LONDON, July 8 — The biological clock may be more than a metaphor. For over a decade, researchers have been building tools to read the subtle chemical marks on human DNA that reveal how fast a body is actually ageing, as opposed to how many birthdays it has logged. The technical reality is that these tools, called epigenetic clocks, measure patterns of DNA methylation — a chemical modification that switches genes on or off without changing the underlying genetic code.
The first such clock, developed by Steve Horvath at the University of California, Los Angeles, in 2013, analysed 353 CpG sites across the genome and could predict chronological age with an accuracy of 3.6 years. CpG sites are regions of DNA where a cytosine nucleotide sits next to a guanine nucleotide; methylation at these points correlates strongly with age.
That initial Horvath clock was a landmark, but it was not the only approach. Gregory Hannum published his own clock in the same year, using 71 CpG sites and training the model exclusively on blood samples.
Mortality and Methylation
The detail that matters for medicine is not just how old someone looks on paper, but whether their epigenetic age predicts how long they will live. A 2018 study by Horvath showed that epigenetic age acceleration — where a person’s clock runs faster than their calendar age — was associated with increased mortality risk in a cohort of 2,000 older adults. The GrimAge clock, published in 2019 by Ake Lu at the University of California, Los Angeles, took this further.
Under the hood, GrimAge incorporated smoking history and other physiological risk factors to predict mortality directly, rather than simply estimating chronological age. The National Institute on Aging has funded epigenetic clock research since 2014, with grants totalling over $30 million.
Education and Ageing
In 2021, researchers at the University of Edinburgh used epigenetic clocks to show that people with higher educational attainment had slower epigenetic ageing. A 2022 study in Aging Cell pushed the evidence base further. Researchers applied epigenetic clocks to a sample of 13,000 individuals from the U.S. Health and Retirement Study and found that the clocks could predict all-cause mortality.
The field is moving from proof-of-concept toward clinical application. The question now is not whether epigenetic clocks work — they clearly do, within limits — but which clock, or combination of clocks, will prove robust enough for routine medical use.
The Horvath clock remains the most cited and most validated, but the GrimAge clock’s focus on mortality risk makes it a strong candidate for clinical adoption. The technical challenge, as ever, is standardisation. Different clocks trained on different tissue types, using different numbers of CpG sites, produce results that are not always directly comparable.
Researchers are working on harmonising these measurements, but the field is not there yet. Consult your doctor for medical advice.
{“@context”: “https://schema.org”, “@type”: “NewsArticle”, “headline”: “Epigenetic Clocks: Measuring Biological Age and Predicting Mortality”, “description”: “LONDON, July 8 — The biological clock may be more than a metaphor. For over a decade, researchers have been building tools to read the…”, “datePublished”: “2026-07-08T09:30:00+00:00”, “author”: {“@type”: “Person”, “name”: “Sebastian Smith”}, “publisher”: {“@type”: “Organization”, “name”: “InfoPulse Today”, “url”: “https://newsfeed.infopulsetoday.com/”}}
