WASHINGTON (AP) - You've heard of the type: They eat whatever they want and maybe they smoke. Some of them exercise, some don't. And they live to be 100.

What's their secret? Is it good genes, good habits - or just good luck? It's a question that researchers are trying to answer.

"We have 100 year-olds who have smoked all their lives; we have 100-year-olds who are fat," said Dr. Nir Barzilai, a Yeshiva University researcher seeking longevity genes.

Juanita Ollman survived the flu epidemic of 1919, and a car accident and pneumonia when she in her 90s. But she has no magic recipe for her longevity: She exercised regularly, including years of ballroom dancing. But she eats anything she wants, including breakfasts of bacon and eggs. Church and family kept her centered, but a son's service in the war drove her to cigarettes for awhile.

"I don't know that I've done anything extra," said Ollman, who turned 100 last July. Maybe it's the treadmill: "Sometimes I skip a day, and I don't always get up to a mile, sometimes it's just three quarters of a mile."

John LaFauci, a 101-year-old who publishes a weekly newsletter for his Smithfield, R.I., retirement complex, swears it's good genes, and his avoidance of beef. Helen Rose, 100, a retired teacher in Waterloo, Iowa, credits a love of learning and Jesus.

"This is a ripe time to begin looking at this extraordinary group," said Dr. Robert Butler, director of the International Longevity Center, a New York City center where researchers look at how societies react to aging.

Just one in 10,000 Americans have lived a century. They're the fastest growing age group, and by 2050 - when the oldest baby boomers would reach 100 - there could be nearly a million people that age or older, the Census Bureau says. An exact number is expected in June.

Scientists record what the centenarians eat, what they don't and how they've handled stress. Children, siblings and spouses are also part of the research, to see what makes their elders different from people who share their genes, or their environments.

So far, centenarians have shattered myths, and raised more questions about extreme old age.

Researchers know for certain that few 100-year-olds have had heart attacks, developed Alzheimer's or been hit by diabetes.

"We're constantly disproving the idea of the older you get, the sicker you get," said Dr. Thomas Perls, director of the New England Centenarian Study at Harvard Medical School. "They are avoiding or delaying these diseases. We've got to find out how and why they do that."

Researchers know that generally, the siblings of centenarians tend to live long themselves; siblings of centenarians are at least four times more likely than the greater population to reach their 90s, and are eight times as likely to get to 100.

So far, genes that extend life have only been identified among insects. When the right human genes are discovered, researchers insist, the goal will not be to create an elixir to prevent aging. The point will be to help everyone live healthier lives by developing treatments for the diseases that kill people well before they reach 100.

There are discoveries researchers haven't explained. Centenarian women outnumber men, but are sicker and more frail. Women who have a child after 40 are five times as likely to reach the century mark than other women.

Centenarians are all races. Some farm, others surf the Internet. A comfortable, wealthy, pampered life doesn't necessarily guarantee long life. Children of slaves have lived to 100, as have Jewish survivors of concentration camps.

The only thing researchers have found they share is that many had a family member who lived long as well.

Some research is showing that genes don't hold all the keys. Perls, a 40-year-old doctor who has studied centenarians for the last seven years, said centenarians score lower on a psychological test for neurotic conditions or traits. In other words, they don't dwell on things.

Past medical advances have contributed to there being more 100-year-olds than ever. Born at the turn of the century, more such babies survived, thanks to vaccines, safe water and better public health. The average life expectancy at the beginning of the 1900s of 46 has nearly doubled now; 74 for men, 80 for women. The world's oldest person, documented by birth records, died at 122 in 1997.

Famous centenarians have stood out in recent years. Entertainer George Burns showed the funny side of pushing 100. Strom Thurmond of South Carolina would be the first 100-year-old senator at the end of his term in 2002.

Copyright 2001 The Associated Press. All rights reserved.