What it means
Healthspan is the period of life spent in good health — functionally independent, free of the chronic diseases that end most lives, and able to do what you want to do. It is contrasted with lifespan, which is simply how long you live. Two people who both die at 85 can have very different healthspans: one declining for fifteen years, the other for one.
There is no single agreed cut-off for when healthspan "ends". Researchers use the onset of a first major chronic disease, the loss of a basic daily activity, or a composite frailty index. The practical definition most coaches use is the one you feel: the years you can train, travel, work and look after yourself.
Why it matters for longevity
The gap between lifespan and healthspan in rich countries is around nine to twelve years, and it has been widening: medicine has become very good at keeping people alive with disease, less good at keeping them without it. Almost every intervention worth discussing — fitness, muscle, metabolic health, sleep — moves healthspan more reliably than it moves lifespan, which is why it is the better target.
What the evidence says
The strongest human evidence is in the large prospective cohorts. Cardiorespiratory fitness (VO2max), grip strength, visceral fat and the metabolic markers each predict both disability-free years and mortality, independently of age. In the Harvard Alumni and Cooper Center cohorts, the fittest fifth of participants not only lived longer but compressed their final period of illness into fewer years — the "compression of morbidity" that James Fries proposed in 1980 and that the data have since largely supported.
What has not been shown is a compound that extends human healthspan on its own. The candidates — rapamycin, metformin, the NAD+ precursors — have animal data and surrogate-marker trials, not disability-free-years trials in people.
How to measure or use it
- Track the predictors, not the concept: VO2max, grip strength, a DEXA for lean mass and visceral fat, and a metabolic panel (ApoB, HbA1c, hs-CRP, fasting insulin).
- Repeat the panel yearly, the fitness tests twice a year. A trend over three years says more than any one reading.
- Functional tests cost nothing: a one-leg stand with eyes closed, a timed sit-to-stand, a dead hang. Decline on these appears years before a diagnosis.
Related
- What is healthspan? — the full article, with the cohorts and the numbers
- Biomarkers of ageing — the panel that tracks it
- The longevity protocol — how it becomes a plan
Frequently asked questions
Is healthspan the same as life expectancy?
No. Life expectancy is the average age at death. Healthspan is the years spent in good health before decline. In most rich countries the two are roughly a decade apart.
Can healthspan be measured directly?
Not with one number. It is inferred from the markers that predict it — fitness, muscle, metabolic health — and from functional tests. Biological-age clocks try to summarise it, with mixed success.
What moves healthspan most?
In the cohort data, cardiorespiratory fitness and muscle strength have the largest and most consistent effects, followed by metabolic health, sleep and not smoking. No supplement comes close.
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