Deficits in controlled processing may predict dementia: A twin study

This study tested for differential patterns of cognitive decline in 33 twin pairs for which both were nondemented, but 1 member of the pair went on to develop dementia. Compared with their nondemented twin partners, twins who later developed dementia already showed poorer performance on tests of mem ory and attention, visuospatial-reasoning skills, and perceptual speed and the Mini-Mental State Examination (MMSE). The authors suggest that this clu ster of tests reflects deficits in controlled rather than automatic cogniti ve processes. Nondemented twin partners of the twins who became demented we re also compared with 33 matched controls selected from pairs in which both members remained nondemented. Nondemented twin partners scored lower than matched controls on tests of verbal ability, memory and attention, and perc eptual speed and the MMSE. This finding indicates that nondemented twin par tners of demented twins are at elevated risk themselves for becoming dement ed, and further suggests that certain areas of cognition are compromised pr ior to diagnosis of dementia.