized severe sepsis rate than did white patients (9.4; 95% confidence interval [CI], 9.3-9.5 vs 5.6; 95% CI, 5.6-5.6 per 1000 population; P < .001) and 80% higher standardized mortality (1.8, 95% CI, 1.8-1.9 vs 1.0, 95% CI, 1.0-1.1 per 1000 population; P < .001). The higher severe sepsis rate was explained by both a higher infection rate in black patients (47.3; 95% CI, 47.1-47.4 vs 34.0; 95% CI, 33.9-34.0 per 1000 population; incidence rate ratio, 1.39; P < .001) and a higher risk of developing acute organ dysfunction (age- and sex-adjusted odds ratio [OR], 1.29; 95% CI, 1.27-1.30; P < .001). Differences in infection presented broadly across different sites and etiology of infection and for community- and hospital-acquired infections and occurred despite a lower likelihood of being admitted for infection from the emergency department (adjusted OR, 0.70; 95% CI, 0.64-0.76; P < .001). The higher risk of organ dysfunction persisted but was attenuated after adjusting for age, sex, comorbid conditions, poverty, and hospital effect (OR, 1.14; 95% CI, 1.13-1.16; P < .001). Racial disparities in infection and severe sepsis incidence and mortality rates were largest among younger adults (eg, the proportion of invasive pneumococcal disease occurring in adults < 65 years was 73.9% among black patients vs 44.5% among white patients, P < .001).

Conclusion: Racial differences in severe sepsis are explained by both a higher infection rate and a higher risk of acute organ dysfunction in black than in white individuals.

Figure 1

Overview of Analysis Cohort HIV indicates human immunodeficiency virus.

Figure 2

Population-Based Severe Sepsis and Infection Hospitalization Rates for Black Patients and White Patients in 7 US States, 2005 Differences were apparent across all age groups, but most pronounced in young adults between age 20 and 64 years, as reflected by the highest incidence rate ratios. The 67% higher severe sepsis rate in black patients was predominantly explained by a higher rate of infection hospitalizations. The y-axes, shown in blue, indicate the range of incidence from 0 to 80 per 1000 population. Class intervals include data for ages equal to the lower limit of each interval and up to but less than the upper limit.

Figure 3

Risk of Severe Sepsis Conditional on Infection by Race The additional risk of developing organ dysfunction conditional on infection was small. Class intervals include data for ages equal to the lower limit of each interval and up to but less than the upper limit.

Figure 4

Infection and Severe Sepsis-Related Hospitalizations and Deaths In contrast to whites, the majority of infections, severe sepsis cases, invasive pneumococcal infections, and deaths occurred in young black patients. For example, 74% of pneumococcal infections occurred in young black patients compared with 45% in young white patients younger than 65 years. Similarly, 49% vs 30% of severe sepsis cases, 74% vs 45% of invasive pneumococcal disease cases, and 36% vs 18% of infection related deaths occurred in black patients and white patients younger than 65 years, respectively. The gray line indicates 65 years of age.