What is Longevity?

Longevity went from a technical term to an everyday word in the space of a few years. What the word means, where it comes from, what the research currently supports and where the market runs ahead of the evidence. The central numbers below carry a source, and every model estimate is labelled as one.

Longevity means long life. In current usage it carries more than that. The word now stands for a research field and for a set of lifestyle decisions built around healthspan: the years someone lives without serious chronic disease and without a lasting loss of independence. A short definition lives in the longevity glossary.

The word is Latin in origin: longus means long, aevum means lifetime. Late Latin longaevitas, from longaevus meaning long-lived, became longevity in English. The pronunciation is [lɒnˈdʒɛvᵻti], stressed on the second syllable, with a soft j sound as in journalist rather than a hard g.

For some years now longevity has carried an extra layer of meaning: healthy years rather than years alone, measurable markers, prevention rather than repair. That is the shift the plain phrase long life does not capture, which is why the technical word keeps showing up in ordinary writing.

Two neighbouring terms show up in the same conversations. Geroscience describes the biology of ageing at the cellular level. Preventive medicine describes the clinical side, meaning early detection and risk factors. Longevity is used colloquially as an umbrella over both, which is why the word is useful in a headline and imprecise in a study.

Two terms carry the whole debate. Lifespan is how many years someone lives. Healthspan is how many of those years pass without serious chronic disease or lasting limitation.

The global picture is well quantified. An analysis of 183 WHO member states put the average gap between life expectancy and healthy life expectancy in 2019 at 9.6 years. The United States recorded the largest gap of any member state at 12.4 years, almost three years above the global average ^[2]. Those are the years people spend on average with cardiovascular disease, diabetes, dementia or reduced mobility.

The upper end is narrower than the trend suggests. The highest fully documented lifespan is 122 years, reached by Jeanne Calment, who died in 1997 ^[17]. An analysis in Nature argues that the maximum reported age of death has plateaued at around 115 years since the 1990s and that 122 years remains a statistical outlier ^[8]. The paper is contested, and several technical comments in Nature dispute the method. A study of the longest lived populations concludes that the probability of reaching 100 is unlikely to exceed 15 percent for women and 5 percent for men unless biological ageing itself can be slowed ^[7].

So the interesting target is the gap, not the record. In the literature this is called compression of morbidity: pushing the sick years into a shorter window at the end rather than adding years at the top.

Read enough longevity writing and the same three claims keep surfacing, however different the packaging.

Healthspan before lifespan. The stated goal is not the maximum number of years but the maximum number of functional years. The term has a known weakness. Matt Kaeberlein argued in 2018 that there is still no single agreed way to measure healthspan, which makes studies hard to compare ^[1]. Careful writing therefore states which definition it is using.

Lifestyle beats genetics. The classic Danish twin study of 2,872 twin pairs estimated the heritability of lifespan at 0.26 in men and 0.23 in women, roughly a quarter ^[3]. A far larger pedigree analysis in 2018 revised that downwards: once you account for people choosing similar partners, estimated heritability falls well below 10 percent ^[4]. A 2026 paper turns the lens again. Strip out extrinsic causes such as accidents and infection and the heritability of intrinsic lifespan lands near 50 percent ^[5]. The range is wide, the practical conclusion is stable: a large share of the difference comes from behaviour and environment. A US cohort of more than 120,000 participants shows how large that share can be. People combining five low-risk factors had a life expectancy at age 50 that was 14.0 years higher for women and 12.2 years higher for men than people with none of them ^[13]. The five factors were never smoking, a healthy body weight, regular activity, moderate alcohol intake and a high-quality diet.

Evidence over hype. The scientific frame is the twelve Hallmarks of Aging, updated in Cell in 2023 ^[6]. They describe linked processes from DNA damage and telomeres through cellular senescence to mitochondria and chronic inflammation. Demography supplies the counterweight. Olshansky and colleagues show that gains in life expectancy have decelerated in the longest-lived countries since 1990, making radical life extension in this century implausible ^[7]. Both belong together: a clear research programme without a promise of rescue.

We group the evidence into six pillars: movement, nutrition, sleep, social connection, stress management and prevention. Different sources count anywhere from three to nine, from a lean three-way split to the Power 9 of the Blue Zones literature. The number is an editorial choice, not a constant. We use six because each of these six behavioural fields has its own large cohort study or meta-analysis behind it. The order follows the strength of the data, not a priority for daily life.

What appears in none of the lists is a supplement: the pillars describe behaviour, not products. Each one has its own body of numbers, from cardiorespiratory fitness through sleep duration to social relationships. The 6 pillars in detail takes each one apart, with the studies, the effect sizes and the limits of the data behind them.

