Three-year follow-up of cerebrospinal fluid tau, beta-amyloid 42 and 40 concentrations in Alzheimer's disease.

Earlier studies have shown elevated levels of tau protein and decreased levels of amyloid beta42 in cerebrospinal fluid (CSF) from patients with Alzheimer's disease (AD). We investigated the concentrations of Abeta42, Abeta40 and tau in CSF from AD patients on the baseline and after follow-up period of 3 years using ELISA assays. There was a significant decrease of Abeta42 (P<0.05) and Abeta40 (P<0.05) levels with time. AD patients with the duration of the disease 2 years or less at baseline had more pronounced decrease of Abeta42 concentrations compared to those with the duration of the disease more than 2 years at baseline (P<0.05). CSF tau protein concentrations increased in 9/17 but decreased in 8/17 patients. These results suggest that Abeta42 and Abeta40 may be useful in monitoring the long-term progression of AD particularly in the early stages of the disease.