BACKGROUND: Plasma biomarkers associated with Alzheimer's disease could improve prognostic assessment for people with Down syndrome in both clinical practice and research settings. We aimed to identify the plasma biomarkers that most accurately predict longitudinal changes in Alzheimer's disease-related pathology and cognitive functioning in individuals with Down syndrome.
METHODS: This longitudinal cohort study included data from 258 adults (aged โฅ25 years) with Down syndrome who were followed up prospectively every 16 months as part of the longitudinal Alzheimer's Biomarker Consortium-Down Syndrome study (recruited from seven university sites in the USA and UK between July 13, 2016, and Jan 15, 2019). Participants had baseline and longitudinal assessments of plasma tau phosphorylated at threonine 217 (p-tau217), glial fibrillary acidic protein (GFAP), amyloid ฮฒ (Aฮฒ), neurofilament light (NfL), or total tau (t-tau). Associations of baseline plasma biomarkers and longitudinal changes in plasma biomarkers with changes in global cognitive functioning (Down Syndrome Mental Status Examination [DS-MSE] scores), Aฮฒ-PET, and tau-PET were examined using linear regression models. Plasma biomarker-associated risk of progression to dementia was assessed using Cox regression analysis. 42/40
FINDINGS: Baseline p-tau217, as well as GFAP, NfL, or t-tau, were individually associated with longitudinal changes in DS-MSE, Aฮฒ-PET, and tau-PET, and with progression to dementia. However, in combined models, only baseline p-tau217 remained associated with changes in DS-MSE (ฮฒ -0ยท30 [95% CI -0ยท45 to -0ยท15], p=0ยท0001, n=220), tau-PET (0ยท42 [0ยท14 to 0ยท70], p=0ยท0039, n=88), and progression to dementia (hazard ratio 3ยท51 [95% CI 1ยท76-7ยท00], p=0ยท0004, n=194), whereas baseline p-tau217 (0ยท29 [0ยท14-0ยท45], p=0ยท0003) and GFAP (0ยท37 [0ยท18-0ยท56], p=0ยท0003) were associated with changes in Aฮฒ-PET (n=106 for both). Similar associations were shown between longitudinal p-tau217 or GFAP and changes in DS-MSE (p-tau217: ฮฒ -0ยท33 [95% CI-0ยท52 to -0ยท13], p=0ยท0015, n=133), tau-PET (p-tau217: 0ยท61 [0ยท40 to 0ยท83], p<0ยท0001, n=87), and Aฮฒ-PET (p-tau217: 0ยท35 [0ยท19 to 0ยท50], p<0ยท0001; GFAP: 0ยท49 [0ยท27 to 0ยท70], p<0ยท0001, n=88).
INTERPRETATION: Baseline and longitudinal plasma p-tau217 were associated with subsequent decline in global cognition, progression to dementia, and increased tau burden, whereas baseline p-tau217 and GFAP were associated with Aฮฒ accumulation. These findings suggest that plasma p-tau217 and GFAP might be valuable for prognostic assessment of Alzheimer's disease in people with Down syndrome in both clinical and research contexts. The results further support evaluation of these biomarkers for monitoring disease progression in clinical trials of Down syndrome-related Alzheimer's disease.
FUNDING: The European Research Council and National Institute on Aging (National Institute of Health).
