Citations

AbstractBackgroundPlasma biomarkers such as Aβ 42/40 have emerged as important tools to detect dementia risk, although whether plasma Aβ 42/40 levels and the associations with dementia risk differ by race is unclear. As part of the Health, Aging, and Body Composition study, we compared the plasma levels of Aβ 42/40 ratio and the associations with 15‐year dementia risk by race among community‐dwelling Black and White older adults.MethodsWe studied 997 dementia‐free participants (55% women, 54% Blacks) aged 70‐79 years (mean age 74.5±2.9) enrolled at baseline (1997‐98). We defined incidence dementia over 15 years based on hospital records, prescription for dementia medication, or a decline ≥1.5 standard deviations in the Modified Mini‐Mental State Examination score. Stored plasma obtained one year after baseline was used to measure Aβ with Innogenetics INNO‐BIA assays at Mayo Clinic, Jacksonville, FL. Plasma Aβ42/40 ratio was categorized into low, medium, and high tertiles. We used linear regression to estimate the difference in log‐transformed Aβ42/40 in Black and White participants and back‐transformed the effect estimates. We assess the association between Aβ42/40 (by tertiles) and dementia risk using Cox proportional hazards model stratified by race. All models were adjusted for age, sex, hypertension, diabetes, high cholesterol, and obesity, and we tested for interactions by race.ResultsBlack participants had significantly lower Aβ42/40 than White participants (‐4.4%, 95% CI ‐8.1% to ‐0.6%). In stratified analysis, lower Aβ42/40 was significantly associated with an increased risk of incident dementia among Black participants: 27.8% in medium (hazard ratio [HR] 1.69, 95% CI 1.07 to 2.68) and 33.5% in low (HR 2.07, 95% CI 1.32 to 3.24) compared with 17.3% in high Aβ42/40 tertile. The associations were somewhat weaker but showed the same trend among White participants: 20.3% in medium (HR 1.49, 95% CI 0.85 to 2.61) and 22.9% in low (HR 1.59, 95% CI 0.92 to 2.76) compared with 15% in high Aβ42/40 tertile. The interaction between Aβ42/40 and race was not statistically significant.ConclusionAmong community‐dwelling, non‐demented older adults, plasma Aβ42/40 differs by race, although the association with dementia risk does not differ by race.