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 the oldest resident of the Friends Nursing Home in Sandy Spring.
Hearing aside, Lois 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's why she's among a growing number of centenarians whose lives are being studied by scientists to sort out the mysterious combination of behavior and genetics that determine why some people live so long.
Vaught's parents lived into their 90s. She was born and raised on a farm in Indiana, taught school and married a Quaker. She and her late husband never drank alcohol or smoked. She has also maintained the right attitude and diet.
"Before it became popular, she was into healthy cooking. There was never anything fried," said 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 aging.
"The holy grail in the field is finding longevity genes, genes that slow down the rate of aging and reduce susceptibility to age-related diseases," said Dr. Thomas Perls, a physician at Boston University Medical Center who enrolled Lois Vaught in his New England Centenarian Study four years ago.
Perls is currently seeking volunteers for a five-year, $18 million study - funded by the National Institute on Aging - that looks for common genetic traits and health habits in families with more than two members who have reached 90. Researchers from the University of Pittsburgh, Columbia University and the University of Southern Denmark are also participating in the study, Perls said.
Perls and other experts are 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 stopped then only because she could no longer light her cigarettes. When she died in 1997, at the age of 122, she was the oldest person whose age has been reliably documented.
"The lifestyles of these people are all across the board," said S. Jay Olshansky, an epidemiologist at the University of Illinois at Chicago.
People can extend their lives with exercise, a healthy diet, routine health checkups and medications. But living longer than a century requires some genetics in your favor, experts say.
"To make it past 100, you have to have been born having already won the genetic lottery," Olshansky said.
Advances in this research come in increments. In mid-December, 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 plays 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 aging process. Second, we'd like to help in the development of compounds to treat these patients," said Jan H.J. Hoeijmakers, head of the department of genetics at the Erasmus Medical Center in Rotterdam, the Netherlands, and a senior author of the study.
But reliable anti-aging therapies are still years away, many experts agree.
"We're still down to diet and exercise," said Dr. S. Mitchell Harman, a former Johns Hopkins researcher who is now director and president of the Kronos Longevity Research Institute, which investigates aging and age-related illnesses.
Experts are unsure whether the average U.S. life expectancy will continue to rise. Overall life expectancy at birth is now about 78 years, according to the National Center 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 industrialized countries that report life expectancy rates to international health groups, U.S. women and men ranked 26th, according to the center.
Few experts see our life span climbing as fast as it has since 1900, when it was a paltry 47 years. Scientists usually attribute the large increase during the 20th century to improved medical care, as well as public health initiatives that cut infant and childhood mortality, such as immunization programs and improved water and sewer systems.
Olshansky thinks life expectancy could drop in the United States over the years as increasing numbers of obese children get older and start to 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," he said.
But other experts say that with medical advances, we should continue to live longer. "There's a feeling in the field that with improved health care, humans will one day be living to be 100," said Siu Sylvia Lee from Cornell University, a researcher who studies the genetics of aging. "I think it's possible, but there's no data to support it. We'll just have to wait and see."
Is there an ultimate age limit?
Humans could eventually max out at about 125, said Dr. L. Stephen Coles, director of the Los Angeles 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 Dec. 11 in a Memphis 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.
At any given time, there are about 80 people listed on the group's Web site (www.grg.org) as "supercentenarians," meaning 110 or older, Coles said.
About 50,000 Americans claimed to have reached 100 in the 2000 census. But unlike the Census Bureau, the group tries to verify claims with a birth certificate that dates to the original birth date or a similarly authentic baptismal certificate or marriage certificate.
Claims must also be supported by valid photo identification, Coles said.
The supercentenarians list is heavily weighted with people from the United States, Western Europe and other developed countries because the group uses volunteers and has limited funds for verifying claims.
"There's a lot of undiscovered people in South America, in Africa, in India and in China," Coles said.
An obstetrician by training, Coles has conducted autopsies on four supercentenarians who died in California over the past three years. He is storing their hearts, lungs, livers and other tissues at a Los Angeles-area tissue bank.
In April, the group also sent an investigator to Ecuador to take a blood sample from a 116-year-old woman who was the world's oldest living person before she died Aug. 27.
What genetic secrets might be learned from analyzing the blood and tissues remains to be seen, Coles said, and answers are likely to be at least 10 years away.
"We're looking for a fountain of youth, but we know the road is going to be long and hard," he said. "This is all uncharted territory."