Effects of Alzheimer’s disease genetic risk on brain morphometric development in three multiple‐ancestry pediatric datasets

Abstract

AbstractBackgroundFew prior studies have investigated whether genetic risk for Alzheimer’s disease (AD) can manifest through altered neurodevelopment of AD‐vulnerable brain regions. This pre‐registered study tests the effects of AD polygenic risk on morphometric neurodevelopment across 3 large datasets totaling 8,364 youths aged 3‐22 (Table 1)MethodPolygenic risk score (PRS) was calculated using PRS‐CS software, with summary scores from Kunkle et al. (2021) for African ancestry individuals (AA) and Jansen et al. (2019) for European ancestry individuals (EA). For EA only, PRS were calculated with (PRS‐APOE+) and without (PRS‐APOE‐) the APOE locus included. All individuals had T1‐weighted MRI processed with FreeSurfer that passed quality assessment checks. ComBAT was used to harmonize sites within‐cohort. Primary analyses investigated effects of PRS, age and their interaction on bilateral hippocampal volume and AD MetaROI cortical thickness using generalized additive models. Age interactions were not evaluated in ABCD due to limited age range. Exploratory analysis examined effects of age and PRS on cortical thickness, volume, surface area and subcortical volume across Desikan‐Killiany regions, adjusting for multiple comparisons (FDR). For exploratory analyses only, ABCD was split into training and test sets. All analyses were conducted for EA and AA separately; sex, total intracranial volume, image quality (Euler number) and ten genetic principal components were included as model covariates.ResultTable 1 summarizes primary results. Hippocampal volume increased with age in 3/6 datasets, while MetaROI thickness decreased with age in all datasets. Surprisingly, increased PRS was associated with larger hippocampi in three datasets. In one dataset only, greater PRS was associated with increased metaROI thickness (Fig 1). 2/3 AA datasets showed age*PRS interactions on hippocampal volume, but in opposite directions. An age*PRS interaction on metaROI thickness was found in one dataset (Fig. 2A‐C). For exploratory analyses, no regions survived multiple comparisons for any contrast in 5/6 datasets; APOE only PRS was associated with larger supramarginal surface area in one dataset (Fig 2E). Effects were not correlated across studies (Fig 2D)ConclusionThis large, pre‐registered study provides little evidence that AD genetic risk manifests during pediatric brain morphometric development.