APOE and Alzheimer disease: Similarly, AD-specific cortical thinning was correlated with the AD polygenic risk score, even after controlling for APOE genotype and cerebrospinal fluid (CSF) levels of β-amyloid (N = 104) (Sabuncu et al., 2012).We also aim to progressively increase the sample size of PISA through ongoing recruitment, and lengthen and increase longitudinal sampling, subject to funding.