Chronological age counts birthdays. Biological age tries to estimate how far ageing has actually progressed in the body. The best known method is the epigenetic clock. Steve Horvath showed in 2013 that age can be estimated with surprising accuracy from DNA methylation patterns across many tissues ^[14]. Many more clocks have followed, they respond differently to health trajectories and they are not interchangeable.

In practice that means a single number is an estimate, not a diagnosis. The methods are covered in the biological age guide. If you want to try one, we run a free age test and a photo-based face age estimate. Both are educational, both return an estimate and neither replaces a medical examination.

Blue Zones are five regions with unusually high numbers of very old residents: Okinawa in Japan, the Barbagia region of Sardinia, Ikaria in Greece, the Nicoya peninsula in Costa Rica and Loma Linda in California. The shared traits drawn from them sound familiar: constant everyday movement, a largely plant-based diet, close social ties, a reason to get up.

The underlying data has been under scrutiny for several years. The demographer Saul Justin Newman showed that regions reporting exceptional numbers of very old people frequently coincide with incomplete birth registration, high poverty and short average life expectancy. His proposed explanation: in the United States these records are predicted by missing vital registration, in the UK, Italy, Japan and France by regional poverty. On top of that, reported birthdates cluster on the first of the month and on days divisible by five ^[15]. The work is a preprint and has not gone unchallenged, but it moved the debate.

What survives is less dramatic and still useful. The lifestyle patterns described in the Blue Zones broadly match what large cohort studies find independently of them ^[13]. It is the record ages that deserve caution, not the patterns. The full case is in the Blue Zones guide.

The word is heavily marketed, so it is worth drawing three boundaries.

Not a supplement programme. The most visible part of the longevity market is capsules. For most of these products there is no human lifespan data, only cell work, animal work and short studies on surrogate markers. A review in Nature Reviews Drug Discovery sets out the state of the search: candidates such as rapamycin, metformin and NAD precursors are scientifically interesting, yet none of them is supported by outcome trials in healthy people ^[16]. What is known about individual compounds sits in NMN and rapamycin.

Not anti-aging cosmetics. Anti-aging in retail usually means appearance: skin, wrinkles, hair. Longevity means function: cardiovascular system, metabolism, muscle, cognition. The terms overlap in marketing, not in research.

Not the Bryan Johnson protocol. The US entrepreneur has documented an extensive self-experiment since 2021 and did more than anyone to popularise the topic. A single case without a control group is not a study design that generalises. As a media phenomenon it is relevant, as evidence it is not.

How to spot unsupported claims is collected in the guide to longevity pseudoscience.

Longevity medicine is not a protected term and not a recognised medical specialty. In practice the phrase describes an offering: clinics and practices that bundle extensive diagnostics, lab panels, imaging and lifestyle coaching, usually paid out of pocket.

There is no defined treatment called a longevity therapy. What gets sold under that label splits into three groups. First, established prevention that ordinary healthcare already provides: blood pressure, lipids, glucose, vaccination status, cancer screening. Second, diagnostics with no demonstrated benefit in people without symptoms. Third, experimental approaches, from infusions to off-label prescribing, whose benefit-risk balance in healthy people is unresolved ^[16].

The evidence-backed core is unglamorous. The causal role of LDL cholesterol in atherosclerotic disease is treated as settled in the expert consensus, supported by genetic, epidemiological and randomised evidence ^[12], and the link between fitness and mortality is well documented ^[9]. Both are standard medicine rather than longevity medicine.

This section describes how the market is structured and recommends no specific service. Which offerings are typically self-funded is covered in self-pay longevity, and the line to non-medical practitioners in practitioners and longevity.

Longevity has a price problem. The visible part of the field is tests, capsules and subscriptions. The evidenced part is mostly free. Three routes that cost nothing:

Meet people. Cities across our network run regular meetups where researchers, clinicians and curious people show up in the same room. Entry is free, and the list of cities sits under chapters. Given the strength of the social-connection data, this is the pillar with the best ratio of effort to evidence ^[11].

Run the numbers. Our tools are free and need no account, from energy requirements through a VO2max estimate to grip strength. They replace no diagnostic work, but they put your own numbers in context.

Use the check-ups you already have. In Germany statutory health insurance covers a general health check from age 35 that includes blood pressure, lipids and fasting glucose ^[18]. Many other systems fund something comparable, so it is worth checking what yours covers. That already covers part of the sixth pillar, and anything beyond it is a conversation with a clinician.

If you take one thing from this page: the difference between people in the large cohort studies was never a product. It was a handful of habits held for decades ^[13].