Comparison of neuropsychological profiles in patients with Alzheimer's disease and mixed dementia

Objects: We designed this study to extensively compare the neuropsychological profiles of Alzheimer's disease (AD) and mixed dementia (MD) in a large multicenter cohort of patients. Specifically, we performed subgroup analyses to examine group differences associated with dementia severity.

Methods: A total of 1021 AD patients and 577 MD patients were included from the Clinical Research Center for Dementia of South Korea (CREDOS) Study. All patients underwent comprehensive neuropsychological and functional ratings, as well as complete physical and neurological examinations. To avoid floor confounds, only patients with Clinical Dementia Rating (CDR) scores of 0.5-2.0 were included.

Results: Overall, MD patients showed worse performance in frontal/executive function than those with AD. Stratification by dementia severity revealed a significant difference in global cognitive function scores between AD and MD patients only in the low severity groups (CDR 0.5). Also, MD patients showed worse performance in frontal/executive function domains in the CDR 0.5 groups whereas they had better performance in the memory domain in the CDR 1 groups than did AD patients. Additionally, AD patients showed better performance than MD patients with respect to activities of daily living at CDR levels 0.5 and 1. All differences had disappeared at the CDR 2 level of global dementia severity.

Conclusion: This study suggests that there are significant differences in neuropsychological profiles between AD and MD patients, with the pattern of this difference varying distinctively according to dementia severity.