Serum beta-amyloid correlates with neuropsychological impairment

AIMS: Evidence suggests a relationship between peripheral Abeta and AD. We hypothesized that higher levels of serum Abeta(1-42) would be associated with memory impairment, thought to occur early in the disease, and rises in serum Abeta(1-40), which occur later, would be associated with impairment in non-memory measures. METHODS: Using a cross-sectional design, we examined the relationship of serum Abeta(1-40), Abeta(1-42), and the ratio of Abeta(1-42/1-40) to neuropsychological measures in 40 cognitively normal controls, 13 MCI subjects, and 25 AD patients. RESULTS: Serum Abeta(1-42) and the ratio of Abeta(1-42/1-40) were significantly higher in the MCI group compared to the controls. A significant relationship in the hypothesized direction (poorer scores associated with higher Abeta(1-40) serum levels) was found between Abeta(1-40) 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 Abeta(1-40,) 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 Abeta levels may be attributed to pathological changes within the brain.