Here's how you can live to be a hundred!

According to Dan Buettner, some of the several ways are: a plant-based diet; regular, low-intensity activity; an investment in family; a sense of faith; and purpose.

"We know that people who make it to a hundred tend to be nice," National Geographic quoted him, as saying.

"They...drink from the fountain of life by being likeable and drawing people to them," he added.

Buettner has explored and studied the world's centenarian hot spots-which he calls blue zones-over the past several years.

"You see it over and over again: people who are living a long time have a reason to get up in the morning," Buettner said.

The other hot spots include Sardinia in Italy, which has the highest concentration of centenarians -- most of which are men --

Costa Rica also makes it onto the list. Nicoya Peninsula has the lowest middle-age mortality in the world, Buettner said.

"A 60-year-old in Costa Rica has more than a four-fold better chance of making it to 90 than a 60-year-old in America. They spend one-fifteenth the amount we do on public health, but they spend it in the right places," he said.

To Buettner, what is clear is that people can take control of improving their longevity.

"Set up your life, your home environment, your social environment, and your workplace so that you're constantly nudged into behaviours that favour longevity," he said.

The study is published in a new book, The Blue Zone: Lessons for Living Longer from the People Who've Lived the Longest.