HELEN IS 108 years old. She hates salads, vegetables, getting up early, and just about everything that has to do with a healthy lifestyle. She loves rare hamburgers, chocolate, cocktails, and nightlife in New York: all the exotic restaurants, Broadway stages, movie theaters (she recently saw Iron Man 2) — and the Metropolitan Opera. That’s where she attended her first opera, Samson et Delila, in 1918. It was a present from her father for her 17th birthday.

She also likes to smoke, of course: "I've been smoking for more than 80 years, all day long, every day. That’s a whole lot of cigarettes," admits Helen, who has been called "Happy" since she was a child. Then she giggles as she falls back into her soft armchair. This 108-year-old woman is wearing lipstick, rouge, a pink cardigan, and a cluster of pearl necklaces. Her skin is nearly spotless, and her brown eyes sparkle merrily behind her glasses.

Since she had a stroke five years ago, her speech has been slightly slurred. But her mind is alert, her curiosity as strong as ever, and her memory often better than that of her 37-year-old Filipino caretaker. Happy is currently nursing a cold and should take it easy — so she is receiving guests in her apartment on Park Avenue, and not at the Indian place around the corner or at one of her other favorite restaurants. "But on Saturday," says Happy, as she sits up again and beams, "on Saturday, we'll meet with my brother Irving for lunch. Okay?"

HELEN FAITH KEANE Reichert, born Nov. 11, 1901, on Manhattan's Lower East Side to Jewish immigrants from Poland, is a certified psychologist, a fashion expert, a former TV presenter, and a professor emeritus at New York University. She was married to a cardiologist and has no children. When her husband died 25 years ago at the age of 88, she decided, at age 84, to travel around the world — to Ireland, Spain, Italy, Turkey, Egypt, China, Japan, and Australia. "The only place I didn't visit was India,” she says, "but I'd like to go there."

In her golden years, Happy, the indestructible woman, has attracted the attention of scientists — together with her brothers Irving, 104, and Peter, 100. Her sister, Lee, died in 2005 at the age of 102.

The surviving members of the world's presumably oldest quartet of siblings have provided blood samples and submitted to hours of interviews with age researchers from Boston and New York. These studies aim to resolve questions that have become increasingly pressing for the aging societies of industrialized countries: How do some lucky individuals manage to live 100 years and longer — and still remain so incredibly healthy and active? How can it be that centenarians are generally less of a burden on the health system than ordinary mortals?

Demographers have calculated that the life expectancy of people in the developed world has risen for the past 170 years by an average of three months per year. In the United States, it is currently 81 years for women and 76 years for men — and there's no end in sight to this trend. How can we prevent this increasingly elderly population from being plagued by the typical afflictions of old age, including protracted illnesses and medical conditions such as arteriosclerosis, diabetes, cancer, and Alzheimer's? Do the lives of individuals who've lived more than a century provide recipes for combating the infirmities of an aging society?

There are some 50,000 people over the age of 100 in the U.S. One in 7 million people in the West even live to the age of 110 or longer — and there is a special word for these living ancients: supercentenarians. Research teams worldwide are searching for centenarians and supercentenarians to comb through their genes, medical records, and life stories for explanations.

Israeli physician Nir Barzilai and his staff at the Institute for Aging Research at the Albert Einstein College of Medicine in New York have asked hundreds of centenarians hundreds of questions, including details of their living circumstances, nutrition, alcohol consumption, smoking, physical activity, sleep, education, status, and spirituality — all in the hope of finding commonalities.

The results are sobering: "There is no pattern," says Barzilai, 54. "The usual recommendations for a healthy life — not smoking, not drinking, plenty of exercise, a well-balanced diet, keeping your weight down — they apply to us average people, but not to them. Centenarians are in a class of their own." He pulls spreadsheets out of a drawer, adjusts his glasses, and reads aloud: "At the age of 70, a total of 37 percent of our subjects were, according to their own statements, overweight; 37 percent were smokers, on average for 31 years; 44 percent said that they exercised only moderately; 20 percent never exercised."

But Barzilai is quick to point out that people shouldn't start questioning the importance of a healthful lifestyle: "Today's changes in lifestyle do in fact contribute to whether someone dies at the age of 85 or already at age 75." But in order to reach the age of 100, says the researcher, you need a special genetic makeup. "These people age differently. Slower. They end up dying of the same diseases that we do — but 30 years later and usually quicker, without languishing for long periods."

