Longitudinal patterns of unawareness of memory deficits in mild Alzheimer's disease

Patients with Alzheimer's disease (AD) frequently demonstrate impaired awareness of their cognitive difficulties. However, less is known about the longitudinal progression of this phenomenon. We examined the longitudinal evolution of unawareness in patients with mild AD to determine whether impaired awareness progresses with cognitive decline. Based on Mini-Mental State Examination (MMSE) score changes after a 1-year follow up, 39 patients were regarded as the stabilized group and 19 patients were regarded as the non-stabilized group. The unawareness of memory impairment was evaluated with a standardized questionnaire system based on the Everyday Memory Checklist (EMC). The EMC scores for the patient's own rating, the caregivers' rating and the unawareness score, defined as the difference between these (caregiver rating - patient rating), were analyzed. Although unawareness scores were similar in the two groups at the initial examination, they were significantly higher in the non-stabilized group than in the stabilized group at the follow up examination. There was a significant and negative correlation between change in unawareness score and change in MMSE score over time (r = -0.56, P < 0.0001). Our results indicated that impaired awareness progressed with cognitive decline. The EMC may be a simple and useful tool for the monitoring of progression in patients with AD.