APOE4 genotypes and the trajectory of biomarkers, neuroimaging, and cognitive measures in Alzheimer's Disease: A mixed-effects disease progression model.

Background: The ε4 allele of the apolipoprotein E gene (APOE4) is a major risk factor for developing sporadic Alzheimer's disease (AD). APOE4 homozygosity has been recently proposed as the defining signature of a genetic form of AD. The goal was to assess the role, if any, of APOE4 in AD progression using a mixed-effects disease progression model-informed approach.

Methods: Data from the Alzheimer's Disease Neuroimaging Initiative (ADNI) were analyzed for 2092 participants categorized as cognitively normal (CN), subjective memory concerns (SMC), early mild cognitive impairment (EMCI), late mild cognitive impairment (LMCI), or AD. Each included subject had a median of 5.00 (IQR: 3-8) follow-ups; there were n = 13,699 follow-ups. Demographics, APOE4 genotype, cerebrospinal fluid biomarkers, MRI measures, and neuropsychological tests from baseline to 6-years of follow-up visits were analyzed. Linear mixed-effects models were used to evaluate the impact of the APOE4 genotype on disease progression.

Results: APOE4 heterozygous and homozygous frequencies were higher in AD vs. CN (p < 0.001). APOE4-positive groups were associated with lower levels of amyloid β1-42, higher levels of Tau and phosphorylated tau-181 proteins, lower hippocampus and entorhinal volumes, and worse AD Assessment Scale Cognitive-11 (ADAS-COG11), ADAS-COG13, and Mini-Mental State Examination neuropsychological test scores. The progression of the biomarkers over time was not associated with APOE4 positivity. The progression of all MRI measures and neuropsychological test scores was associated with APOE4 positivity.

Conclusions: APOE4 genotypes adversely influence the levels of biomarkers and the progression of neuroimaging and cognitive outcomes in AD.