Standardised measurement of self-awareness deficits in FTD and AD

Abstract

Background: Diminished ability to perceive one's own impairments, whether cognitive or social, is common in dementia, in particular frontotemporal dementia (FTD), where 'lack of insight' is listed as a core diagnostic feature. Yet, there is no currently accepted method for measuring insight in dementia. The most commonly used methods, which involve comparing patients' opinions of their level of impairment with the opinions of care givers or close family members, are subjective and require the participation of a knowledgeable informant. Here, the authors introduce a new method that allows objective quantification of an individual's awareness of their cognitive abilities and relies upon objective bedside testing.

Methods: The authors administered several tests of everyday, real-world functions to patients with FTD (n=10) and Alzheimer's disease (AD, n=10) and to control subjects (n=10). Prior to the tasks, participants were asked to predict their performance using a percentile-based rating system. They were also asked to estimate their performance after task completion. Differences between their self-rated and actual performances were calculated.

Results: Whereas the control group showed very little discrepancy between pretest predictions, post-task estimates and actual performance (mean difference of 3.9 percentile points for prediction/3.0 percentile points for post-task estimate), both patient groups overpredicted and overestimated their performance, with a significantly greater discrepancy for FTD (49.0/54.3 percentile points) than AD (27.2/28.3 percentile points).

Discussion: Failures of insight and self-awareness of cognitive dysfunction can be objectively measured in dementia without the assistance of an informant, which will facilitate further study of this key component of higher cognitive functioning.

Figure 1

Bell curve picture used to help patients predict and estimate their performance.

Figure 2

Mean and standard error of the post-test performance estimates in control, FTD, and AD subjects.

Figure 3

Left side: Mean and standard error of the discrepancies between pre-test performance prediction and actual NAB performance on a percentile scale. Right side: scatterplots of these discrepancies in each group.

Figure 4

Mean and standard error of the discrepancies between post-test performance rating and actual NAB performance on a percentile scale. Right side: scatterplots of these discrepancies in each group.