Neuropsychological correlates of self-reported performance in instrumental activities of daily living and prediction of dementia.

This study examines the relationships between performance on neuropsychological tests and 4 instrumental activities of daily living (IADL) associated with an increased risk of dementia, in 1,792 nondemented elderly people included in the Personnes Agées Quid (PAQUID) study. There was a decline of neuropsychological performance on each test with increasing IADL dependency, in particular between Grades 1 and 2. Performances of the independent participants were very homogeneous. Each IADL had different specific associations with the neuropsychological tests. A principal component analysis showed three main factors explaining 49.6% of variance. The first factor was the common cognitive component of both instrumental tasks and neuropsychological tests. The second factor was specific to three IADL, whereas use of transportation had its main loading on the third factor. Only the first factor was predictive of the risk of incident dementia, suggesting that the predictive value of the 4 IADL was explained by their cognitive component.