Obesity, smoking, and an extremely low level of physical activity certainly don't promote good health. But the interviews have revealed no magic formula for how we should live, eat, and behave to reach a ripe old age. Stefan Schreiber, head of the Research Group on Healthy Aging at the University of Kiel, in Germany, has made similar findings. "None of the centenarians went on an algae diet," he quips. He has noticed one thing that they have in common, though: "Many of them have only kissed one woman in their lives" — kissed, mind you, he says again, and laughs. "Perhaps that is the essence of why someone becomes 100?"

HAPPY'S YOUNGER BROTHER Irving, 104, can be found on weekdays between 8:30 a.m. and 3:30 p.m. in his office on the 22nd floor of a skyscraper on Madison Avenue. Kahn Brothers is the name of the investment firm that he and two of his three sons founded in 1978. His eldest son — now age 72 — retired five years ago.

Irving Kahn, a small, plump man who wears reading glasses and a hearing aid, is sitting in front of a flat screen, and on his desk lie piles of paper and a large magnifying glass. He has no intention of quitting: "I'm interested in a wide range of industries and technologies," he explains, "and I'm a passionate reader. That's why being an investor is the perfect job for me." Since his wife's death 14 years ago, he has actually worked even more: "I simply wasn't able to find anyone else as interesting as the woman I shared a bed with for 65 years."

What is his personal recipe for living to the age of 100? He raises three fingers into the air and starts pontificating: "First, you need a nutritious diet, with a lot of vegetables and salads. Second, get plenty of fresh air. Third, don't drink, don't smoke. I drink at most one glass of wine every three months." Now his ring finger and pinkie also shoot into the air: "Fourth, you have to always stay in motion, be open, get to know people from all over the world. And, fifth, have a lot of interests and learn things that you can't do yet — that keeps you young!"

But what about his oldest sister? Irving shakes his head: "Sure," he says, a bit miffed, "that's an old joke in our family. Happy loves to have her picture taken with a cigarette in one hand and a cocktail in the other."

Irving's fourth and fifth commandments, however, have been scientifically proved: "We've found a few interesting personality traits," says Tom Perls, 50, from Boston University, who directs the New England Centenarian Study, the largest research project of its kind in the world, with some 2,600 participants. "Our subjects are generally extroverted and gregarious and have a stable social network." Furthermore, they aren't neurotic — in other words, they don't bemoan life's difficulties; they are masters of the art of letting go. German researcher Schreiber concurs: "This alertness of the mind, the openness, it's remarkable — especially when you consider that these people haven't had easy lives. They have experienced war, hunger, and poverty."

Is it possible to extend our lives by deliberately adopting a more optimistic attitude? Or are centenarians just inherently blessed with a cheerful disposition? "We don't know how much of this is genetically determined," says Perls. "But we learn how useful it is to come out of your shell."

PETER, WHO AT 100 is the baby of the Kahn family, is also the frailest of the three surviving siblings. The former Hollywood cinematographer went blind three years ago, and he has had to wear a neck brace ever since he took a bad fall. His favorite activity now is sitting in front of his living room fireplace in Westport, Conn., listening to mystery stories, along with scientific works and historical fiction.

Peter's wife, Beth, 66, takes care of him and directs him when he blindly moves around the house with his walker (he could use a wheelchair, but he prefers to walk). He met Beth at a party more than a quarter-century ago. She didn't notice his age, she says, and smiles. "I only thought: What a charming man!" Now Peter is smiling. He doesn't understand much about genetic research, he says, "but the researchers maintain that I have unusual genes."

This summer, in fact, Perls' research group in Boston caused a stir worldwide: In the journal Science, the researchers reported that they had discovered 150 genetic variants linked to extreme longevity. They said that they could use the variants to predict a person's longevity with 77 percent accuracy. Centenarians have only a negligibly lower risk of developing age-related conditions like diabetes and high blood pressure, Perls explains, but they have genetically determined protective mechanisms that delay the outbreak of these disorders and foster a longer life.

Academic peers hailed the study as a milestone — and other research groups began rushing to replicate Perls' results. "Perls' idea is smart and sexy," says Schreiber. "If it can be substantiated, then this would indeed be a breakthrough." Age researcher Barzilai is thinking one step further: "First, we need to understand how these 150 variants protect their owners from diseases so we can develop therapeutic approaches," he says. He hopes this will allow doctors to control many age-related illnesses.

Meanwhile, Happy has recovered from her cold. She spent five days in her apartment, but she was going a bit stir-crazy. Now she is meeting her brother Irving for lunch at a restaurant on Central Park; they both arrived with caretakers. "I feel like I’ve been cooped up for two weeks," she says, before polishing off a plate of crab cakes and potatoes. For dessert, she orders — and devours — a piece of chocolate pie.

By Samiha Shafy. © Spiegel Online 2010. Reprinted by permission.