Apolipoprotein ε4 and neuropsychological performance in Alzheimer's disease and vascular dementia

The apolipoprotein (APOE) epsilon 4 allele is a genetic risk factor for the development of Alzheimer's disease (AD). It has also been associated with vascular dementia (VaD) in some but not all studies. Previous studies have examined the role of APOE in predicting performance on cognitive tests in both demented and non-demented populations. In cognitively intact individuals, statistically significant group differences between APOE epsilon 4 carriers and non-carriers have been demonstrated for several cognitive domains. In AD studies of the impact of APOE epsilon 4 on cognition have been conflicting while no previous study has assessed cognition and impact of APOE epsilon 4 in VaD. In this study we investigated the impact of APOE epsilon 4 on performance in neuropsychological tests including information processing speed in patients with mild-moderate AD and VaD. We incorporated both computerized and pen and paper tests to ensure a sensitive method of assessing cognition. 109 patients participated in the study (VaD = 41, AD = 68). Neurocognitive performance of 44 epsilon 4 present AD patients was compared to 24 epsilon 4absent patients and performance of 23 epsilon 4 present VaD patients was compared to 18 epsilon 4 absent patients. There was evidence that APOE epsilon 4 conferred a risk of poorer cognitive functioning in both patient groups. In the AD group presence of epsilon 4 conferred a negative impact on some measures of speed of information processing and immediate recall while in the VaD group epsilon 4 present patients had evidence of poorer accuracy on tasks such as choice reaction time and spatial working memory. In AD and VaD groups epsilon 4 present patients showed impairment in selective attention. These findings provide further support of the negative impact of the epsilon 4 allele in cognition. (C) 2010 Elsevier Ireland Ltd. All rights reserved.