Racial differences in the effect of APOE‐ε4 genotypes on trail making test B in Alzheimer's disease: A longitudinal study

Abstract

AbstractObjectivesThe trail making test part B (TMT‐B) evaluates executive functions, memory, and sensorimotor functions. No previous study was found to examine the longitudinal effect of APOE‐ε4 genotypes on the TMT‐B scores in Alzheimer's disease (AD) across racial groups.MethodsThis study used the data from Alzheimer's Disease Neuroimaging Initiative (ADNI): 382 participants with AD, 503 with cognitive normal (CN), 1293 with mild cognitive impairment (MCI) at baseline and follow‐up of four years. The multivariable linear mixed model was used to investigate the effect of APOE‐ε4 genotypes on changes in TMT‐B scores.ResultsCompared with Whites, African Americans (AA) and Hispanics had higher TMT‐B scores (poor cognitive function). Furthermore, Whites subjects with 1 or 2 APOE‐ε4 alleles had significantly higher TMT‐B scores compared with individuals without APOE‐ε4 allele at baseline and four follow‐up visits; however, no differences in TMT‐B were found between APOE‐ε4 alleles in the Hispanic and AA groups. No APOE‐ε4 by visit interactions was found for 3 racial groups. Stratified by AD diagnosis, the APOE‐ε4 allele was associated with TMT‐B scores only in the MCI group, while there were significant interactions for visit by education, APOE‐ε4 allele, and the Mini Mental State Examination (MMSE) score in the MCI group. In addition, TMT‐B was significantly correlated with the MMSE, AD Assessment Scale‐cognitive subscale 13 (ADAS13), tTau, pTau, Aβ42, and hippocampus.ConclusionsAPOE‐ɛ4 allele is associated with TMT‐B scores in Whites subjects, but not in the Hispanic and AA groups. APOE‐ε4 showed interaction with visit in the MCI group.