Type Epigenetic Clock Tissue Type Methodology Used Methylation Technology Strengths Limitations
Single Tissue 57 Single Tissue: Saliva Association Analysis Illumina 27K array First epigenetic clock Low accuracy (mean AE:5.2 years)
67
Single Tissue: Whole Blood
Elastic Net with bootstrapping
Illumina 450K Array
Accurate in blood. Extensively used
Limited age range of training samples: 19-101 years
93 Single Tissue: Whole Blood Multivariate Linear Regression Pyrosequencing Consists of only three CpG sites Low accuracy (mean AE:5.4 years)
94 Single Tissue: Breast Tissue Elastic Net Regression with cross-validation TruSeq Methyl Capture EPIC library Improved accuracy in breast tissue TruSeq Methyl Capture not yet widely used
Multi-Tissue 71 Multi-Tissue: Epidermis, dermis, T-cells, cervical smear, monocytes Pearson Correlation Illumina 27K array First multi-tissue clock Relative low accuracy (mean AE:11 years)
75
Multi-Tissue: 51 tissue and cell types
Elastic Net with ten-fold cross-validation
Illumina 27K array & Illumina 450K Array
Accurate across tissues; Extensively used
Mostly adult samples Age of neonate samples set at “0”
68 Multi-Tissue including blood Elastic Net with ten-fold cross-validation Illumina 450K & Illumina EPIC array Accurate (mean AE: 2.5 years) Not widely used yet
Pediatric Single Tissue 69 Single Tissue: Buccal Cells Elastic Net with cross-validation Illumina EPIC Array Pediatric-only clock Low accuracy in blood
Gestational Age
74
Cord Blood
Elastic Net Regression with cross-validation
Illumina 27K array & Illumina 450K Array
Median error :1.24 weeks
Gestational Age Only
95 Cord Blood Lasso Regression with cross-validation Illumina EPIC array Uses EPIC array Gestational Age Only