The apolipoprotein E epsilon 4 (ApoE4) allele is the strongest genetic risk factor for Alzheimer's disorder (AD) and is associated with semantic and episodic memory deficits. The aim of this study was to examine the associations between ApoE alleles (E2, E3, E4) and genotypes and neuropsychological tests, behavioral functions, and dementia symptoms as assessed using Consortium to Establish a Registry for Alzheimer's Disease (CERAD). This study included 60 patients with Alzheimer's disorder (AD), 60 with mild cognitive disorder (MCI), and 62 normal volunteers. ApoE4 carriers and individuals with E3/E4 and E4/E4 genotypes show an increased incidence of AD, but not MCI. ApoE4 carriers and especially E4/E4 homozygotes show a worse outcome on the CERAD total score, Blessed Dementia Scale, and Short Blessed Test and lower scores on the Verbal Fluency Test, Boston Naming Test, Constructional Praxis Recall, and Word List Memory, Recall, and Recognition. ApoE4 carriers and E4/E3 heterozygotes show higher scores on the Clock Drawing Test. ApoE4 carriers show a worse outcome on the CERAD clinical history scores of memory, language, personality, ADL, orientation, and social skills, while allele AopE3 carriers show better scores on activities of daily living (ADL) and social skills. ApoE3 carriers show lower total weighted, irritability/aggression, and behavioral dysregulation scores on the Behavior Rating Scale for Dementia. The results show that in Thai individuals, the presence of ApoE4 allele is accompanied by a multifarious decline in neurocognitive functions and behavioral features and that ApoE3 may convey protection against neuropsychiatric symptoms and a decline in social skills. ApoE4 and especially the E4/E4 genotype may affect multiple domains of cognitive, biobehavioral, and social functioning thereby contributing to AD phenomenology.
Keywords: Alzheimer; ApoE; ApoE4; Behavior; CERAD; Cognition; Dementia.