What Is Longevity? Why the Real Goal Is Healthy Years, Not Just a Long Life

The word "longevity" seems to be everywhere right now: clinics offering in-depth health check programmes, supplements sold as "anti-ageing", and wellness content telling us we should start working on living longer today. If you've read some of it and wondered what it actually means, whether you really need to do that much, and how it applies to you, this article is for you.

The short answer: longevity literally means "length of life". But in a health context, the useful goal isn't simply to live as long as possible. What most people actually want is healthspan, the number of years we're still well enough to live the way we want: getting around on our own, looking after ourselves, working or doing what we love, and spending time with the people who matter. Reaching 85 after spending the last 15 years depending on others for almost everything, and reaching 85 while still doing your own market run, are two very different lives, even though the age is the same.

In this article, we'll start with the difference between lifespan and healthspan, and how the World Health Organization measures "healthy years". Then we'll look at data from 183 countries to see how wide the gap is between living long and living well. Next comes the question many people want answered: how much do our genes decide how long we live? After that, we'll look at a study that followed more than 100,000 people to see which habits are linked to more disease-free years.

Finally, we'll talk about where to start. As a blog that believes health isn't measured by clothing size alone, we'll invite you to judge your strength by what your body can do, like climbing stairs, carrying things, or getting up off the floor with ease. Those are things anyone can start improving, whatever the scale says today.

Lifespan vs Healthspan: What's the Difference?

These two words sound alike but answer different questions. Lifespan asks, "How many years do we live?" Healthspan asks, "Of those years, how many are we healthy enough to live fully?" Separating the two makes it clear that looking after our health isn't only about pushing back the day we die. It's about adding quality years to our lives.

Lifespan and life expectancy: counting the years

Lifespan is the span of a person's life from birth to death. At the national level, we usually talk about life expectancy, an average calculated from death rates at each age in a population. It tells us how long people in a country tend to live on average, but not what those years are like. Two people who both die at 80 may have had completely different final years.

Healthspan and HALE: counting the healthy years

Healthspan is the part of life we spend in good health. The term is used loosely, and studies may define it slightly differently. At the population level, though, the common measure is the World Health Organization's (WHO) healthy life expectancy, or HALE.

According to the WHO's indicator definition for HALE, HALE is the average number of years a person at a given age can expect to live in "full health". Time spent living with disease or injury counts as less-than-full health and is deducted according to severity. So if a country has a life expectancy of 78 years but a HALE of 68, that roughly means people there spend about 10 years, on average, living with health problems that limit their lives to some degree. These are made-up numbers just to illustrate the idea; we'll look at the real figures in the next section.

The WHO also notes HALE's limitations. Reliable illness and death data are still lacking in many countries, and self-rated health may not compare perfectly across countries. HALE is therefore best for seeing the big picture and trends, not for predicting any one person's life.

Healthy ageing: being well doesn't mean having no disease

Many people assume that "healthy in old age" means having no chronic conditions at all. The WHO sees it differently. In its explanation of healthy ageing and functional ability, the WHO defines healthy ageing as the process of developing and maintaining the "functional ability" that enables wellbeing in older age.

In the WHO's framework, functional ability covers very concrete things: meeting your own basic needs, learning and making decisions, moving around, building and maintaining relationships, and taking part in or contributing to society. These abilities come from two parts working together. The first is intrinsic capacity, the physical and mental capacities within us, such as moving, thinking, seeing, hearing and remembering. The second is our environment, such as our home, community, transport and the people around us.

This view is useful in practice. Someone with a well-controlled chronic condition, such as high blood pressure that's treated consistently, may still travel independently, enjoy hobbies and fully care for their family. On the other hand, someone with normal blood test results who can't manage the stairs or rarely sees anyone may have a life that's far more limited than the numbers suggest. Measuring strength by what we can still do is therefore closer to the goal of longevity than tracking only the values on a check-up report.

