Do the known deleterious effects of APOE ε4 affect individuals with ASD more strongly?
Autism spectrum disorder (ASD) is a neurodevelopmental disorder with two main diagnostic criteria: (1) impairment in social communication and interaction, and (2) restrictive, repetitive patterns of behavior. The APOE gene ε4 allele is implicated in Alzheimer’s disease risk and general cognitive impairment. Previous research has found that individuals with ASD have worse visual memory and smaller right hippocampus volumes relative to non-carriers. It has also been reported that those who carry the APOE gene ε4 allele also have worse visual memory and smaller right hippocampus volumes, as compared to non-carriers. In this study, we looked to see if the APOE genotype differentially affects visual memory and right hippocampal size in aging adults with ASD compared to NT. We hypothesized that the presence of an APOE ε4 allele will have a greater detrimental effect on age-related changes to visual memory and right hippocampal size in adults with ASD, than NT adults. We conducted the Weschler Memory Scale Visual Reproduction subtest to measure visual memory function. Participants underwent a magnetic resonance imaging (MRI) scan to ascertain hippocampal volume using FreeSurfer software. Hippocampal size was corrected in intracranial volume. DNA isolated from saliva was APOE genotyped through a polymerase chain reaction (PCR) amplification, and fragments were analyzed on an Agilent Tapestation D1000. Individuals were grouped based on their ε4 carrier status. Data was analyzed through ANCOVA to assess the effects between age (young < 40 vs. middle-aged ≥ 40), diagnosis (ASD vs. NT), and APOE status (ε4 carriers vs. non-carriers) on visual memory and right hippocampal structure. We found that age affects short-term visual memory [F(1,133)= 7.12, p = 0.009] and has a trending effect on right hippocampus size [F(1,133) = 3.096, p = 0.083), and ASD diagnosis has a trending effect on long-term visual memory [F(1,71)= 2.983, p = 0.07]. Our results did not corroborate our hypothesis that APOE ε4 allele would have greater detrimental effects on age-related changes to visual memory and right hippocampal size in adults with ASD, than NT adults. However, these are preliminary results for an ongoing longitudinal study. With a larger sample size and more power, in the future we may find different results. With earlier awareness of biological factors, individuals may be able to undergo earlier preventative care for memory, a crucial function for quality of life. This may come in the form of cognitive therapies for visual memory. It will be important to elucidate how age may affect cognitive and brain aging uniquely for individuals with ASD to ensure they receive adequate care throughout the lifespan.
