Senior Psychcare

When Robert Young was little, he found himself wishing he had gotten to know the elderly individuals in his life before they passed away. "I wanted to meet them and stay around them first, because they would be passing away first," Mr. Young recalls. The more youthful people, he would get to afterwards.

Now Mr. Young's childhood tendency has grown into his profession, as the geriatrician tracks the world's oldest individuals for a diversity of research groups.

His work and that of other researchers' has served to create a new branch of demography: Statistics about the world's best agers. Though major snags remain in the field of study of such a rare group of individuals, it has rendered fascinating figures about how rare it is to live to 110—and how likely those who get there are to reach 111, or beyond.

Much of the work in the area has grown from public enchantment with rankings of all varieties. Guinness World Records has tracked the world's oldest people since 1955. Two decades ago, researchers occupied in constituting their own lists united together in the Los Angeles-based Gerontology Research Group, which ascertains extreme-age claims around the globe through birth certificates and picture IDs. Now Mr. Young works for Guinness as its chief advisor on ascertaining such claims, and also verifies claims for GRG.

Among the findings: Uneasy lies the head that wears the crown of world's oldest person. Since Jeanne Calment passed away at age 122 in 1997, as the oldest person ever to fulfill Guinness's standards, the claim has turned over 17 more times, with no one reaching age 120 and just one person reaching age 118. The world's oldest verified person today, Eugénie Blanchard in the French territory of Saint Barthélemy, turned 114 in February.

There may be older people. About 800 million people, or less than one-eighth of the world's population, live in spots that, at the turn of last century, had birth records dependable enough to be trusted, according to Mr. Young. That implies the true number of supercentenarians, or individuals at least 110 years old, could be at least eight times larger than the 75 adult females and three men considered by GRG as of Wednesday.

Thanks to advances in geriatric care, the amount of centenarians is increasing quickly—by 32% in just the past five years in the U.S., according to Census Bureau estimates.

But some researchers also have ascertained a startling disconnect between that trend and a decline in the number of people who live to 110. The number of supercentenarians world-wide tracked by GRG has been flat over the past decade. "If the numbers of centenarians are increasing exponentially, the number of supercentenarians should be, too," says GRG co-founder L. Stephen Coles. "But it's not."

Still, the compiled data have began to resolve some enigmas about old age.

One important research area is fatality rate. Since 1825, statisticians have acknowledged that mortality rates increment exponentially with age, more or less, not counting gender differences or risk components such as obesity or smoking. For example, in 2007, the latest year for which U.S. death figures by age are available, the chance of passing away doubled roughly every nine and a quarter years. Among 52-year-olds, 50 of 10,000 passed away. The death rate among 61-year-olds was 101 of 10,000.

This so-called Gompertz Law, developed in 1825 by English mathematician Benjamin Gompertz, applies until around age 70 or 75, says Sam Gutterman, a director and consulting actuary at PricewaterhouseCoopers LLP. Afterward, mortality rates proceed to increment, but more gradually. "The population of survivors tends to be more robust than the group of the expired," says Jutta Gampe, chief of the lab of statistical demography at the Max Planck Institute for Demographic Research in Rostock, Germany.

That doesn't mean the eventual survivors are likely to keep living. But it does mean that mortality rates increase slowly at ages over 100.

In Italy and France, 100-year-old women have about a two-thirds probability of getting to age 101, according to a database housed at the Max Planck Institute. At age 105, their chance of reaching 106 is just under 60%. Survival rates are around 50% at ages 110, 111, 112 and 113, according to the GRG's records. Then, abruptly, they deteriorate to 30% at 114 and 115—the ages at which most of the world's most elderly people have died in the past decade.

Science will have to step in to answer what the statistics can't. There just haven't been enough verified 114-year-olds to know whether that is a magic number marking a natural roadblock to continuing endurance. Maybe as more individuals with better birth records duck the accidents, life style foibles and diseases that struck their peers to reach triple-digit years, that greater pool will yield more supercentenarians and more of them will survive the annual experiential coin flip that is life after 110.

"The supercentenarians are the crème de la crème," says Thomas Perls, director of the New England Supercentenarian Study, which has recruited 108 supercentenarians since 1997. "That's why I'm analyzing them."