Morris Zysblat and Johanna "Jo" Meyne were born in 1913, a year before the outbreak of World War I. Their similarities would seem to end there.

HACKENSACK, N.J. — Morris Zysblat and Johanna "Jo" Meyne were born in 1913, a year before the outbreak of World War I. Their similarities would seem to end there.

Zysblat, who is Jewish, fled Nazi Germany; Meyne, a devout Christian, was reared on a Wyckoff, N.J., farm. Zysblat supported his family as a globe-trotting businessman; Meyne kept a nice home for her carpenter husband. Zysblat plays the markets, watches CNBC and has 40 Facebook friends; Meyne knits, watches "The Price is Right" and goes to church.

What Zysblat, 98 in February, and Meyne, 98 in July, have in common are robust physical health, sharp minds and sunny dispositions. There's every reason to believe they'll be joining that exclusive fraternity of centenarian Americans — now 80,000 strong, 85 percent of them women.

Why some people live 100 years or more is tantalizing to experts and laymen alike. Genetics plays a big role; scientists in Boston recently spotted genes related to super-longevity. One of those scientists, Dr. Thomas Perls, founded the New England Centenarian Study, which maintains that a positive outlook and ability to manage stress are predictors of a long life, along with the holy trinity of smart health habits: good diet, exercise, no smoking.

There's no hard-and-fast map on the road to 100, but there are lessons to be learned from the real experts — those, like Morris Zysblat and Jo Meyne, who can almost taste the birthday cake.

Zysblat, who lives independently at Classic Residence in Teaneck, and Meyne, who lives independently at Holland Christian Home in North Haledon, likely have genetics on their side.

Zysblat's father died of cancer at 52 but his mother lived to her 80s and his only sister is 96. Meyne's parents lived to their 80s and six of her seven siblings made it at least to their 80s.

Good genes, though, aren't a be-all-and-end-all, says Dr. Edward Schneider, professor of gerontology at the University of Southern California.

"You can modify the genetics by stepping in front of a train or a car," he said, "and you also can have bad health habits."

1. Don't get sick

"So much depends on being free of illness through one's lifetime. Not having your body debilitated is critical to longevity," said Dr. Elaine Leventhal, professor of medicine at New Brunswick's Robert Wood Johnson Medical School and a specialist in geriatric medicine and gerontology.

"You certainly want to be free of lung disease, free of significant cardiac disease, free of diabetes" — and personal behavior has a lot to do with that.

Zysblat and Meyne kept illness and the risk factor of obesity at bay. They feel fine, they seldom go to the doctor and the only pills they take are for blood pressure. But the lives they have led go only so far in explaining their good shape.

Neither smoked — but their spouses did, suggesting exposure to secondhand tobacco smoke. Meyne says her main physical exercise was gardening and walking around Wyckoff, while Zysblat cheerfully admits, "I don't exercise — never did in my life. How about that? And I haven't walked very much either."

As for diet, Meyne says "I'll eat what you give me — I was never fussy." And Zysblat says "all my life I ate foods that were not good for me." A peek inside his refrigerator bears him out: butter, salami, frankfurters, pastrami. But the key, he says, is eating the salty, fatty, not-good-for-you stuff in moderation.

2. Thank God

Meyne credits God for bringing her this far. The former Sunday school teacher attends Sixth Reformed Church in North Haledon, listens to Christian music on the radio and keeps the Lord's Prayer over her bed in an embroidery she stitched as a young bride.

Others around her feel likewise. "Because we are a Christian home, our residents feel blessed to be here," said Carol Moore, administrator of Holland Christian Home, where six of the 150 residents are centenarians. "They are brought up in their church and their spirituality carries them through, and gives meaning and purpose to their life."

Does prayer contribute to a long life? There are no data, Schneider says, but there is value to being part of a church or a religious community because it increases one's social network — which gives the elderly an extra measure of support.

3. Exercise your brain

In the "Living to 100 Life Expectancy Calculator," devised by Perls of the New England Centenarian Study, people who engage in mind-challenging activities add five years to their life expectancy.

It's worked for Zysblat, who's been retired nearly 40 years. The lifelong reader still devours books — three a week on his Kindle. After finishing a book, he adds the title to the computerized list he's been keeping since 2004. The list has 800 books, ranging in authors from Diane Ackerman ("The Zookeeper's Wife") to Emile Zola ("Nana.")

When not reading, Zysblat trades gold and silver at one of his three computers. He started day-trading stocks in the 1990s, but switched to a less volatile sector. It's a hobby, and he is convinced the buy-and-sell decisions he makes in the course of a trading day keep his mind razor sharp.

4. Set goals

There's no computer in Jo Meyne's room at Holland Christian Home, but there is a knitting bag.

"I guess I wore out my eyes with all my fancy knitting," said Meyne, who is mostly blind. "I don't know how to say it, but I just enjoy doing it."

Her handiwork has a greater purpose. Meyne knits 7-by-9-inch squares that are assembled into blankets, which are then donated to the homeless and disaster victims through a charity called Warm Up America! Knowing others benefit, she aims to complete one square a day. Setting and achieving goals is important, even more so for those of a certain age.

Zysblat, too, is a man of goals, as evidenced by his ever-growing list of books read.

A man satisfied with his accomplishments, Zysblat wanted to live to see the new millennium. He did, at age 86.

At 95, he set his sights on 100.

"To be healthy and be able to do what I'm doing? It's amazing," said Zysblat, who last year blessed the challah at his grandson's wedding.

Robin Granat, executive director of the Teaneck retirement complex where Zysblat lives, regards her most technologically wired resident as a poster boy for successful aging.

"Morris' outlook is realistic," she said. "He himself decided last year it was time to stop driving. He himself decided to use a cane because he's aware of being a fall risk. He is aware of his limitations, but doesn't let them get in the way."

Granat's experience is that 98-year-olds of sound body and mind will join the centenarian ranks.

Zysblat's counting on it. He has cousins and friends coming from Europe for the 100th birthday party his son and daughter are planning.

Jo Meyne also is up for a little cake.

Pausing from her knitting, she said slyly, "We should have some little celebration, shouldn't we?"