Centenarian lives

Lois Vaught has a sweet smile, a soft voice and an aversion to hearing aids. Although she's deaf, she will not use one. When you're 104, you can decide these things for yourself.

"My husband had a hearing aid, but it wasn't satisfactory. It never worked right," says Vaught, the oldest resident of the Friends Nursing Home. Hearing aside, Vaught is alert, reads a newspaper every day and responds to questions put to her in writing. She also has the kind of background that increases her odds of living into the triple digits.

That is why she is among a growing number of centenarians whose lives are being studied by scientists to sort out the mysterious combination of behaviour and genetics that determine why some people live so long. Vaught's parents lived into their 90s. She and her late husband never drank alcohol or smoked. She also has maintained the right attitude and diet.

"Before it became popular, she was into healthy cooking. There was never anything fried," says her only daughter, Ann Larson, who lives near Chicago. "Second, she's very serene. She doesn't have huge mood swings or get stressed."

Researchers look for patterns like these in their quest to understand the genetic and molecular underpinnings of ageing.

"The holy grail in the field is finding longevity genes, genes that slow down the rate of ageing and reduce susceptibility to age-related diseases," says Dr Thomas Perls, a physician at Boston University Medical Centre who enrolled Vaught in his New England Centenarian Study four years ago.

Perls is seeking volunteers for another five-year, $18 million study — funded by the National Institute on Ageing — that looks for common genetic traits and health habits in families with more than two members who have reached 90. Perls and other experts are still stumped as to why some people who don't work at it manage to lead long lives.

For every clean-living Lois Vaught, there's a Jeanne Louise Calment. Calment was a Frenchwoman who, by all accounts, smoked until a few years before her death — and only stopped then because she no longer could light her cigarettes. When she died in 1997, at the age of 122, she was the oldest person whose age has been reliably documented.

Genetic lottery

People might extend their lives with exercise, a healthy diet, routine health checkups and medications. But living longer than a century requires some genetics in your favour, say experts.

"To make it past 100, you have to have been born having already won the genetic lottery," says S. Jay Olshansky, an epidemiologist at the University of Illinois at Chicago. Advances in this research come in increments.

Dutch scientists reported a key genetic link in the process — evidence that the ability to repair the kind of DNA damage that routinely occurs in our cells play a critical role in how rapidly we age.

Mice, genetically designed to lack a critical DNA repair gene, not only aged more quickly than normal mice but also showed the same symptoms as a 15-year-old suffering from progeria, a rare genetic disorder that rapidly ages children and shortens their lives.

The goal of the study, which appeared in Nature and two journals published by the Public Library of Science, was to examine what happens at the cellular level when we age, the authors say. "First of all, we're trying to understand the ageing process. Second, we'd like to help in the development of compounds to treat these patients," says Jan H.J. Hoeijmakers, head of the genetics department at the Erasmus Medical Centre in Rotterdam and author of the study.

But reliable anti-ageing therapies are years away, many experts agree. "We're still down to diet and exercise," says Dr S. Mitchell Harman, a former Johns Hopkins researcher, who is now director and president of the Kronos Longevity Research Institute, which investigates ageing and age-related illnesses.

Experts are unsure if the average American life expectancy will continue to rise.

Overall life expectancy at birth is about 78 years, according to the National Centre for Health Statistics.

Males at birth can expect to live to 75.2 while females can expect to reach 80.4, according to estimates based on 2004 health statistics. Of 37 industrialised countries that report life expectancy rates to international health groups, American women and men ranked 26th, according to the centre.

Outer age limit

Experts see our life span climbing as fast as it has since 1900. Scientists attribute the large increase during the 20th century to improved medical care, as well as public health initiatives that lower child and infant mortality, such as improved water and sewer systems.

Olshansky thinks life expectancy could drop in the US over the years as increasing numbers of obese children get older and die from obesity-related diseases, such as diabetes and heart disease.

"There isn't any question something like this is going to happen, if we don't intervene," Olshansky says.

Is there an ultimate age limit? Humans eventually could peak at about 125, says Dr L. Stephen Coles, director of the Los Angeles-based Gerontology Research Group, which tracks the ages of the world's oldest people. The best evidence, he says, is that there are no documented cases of anyone living longer. The group confirmed that the oldest person in their records, Elizabeth Bolden, had died in a Memphis, Tennessee, nursing home at the age of 116.

With Bolden's death, the oldest-known person in the group's listings is Emiliano Mercado del Toro, a Puerto Rican who is 115. There are about 80 people listed on the group's website as "super centenarians", meaning 110 or older, Coles says.

"We're looking for a fountain of youth, but we know the road is going to be long and hard," he says. "This is all uncharted territory."