Should you buy a test that tells you how fast you are ageing?

Bryan JohnsonNo clinical or scientific credential claimed · technology founder and quantified-self subject

Yes, and re-test, because the value is the trend rather than the snapshot

What it rests onHis argument is that ordinary labs answer whether you are sick today and the useful question is the rate of change, which only repeat measurement can answer. He publishes his own figure, an epigenetic speed of aging of 0.48 averaged across three tests, as the demonstration. He sells the panel at $365 per year.

Source: blueprint.bryanjohnson.com ↗

Matt KaeberleinPhD · biogerontologist

No, do not buy a direct-to-consumer biological age test. Spend the money on biomarkers that have outcome data

What it rests onThree stated grounds: the tests are statistically meaningless at the level of an individual result, they lack regulatory validation and oversight, and they produce nothing a person can act on. His replacement is not to stop measuring, it is to measure things with outcome data behind them (kae-realmarkers). He has no product in this market.

Source: podcasters.spotify.com ↗

Overview

Both address general adults, but they are answering different questions inside the same purchase. Johnson's case is longitudinal: the same test, repeated, on one person, read as a trend. Kaeberlein's case is about the individual result: whether any single number means anything. Those can both be true. Reading Kaeberlein as anti-measurement misrepresents him, and reading Johnson as claiming a validated absolute age misrepresents him too.

Where they agree

Both think measuring is the right instinct and neither says track nothing. Both, remarkably, concede the statistical problem: Johnson's own protocol page states that claims about measuring or reversing biological age are preliminary, subject to biostatistical error, and that the tests are experimental and intended solely for research purposes. That concession sits on his site while his store sells the panel.

What would settle it

A consumer clock publishing test-retest reliability at the individual level, and a prospective association between a change in the score and a hard outcome. One thing is still unchecked: whether Kaeberlein accepts repeat testing over time as the one defensible use, which would narrow this dispute considerably.

Should you buy a test that tells you how fast you are ageing?

What the experts say

Overview

Where they agree

What would settle it

Practice does not pick a winner here