The P1 component of the middle latency auditory evoked potential predicts a practice effect during clinical trials in Alzheimer's disease.

Abstract

Thirty-five patients with probable Alzheimer's disease who were enrolled in an experimental drug trial of linopirdine underwent repeated testing that included recording the middle latency auditory evoked potential (MLAEP), the Mini-Mental State Examination (MMSE), and the Alzheimer's Disease Assessment Scale Cognitive Subscale (ADASCOG). Patients lacking the P1 component of the MLAEP exhibited a significantly greater decline in cognitive function as measured by the ADASCOG over 56 weeks. This decline appeared to be due to a less robust practice effect, which was maximal in all patients at 16 weeks. At the end of 56 weeks the entire group of patients was near baseline with respect to the ADASCOG. This lack of the annualized decline expected from other longitudinal studies may be explained by practice and placebo effects. The MMSE did not exhibit a practice effect and showed the expected decline in scores.