Figure 2. Epigenetically predicted vs. chronological age in semen samples based on the model training (N = 125) and model test (N = 54) datasets, respectively. The accuracy of prediction achieved with the developed epigenetic age prediction model for semen equals a MAE of 4.3 years (RMSE = 5.2) in the training set and a MAE of 5.1 years (RMSE = 6.3) in the test set. The six CpGs included in the model explained 60% of the age variation observed in the training set.