Reaching the century-mark is still quite an accomplishment. Understanding why some people reach their 100th birthday and other people do not could lead to breakthroughs in treatments for everything from Alzheimer's to heart attacks.
Mary Jeffery has seen plenty of birthdays, and she expects to celebrate many more. At 98, she's not yet part of the elite triple-digit crowd, but she is easily peddling in that direction.
Dr. Joseph Kirsner has been reporting to work as a gastroenterologist at the University of Chicago Medical Center for more than 70 years now. The renowned physician and researcher has passed the century mark and he still makes it into the office at least once a week.
"I'm 102, on my way to 103," said Kirsner.
What these rock stars of aging seem to have in common is that they are not only living long, but well.
How do they and others do it? Researchers are trying to crack the code.
"We think that the limit of human life span is probably around 120 or 130," said Dr. Thomas Perls, a geriatrician at the Boston University School of Medicine.
There are an estimated 50,000 centenarians in the U.S., and about 60 to 70 super centenarians, those who live to 110 and older.
Their long-life success is a complex puzzle. Experts say a lot has to do with environment, such as having good health habits, not smoking, eating well, exercising, and keeping mentally active.
Getting the most recent attention is what some people may be born with - a possible genetic edge.
Some researchers like Dr. Perls believe certain genes play a significant role in unusually long life.
"Our hope is not to get a lot of people to extreme old age, but rather to learn how they markedly delay or escape a terrible disease like Alzheimer's," said Perls. "Understanding how they do that might lead to some prevention strategies as well as even some therapies."
Perls runs the New England Centenarian Study, the largest study of 100-year-olds in the world.
Some critics insist long life is too complex to attribute to just what is in our DNA. While there is controversy and skepticism surrounding newer research, Perls remains confident that he and colleagues have pinpointed specific genes that could help predict how long someone may live.
Another genetic surprise: centenarians have the same disease risk as everyone, but they may also have something else.
"They also like have what we call longevity genes or genetic variants that kinda trump these bad variants and may help you age slowly," said Perls.
At 98, Mary Jeffery still works out. To the amazement of staff at Advocate Good Shepherd Health and Fitness Center, the spunky senior is at the club about three times a week for 45 minutes to an hour.
"I'd just like to keep going," said Jeffery. "I'm so nosy - I don't want to miss anything." Researchers also want to better understand that positive attitude. Keeping the mind active as well as the body seems to factor into long life.
Dr. Kirsner no longer sees patients, but he still consults with other doctors. Kirsner is still in the game and is determined to find a cure for inflammatory bowel disease.
"I think you need a great cause that should drive you and then you work," said Kirsner. "Your goal should be to help people."
Dr. Perls says that if we follow a healthy lifestyle, most of us have the genetic make-up to get us to our late 80s - almost 90.
Again, he says the goal is not to create immortals, but to really understand how genes and environment can help us live long and live well.