An older couple smiling at each other at a cafe table, showing an active social life in later years

The differences side by side

Lifespan or life expectancy measures the number of years lived, or the population average. It answers: how old will we live to be?
Healthspan or HALE measures years lived in good health, deducting time spent with disease or injury. It answers: how many years will we be well enough to live fully?
Healthy ageing measures the ability to live your life that remains as you get older. It answers: can we still do the things that matter to us?

With these three terms in mind, "longevity" in this article means adding both years and the quality of those years together, with healthspan as the main focus.

The 10-Year Gap Most People Don't Know About: Data from 183 Countries

Are people living longer today? Yes. But are all the extra years healthy ones? The answer is less rosy. A study by Armin Garmany and Andre Terzic of the Mayo Clinic, published in JAMA Network Open in December 2024, used WHO data from 183 member states to compare life expectancy with HALE in 2000 and 2019, and calculated the "gap" between them: the average number of years people live with health problems.

Key findings

The results raise several points worth thinking about.

The global gap was about 9.6 years in 2019, up from 8.5 years in 2000, a widening of about 13%.
Life expectancy rose faster than healthy years. Over the same period, global life expectancy increased by 6.5 years, but HALE rose by only 5.4 years. In other words, some of the extra years were spent with disease or health limitations.
The United States had the widest gap, at 12.4 years, up from 10.9 years in 2000. Mental health and substance use disorders, along with musculoskeletal diseases, were the conditions that accounted for the most years Americans lived with disability.
Women's gap was wider than men's, by about 2.4 years on average across all countries, meaning women spent longer living with health problems. In the US, the researchers found that musculoskeletal, genitourinary and neurological conditions contributed most to the difference between the sexes.
The gap was linked to the burden of noncommunicable diseases. Countries with a heavier burden of chronic noncommunicable diseases, such as heart disease, diabetes, cancer and mental health conditions, tended to have wider gaps.

These numbers help explain why health experts are talking more about healthspan. Medicine's success in helping people survive many diseases has made us live longer, but many chronic diseases don't kill quickly. They leave us living with limitations for a long time.

Picturing those 10 years

Imagine a woman who lives to 80. If her life roughly follows the global average, her last 10 or so years may be a period when health starts to limit her life. In practice, that could mean knee pain that stops her walking to her favourite market, waiting until her children or grandchildren are free before she can see a doctor, no longer managing the stairs in her own home, or cancelling plans with friends because getting around is hard. This is a hypothetical picture to show what the "gap" means in real life, not a prediction that everyone will experience it.

On the other hand, if she could delay the point at which her body starts limiting her life, or make those limits milder, her quality of life in that decade would be very different, even if she still lived to exactly 80. That's the heart of meaningful longevity: shortening the period of illness or dependence, and lengthening the period in which we can fully be ourselves.

What to keep in mind before using these numbers

These are national averages; they don't tell you how many years of gap you or your family will have. The researchers note that the results depend on how accurate the estimates of life expectancy and HALE are, including the disease-severity weights used in the calculation, and that the analysis looks back at aggregate data. It's good for seeing trends but doesn't explain causes at the individual level.

For Thailand, country-level figures are in the study's supplementary material, which this article doesn't draw on, so we won't quote Thailand's number. The big-picture conclusion still applies to us: living longer doesn't guarantee that the extra years will be healthy, and chronic noncommunicable diseases are a major reason the gap is wide.

How Much Do Genes Decide How Long We Live?

A common thought when people talk about longevity is "Everyone in my family lives long, so I'll probably be fine", or the opposite, "My parents got sick young, so I can't escape it." The answer from the latest research is more complicated than that, and interestingly, the numbers changed only recently.

The old numbers: genes play a small role

In genetics, researchers use the term heritability to describe how much of the variation in a trait within a population can be explained by genetic differences. As reviewed in the study by Shenhar and colleagues, past twin studies estimated the heritability of lifespan at 15–33%, with about 20–25% being the most often quoted figure. Some large family-tree studies gave even lower values, at about 6–16%.

These figures led to a conclusion that spread widely in the health world for years: longevity is almost entirely about lifestyle and environment, and genes play only a tiny part.

