Risk Factors for Septicemia Deaths and Disparities in a Longitudinal US Cohort

Abstract

Background: There are few longitudinal data on the risk factors and mediators of racial disparities in sepsis among community- dwelling US adults.

Methods: This is a longitudinal study of adult participants in the 1999-2005 National Health Interview Survey with data linked to the 1999-2011 National Death Index. We utilized National Vital Statistics System's ICD-10 schema to define septicemia deaths (A40-A41), utilizing influenza and pneumonia deaths (J09-J11) and other causes of death as descriptive comparators. All statistics utilized survey design variables to approximate the US adult population.

Results: Of 206 691 adult survey participants, 1523 experienced a septicemia death. Factors associated with a >2-fold larger hazard of septicemia death included need for help with activities of daily living; self-reported "poor" and "fair" general health; lower education; lower poverty index ratio; self-reported emphysema, liver condition, stroke, and weak or failing kidneys; numerous measures of disability; general health worse than the year prior; >1 pack per day cigarette use; and higher utilization of health care. Blacks had age- and sex-adjusted hazards that were higher for septicemia deaths (hazard ratio [HR], 1.92; 95% confidence interval [CI], 1.65-2.23) than for other causes of death (HR, 1.32; 95% CI, 1.25-1.38). The strongest mediators of the septicemia disparity included self-reported general health condition, family income-poverty ratio, and highest education level achieved.

Conclusions: In this cohort, the major risk factors for septicemia death were similar to those for other causes of death, there was approximately a 2-fold black-white disparity in septicemia deaths, and the strongest mediators of this disparity were across domains of socioeconomic status.

Keywords: epidemiology; sepsis; sepsis mortality.

Figure 1.

Framework for mediation analyses.

Figure 2.

Age group– and sex-adjusted medical comorbidity hazards for death, National Health Interview Survey 1999–2005. Graph includes results of 3 separate Cox proportional hazards models in the same cohort: 1 for septicemia (A40-A41) deaths that censors for other causes of death (blue), 1 for influenza/pneumonia (J09-J11) deaths that censors for other causes of death (red), and 1 for other causes of death that censors for septicemia and influenza/pneumonia deaths (green). Whiskers denote 95% confidence intervals.

Figure 3.

Comparisons of covariates’ proportional mediation of the black-white disparities for septicemia and other causes of death, National Health Interview Survey 1999–2005. The proportions for this graph are calculated by dividing the indirect effect of the age- and sex-adjusted black-white disparity when adjusting for a particular mediator by the total age- and sex-adjusted black-white disparity without adjustment for that mediator. This is conceptualized as the relative amount of the total age- and sex-adjusted black-white disparity accounted for by the specific variable. This is performed separately for septicemia and other causes of death to calculate cause of death–specific proportional mediation for each variable. Abbreviations: ADL, activity of daily living; ER, emergency room; IADL, instrumental activity of daily living.