For a growing number of Americans, 100 is the new 80.
There are about 84,000 centenarians living in the United States, a number that is expected to increase 10 times by the year 2050, according to the U.S. Census Bureau.
The secrets of longevity have been a source of fascination for millenniums. Over the course of human history, numerous diets, lifestyle regimens and supplements have been touted.
In a special section called "The Science of Living Longer," Time magazine explores what experts have found out through the study of the genes and lifestyles of those who have lived to be 100 years old and older.
While most centenarians seem almost hard-wired to live beyond the average life expectancy, Time senior editor Jeffrey Kluger said there's no reason the rest of the population can't strive for the same longevity.
"They key here is the cause and effect," he said. "It's not that they just live to 100 and get lucky."
Researchers are now studying people who live to be 100 in hopes they can find away to reproduce in everyone else what comes naturally to the centenarians.
Time's research found that today's centenarians are mostly very healthy people. The Long Life Family Study from the National Institute on Aging has determined that there is a 70 to 30 percent split in the reasons for longevity.
Many centenarians aren't able to avoid the diseases that typically plague people as they get older, including cancer and heart disease, Kluger said, but they can bounce back faster and more effectively.
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For some people, genetics plays a 70 percent role in determining longevity, with the remaining role attributed to lifestyle. For others, though, it's the reverse.
"Lifestyle plays a much bigger role on the larger part of the population that isn't genetically hard-wired," Kluger said.
People's life expectancy has gone up 30 percent since the 1900s, in part because of vaccines, preventive care and antibiotics, Kluger said.
While most people would love to be born with genes that favor longer life, Kluger said those who arent's so blessed do have some control, and that some simple changes can have a favorable impact.
One of the best ways for people to improve their life expectancy is to exercise regularly. Thirty minutes of exercise, at least three times per week – and breaking a sweat – is a good routine. Add 30 minutes of weight lifting and 30 minutes of stretching to that weekly routine, and joint strength and muscle tone improves, he said.
The secret to living longer, Kluger said, isn't a secret at all. Keeping weight down, not smoking, not drinking to excess -- "all of the things we know. It's just a matter of putting those things into play."
Keeping mentally fit, Kluger said, can be just as important as being physically active.
Doing a crossword puzzle or Sudoku helps keep cognitive processes sharp. Talking, engaging in conversation and reading are also good ways to help a person's mind remain agile, Kluger said. Research has found that staying mentally active and engaged reduces the symptoms of dementia.