Abstract
Abnormal β-amyloid (Aβ) levels were found in patients with Down syndrome (DS). However, Aβ levels in patients with DS and DS with dementia (DSD) vary considerably across studies. Therefore, we performed a systematic literature review and quantitatively summarized the clinical Aβ data on the cerebrospinal fluid (CSF) and blood of patients with DS and those with DSD using a meta-analytical technique. We performed a systematic search of the PubMed and Web of Science and identified 27 studies for inclusion in the meta-analysis. Random-effects meta-analysis indicated that the levels of blood Aβ1-40 and Aβ1-42 were significantly elevated in patients with DS compared with those in healthy control (HC) subjects. In contrast, there were no significant differences between patients with DS and those with DSD in the blood Aβ1-40 and Aβ1-42 levels. The CSF Aβ1-42 levels were significantly decreased in patients with DS compared to those in HC subjects. Further, CSF Aβ1-42 levels were significantly decreased in patients with DSD compared to those with DS, with a large effect size. Taken together, our results demonstrated that blood Aβ1-40 and Aβ1-42 levels were significantly increased in patients with DS while CSF Aβ1-42, but not Aβ1-40 levels were significantly decreased in patients with DS.
Highlights
It is well known that patients with Down syndrome (DS), which is a common chromosomal abnormality disease caused by the presence of an extra copy of chromosome 21, have an increased risk of developing early-onset Alzheimer's disease (AD) [1, 2]
The cerebrospinal fluid (CSF) Aβ1-42 levels were significantly decreased in patients with DS compared to those in healthy control (HC) subjects
Meta-analysis of the blood Aβ1-42/Aβ1-40 ration reported in patients with DS by 5 studies encompassing 424 individuals revealed no significant difference between patients with DS and HC subjects (Hedges’ g = -0.830, 95% confidence interval (CI) = -1.919 to 0.259, P = 0.135, Supplementary Figure 1A)
Summary
It is well known that patients with Down syndrome (DS), which is a common chromosomal abnormality disease caused by the presence of an extra copy of chromosome 21, have an increased risk of developing early-onset Alzheimer's disease (AD) [1, 2]. The results of these studies have been inconsistent, a high-profile systematic review and metaanalysis concluded that patients with AD did not have significantly altered blood Aβ1-42 and Aβ1-40 levels compared to those in healthy control (HC) subjects. It indicated that the CSF Aβ1-42 levels were consistently reduced in the patients with AD patients compared to in HC subjects and suggested that CSF Aβ142 is a good biomarker for AD diagnosis [5]. Www.aging-us.com there have been inconsistent results regarding CSF Aβ1-42 and Aβ1-40 levels in patients with DS with dementia (DSD) or without dementia [20, 21]
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