Figure 1.

Comparison of chronological age with DNA methylation age derived using four DNA methylation age clocks. Shown are comparisons of chronological age with predicted age in (A) the testing dataset (n = 350 cortical samples) and (B) the independent test dataset (n = 1221 cortical samples). DNAm age was predicted using four DNA methylation age clocks: (i) our novel DNAmClock_Cortical; (ii) Horvath’s DNAmClock_Multi; (iii) Zhang’s DNAmClock_Blood and (iv) Levine’s DNAmClock_Pheno. The x-axis represents chronological age (years) and the y-axis represents predicted age (years). Each point on the plot represents an individual sample. Our cortical clock out-performed the three alternative DNAm clocks across all accuracy statistics. DNA methylation age estimates derived using the DNAmClock_Multi [A(ii) testing and B(ii) independent test] and the DNAmClock_Blood [A(iii) testing and B(iii) independent test] appear to have a non-linear relationship with chronological age.