We added years to life faster than health to those years. The gap is widening.

Living longer and living well for longer are not the same achievement, and the modern record separates them clearly. A 2024 analysis of 183 countries found that the years people gain in life expectancy have outpaced the years they spend in good health, opening a global "healthspan–lifespan gap" of 9.6 years — and 12.4 years in the United States, the widest of any nation studied [s2]. That is the opposite of what the field's founding hope, the "compression of morbidity," predicted [s1].

The idea, stated in 1980

The concept that frames all of this comes from a 1980 paper by James Fries in the New England Journal of Medicine [s1]. Fries observed that average life expectancy had risen from 47 to 73 years over the twentieth century while the maximum human lifespan had not moved, which pushed survival curves into an ever more "rectangular" shape — most people surviving to a similar advanced age rather than dying spread across the lifespan [s1]. From present data he calculated an "ideal" average lifespan of roughly 85 years [s1].

His hopeful inference was the compression of morbidity. If the onset of chronic illness could be postponed by changes in lifestyle, and if the maximum lifespan was fixed, then the sick period at the end of life would be squeezed into a shorter and shorter window — people staying vigorous almost to a fixed endpoint, then declining quickly [s1]. It was an elegant target: not merely more years, but more healthy years, with suffering compressed rather than extended.

What actually happened

The 2024 study measured whether that compression occurred, using health-adjusted life expectancy — the number of years lived in good health — against total life expectancy across all 183 WHO member states, over two decades of data [s2]. The gap between the two is the number of years, on average, that a person lives in less-than-good health.

That gap has widened globally over the last two decades, reaching 9.6 years [s2]. The United States had the largest gap of any country, at 12.4 years, driven by a rise in non-communicable diseases [s2]. The study also found a consistent sex difference: women's healthspan–lifespan gap was on average 2.4 years wider than men's, meaning the extra years women tend to live are disproportionately years in poorer health [s2]. Across countries, wider gaps went with a heavier burden of non-communicable disease and total morbidity [s2].

In other words, the world got the added years but not, on the whole, the added health to fill them — expansion of morbidity, not compression.

Why the hopeful version underdelivered

The mismatch is not evidence that Fries was wrong about the mechanism so much as that the mechanism was only half-achieved. Compression requires postponing the onset of chronic disease faster than you postpone death. Modern medicine has become very good at the second part — keeping people alive with heart disease, diabetes, kidney disease and dementia for years — while making slower progress on preventing those conditions from starting. Survival with chronic illness lengthens the sick period even as it extends life, which pulls the two curves apart rather than together.

This reframes what "longevity" should mean. Interventions judged only by whether they extend lifespan can widen the gap if the added years are unhealthy ones; the goal implied by the data is to move health-adjusted life expectancy, not just life expectancy. It is why so much ageing research now centres on function — whether an older person is frail, how fast they walk, whether they retain strength — rather than on survival alone.

How to read a "live longer" claim

For a reader, the healthspan–lifespan gap is the question to put to any longevity promise: not "will this add years?" but "will it add healthy years, or just years?" A drug, diet or clinic that extends survival while the sick period stretches to match has not delivered what people actually want from long life.

The compression of morbidity remains a coherent and worthwhile goal — arguably the right one [s1]. The 2024 data are the sober progress report: on a global scale, we are not compressing morbidity, we are accumulating it, and the country that spends the most on health care has the widest gap of all [s2]. Closing it is a different and harder task than simply pushing the endpoint further out.

This article is informational and is not medical advice.

Sources

1. [s1] Aging, Natural Death, and the Compression of Morbidity. New England Journal of Medicine, 1980. https://doi.org/10.1056/NEJM198007173030304
2. [s2] Global Healthspan-Lifespan Gaps Among 183 World Health Organization Member States. JAMA Network Open, 2024. https://doi.org/10.1001/jamanetworkopen.2024.50241