Individuals with Down syndrome (DS) are at high risk of developing Alzheimer's disease (AD). Discovering reliable biomarkers which could facilitate early AD diagnosis and be used to predict/monitor disease course would be extremely valuable. To examine if analytes in blood related to amyloid plaques may constitute such biomarkers, we conducted meta‐analyses of studies comparing plasma amyloid beta (Aβ) levels between DS individuals and controls, and between DS individuals with and without dementia. PubMed, Embase, and Google Scholar were searched for studies investigating the relationship between Aβ plasma concentrations and dementia in DS and 10 studies collectively comprising >1,600 adults, including >1,400 individuals with DS, were included. RevMan 5.3 was used to perform meta‐analyses. Meta‐analyses showed higher plasma Aβ₄₀ (SMD = 1.79, 95% CI [1.14, 2.44], Z = 5.40, p < .00001) and plasma Aβ₄₂ levels (SMD = 1.41, 95% CI [1.15, 1.68], Z = 10.46, p < .00001) in DS individuals than controls, and revealed that DS individuals with dementia had higher plasma Aβ₄₀ levels (SMD = 0.23, 95% CI [0.05, 0.41], Z = 2.54, p = .01) and lower Aβ₄₂/Aβ₄₀ ratios (SMD = −0.33, 95% CI [−0.63, −0.03], Z = 2.15, p = .03) than DS individuals without dementia. Our results indicate that plasma Aβ₄₀ levels may constitute a promising biomarker for predicting dementia status in individuals with DS. Further investigations using new ultra‐sensitive assays are required to obtain more reliable results and to investigate to what extent these results may be generalizable beyond the DS population.

中文翻译：

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血浆淀粉样蛋白和 tau 作为唐氏综合征痴呆生物标志物：系统评价和荟萃分析。

患有唐氏综合症 (DS) 的人患阿尔茨海默病 (AD) 的风险很高。发现可促进 AD 早期诊断并用于预测/监测病程的可靠生物标志物将非常有价值。为了检查与淀粉样蛋白斑块相关的血液中的分析物是否可以构成此类生物标志物，我们对比较 DS 个体和对照组以及患有和不患有痴呆症的 DS 个体之间的血浆淀粉样蛋白 (Aβ) 水平的研究进行了荟萃分析。在 PubMed、Embase 和 Google Scholar 中搜索了调查 Aβ 血浆浓度与 DS 痴呆之间关系的研究，并纳入了 10 项研究，总共包含 >1,600 名成人，其中包括 >1,400 名 DS 患者。RevMan 5.3 用于进行荟萃分析。荟萃分析显示更高的血浆 Aβ₄₀ (SMD = 1.79, 95% CI [1.14, 2.44], Z  = 5.40, p  < .00001) 和血浆 Aβ ₄₂水平 (SMD = 1.41, 95% CI [1.15, 1.68], Z  = 10.46, p  < .00001) 00001) 在 DS 个体中比对照组具有更高的血浆 Aβ ₄₀水平 (SMD = 0.23, 95% CI [0.05, 0.41], Z  = 2.54, p  = .01) 和更低的 Aβ ₄₂ /Aβ _{40 个}比率（SMD = -0.33，95% CI [-0.63，-0.03]，Z  = 2.15，p  = .03）比没有痴呆的 DS 个体。我们的结果表明血浆 Aβ ₄₀水平可能构成预测 DS 患者痴呆状态的有希望的生物标志物。需要使用新的超灵敏检测进行进一步研究，以获得更可靠的结果，并研究这些结果在多大程度上可以推广到 DS 群体之外。