Reaction time prolongation in the early stage of presenile onset Alzheimer's disease.

Simple reaction times (RT) to clicks, flashes and numerical signals were measured in four groups of subjects: 21 patients with mild presenile onset dementia of the Alzheimer type (PDAT, mean age 56 years), 14 patients with chronic cardiovascular disease and incipient cognitive deficit (mean age 55 years), 15 healthy older controls (mean age 53 years) and 16 younger controls (mean age 23 years). Both patient groups had significantly prolonged RTs, the PDAT group especially to the numerical signal (149%), compared with the age-matched controls.