Healthspan is the part of a life that still works
Lifespan counts years. Healthspan counts the years you spend free of disease and able to do what you want to do, and the two have not grown at the same rate.
Using health-adjusted life expectancy, a measure that subtracts years lived with disability and premature death from disease, the gap between the two is estimated at around nine years globally. Roughly a fifth of an average life is spent in that gap.
That is the number worth reacting to. Adding years to the end of a life is mostly outside your control. Reducing the share of those years spent unable to climb your own stairs is not.
What the World Health Organization means by healthy ageing
The WHO defines healthy ageing as “the process of developing and maintaining the functional ability that enables wellbeing in older age”. Two terms sit underneath that, and the distinction between them is useful.
Intrinsic capacity is all the mental and physical capacities a person can draw on: the ability to walk, think, see, hear, and remember. Functional ability is what those capacities let you do in the environment you live in. A flight of stairs, a bus route, a job, and a household are part of the equation.
The WHO groups functional ability into five domains: meeting your basic needs; learning, growing, and making decisions; being mobile; building and maintaining relationships; and contributing to your community. Only one of those five is strictly physical, which is a reasonable corrective to a longevity industry that measures almost nothing else.
Two points from the same source are worth carrying with you. Age tells you little: some 80-year-olds have physical and mental capacity comparable to 30-year-olds, and others the same age need extensive support. And around 75% of the variation in capacity in older age is the accumulated result of a whole life, not of a decade of it.
Measures that carry real information
Healthspan itself is a population statistic. You cannot measure yours. What you can measure are the capacities it is built from, and a few of them predict a great deal for how simple they are.
Walking speed is the clearest example. A pooled analysis of nine cohort studies followed 34,485 community-dwelling adults aged 65 and over (mean age 73.5, mean gait speed 0.92 m/s) for between 6 and 21 years. Each 0.1 m/s of additional gait speed was associated with a 12% lower rate of death (hazard ratio 0.88, 95% CI 0.87 to 0.90). The spread that produces is large: at age 75, predicted 10-year survival ranged from 19% to 87% across the range of gait speeds in men, and from 35% to 91% in women.
Read that carefully. Gait speed is a summary of many systems at once: heart, lungs, muscle, joints, balance, nerves, and motivation all show up in how fast you walk down a corridor. It is a marker, not a lever. Nothing in that study says that practising walking faster changes the outcome it predicts.
Other measures in the same family, such as how many times you can stand from a chair in thirty seconds, how long you can balance on one leg, how far you walk in six minutes, and grip strength, share the same property. They are cheap, repeatable, and mostly ignored by the testing market, because nobody can sell you a subscription to a chair.
The measurements guide covers how to interpret a single reading, and why direction over time is the only signal worth acting on.
How much is still open after 40
The honest framing is that this is a slope, not a cliff, and that intervention studies have mostly been run at the point where the slope is steepest.
The strongest single piece of evidence is the LIFE trial. It randomised 1,635 sedentary adults aged 70 to 89 (mean age 78.9, all scoring 9 or below on the Short Physical Performance Battery, all still able to walk 400 metres) to either a structured physical activity programme or health education. The activity arm walked toward a goal of 150 minutes a week and added strength, flexibility, and balance training, at two centre-based sessions and three to four home sessions per week. Follow-up averaged 2.6 years.
Over that period, 30.1% of the activity group developed major mobility disability, defined as being unable to complete a 400-metre walk within 15 minutes, without sitting and without help, against 35.5% of the education group (hazard ratio 0.82, 95% CI 0.69 to 0.98). Persistent mobility disability, the outcome that matters more for independence, occurred in 14.7% versus 19.8% (hazard ratio 0.72, 95% CI 0.57 to 0.91).
That is a real effect, produced in people who were already sedentary and already limited, at an average age of 79, over less than three years. It is the best available answer to “is it too late”, and the answer is no.
It is also a modest effect, and worth stating as one. Roughly three in ten people in the activity arm still lost mobility. Training changes the odds; it does not remove them.
Building a plan that survives contact with a real year
A healthspan plan is not a separate category of training. It is ordinary strength, aerobic, and balance work, chosen for the capacities you are furthest behind on and repeated long enough to matter.
- Start from a baseline you wrote down. A measurement you can repeat under the same conditions is worth more than a plan built on how you feel this week.
- Pick the system that is furthest behind, not the one you enjoy. Most people are well covered in one domain and have not touched another in years.
- Train the thing you want to keep. Getting off the floor, carrying shopping, and climbing stairs respond to being practised.
- Use a horizon of months. The LIFE trial ran for years, and the effect it found was not visible in a fortnight.
- Re-measure on a schedule, not on a mood. Quarterly is enough for most functional measures.
The Healthspan Baseline walks through the domains and returns a priority. It does not return a score, and it does not return an age.
When to bring this to a clinician
Most changes in capacity are slow and respond to training. A few are signals, and treating them as a motivation problem wastes the time in which something could be done.
- A functional measure that drops quickly. Walking speed, stair climbing, or chair rise that is noticeably worse over weeks rather than years is worth investigating rather than training through.
- Breathlessness or chest discomfort at a level of effort that used to be easy. That is a same-week conversation, and chest pain at rest is an emergency.
- A fall, or a near-fall you cannot explain. Falls have causes, among them blood pressure, medication, vision, and the inner ear, and several are treatable.
- Unintentional weight loss, or muscle you are losing while still training. Both warrant a look rather than more protein.
- New difficulty with memory, words, or familiar tasks. Intrinsic capacity is cognitive as well as physical, and this belongs with a doctor early.
- Any new medication, or a change in dose, that coincides with feeling weaker or unsteadier. Ask whether the two are connected.
If you have a diagnosed heart, lung, joint, or neurological condition, get a plan checked before you change your training substantially. The LIFE participants were screened and supervised; that is part of why the trial was safe.
What the evidence does not show
- That healthspan is something you can measure in yourself. The nine-year figure is a population estimate built from health-adjusted life expectancy. There is no validated personal healthspan number, and any product selling you one has invented the arithmetic.
- That walking faster makes you live longer. The gait speed finding is observational. It shows that walking speed summarises health well enough to predict survival, not that changing it changes survival.
- That the LIFE result applies to a healthy 45-year-old. The trial recruited sedentary adults aged 70 to 89 with measured physical limitation. The direction is encouraging at any age; the size of the effect is not transferable.
- That any single habit adds years to a life. Nothing in this guide supports that claim, and the studies that get reported that way are almost always observational.
- That an eighty-year-old’s capacity was decided in their seventies. The WHO attributes about three-quarters of the diversity in older-age capacity to advantages and disadvantages accumulated across a whole life, much of it outside individual control. Training helps. It is not the only input, and framing it as one is unfair to the people it does not work for.