Prospective Associations between Plasma Amyloid-Beta 42/40 and Frailty in Community-Dwelling Older Adults.

Background: Brain amyloid-beta (Aβ) plaques, a hallmark of the pathophysiology of Alzheimer's disease, have been associated with frailty. Whether the plasma Aβ markers show similar relationship with frailty is unknown.
Objectives: To investigate the prospective associations between plasma Aβ42/40 ratio and overtime frailty in community-dwelling older adults.
Methods: From the 5-year Multidomain Alzheimer Preventive Trial (MAPT), we included 477 adults ≥70 years with available data on plasma Aβ42/40 ratio (lower is worse). Fried frailty phenotype (robust, pre-frail and frail) was assessed at the same time-point of plasma Aβ measures and after until the end of follow-up. The outcomes of interest were the change in the frailty phenotype over time (examined by mixed-effect ordinal logistic regressions) and incident frailty (examined by Cox proportional hazard models).
Results: Plasma Aβ42/40 did not show significant associations with incident frailty; however, after adjusting for Apolipoprotein E (APOE) ε4 genotype, people in the lower quartile of plasma Aβ42/40 (≤0.103) had higher risk of incident frailty (HR=2.63; 95% CI, 1.00 to 6.89), compared to those in the upper quartile (>0.123). Exploratory analysis found a significant association between the lower quartile of plasma Aβ42/40 and incident frailty among APOE ε4 non-carriers (HR=3.48; 95% CI, 1.19 to 10.16), but not among carriers. No associations between plasma Aβ42/40 and evolution of frailty were observed.
Conclusion: No significant associations between plasma Aβ42/40 and frailty were found when APOE ε4 status was not accounted into the model. Nevertheless, APOE ε4 non-carriers with high Aβ burden might be more susceptible to develop frailty.
Competing Interests: Washington University and Randall Bateman have equity ownership interest in C2N Diagnostics and receive income based on technology (blood plasma assay) licensed by Washington University to C2N Diagnostics. RJB receives income from C2N Diagnostics for serving on the scientific advisory board. Washington University, with RJB as co-inventor, has submitted the US nonprovisional patent application “Plasma Based Methods for Determining A-Beta Amyloidosis.” RJB has received honoraria as a speaker/consultant/advisory board member from Amgen, AC Immune, Eisai, Hoffman-LaRoche, and Janssen; and reimbursement of travel expenses from AC Immune, Hoffman-La Roche and Janssen.