evidence graded, limits stated

What Is VO2 Max?

12 min read

The single number for how much oxygen your body can use at full effort. What sits underneath it, what counts as a strong score for your age, and why it predicts longevity more reliably than almost any other fitness metric.

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HbA1c Explained

10 min read

A glucose reading tells you about one moment. HbA1c reflects roughly three months at once. How the test works, what separates a good result from a borderline one, and why clinicians lean on it so heavily.

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Resting Heart Rate

10 min read

Counted properly, your resting pulse is the cheapest fitness signal you have. Why a lower number usually means a more efficient heart, what the mortality research found, and how to measure it without inflating the result.

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Waist-to-Height Ratio

10 min read

One tape measure, two numbers, and a ratio that beats BMI across heights, ages and sexes. Where the 0.5 threshold came from, why central fat carries more risk than total fat, and how to measure so it stays comparable.

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ApoB vs. LDL Cholesterol

10 min read

A standard panel counts how much cholesterol is present. ApoB counts how many particles carry it. The two set side by side, what a good ApoB level looks like, and why guidelines keep shifting toward it.

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Gait Speed

7 min read

Your usual walking pace is one of the most replicated survival predictors in ageing research. What a pooled analysis of 34,485 adults found, how to measure it with a stopwatch, and why walking fast for the test defeats the point.

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Single-Leg Balance

6 min read

Standing on one leg for ten seconds sounds trivial and isn’t. The study where those who failed had nearly four times the death rate, how to run the test properly, and what actually improves balance.

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Grip Strength

10 min read

Grip works as a proxy for whole-body strength, which is why a squeeze test keeps showing up in mortality research. What those studies found, what a good score looks like at your age, and why a dynamometer and a dead hang measure different things.

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Body Fat Percentage

8 min read

The one marker here where lower isn’t automatically better. Why the healthiest range is a band rather than a floor, how that band sits differently for men and women, and why top-percentile leanness and a top score aren’t the same thing.

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What Is a DEXA Scan?

10 min read

A scan that separates fat, lean tissue and bone instead of collapsing them into one number on a scale. How the imaging works, what it shows that calipers and bioimpedance can’t, and how body fat reference ranges get set.

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Continuous Glucose Monitors

10 min read

A fasting blood draw captures one moment. A CGM captures the whole day, including spikes you’d never otherwise see. How the sensors work, how the data compares with fasting glucose and HbA1c, and what Time in Range targets mean.

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hs-CRP & Inflammation

10 min read

Chronic low-grade inflammation leaves a measurable trace in the blood, and hs-CRP is how it’s usually read. What the marker responds to, where the cut-offs sit, how it differs from standard CRP, and why the JUPITER trial put it on the map.

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Sit-to-Stand Test

11 min read

Rising from the floor without your hands tests strength, balance, mobility and coordination in one movement. How the ten-point scoring works, what the mortality research found, and why one score captures so much.

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Biological Age Tests, Explained

10 min read

Epigenetic clocks read chemical marks on your DNA and return an age that may not match your birthday. How the major clocks are built, how they compare, why GrimAge behaves differently, and how much weight the result deserves.

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Blood Pressure Categories

10 min read

“Normal,” “elevated” and “stage 1” are specific numbers, not vague labels. The AHA categories as they’re actually defined, the damage sustained pressure does to arteries over years, and how to take a reading that reflects your real baseline.

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The 6-Minute Walk Test

7 min read

Walk at your own pace for six minutes and measure the distance. Scored against what someone of your age, sex, height and weight would be predicted to cover, rather than a fixed target. Built as a route into a functional capacity score for anyone who can’t do push-ups or pull-ups.

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The Trail Making Test

8 min read

Connect 1-A-2-B-3-C as fast as you can. It measures processing speed and cognitive flexibility, the abilities that decline earliest. What the times mean, why sleep and cardio are the strongest levers, and an honest note on where the tier boundaries come from.

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Triglycerides

8 min read

The lipid marker that answers fastest. What counts as a good level, why added sugar and alcohol move it within weeks where ApoB takes months, and why an isolated elevation is worth treating as an early metabolic signal.

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Lipoprotein(a)

8 min read

Effort barely touches this one. Roughly largely genetic, deliberately excluded from projections, and still worth knowing, because it changes how aggressively everything you can control is worth managing.

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Homocysteine

7 min read

A strong observational link to dementia risk, and trials that lowered it with B vitamins without improving cognition. Both are true, and the gap between them is the most important thing to understand here.

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Cystatin C

7 min read

A kidney marker that muscle mass doesn’t confound, unlike creatinine. Why it catches early changes creatinine misses, why creatine supplementation makes it more useful still, and which levers actually exist.

