The Association of Plasma Amyloid-β and Cognitive Decline in Cognitively Unimpaired Population

Purpose: This study investigates the relationship between baseline plasma AP and cognitive decline during follow-up in cognitively unimpaired population. Materials and Methods: Cognitively unimpaired population was selected from people who lived in the suburbs of Xi'an, China. The levels of plasma A beta(1-42) and A beta(1-)(40) were tested using commercial enzyme-linked immunosorbent assay (ELISA). The mini-mental state examination (MMSE) and neuropsychological battery were used to assess cognition. Two years later, MMSE was tested again, and significant cognitive decline was defined as a decrease in MMSE scores >= 5 points. Logistic regression analysis was performed to analyze the relationship between baseline plasma A beta and cognitive change during the two-year follow-up. Results: A total of 1144 participants completed the study, among whom 59 subjects (5.2%) presented significant cognitive decline. The high plasma A beta(1-)(42) level group had more significant cognitive decline (P = 0.023). Multivariable logistic regression analysis showed that significant cognitive decline was associated with the high levels of baseline plasma A beta(1-)(42) (OR = 1.043, 95% CI: 1.005-1.083, P = 0.026). However, significant cognitive decline was not associated with baseline plasma A beta(1-)(40) levels and A beta(1-)(42)/A beta(1-)(40) ratio. Conclusion: Population with high level of baseline plasma A beta(1-)(42) manifested significant cognitive decline over 2 years; however, further investigation on the dynamics of plasma A beta and long-term follow-up are needed.