A 2026 study: possibly about half

In January 2026, Ben Shenhar, Uri Alon and their team at the Weizmann Institute published a study in the journal Science that challenged the old figures. Their point was that the older twin data came from people born around 1870–1935, an era when many people died from external causes such as infectious diseases, accidents and environmental hazards. These deaths have nothing to do with the body's age-related decline, so they act like "noise" that hides the role of genes in ageing.

The team used mathematical models to separate out deaths from external causes, then analysed twin data from Denmark and Sweden, including twins raised apart. They found that the heritability of "lifespan driven by age-related decline" was about 50%, as summarised by the Weizmann Institute, with the paper itself reporting a value slightly above 50%. That's similar to the heritability of other human physiological traits.

What 50% means, and what it doesn't

It might sound like "so half of it is already decided", but it needs to be read carefully.

It's a population figure, not a personal one. A heritability of 50% doesn't mean 50% of your lifespan comes from your genes. It means that, in the group studied, about half of the differences in lifespan between people can be explained by genetic differences.
It depends on place and time. The researchers themselves state that heritability is specific to the population, environment and period studied. The main data come from Scandinavians born over a century ago. Although the researchers checked their results against data on siblings of US centenarians and found them consistent, the figure isn't a constant that applies to every country and every era.
The other half isn't explained by additive genetics. The researchers say the remainder comes from the environment, including lifestyle, socioeconomic factors and access to healthcare, along with biological chance, complex interactions between genes, and epigenetic changes.
It measures lifespan, not healthspan directly. The study addresses how much genes relate to the age at death, but says nothing about whether the final years of life will be healthy.

So how should we use this information?

Family history is valuable information. If your parents or siblings have heart disease, diabetes or dementia, that's a good reason to tell your doctor and get screened as recommended. But family history isn't a verdict, for better or worse. People from long-lived families still need to look after themselves, and people whose families got sick early still have many factors they can change.

Another important point: even if genes play a bigger role in the "number of years" than we used to think, the "quality of those years" is still an area where everyday living clearly makes a difference. The next section looks at research that measured exactly that: the number of years people live without developing major chronic diseases.

What Research Says About Habits and "Disease-Free Years"

Most lifestyle research looks only at whether people die earlier or later. But if our goal is healthspan, what we should look at is how many years people live without getting sick. One study that answers this question directly is by Yanping Li and colleagues at Harvard, published in the BMJ in January 2020.

What the study looked at

The research team used data from two long-term US studies: the Nurses' Health Study, which followed 73,196 female nurses, and the Health Professionals Follow-Up Study, which followed 38,366 male health professionals, for a total of 111,562 people. Participants were followed for decades, from the 1980s to 2014, regularly reporting their own behaviours.

The researchers then calculated how many more years people in each group could expect to live, from age 50, without developing three major disease groups: cancer, cardiovascular disease and type 2 diabetes. They compared this by the number of "low-risk factors" each person had, defined as five items:

Never having smoked
A body mass index (BMI) of 18.5–24.9
At least 30 minutes a day of moderate-to-vigorous physical activity
Moderate alcohol intake: 5–15 grams a day for women and 5–30 grams a day for men
Diet quality in the top 40% of each study cohort, measured by the Alternate Healthy Eating Index (AHEI), an index used to assess overall diet quality

The results: a difference of up to a decade

From age 50, the expected number of further disease-free years was:

Women: 23.7 years with no low-risk factors and 34.4 years with 4–5 factors, a difference of about 10.6 years.
Men: 23.5 years with no low-risk factors and 31.1 years with 4–5 factors, a difference of about 7.6 years.

These differences were calculated by the researchers from unrounded values, so they may differ slightly from subtracting the figures above directly.

Put simply, women in this study with all or nearly all of the healthy habits stayed free of cancer, heart disease and diabetes until about age 84 on average. For the group with none of these factors, the disease-free period ended around age 74 on average, whether because of a diagnosis or death. These are group averages, not individual predictions, but they fit the idea of healthspan better than death rates alone, because they measure years without illness.

