Unlocking the Secrets to Longevity

PHOTO Identical twin sisters Inez Harries and Venice Shaw from California celebrated their 100th birthdays on Jan. 15, 2011. Watch their story on ?Nightline.?PlayABC News
WATCH 100-Year-Old Identical Twins' Secrets to Longevity

It's long been said that always looking on the bright side and not working too hard will lead to a long and happy life, but a new study blows both of those shibboleths out of the water.

Howard Friedman and Leslie Martin, psychologists at the University of California at Riverside who specialize in aging, spent the past 20 years analyzing the findings of social scientist Lewis Terman.

Terman launched the famous personality and behavioral study of 1,500 children in 1921 that recorded each participant's progression through life. It created a treasure trove of data, which Friedman and Martin mined for clues as to what behaviors and practices could mean a longer life.

They recently published their findings in a new book, "The Longevity Project: Surprising Discoveries for Health and Long Life from the Landmark Eight-Decade Study."

Watch the full story on "Nightline" tonight at 11:35 p.m. ET

"We really wanted to ask the big questions," Friedman said. "What happens across long periods of time, and how do all those things go step by step to keep some people healthy and make some people ill."

Their findings produced several surprising results.

"You always hear don't worry, don't worry you'll make yourself sick," Friedman said. "But we didn't find that at all."

"What we have found is that a moderate amount of worry is not a bad thing and particularly for men," said Martin. "And men facing crisis, like the death of a spouse, those were the men who seemed to step it up and sort of channel that worry into better self-care and sort of took care of the things that the wife would have taken care of beforehand."

Another surprise they found was that people who were consistently too cheerful or too optimistic didn't live as long as their worrywart counterparts.

"When we first started this study, we thought, well, maybe these really cheery kids will go on to live long lives," Friedman said. "It turns out they didn't."

Courtesy of Penguin Publishing

"To come to every decision with an attitude that it is going to be fine and you think nothing bad will ever happen, that pushes you in a particular direction," Martin said. "You know, I won't wear my seatbelt, sure I will have another drink. I will have another doughnut. It is a bad approach if you approach everything like that."

Enjoy the Single Life

Perhaps the most startling finding, they said, was that it was better for a person's health to never have been married than to have a marriage fail and result in divorce.

"If you experience divorce, that does increase your risk for earlier mortality," Martin said. "That was a real kind of a shocker. ... Healthy marriages, that is great for your longevity, but being steadily single, particularly for women, was almost as good."

And finally, it seemed that those who enjoyed what they did for a living rarely worked themselves to death. Friedman and Martin said they found those who were committed to their work felt happier and more fulfilled in life.

"Clearly, work you hate is not good for you, but people who were really involved and even worked into old age often thrived," Friedman said.

These secrets to longevity -- the hardworking, slightly worrying, not overly optimistic, non-divorcing individual -- form a personality pattern that Friedman and Martin call "conscientious."

"Conscientious people do a lot of things," Martin said. "They are more likely to gravitate into stable marriages. They are more likely to be in stable jobs that they are happy and passionate about. We know that both of these things are very important. Their social ties tend to be good. They are not the hardcore drinkers. Probably today, they would not smoke at all. It's that sort of pattern that encompasses a whole kind of specific behaviors that they do."

Do 100-Year-Old Twins Hold the Secret to Long Life?

Identical twins are uncommon, but identical twins who live to be 100 are exceedingly rare, which is what makes Inez Harries and Venice Shaw so special.

Born 15 minutes apart on Jan. 15, 1911, the two sisters said they had been doing everything in sync since then, including celebrating their 100th birthdays together last month in California's San Fernando Valley.

Harries and Shaw were not part of Friedman and Martin's study, but they do fit several criteria of the authors' "conscientious" personality pattern. Although they are both divorced, each held jobs they loved for several years -- Harries worked for Lockheed Aircraft for 27 years and Shaw worked as a supervisor for 12 years in a plastics injection plant.

Both said they had stayed connected to people through their families and church.

"We were always close," they chimed in unison.

The twins also picked up hobbies and ate well -- all without worrying too much.

"Life goes on," Harries said. "No matter what happens you have to accept it and make the best of it."