The New England Centenarian Study at Boston University has been following people who live past 100 since 1994. It is the largest study of its kind in the world, and the longest-running. The results, accumulated over three decades, have substantially complicated the popular picture of centenarians as a special category of human being whose cells simply age more slowly than everyone else’s. The picture that has emerged from the study is more interesting and more useful than that. Centenarians, as a group, are not biologically distinct from the rest of the population for most of their lives. What they do, and what distinguishes them, is to delay the onset of the chronic diseases that kill most people in their seventies and eighties, by something like 15 to 20 years on average. The longer they live, the more compressed their period of serious illness becomes, until in the most extreme cases — supercentenarians of 110 and older — disability and disease occupy only the last five years or so of life.
The finding overturns the assumption, dominant in gerontology for most of the 20th century, that exceptional longevity meant exceptionally slow aging. According to a 2012 review by Paola Sebastiani and Thomas Perls in Frontiers in Genetics, the older view assumed that any human who reached 100 must necessarily have aged at a fundamentally slower biochemical rate. The Boston University researchers, working with cohorts that eventually numbered more than 2,000 centenarians, found that this was largely wrong. Most centenarians have aged at roughly normal rates, accumulated the same metabolic and cellular damage as everyone else, and developed the same age-related diseases. What they have done differently is push back the point at which those diseases produce serious functional impairment.
Three kinds of centenarian
In 2003, a research team led by Jesse Evert analysed the Boston University centenarian cohort and produced a classification that has since been widely cited in the gerontology literature. According to the New England Centenarian Study’s institutional summary, three categories emerged. The first, “survivors,” accounted for approximately 43 percent of the centenarians studied. These were individuals who had developed at least one major age-related disease — heart disease, stroke, cancer, diabetes, or dementia — before the age of 80, but who had nevertheless survived with the disease into their hundreds. The second, “delayers,” accounted for approximately 42 percent. These were people who managed to avoid major age-related disease until after age 80. The third category, “escapers,” accounted for approximately 15 percent. These were the centenarians who had reached 100 with no diagnosis of any mortality-associated disease at all.
The three categories complicate the popular image in different directions. The “survivors” demonstrate that having a major age-related illness in one’s seventies does not preclude survival to 100, provided one’s overall constitution can cope with the disease over the following two decades. The “delayers” represent the pattern most consistent with the older popular framing — postponement of disease until late in life. The “escapers” are the closest thing to the popular image of the “exceptionally healthy old person,” but they are a minority. Most centenarians have lived with chronic illness for years before reaching 100, and most have done so by being resilient rather than immune.
The cancer delay
One of the most thoroughly documented examples of the disease-delay pattern involves cancer. According to the research profile of Stacy Andersen, the behavioural neuroscientist who co-directs the New England Centenarian Study, centenarians develop cancer diagnoses on average 17 years later than the broader population, when compared against the United States national cancer database. The 17-year figure is striking because cancer is not generally regarded as a disease that one can simply postpone — its incidence rises with age, driven by accumulating DNA damage that cells acquire over a lifetime, and the genetic and environmental factors that contribute to it are extensively studied. A 17-year postponement is, by the standards of any individual cancer risk factor, an enormous effect.
Similar patterns appear for cardiovascular disease, dementia, and other major causes of late-life mortality. The centenarians of the New England study are not protected against these conditions in any absolute sense. They develop them. But they develop them at ages when the broader population has already died of the same diseases. The pattern is consistent enough across multiple chronic conditions that it suggests a common underlying factor rather than a series of disease-specific protections.
The compression of morbidity
The framework that gerontologists use to describe this pattern is called the compression of morbidity, a hypothesis proposed by the Stanford physician James F. Fries in a 1980 paper in the New England Journal of Medicine. Fries argued that if the maximum human lifespan is approximately fixed by biology — somewhere in the range of 110 to 120 years — then the period of serious illness at the end of life can in principle be compressed into a smaller and smaller window as people learn to delay the onset of disease. A person who develops chronic illness at age 60 and dies at 80 has 20 years of morbidity. A person who develops the same illness at age 90 and dies at 100 has 10 years. A person who develops illness at age 105 and dies at 110 has only 5 years. The total lifespan need not change, but the duration of suffering and disability at the end can shrink substantially.
The supercentenarians — people over 110 — are the strongest empirical support for Fries’s hypothesis. According to the 2012 Sebastiani-Perls review, supercentenarians spend an average of approximately the last five years of their lives with one or more age-related diseases, compared with approximately nine years for centenarians under 105 and substantially longer periods for the broader elderly population. The closer a person comes to the apparent ceiling of human lifespan, the more compressed their period of serious illness becomes. The trajectory does not look like slow ageing. It looks like deferred ageing — the same biological clock as everyone else, but with the hardest part packed into a much shorter window at the very end.
What this means for the rest of us
The implications for the general population are less dramatic than the popular framing of centenarian research sometimes suggests. The Boston University researchers have been careful to emphasise that exceptional longevity has a substantial genetic component, particularly at the extreme ages above 105, and that the genetic variants involved are typically many in number with modest individual effects. There is no single “longevity gene” to target. The behavioural patterns associated with extreme longevity — modest diet, regular physical activity, strong social ties, late-life mental engagement — are the same patterns associated with reduced risk of the chronic diseases that compress at the end of life. There is, in other words, considerable overlap between “what centenarians do” and “what public health authorities have been recommending for decades.”
The more useful framing, the centenarian researchers argue, is that human lifespan is not primarily limited by the rate at which our cells age. It is primarily limited by the diseases that kill us. A person who can delay the onset of cardiovascular disease, cancer, diabetes, and dementia by even a decade adds substantial years of functional life. A person who can delay all of them by 20 years approaches the territory of the centenarians. The mechanisms by which centenarians achieve this delay are partly genetic, partly behavioural, and partly stochastic — but they are not, in most cases, a matter of unusually slow ageing. They are a matter of avoiding the conditions that cause the most common causes of death long enough that the body has time to reach the upper end of its biological range. Most people who live past 100, in the end, are not biologically younger than their peers. They have just postponed the things that would otherwise have killed them.