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Liver Enzymes: GGT & ALT

8 min read

Two enzymes that work as early metabolic stress markers. Where optimized targets sit against standard lab ranges wide enough to call a doubled value normal, the two levers that move both, and an honest note on the weakest sourcing in the projection system.

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Which Markers Should You Test First?

7 min read

A sequenced order rather than a list of 32. What costs nothing, what your GP will already run, what’s worth paying for, and which paid tests most people should skip.

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Can You Track Longevity Without Bloodwork?

7 min read

Four of the six scored domains open with a tape measure, a floor and a stopwatch. The other two don’t, and this entry is specific about what stays hidden without a blood draw.

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How Often Should You Retest?

6 min read

Retest intervals differ enormously between markers, from weeks for triglycerides to once in a lifetime for Lp(a). What happens when you measure faster than the biology moves.

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What the numbers are actually telling you

The cheapest markers are often the strongest. A stopwatch, a tape measure and a floor cover a surprising amount. Walking pace, a single-leg stand, a sit-to-stand score and a waist measurement all carry mortality evidence behind them, and none of them need a lab.

They split into three practical groups. Some need nothing but a tape measure and a floor. Some need a physical test but no laboratory. The rest require bloodwork. That grouping matters more than the biology when you are deciding what to do first, because the first group costs nothing.

Bloodwork answers a different question. Functional tests tell you what your body can do today. Blood markers tell you what is building up quietly: lipid particles, glucose control, inflammation, kidney filtration. Neither replaces the other, which is why the scoring uses both.

Some of what you measure is already downstream. Aerobic capacity, glucose control and blood pressure are not independent of each other, and improving one often moves the others. Zone 2 training raises aerobic capacity and improves insulin sensitivity at the same time, which is part of why it appears so often.

Your measured age can differ from your real one. Two people born the same year can be measurably different biological ages. The markers here are how that difference becomes visible, and how you find out which direction yours is heading.

Common questions about longevity biomarkers

What are longevity biomarkers?

Longevity biomarkers are measurable things about your body that predict how long you stay healthy. They include aerobic fitness, strength, blood pressure, blood lipids, glucose control and markers of inflammation. What separates them from ordinary lab values is that each one has published evidence linking it to how long people live in good health.

What’s the difference between a biomarker and a lab test?

A lab test is the procedure. A biomarker is the thing being measured. One blood draw can produce a dozen biomarkers at once. Some biomarkers need no lab at all: a walking pace, a grip squeeze or a waist measurement are all biomarkers, and three of the strongest ones need only a stopwatch and a tape measure.

Why do lab reference ranges differ from the targets used here?

A reference range is built to flag illness, so it’s wide enough to include almost everybody. A percentile compares you to people of your own age and sex. You can sit comfortably inside a normal range and still be in the bottom quarter for your age. The range tells you whether you’re sick. The percentile tells you where you stand.

What counts as a good score?

It depends on your age and sex, which is why a single target number is misleading. Each entry gives the range that matters for the marker in question, benchmarked against published percentile data rather than a clinical reference range. A reference range tells you whether you are ill. A percentile tells you where you stand.

Do wearables count as biomarker tracking?

Partly. A wearable is good at resting heart rate and at trends over time, which is genuinely useful. It’s weaker at anything needing a precise single reading, and it can’t see blood markers at all. Treat wearable data as a direction of travel rather than a measurement.

Can biomarkers still be improved later in life?

Yes, and it’s one of the more consistent findings in the research. Aerobic capacity, strength, balance and blood pressure all respond to training well into later decades. The rate of improvement slows with age, but the direction doesn’t reverse. Starting later means a smaller gain, not no gain.

What’s the difference between a biomarker and a risk factor?

A biomarker is something measured directly from your body. A risk factor is anything that shifts your odds, which includes measurements but also age, family history and behaviour. Every biomarker here is a risk factor. Not every risk factor is a biomarker, and only the biomarkers can be tracked.

Which biomarker predicts the most?

A small number carry far more weight than the rest in the mortality research. Aerobic capacity is the most consistently replicated. Simple functional tests do better than most people expect: a pooled analysis of 34,485 adults found walking pace alone predicted survival about as well as a full clinical history.

What makes a good biomarker?

Four things. It has to predict an outcome people care about, not just correlate with age. It has to be measurable reliably, so the same person tested twice gets a similar answer. It should respond to something you can change, or it is information rather than a lever. And it needs population data behind it, so your result can be read as a position rather than a bare number. Most marketed markers fail at least one of those.

See where you stand

Every marker on this page, benchmarked against your own age and sex.

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