Impaired insight in Alzheimer's disease.

We studied insight into illness in 41 patients with probable Alzheimer's disease. An impaired insight score was developed by measuring discrepancies between patient report and caregiver report on standard instruments of activities of daily living. Insight was more impaired in subjects with greater dementia severity and subjects with paranoid delusions. In a multivariate analysis, the best neuropsychological predictors of impaired insight were the Continuous Performance Test and the Visual Reproduction Test. We speculate that the impaired insight of Alzheimer's disease has two components: confabulation reflecting prefrontal dysfunction and anosognosia reflecting right-hemisphere dysfunction.