Differences in inflammation among black and white individuals: A systematic review and meta-analysis.

Abstract

Importance: Despite persisting health disparities between Black and White individuals, racial differences in inflammation have yet to be comprehensively examined.

Objective: To determine if significant differences in circulating levels of inflammatory markers between Black and White populations exist.

Data sources: Studies were identified through systematic searches of four electronic databases in January 2022. Additional studies were identified via reference lists and e-mail contact.

Study selection: Eligible studies included full-text empirical articles that consisted of Black and White individuals and reported statistics for inflammatory markers for each racial group. Of the 1368 potentially eligible studies, 84 (6.6 %) representing more than one million participants met study selection criteria.

Data extraction and synthesis: Risk of bias was assessed via meta regressions that considered relevant covariates. Data heterogeneity was tested using both the Cochrane Q-statistic and the standard I² index. Random effects models were used to calculate estimates of effect size from standardized mean differences.

Main outcomes and measures: Outcome measures included 12 inflammatory markers, including C-reactive protein (CRP), Fibrinogen, Interleukin-6 (IL-6), Tumor necrosis factor-alpha (TNF-α), and soluble intercellular adhesion molecule 1 (sICAM-1).

Results: Several markers had robust sample sizes for analysis, including CRP (White N = 934,594; Black N = 55,234), Fibrinogen (White N = 80,880; Black N = 18,001), and IL-6 (White N = 20,269; Black N = 14,675). Initial results indicated significant effects on CRP (k = 56, pooled Hedges' g = 0.24), IL-6 (k = 33, g = 0.15), and Fibrinogen (k = 19, g = 0.49), with Black individuals showing higher levels. Results also indicated significant effects on sICAM-1 (k = 6, g = -0.46), and Interleukin-10 (k = 4, g = -0.18), with White individuals showing higher levels. Sensitivity analyses confirmed robust effects for CRP, IL-6, Fibrinogen, and sICAM-1 while also revealing significant effects on TNF-α (k = 18, g = -0.17) and Interleukin-8 (k = 5, g = -0.19), with White individuals showing higher levels of both.

Conclusions and relevance: Current meta-analytic results provide evidence for marked racial differences in common circulating inflammatory markers and illustrate the complexity of the inflammatory profile differences between Black and White individuals. Review Pre-Registration: PROSPERO Identifier - CRD42022312352.