She walks a bit slower, and her hearing isn't what it used to be. But Fumi Chinen, just a few months shy of her 100th birthday, hasn't given much thought to retirement.

"I would hate just sitting around the house," Chinen said during an afternoon break from tending her family's small clothing shop in a public market. "I think I'd go senile."

Nowhere else on Earth do people have a longer life expectancy than they do in Japan. And nowhere in Japan do people live longer than they do on sun-drenched Okinawa, a coral-ringed island just north of Taiwan.

Heart disease and strokes are rare. Cancer rates are low. Instead of being shunted into homes and forgotten about, old people are out and about. Like Chinen, many work well into their 80s and 90s.

Now, a group of scientists say they may know some of the reasons why. They have collaborated on a best-selling book on how the rest of the world might benefit.

"There is a lot people can learn from Okinawa -- diet, exercise and lifestyle. It's a Shangri-La," said Makoto Suzuki, a cardiologist and professor at Okinawa International University who co-wrote the book, "The Okinawa Program."

Using statistics from a 25-year study backed by Japan's Health Ministry, the book paints an almost too-good-to-be-true picture of Okinawan health, and even cites ancient Chinese legends calling Okinawa the "land of the immortals."

It offers a raft of health tips, including exercises from karate -- an Okinawan invention -- and relaxation techniques, along with nearly 100 recipes ranging from "Shangri-La Spinach Lasagna" to "Immortal Pate."

Once an independent kingdom, Okinawa was forcibly assimilated into Japan in the late 1800s. It was one of the bloodiest battlefields of World War II, and today is the poorest of all of Japan's provinces.

But Okinawa's health figures are impressive.

According to the Health Ministry, the average life expectancy on Okinawa is 81.2 years -- 86 for women, 75 for men -- the highest in the world. Okinawa's average age is significantly higher than that for all of Japan -- 79.9 -- which tops all countries in life expectancy. Hong Kong, at 79.1 years, is second.

Okinawa also has an unusually high concentration of people 100 years or older. There are currently about 400 centenarians in Okinawa, or 34 for every 100,000 people. The equivalent figure for the United States is about 10 in 100,000.

But it is the quality of the lives the centenarians are living that really struck Suzuki and co-authors Bradley Willcox, a geriatrics fellow at Harvard Medical School, and his twin brother, D. Craig Willcox, an assistant professor at Okinawa University.

Okinawans suffer 80 percent fewer heart attacks than North Americans, and are twice as likely to survive one if they do. Stroke, hormone-related cancers and dementia are rare. There is little obesity. Old people have stronger-than-expected bones.

While acknowledging that genes can provide some beneficial propensities, the book argues heredity doesn't necessarily weigh all that heavily in the Okinawans' favor. Okinawans living in Brazil and elsewhere overseas have lower life expectancies, the authors note.

Of more importance, they say, is the Okinawan diet, which is very heavy on fruits, vegetables, fish and moderation. Another factor is the low level of stress felt by old people, which the authors attribute largely to a strong social network that keeps old people actively involved in the community.

"People, especially older people in villages, simply look out for one another," the Willcoxes say in the book. "It enables the elderly to go about their daily lives while still living in the community, even if they are slowing down a little."

Not far from Chinen's clothing shop, a health food store touts Okinawa as the longevity capital of the world and offers brown sugar from Okinawan sugar cane, turmeric tea, kombu seaweed.

Reptiles are big items as well -- dried and cured sea snakes hang in long coils from a high shelf above bottles of powerful liquor containing "habu," a poisonous snake.

"Old people here and tourists buy lots of this stuff," said shopkeeper Masako Nagamine.

But Nagamine admitted she doesn't believe exotic food is the secret behind Okinawan longevity.

"People here live at a slow pace," she said. "We've got good, warm weather. We know how to take it easy."