Research Paper Volume 8, Issue 5 pp 1034—1044

Figure 4. Buccal-Cell-Signature improves epigenetic age prediction. (A) The differences of chronological age and predictions by the 3-CpG-blood-model were compared to the predicted percentage of buccal epithelial cells (according to the Buccal-Cell-Signature). Deviations were higher in samples with more buccal epithelial cells. (B) In analogy, we compared age predictions by the 3-CpG-swab-model to the estimated percentage of buccal epithelial cells and here the impact of the cellular composition was less clear. (C) Combination of age-associated CpGs and Buccal-Cell-Signature in a multivariate regression model of five CpGs (5-CpG-model) facilitated age predictions in the training and validation set. (D) Mean absolute deviations of predicted and chronological age were significantly smaller in the validation set when using the 5-CpG-model as compared to the 3-CpG-swab-model. (E) The models for age-prediction were subsequently validated in a second, independent dataset of 37 samples (18 to 35 years). (F) Samples of the validation group were stratified by an age of 35 years. Comparison of the 3-CpG-swab-model and the 5-CpG-model revealed that the additional analysis of the Buccal-Cell-Signature was particularly relevant for samples of older donors (*** P < 0.0005).