The Biomarker Letters
Longevity Science, Decoded
A public education series. Each letter decodes one longevity biomarker — what it measures, what the research actually says, its real limitations, and how to think about tracking it.
Educational content, not medical advice.
HRV: The Body's Daily Weather Report
Heart rate variability is the beat-to-beat variation in your heart's rhythm — a real-time window into how your autonomic nervous system is balancing effort and recovery.
Read the letterDunedinPACE and the Science of Biological Age
DunedinPACE is an epigenetic clock that estimates how quickly your biology is aging — a compass bearing on the pace of aging, best read as direction over time, not a single verdict.
Read the letterVO2 Max: The Biomarker Kings Fight Over
VO2 max is the gold-standard measure of cardiorespiratory fitness — and one of the few biomarkers where the research is unusually unanimous about its link to a longer life.
Read the letterResting Heart Rate: The Humblest Signal
Resting heart rate is the humblest signal in the longevity toolkit — free, ancient, and almost trivial to measure, yet quietly one of the most informative when read as a personal trend.
Read the letterGrip Strength and What It Predicts
Grip strength sounds too simple to matter. It is one of the strongest predictors in all of longevity research — and, happily, a marker that responds to the thing it predicts.
Read the letterBlood Glucose Variability, Explained Without Fear
Continuous monitors have made glucose swings visible — and popular. The science is more measured than the hype: here is how to read the signal without anxiety.
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