LAGUNA WOODS, Calif. — Gordon Bern doubled his treadmill time in the Leisure World gym so he could walk on uneven cobblestones during his first visit to Europe over the summer.

Such are travel preparations at 95.

At the London airport, he bid farewell to his best friend, who was headed home to Florida. They shook hands, hugged and wondered out loud if they would ever see each other again.

Such are goodbyes at 95.

A week later, Bern's buddy died.

Such are friendships at 95.

"That's what happens when you get to our age," Bern said. "We don't buy green bananas."

Bern said he has lived an ordinary life of career, family and community service. Why he has survived and thrived, he can't explain.

But researchers at the University of California-Irvine hope to learn more about longevity from Bern and others in their 90s. The former salesman is among nearly 1,000 study subjects recruited from Leisure World, as the U.S. Census reports people 85 and older have become the fastest growing segment of the population.

Americans in their 90s are expected to surge in number from nearly 2 million to roughly 10 million by 2050.

"As to how I arrived at this age, I don't know," Bern said. "I lived a normal life. I think I had as much stress as the next person."

Bern eats a normal diet, excluding the fish eyes he loved as a boy growing up in Canada, and he exercises. Having played tennis in his youth, he switched to paddle tennis once glaucoma limited his field of vision.

Every six months, Bern undergoes physical and cognitive testing. His blood is drawn. He gives a swab of DNA from his cheek. He is filmed as he walks to monitor his gait and mobility.

"He's very together," said Barbara Agee, a nurse practitioner for the study led by Dr. Claudia Kawas. "People have a picture in their head of what someone in their mid-90s might look like — unfortunately someone in bed or completely helpless or needing a nursing home. He's not any of that. We're just trying to find out his secrets."

Bern's participation will only end when he dies, but even then, he's agreed to have his brain dissected for signs of dementia.

"They'll do what they have to do after I'm gone, but they'd better not do it while I'm alive," Bern joked.

Bern said researchers have commented on his knack for remembering numbers. He can recall a new phone number without writing it down. He mentions he snapped 143 digital pictures in Europe. He easily tracks the fluctuations in his stock portfolio.

"I remember how much I'm losing every day," he said dryly.

Bern said he tries to roll with the punches and not get worked up about things he can't control.

He cared for a sick wife for five years until she died. He cooks favorite meals for his schizophrenic son, 60, who lives with him. He changed jobs many times and moved from Canada to California.

But stress these days comes from how others see his age, not his own complaints about growing older.

"What is old? It's a state of mind," Bern said.

Age has sometimes been a challenge in his relationship with his "gal friend" Ellen.

Eight years ago, they met at Temple Judea, where Bern was honoring the memory of his father. He found her lovely, bright and knowledgeable. And she made him happy. Their first kiss was on her doorstep at her Leisure World home, three miles from his.

"I enjoy her company and she enjoys mine," Bern said. "We talk over the stock market or stories in the newspaper. I enjoy listening to her and she sometimes listens to me."

Bern wants to marry Ellen, who is 87. But she's said no many times.

"She says I'm too old," Bern said. "She buried two husbands. She evidently feels that's just too much."

Bern felt most old — and sad — when Ellen's daughters told her they didn't want her riding on the freeway with him anymore.

"I've never thought age meant anything," he said. "All of a sudden someone mentioned that my age was a real problem. I began to realize how old I am. It shocked me."

He doesn't see an old man when he looks in the mirror. He feels 75 and is determined to live that way.

Every Saturday, he volunteers at Saddleback Memorial Medical Center where his wife was treated before she died. Bern cared for Goldie in the five years after she had a stroke, learning to cook and wash windows under her direction.

"When she finally died, I thought it was the end for me," Bern said. "I was in the 80s, and I had nothing to live for. It was a bad time. To be alone is no fun at all."

Volunteering became a meaningful outlet. In the 13 years since Goldie passed, he's put in more than 2,500 hours.

"I figured I owed something to the community. I still feel I'm doing useful work."

Working in a hospital, as well as outliving friend after friend, has left him well acquainted with death.

"That's inevitable," Bern said. "There's nothing I can do about that. I'm not afraid. It's going to happen to me, it's going to happen to everyone around me. I have no friends left. I lose one after the other."

But that reality never stops him from learning or thinking about the future.

"People my age, most of them, don't have any curiosity," Bern said. "They either know it all or they don't want to know it all."

Bern recently visited his brother in Berkeley, Calif., and said he hopes to go to Hawaii sometime this month with Ellen. He also intends to vote in November, and his doctor doesn't think he'll die before 100.

"I'm certainly not ready," Bern said. "I don't feel up to it yet. I'm enjoying life too much."