Serum -Amyloid Correlates with Neuropsychological Impairment

Aims: Evidence suggests a relationship between peripheral A and AD. We hypothesized that higher levels of serum A1-42 would be associated with memory impairment, thought to occur early in the disease, and rises in serum A1-40, which occur later, would be associated with impairment in non-memory measures. Methods: Using a cross-sectional design, we examined the relationship of serum A1-40, A1-42, and the ratio of A1-42/1-40 to neuropsychological measures in 40 cognitively normal controls, 13 MCI subjects, and 25 AD patients. Results: Serum A1-42 and the ratio of A1-42/1-40 were significantly higher in the MCI group compared to the controls. A significant relationship in the hypothesized direction (poorer scores associated with higher A1-40 serum levels) was found between A1-40 and measures of executive functions across the entire cohort of individuals tested and with measures of language and processing speed in the AD group. Regression analysis found that neuropsychological measures accounted for 26% of the variance in serum A1-40, in the MCI/AD but not the controls. Furthermore that language and executive measures were significant predictors. Conclusions: Results provide preliminary data to partially support our hypotheses and suggest that changes in serum A levels may be attributed to pathological changes within the brain.