Guides to the science behind your score.
Twelve guides on what shapes healthspan — the seven factors the calculator scores, the important things it doesn't, and how to read the research for yourself.
Written and edited by Healthworks. Educational only and not medically reviewed — see our editorial standards.
What the calculator measures
Each input in the model draws on a body of population research. These guides go deeper than the homepage summaries — the mechanisms, the weights we chose and why, and where the evidence is weaker than the confident version you usually read.
What is healthspan, and why isn't it the same as lifespan?
The concept behind the whole model: healthy life expectancy, compression of morbidity, and why chronic illness concentrates into the last decade of life.
6 min read Factor · SmokingSmoking and healthspan: what quitting actually recovers
The largest modifiable factor in the model — how much it costs, what comes back after quitting, and what the age-40 finding really says.
5 min read Factor · Body weightThe U-shaped curve: BMI and healthy life expectancy
Why both underweight and severe obesity carry a cost, why the healthy range is wider than most people assume, and what BMI cannot see.
6 min read Factor · ExerciseThe minimum effective dose of exercise for healthspan
Why the biggest gains come from going from nothing to something, where returns flatten, and why strength training matters for healthspan specifically.
6 min read Factor · SleepWhy sleep has a U-shaped mortality curve, not a more-is-better one
The evidence behind the 7–8 hour window, why long sleep is mostly a risk marker rather than a cause, and why regularity may matter as much as duration.
6 min read Factors · Diet, alcohol, stressDiet quality, alcohol thresholds, and chronic stress
Three smaller modifiers: what a Mediterranean diet score measures, where the alcohol curve bends and why the old J-curve collapsed, and how stress compounds.
6 min readWhat the calculator leaves out
A seven-question tool cannot capture everything that matters, and pretending otherwise would be the wrong kind of simple. These guides cover factors we deliberately excluded — either because most people can't answer for them, or because we couldn't justify a weight.
VO₂ max and healthspan: the measure that outpredicts exercise minutes
Measured fitness predicts mortality more strongly than self-reported activity. What it captures, how to estimate it, and why the calculator asks about minutes instead.
6 min read Blood pressureBlood pressure: the risk factor this calculator doesn't ask about
Among the largest contributors to global disease burden, and silent until it has caused damage. What it does, and why it sits outside the model.
5 min read Metabolic healthMetabolic health beyond BMI: insulin resistance and what to test
Why two people at the same BMI can be in very different condition, what insulin resistance is, and which blood markers are actually worth knowing.
5 min read Social connectionSocial connection and healthspan: the factor nobody counts
Effect sizes large enough to rival known lifestyle risks — and a causal problem serious enough that we won't assign it a weight.
5 min read SupplementsSupplements and healthspan: what the evidence actually supports
Why promising observational findings keep failing in randomised trials, the deficiency distinction that explains most of it, and the longevity supplement category.
6 min readHow to check our work
Every other guide asks you to accept our reading of the research. This one is about not having to.