The results also show a clear gradient: the more low-risk factors people had, the more disease-free years they had, step by step. For women, for example, it rose from 23.7 years with none to 26.4, 29.1, 31.8 and 34.4 years respectively.

Limitations to know

This is an observational study: it followed people who lived differently to see how their health differed, rather than randomly assigning anyone to change their behaviour. So it can show an association, but can't fully prove that each factor directly causes the outcome. The researchers note that behaviour data were self-reported, that there may be unmeasured confounding factors, and that most participants were white US health professionals, so the results may not apply to every other population.

Two factors on the list also deserve especially careful reading.

On weight: fitness may tell us more than BMI

BMI is easy to use in large studies, but it doesn't tell us how fit someone is. A systematic review and meta-analysis by Weeldreyer and colleagues in the British Journal of Sports Medicine (2025) pooled 20 prospective studies, covering nearly 400,000 observations, to examine how cardiorespiratory fitness and BMI relate to the risk of death.

Compared with people of normal BMI who were fit, the findings were:

People in the obese BMI range who were fit had no statistically significant increase in risk of death from any cause (hazard ratio 1.11, with a confidence interval that crosses 1).
People who were unfit had roughly double the risk of death in every BMI group, including people with a normal BMI who were unfit (hazard ratio 1.92).

The researchers concluded that fitness is a strong predictor of mortality and reduces the risks often associated with overweight and obesity. The limitations are that most of the data came from men, white people and relatively well-off people in the US, and that BMI is an imperfect stand-in for body fat.

This doesn't mean weight has no effect on health. It means fitness is a very important factor, and one that anyone can start improving right away without waiting for the number on the scale to change. We'll go deeper into this in a separate article on fitness and weight.

On alcohol: don't start drinking hoping to live longer

In Li and colleagues' study, moderate drinking was counted as one of the low-risk factors, but that shouldn't be read as advice to drink. In a statement in January 2023, published in The Lancet Public Health, the World Health Organization said there is no level of drinking that is safe for health, and that no studies have shown the claimed heart or diabetes benefits of light-to-moderate drinking outweigh the cancer risk for people who drink. The WHO explains that apparently protective associations depend on which comparison group is used and which statistical methods are applied. If you don't drink already, there's no health reason to start.

The takeaway from this section

Overall, the evidence suggests that what's linked to more disease-free years isn't a single trick, but several basic habits kept up over the long term: not smoking, moving regularly enough to get fitter, and eating a good-quality diet. The good news is that none of them costs much, and the more of them people had, the better the results in the study.

Where to Start: Measure Strength by What Your Body Can Do

If healthspan is the number of years we can still live fully, the easiest place to start is by looking after the things that let us live our lives. In the WHO framework described in the first section, the ability to move is one of the pillars of healthy ageing, and it's the part we can most clearly work on in daily life.

Movement goals from WHO recommendations

The WHO's physical activity recommendations for adults aged 18 and over, including older adults, have three main parts:

Aerobic activity: at least 150 minutes a week of moderate intensity, such as brisk walking, or at least 75 minutes a week of vigorous intensity, or a mix of both. For extra benefits, build moderate activity up to 300 minutes a week.
Muscle strengthening that works the major muscle groups, at least 2 days a week.
Balance combined with strength training for older adults aged 65 and over. The WHO's 2020 guidelines recommend varied activities that emphasise functional balance and strength, at moderate or greater intensity, on at least 3 days a week, to improve functional capacity and prevent falls. This recommendation applies to all older adults, not only those with poor mobility as in the previous version.

The most important message from these recommendations is that the WHO says some physical activity is better than none. The 150-minute figure is a long-term goal, not a line you have to hit in your first week. If you hardly exercise right now, going from zero to a 10-minute daily walk counts as progress.

An older man hanging from an exercise bar in a public park, an everyday example of muscle-strengthening activity — Photo: Trung Nhan Tran / Unsplash

A realistic first week

This is a starting example for people who don't exercise much yet. Adjust it to your schedule and your body.

