Decreased awareness of cognitive deficits in patients with mild dementia of the Alzheimer type

Abstract

Objective: To study the unawareness of cognitive deficits in patients with mild dementia of Alzheimer type (DAT).

Design: Retrospective study. We surveyed the medical records of outpatients meeting the NINCDS-ADRDA criteria for probable DAT who were able to complete the Cognitive Difficulties Scale (CDS) and had a close informant relative (IR) who could complete the family form of the same questionnaire.

Setting: A department of neurology in a general teaching hospital.

Subjects: Eighty-eight patients, aged 73.2+/-8.6 years with a mean MMSE score of 22.5+/-3.2. Fifty-two of the 88 patients had a follow-up examination after a mean interval of 21 months.

Methods: Awareness of cognitive deficits was mainly assessed as the difference between the scores on the CDS completed by the IR and the patient (Index of Unawareness, IU). Two secondary assessments of unawareness were performed: (1) an assessment by the clinician on the basis of the patient's answers to questions probing the awareness of memory deficits; (2) an evaluation by the IR of the frequency of behavioural manifestations of unawareness in everyday life. SPECT was performed in 78 patients to study the relationship between unawareness and the topography of perfusion deficits.

Results: Awareness of the cognitive deficits varied greatly between patients, according to the assessment method used and the stage of progression of the disease. Most patients with mild DAT were cognitively aware of their cognitive deficits but failed to appraise their severity and their consequences in everyday life. Decreased awareness was positively correlated with age and perfusion deficits in the frontal regions and negatively with the anxious symptomatology. However, the main correlate of unawareness was apathy.

Conclusion: The nature of unawareness of cognitive deficits appeared to be more dimensional than categorical. In patients with mild dementia, decreased awareness appeared to be more related to affective disturbances, especially to emotional deficit or apathy, than to cognitive deficits.