No fountain of youth holds the key to long life. That much seems certain. Rather, science suggests it lies in people's genes and in their choices.

Study after study seems to promise that doing this or not doing that will add years to life. But how far can humans go?

The answer at the moment is 115 to 120 years, said Dr. Richard Sollazzo, an emergency medicine physician at St. Catherine of Siena Medical Center in Smithtown who studies longevity. There doesn't seem to be anything on the horizon that would boost life span past that point, he said.

Lives have, however, been lengthening steadily in the United States. Someone born in 1929 was expected to live, on average, just 57 years, according to the U.S. Centers for Disease Control and Prevention. By 2007, the average life span had grown to 78 years -- 75 for men, 80 for women.

Better medications, medical technology and better diets have all contributed to a lengthened life span. But those who live especially long may get more of a boost from their genes than from anything they do or any medications they take.





It's a simple equation: If your relatives live a long time, your chances of sticking around will go up, Sollazzo said.

In fact, research suggests that genes play the most crucial role in the survival of people who live into their 100s. A study published last year in the Journal of the American Geriatrics Society found that a group of Ashkenazi Jews older than 100 years generally did not have better diets than other people, nor did they exercise more than others when they were younger.

So, what should you do if you want to live a very long time? "There's no one cause of the aging process and no one answer," Sollazzo said. But people do have options, he noted, especially those whose genes aren't built for the long haul. For one thing, get checkups and undergo regular screening for diseases such as cancer. And make sure you're up to date on the symptoms of medical problems.

Education also pays dividends in terms of life span, said Dr. Jean Cacciabaudo, chief of cardiology at Southside Hospital in Bay Shore. Heart disease, for instance, has been on the decline in recent years because of gains in knowledge about the disease and more widespread treatments, such as anti-cholesterol drugs, she said.





"People know what the symptoms of their heart attacks are, and they seek medical help in a timely fashion," Cacciabaudo said. "They know to take an aspirin right away if they're concerned about having a heart attack. And the technology has improved: We have clot-busting medications, we can go in and open up arteries and clean up the blockage with balloons and stents. This has all prevented people from dying of heart attack."

And, of course, scientists think that a healthy diet and exercise can make a major difference in the life span of people who don't have genes primed to give them long lives.

As for other options, Sollazzo said he takes resveratrol, available as an over-the-counter supplement. Scientists who've tested the substance in mice have been excited about its effect because it appears to extend the mice's lives. Resveratrol is found in red grapes, red wine, pomegranates and some other foods.

Research has also shown that greatly decreasing food intake below normal helps animals to live longer, Sollazzo said, though he noted that can be hard for people to handle and makes some feel less energetic.

But what about living forever, or at least past 120 or so? For now that seems out of the question.

"There's a duration of how long cells can be vital and healthy," Cacciabaudo said. "After a certain point, they can't sustain themselves. That's why people need pacemakers -- the electrical system of their heart starts giving out. And that's why people need joint replacement, when the cartilage on their knees starts wearing away."

In the long run, she said, the big questions are about the quality and quantity of life.

"I have patients who say to me, 'All I want from you is to keep me alive until I'm 100,' " Cacciabaudo said. "I say, 'Is that really what you want?' That prospect makes me so fatigued!"

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