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 Aβ(1-40) and Aβ(1-42) 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 Aβ(1-40) and Aβ(1-42) levels. The CSF Aβ(1-42) levels were significantly decreased in patients with DS compared to those in HC subjects. Further, CSF Aβ(1-42) 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 Aβ(1-40) and Aβ(1-42) levels were significantly increased in patients with DS while CSF Aβ(1-42), but not Aβ(1-40) levels were significantly decreased in patients with DS.