Investigating the role of chronic stress and perceived discrimination in racial disparities in incident dementia among U.S. older adults.

BACKGROUND: Given notable disparities between White and Black Americans, identifying factors contributing to racial differences in dementia incidence is essential. This study i) investigates the extent to which adulthood chronic stress or perceived discrimination could explain these disparities and ii) estimates the potential reduction in Black-White disparity in dementia risk if racial differences in these factors were eliminated.

METHODS: We utilized data from 5602 participants (4913 White, 689 Black) from the Health and Retirement Study-a longitudinal, nationally representative study of Americans over the age of 50 and causal mediation analysis via the parametric g-formula to estimate effects. Missingness and loss to follow-up was addressed using doubly-robust multiple imputation with inverse probability of censoring weights. Incident dementia was identified using the validated Langa-Weir Classification. Perceived discrimination was measured using the Everyday Discrimination Scale.

RESULTS: Black individuals had a higher risk of dementia compared to White individuals (RR: 2.21 [95 % CI: 1.69, 2.74]). Neither chronic stress (ER: 0.00 [95 % CI: -0.01, 0.02]) nor perceived discrimination mediated the race-dementia relationship (ER: 0.01 [95 % CI: -0.01, 0.02]). However, there was an interaction between race and perceived discrimination ( [Formula: see text] : 0.29 [95% CI 0.06, 0.53]), and race and chronic stress ( [Formula: see text] : 0.29 [95 % CI - 0.54, 1.11]) which accounted for an important portion of the excess risk. Altogether, eliminating chronic stress or perceived discrimination could eliminate 24 % and 25 % respectively of the Black-White racial disparity.

CONCLUSIONS: Differences in chronic stress and perceived discrimination explain about a quarter of the observed Black-White disparities in dementia risk. The presence of interaction suggests that interventions efforts aiming to reduce these disparities should be primarily target Black individuals who have higher levels of chronic stress and perceived discrimination. Further research should seek to comprehensively identify additional mechanisms and interactions contributing to these disparities.