Figure 1. Training and testing of multiple iterations of PCBrainAge. Using the dataset from GSE74193, elastic net was used to predict age using principal component loadings in both sexes (A), only males (B), or only females (C). Here, we show the resultant predictions for each model in both females (purple) and males (green) regardless of training sex. Each model so trained is then predicted in all individuals from syn5850422 (D–F), regardless of sex or AD status. Each model selected a number of principal components to use for prediction, and we compared the selection of each model using a Venn diagram (G). Subsequent training of an elastic net model using only the 15 core principal components in both sexes is visualized (H) and compared to performance in the test dataset (I).