Epigenetic clocks measure DNA methylation patterns at specific genomic sites to estimate biological age — a measure that predicts mortality, disease risk, and healthspan more accurately than chronological age.
Epigenetic clocks measure DNA methylation — chemical modifications to DNA that regulate gene expression — at hundreds of specific genomic sites. These patterns change predictably with age and can estimate biological age with high accuracy. Biological age predicted by epigenetic clocks is a better predictor of mortality and disease risk than chronological age, and is modifiable by lifestyle factors.
Horvath (2013) in Genome Biology developed the first pan-tissue epigenetic clock, demonstrating that DNA methylation at 353 CpG sites could predict biological age across multiple tissue types with a median error of 3.6 years. Levine et al. (2018) developed PhenoAge, a clock trained on phenotypic biomarkers of aging that better predicts mortality and disease risk than Horvath's original clock. Lu et al. (2023) developed DunedinPACE, a clock that measures the pace of aging (how fast someone is aging) rather than their current biological age — a potentially more actionable measure. Smoking, obesity, and chronic stress accelerate epigenetic aging; exercise, Mediterranean diet, and adequate sleep decelerate it.
"Epigenetic age acceleration — being biologically older than your chronological age — is associated with significantly higher mortality risk, independent of traditional risk factors."
— Levine et al., Aging 2018
The NIA identifies epigenetic clocks as important research tools for measuring biological aging and evaluating the effects of longevity interventions. The NIA notes that epigenetic clocks are being used in clinical trials as outcome measures to assess whether interventions slow biological aging. Commercial epigenetic age testing is available but the NIA cautions that the clinical utility of these tests for individual health decisions is not yet established.
Commercial epigenetic age tests (TruMe, Elysium Index, Biological Age Test) are available but should be interpreted cautiously — they provide an estimate of biological age at a single point in time, and the clinical implications of a specific result are not well established. The lifestyle factors that most consistently reduce epigenetic age acceleration are: regular aerobic exercise, Mediterranean diet, adequate sleep, stress management, and smoking cessation. These are the same interventions recommended for overall health, making epigenetic clocks useful for motivating behaviour change rather than directing specific interventions.
Vitaei verdict
Epigenetic clocks are the most accurate available measures of biological age and predict mortality better than chronological age. Commercial testing has limited clinical utility but may motivate healthy behaviour change.
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