Split walking into short sessions. Walk briskly for 10–15 minutes after lunch or dinner, 4–5 days a week. If you do all 5 days at 15 minutes, that's 75 minutes, halfway to the goal. Then add 5 minutes at a time in the following weeks.
Train your muscles with everyday movements 2 days a week: for example, standing up from a chair without using your hands, wall push-ups, and lifting water bottles or a loaded tote bag up and down. Do 2–3 rounds of each, choosing a number of reps you can do steadily while feeling your muscles work.
Add balance to your routine, for example standing on one leg while brushing your teeth, with the sink or a wall right there to hold on to. It's an easy way to fit practice into your day without finding extra time. If you're 65 or older, practise balance together with strength regularly, as the WHO recommends above.

If you have a health condition, such as heart disease, uncontrolled high blood pressure, or ongoing joint or back pain, talk to a doctor or physiotherapist before making your exercise harder.

Track progress by what your body can do

For many people, the scale is both discouraging and not very informative about strength. We suggest another way to track progress that fits the idea of functional ability: note down what your body can do in real life, and check back every month. For example:

Can you climb two flights of stairs without stopping, and do you catch your breath faster than before?
Is it easier to get up from the floor or a low chair, and do you need your hands less?
Can you carry your market shopping further, or carry more?
After a full day out, do you still have energy the next day?

These questions aren't a medical test and there's no pass or fail. They're a way to see how each week's effort changes your real life, and to notice progress the scale may not show.

Don't forget the other evidence-backed basics

Moving more is a great place to start, but the research in the previous section linked several habits to disease-free years. One with clear results that shouldn't be overlooked is not smoking. If you smoke, quitting is a step worth prioritising, and you don't have to do it alone: you can talk to a doctor, a pharmacist, or a smoking cessation clinic at a hospital near you.

As for food, there's no need to start by cutting everything out. The research in the previous section measured overall diet quality, not any single food, so you can gradually shift your plate in a better direction, for example eating more vegetables and fruit and fewer sweetened drinks. Changing one thing at a time, such as switching your usual Thai iced tea to less sweet, or adding a plate of blanched vegetables to lunch, is easier and lasts longer than changing everything at once.

Conclusion: The Longevity Worth Having Is Years Lived the Way You Want

Longevity sounds like it's about reaching 100, but based on everything in this article, the more useful question is how many strong, healthy years we can have. Data from 183 countries show that, on average, people spend almost a decade living with health problems; the gap widened between 2000 and 2019, and women's gap is wider than men's on average.

Genes play a bigger role in lifespan than we once believed. The latest research estimates they may explain about half of the differences in lifespan in the groups studied, but that means the other half relates to other things: environment, lifestyle, access to healthcare, and chance. And looking specifically at disease-free years, a study of more than 100,000 people found that those with several healthy habits had about 10.6 more years free of major chronic disease in women, and 7.6 in men, than those with none.

If you want to start, you don't need an expensive package. Start with what your body can do: walk more often, train your muscles twice a week, don't smoke, and gradually nudge your plate in a better direction. Then measure your progress by climbing stairs, carrying shopping, or spending a whole day out without running out of energy.

When you come across products or services sold under the "longevity" label, whether supplements, in-depth testing programmes or new treatments, always ask: is there research in humans showing it actually adds healthy years, who was studied, and for how long? If the answer isn't clear, spending your time and money on the basics that already have evidence behind them is usually the better deal.

In upcoming articles in this series, we'll dig into one topic at a time, from fitness and weight, weight training, walking and sleep, to longevity clinics and supplements, to help you choose what fits your life with more confidence. Because the goal isn't the longest possible life. It's a life that stays your own for as long as possible.

What Is Longevity? Why the Real Goal Is a Long, Healthy Life, Not Just a Long One

Lifespan vs Healthspan: What's the Difference?

Lifespan and life expectancy: counting the years

Healthspan and HALE: counting the healthy years