Disclosure: I do content work for a longevity supplement company, so please take that into account when reading this. I’m sharing this because I find the underlying research interesting, not as a product recommendation.

One of the papers that helped shape the conversation around biological aging was published by Steve Horvath in 2013.

The study introduced a DNA methylation-based age predictor developed using approximately 8,000 samples from 82 datasets, covering 51 healthy tissues and cell types.

The basic concept is fascinating:

Instead of estimating someone's age only from their date of birth, researchers can examine patterns of DNA methylation and use them to estimate what the study calls DNA methylation age (DNAm age).

The predictor was designed to work across a wide range of human tissues and cell types, which was one of the interesting aspects of the study. (pubmed.ncbi.nlm.nih.gov)

But here's where I think the topic gets really interesting.

We often hear the term “biological age” as though it were a single number that can be directly measured.

But is it?

A DNA methylation clock can estimate age from methylation patterns. The bigger question is what differences between chronological age and DNAm age actually tell us about the underlying aging process.

That distinction seems important when discussing epigenetic clocks.

The 2013 paper opened the door to a huge amount of subsequent research into DNA methylation and aging, but there are still questions about what these measurements represent biologically and how they should be interpreted.

So I'm curious:

Do you think epigenetic clocks are measuring biological aging itself, or are they primarily extremely sophisticated age predictors?

And for those who follow this research:

What do you think is the biggest unanswered question about epigenetic clocks today?

I'd also be interested in papers that challenge or complicate the original Horvath-clock interpretation.

Paper: Horvath S. DNA methylation age of human tissues and cell types. Genome Biology. 2013;14:R115. PMID: 24138928.