Contribution of Individual and Neighborhood Factors to Racial Disparities in Respiratory Outcomes

Abstract

Rationale: Black adults have worse health outcomes compared with white adults in certain chronic diseases, including chronic obstructive pulmonary disease (COPD).Objectives: To determine to what degree disadvantage by individual and neighborhood socioeconomic status (SES) may contribute to racial disparities in COPD outcomes.Methods: Individual and neighborhood-scale sociodemographic characteristics were determined in 2,649 current or former adult smokers with and without COPD at recruitment into SPIROMICS (Subpopulations and Intermediate Outcome Measures in COPD Study). We assessed whether racial differences in symptom, functional, and imaging outcomes (St. George's Respiratory Questionnaire, COPD Assessment Test score, modified Medical Research Council dyspnea scale, 6-minute-walk test distance, and computed tomography [CT] scan metrics) and severe exacerbation risk were explained by individual or neighborhood SES. Using generalized linear mixed model regression, we compared respiratory outcomes by race, adjusting for confounders and individual-level and neighborhood-level descriptors of SES both separately and sequentially.Measurements and Main Results: After adjusting for COPD risk factors, Black participants had significantly worse respiratory symptoms and quality of life (modified Medical Research Council scale, COPD Assessment Test, and St. George's Respiratory Questionnaire), higher risk of severe exacerbations and higher percentage of emphysema, thicker airways (internal perimeter of 10 mm), and more air trapping on CT metrics compared with white participants. In addition, the association between Black race and respiratory outcomes was attenuated but remained statistically significant after adjusting for individual-level SES, which explained up to 12-35% of racial disparities. Further adjustment showed that neighborhood-level SES explained another 26-54% of the racial disparities in respiratory outcomes. Even after accounting for both individual and neighborhood SES factors, Black individuals continued to have increased severe exacerbation risk and persistently worse CT outcomes (emphysema, air trapping, and airway wall thickness).Conclusions: Disadvantages by individual- and neighborhood-level SES each partly explain disparities in respiratory outcomes between Black individuals and white individuals. Strategies to narrow the gap in SES disadvantages may help to reduce race-related health disparities in COPD; however, further work is needed to identify additional risk factors contributing to persistent disparities.

Keywords: COPD; neighborhood disadvantage; racial disparities; socioeconomic status.

Figure 1.

Differences in respiratory outcomes between Black individuals and white individuals are attenuated by individual and neighborhood socioeconomic status (SES). Predicted mean difference in chronic obstructive pulmonary disease outcomes and their 95% confidence intervals are shown sequentially across the following three models: model 1 (blue), which adjusts for demographic and individual characteristics; model 2 (red), which also adjusts model 1 for individual SES; model 3 (gray), which also adjusts model 2 for neighborhood SES. The y-axis represents the differences between Black individuals and white individuals in the levels of the outcome (e.g., index score) except for severe exacerbation, for which the y-axis represents log incident rate ratio. The modified Medical Research Council scale, 6-minute-walk test distance, and airway wall thickness (internal perimeter of 10 mm) were rescaled to fit the chart; the modified Medical Research Council score was multiplied by 10, the 6-minute-walk test distance was divided by 10, and the airway wall thickness (internal perimeter of 10 mm) was multiplied by 100. *Statistical significance of difference in the outcome between Black individuals and white individuals. 6MWD = 6-minute-walk test distance; CAT = COPD Assessment Test; COPD = chronic obstructive pulmonary disease; IRR = incident rate ratio; mMRC = modified Medical Research Council scale; Pi10 = internal perimeter of 10 mm; SGRQ = St. George’s Respiratory Questionnaire.