Relationship between cognition and awareness of deficit in mild cognitive impairment.

OBJECTIVE: Although anosognosia is common in Alzheimer's disease (AD), limited research has investigated awareness among patients with mild cognitive impairment (MCI). The current study examined cognitive performance differences between MCI patients who were aware or unaware of their deficits.
METHODS: Participants were 65 patients who underwent a comprehensive neuropsychological evaluation and diagnosed with MCI according to Petersen's criteria. Participants were divided into groups based on clinician rating of awareness (aware n=30 or unaware n=35), which was determined following interview with the patient and family member. Neuropsychological measures were converted into z-scores based on sample mean and standard deviation and averaged across cognitive domains. Frontal behavioral ratings were also collected.
RESULTS: No significant differences were found between awareness groups for age, education, gender, or MMSE score. Individuals rated as unaware performed significantly worse in the learning domain and a trend for worse performance on the Dementia Rating Scale-II total score than those rated as aware. None of the other cognitive or behavioral domains differed between the groups. Clinician and informant ratings of anosognosia were only modestly correlated, and we found an unexpected pattern of relationships between informant ratings and cognitive performance.
CONCLUSIONS: Awareness deficits are common in MCI patients. Our results argue against the most common etiologic hypotheses in AD (i.e., executive and right hemisphere) and suggest that severity of encoding deficits underlie anosognosia in MCI.