Longevity Science

Epigenetic Clock

A biological age assessment using DNA methylation patterns that change predictably with aging. Epigenetic clocks can measure "biological age" — which may differ from chronological age based on health, lifestyle, and genetics.

An epigenetic clock is a computational model that estimates biological age based on DNA methylation patterns — chemical modifications to DNA that accumulate in tissue- and age-specific patterns throughout life. Unlike chronological age (time since birth), biological age reflects the cumulative effects of genetics, lifestyle, environment, and disease on the aging process.

DNA Methylation and Aging

DNA methylation involves the addition of methyl groups to cytosine bases (specifically CpG dinucleotides) in DNA. Methylation at specific genomic sites changes predictably with age across individuals — some sites gain methylation, others lose it, in consistent patterns.

Horvath et al. (2013) developed the first human epigenetic clock using ~353 CpG sites to predict chronological age with high accuracy. Since then, clocks have been developed for multiple species including dogs.

Canine Epigenetic Clock

Researchers at UC San Diego (Lu et al., 2023) developed a canine epigenetic clock and made a notable discovery: when dog ages are mathematically transformed to account for the non-linear nature of dog aging (a 1-year-old dog is roughly equivalent to a 30-year-old human developmentally), the epigenetic clocks of dogs and humans align closely.

The non-linear transformation: dog age in equivalent human years = 16 × ln(dog age) + 31

This means a 1-year-old dog is methylation-equivalent to ~31 human years; a 7-year-old dog to ~62 years; a 12-year-old dog to ~70 years.

Biological vs. Chronological Age

Dogs — like humans — can age faster or slower than expected for their chronological age. Factors associated with accelerated epigenetic aging in dogs include:

  • Obesity and metabolic syndrome
  • Chronic inflammation
  • Insufficient exercise
  • Poor diet quality

Factors associated with slower epigenetic aging:

  • Lean body condition
  • Regular moderate exercise
  • Diverse, high-quality diet
  • Active social life (Dog Aging Project preliminary data)

Commercial Testing

Commercial epigenetic age testing for dogs is now available through services like EpiVetDx and Dog Aging Project research protocols. Utility in individual clinical decision-making is still being established — epigenetic clocks are currently most useful as research tools measuring intervention effects rather than individual diagnostic tests.