Association of Plasma Amyloid-β and Dementia Among Black and White Older Adults

Abstract

Background:

Plasma amyloid-β (Aβ) has emerged as an important tool to detect risks of Alzheimer’s disease and related dementias, although research in diverse populations is lacking.

Objective:

We compared plasma Aβ_42/40 by race with dementia risk over 15 years among Black and White older adults.

Methods:

In a prospective cohort of 997 dementia-free participants (mean age 74±2.9 years, 55% women, 54% Black), incident dementia was identified based on hospital records, medication, and neurocognitive test over 15 years. Plasma Aβ_42/40 was measured at Year 2 and categorized into low, medium, and high tertile. We used linear regression to estimate mean Aβ_42/40 by race and race-stratified Cox proportional hazards models to assess the association between Aβ_42/40 tertile and dementia risk.

Results:

Black participants had a lower age-adjusted mean Aβ _42/40 compared to White participants, primarily among APOE ɛ4 non-carriers (Black: 0.176, White: 0.185, p = 0.035). Among Black participants, lower Aβ _42/40 was associated with increased dementia risk: 33% in low (hazard ratios [HR] = 1.77, 95% confidence interval 1.09–2.88) and 27% in medium tertile (HR = 1.67, 1.01–2.78) compared with 18% in high Aβ _42/40 tertile; Increased risks were attenuated among White participants: 21% in low (HR = 1.43, 0.81–2.53) and 23% in medium tertile (HR = 1.27, 0.68–2.36) compared with 15% in high Aβ 42/40 tertile. The interaction by race was not statistically significant.

Conclusions:

Among community-dwelling, non-demented older adults, especially APOE ɛ4 non-carriers, Black individuals had lower plasma Aβ _42/40 and demonstrated a higher dementia risk with low Aβ_42/40 compared with White individuals.