Contribution of Four Comorbid Conditions to Racial/Ethnic Disparities in Mortality Risk.

INTRODUCTION: The prevalence of key forms of morbidity such as obesity, diabetes, and chronic kidney disease have increased dramatically in the U.S. and elsewhere for decades. Hypertension is etiologically related but its prevalence has been reduced through improved treatment. These diseases are known to have higher than expected rates of comorbidity, but it is not known whether and how these cluster together differentially by race, nor the degree to which they contribute to racial disparities in mortality.

METHODS: Using data from the National Health Interview Survey mortality follow-up (1997-2009, analyzed in 2016), this paper modeled interdependencies between each combination of these four types of morbidity, overall and net of demographic, socioeconomic, and behavioral controls. It then analyzed whether these diseases mediate the relationship between race/ethnicity and mortality risk using discrete time complementary log-log survival models.

RESULTS: American Indians and blacks had significantly elevated rates of comorbidity compared with whites, and Asians' and Pacific Islanders' rates were often significantly lower than whites'. Controlling for these diseases significantly moderated the mortality risk disparity between African American, Hispanic, and Asian/Pacific Islanders and whites. This remained true when individual health behaviors and neighborhood fixed effects were statistically adjusted for. Notably, the full controls model statistically eliminated the association between African American race and mortality risk.

CONCLUSIONS: These diseases contribute significantly to racial/ethnic mortality disparities, particularly between blacks and whites. Future research should consider the mediating role of these diseases for the relationship between social conditions and mortality risks.