Patterns of Neuropsychological Impairment in Alzheimer’s Disease and Mixed Dementia

Abstract

Background Mixed dementia (MD), i.e., the coexistence of Alzheimer's disease (AD) and cerebrovascular disease (CVD), is a common dementia subtype. Few studies have attempted to establish the cognitive profiles of mild-moderate MD and compare it to the profiles of AD using a comprehensive neuropsychological test battery. We aimed to establish the neuropsychological profile of mild-moderate MD in relation to mild-moderate AD.Methods Patients with consensus diagnoses of MD and AD of mild-moderate severity (Clinical Dementia Rating score of 1-2) were recruited from a memory clinic. Cognitive performance was measured by a formal neuropsychological battery covering domains of attention, language, verbal and visual memory, visuoconstruction, visuomotor speed and executive function. Cognitive domain scores are z-scores calculated using the mean and SDs of the AD group. ANCOVAs with age and education as covariates were employed to examine differences in mean score difference of cognitive domains and subtests between patients with MD and AD.Results 151 patients were recruited with the majority of AD (n=96, 63.6%) and a minority of MD (n=55, 36.4%). There were no significant differences in the demographic characteristics of patients with MD and AD. However, patients with MD were significantly more impaired than AD patients in global cognitive composite, attention and visuoconstruction (global cognitive composite: -0.32±0.98 vs 0±1, p=0.011; attention: -0.32±0.90 vs 0±1, p=0.013; visuoconstruction: -0.27±0.99 vs 0±1, p=0.024, respectively).Conclusion The neuropsychological profile of patients with MD of mild-moderate severity is characterized by a poorer global performance, as well as attention and visuoconstruction than those with AD of mild-moderate severity.