Examining Cognitive Decline Across Black and White Participants in the Harvard Aging Brain Study

Abstract

Background: Black Americans are approximately twice as likely to develop dementia as compared to White Americans and the magnitude of this disparity is often attributed to a variety of factors that include psychosocial and vascular risk factors. However, less is known about the potential contribution of Alzheimer's disease pathological differences.

Objective: To examine potential differences incross-sectional and longitudinal cognitive performance in black and white participants who were clinically normal at baseline.

Methods: 296 participants (48 African-American/black participants) underwent MRI and amyloid PET at baseline. Linear mixed models were used to examine the main effects of race, years of education, reading ability, Framingham Heart Study cardiovascular risk score (FHS-CVD), white matter hyperintensities (WMH), and amyloid (Aβ) burden on the Preclinical Alzheimer Cognitive Composite-5 (PACC5).

Results: Lower levels of educationalattainment and reading ability were found for blacks compared to whites. By contrast, no differences in FHS-CVD, WMH, or Aβ were found by racial group. Baseline differences in PACC5 score were attenuated after adjusting for educationalfactors, vascular factors, and Aβ, but remained lower for blacks compared to whites (β= -0.24, p = 0.014). Further, blacks demonstrated a faster rate of PACC5 decline longitudinally compared to whites (β = -0.055, p = 0.025) after adjusting for covariates.

Conclusion: Accounting for educationalfactors, vascular factors, and Aβ burden diminished, but did not eliminate, racial differences in PACC5 performance longitudinally. Understanding potential differences in longitudinal cognitive outcomes by race may be important for upcoming secondary prevention trials.

Keywords: African-American; amyloid; cognitive decline; preclinical Alzheimer’s disease.

Figure 1.

Longitudinal cognitive trajectories of participants by race PACC=Preclinical Alzheimer’s cognitive composite (z score), time is in years. Model controlling for demographic factors, educational factors, vascular factors, and amyloid. Continuous variables centered to sample mean.

Figure 2.

Longitudinal PACC performance as a function of race and amyloid level (by tertile). ACC=Preclinical Alzheimer’s cognitive composite (z score), time is in years. Model controlling for demographic factors and educational factors. Continuous variables centered to sample mean.