RT Journal Article SR Electronic T1 Improved prediction of chronological age from DNA methylation limits it as a biomarker of ageing JF bioRxiv FD Cold Spring Harbor Laboratory SP 327890 DO 10.1101/327890 A1 Qian Zhang A1 Costanza L. Vallerga A1 Rosie M Walker A1 Tian Lin A1 Anjali K. Henders A1 Grant W. Montgomery A1 Ji He A1 Dongsheng Fan A1 Javed Fowdar A1 Martin Kennedy A1 Toni Pitcher A1 John Pearson A1 Glenda Halliday A1 John B. Kwok A1 Ian Hickie A1 Simon Lewis A1 Tim Anderson A1 Peter A. Silburn A1 George D. Mellick A1 Sarah E. Harris A1 Paul Redmond A1 Alison D. Murray A1 David J. Porteous A1 Christopher S. Haley A1 Kathryn L. Evans A1 Andrew M. McIntosh A1 Jian Yang A1 Jacob Gratten A1 Riccardo E. Marioni A1 Naomi R. Wray A1 Ian J. Deary A1 Allan F. McRae A1 Peter M. Visscher YR 2018 UL http://biorxiv.org/content/early/2018/10/28/327890.abstract AB DNA methylation is associated with age. The deviation of age predicted from DNA methylation from actual age has been proposed as a biomarker for ageing. However, a better prediction of chronological age implies less opportunity for biological age. Here we used 13,661 samples (from blood and saliva) in the age range of 2 to 104 years from 14 cohorts measured on Illumina HumanMethylation450/EPIC arrays to perform prediction analyses. We show that increasing the sample size achieves a smaller prediction error and higher correlations in test datasets. We demonstrate that smaller prediction errors provide a limit to how much variation in biological ageing can be captured by methylation and provide evidence that age predictors from small samples are prone to confounding by cell composition. Our predictor shows a similar or better performance in non-blood tissues including saliva, endometrium, breast, liver, adipose and muscle, compared with Horvath’s across-tissue age predictor.