The number of Americans living to 100 — and beyond — has increased dramatically in recent decades, while those over the age of 80 comprise the world’s fastest-growing segment of the population, according to the latest research.

Between 1980 and 2014, life expectancy in the United States increased from 73.8 years to 79.1 years. Meanwhile, the number of Americans reaching and surpassing age 100 has exceeded 100,000, and that figure is expected to grow eight times — to 800,000 — by 2050, according to the National Institutes of Health and the U.S. Census Bureau.

So what’s the secret to living long enough to celebrate your 100th birthday?

While there are no sure-fire prescriptions for living to an extremely advanced old age, longevity researchers have found the ticket is a mixture of genetics and lifestyle — which means there are steps you can take to up your odds of living longer.

A landmark Swedish study, for example, showed that men who celebrated their 100th birthday all had mothers who lived into their 80s and 90s. But genetics wasn’t the only factor. The study also showed that the men had many controllable lifestyle factors in common. For instance:

• All of them were non-smokers.
• They generally stayed fit and trim by eating nutritious diets and exercising regularly.
• Nearly all had healthy levels of cholesterol and blood pressure, which reduced their risk of developing cardiovascular disease, the No. 1 cause of death worldwide.
• They owned their own homes or rented expensive residences, allowing them to live independently and stay mentally, physically, and socially active.
• Most did not retire early, but instead actively worked until at least age 54.
• None drank more than four cups of coffee per day.
• Many reported having an optimistic outlook on life, which researchers said helped them embrace the power of positive thinking and combat stress and anxiety.

Studies of American centenarians have reached similar conclusions about the links between healthy lifestyles and longevity.

A recent study that compared and contrasted the lifestyles of Americans with the highest and lowest life expectancy found significant differences the daily habits of those individuals. For the study, researchers examined residents of Summit County, Colo., which has the nation’s highest life expectancy (86.8 years, two years higher than that of Andorra, the tiny country with the world’s highest life expectancy) and Lakota County, S.D. — which has the nation’s lowest life expectancy (66.8 years, comparable to Third World countries such as Sudan.

Researchers concluded that 74 percent of this disparity can be explained by controllable risk factors such as levels of physical activity, diet, tobacco use, and obesity, which increases the risk of developing life-threatening conditions diabetes, high blood pressure, heart disease, and certain cancers.

Worldwide, the rate of chronic illnesses such as heart disease is lowest in the Okinawa Archipelago, a group of 161 coral islands in the East China Sea that are home to the Earth’s longest-living people.

Here are some of the reasons why so many of them live to 100:

Diet. Okinawans primarily rely on plant sources such as sweet potatoes, greens, and whole grains. They supplement their diet with two or three servings per week of freshly caught fish, soya products, and an occasional serving of boiled pork with the fat trimmed off. They also drink antioxidant-rich green tea supplemented with jasmine flowers.

Exercise. Since most Okinawans are fishermen or farmers, they usually work outdoors into extreme old age. They get additional exercise from walking, gardening, martial arts and traditional dance.

Social life. Like other long-lived people, Okinawans maintain close social ties.

Stress. They also engage in stress-relieving strategies such as regular meditation.

Another longevity hot spot is the Greek island of Symi, where residents routinely live into their 90s. They, too, rely on fruits, vegetables, fish, and little meat. But they tend to slather their food tomato sauce, extra virgin olive oil and garlic. They also drink red wine with most meals, which helps account for their low rate of heart attacks.

So how long can life expectancy to continue to grow?

McGill University biologists Bryan G. Hughes and Siegfried Hekimi attempted to answer that question by analyzing the genetics and lifestyles of the longest-living individuals from the U.S., U.K., France, and Japan.

Their findings, published in the journal Nature, explodes the commonly held belief that the upper limit of the human lifespan is around 115 years.

“We just don’t know what the age limit might be. In fact, by extending trend lines, we can show that maximum and average lifespans, could continue to increase far into the foreseeable future,” Hekimi says.

It’s impossible to predict what future lifespans in humans might look like, Hekimi says. Some scientists argue that technology, medical interventions, and improvements in living conditions could all push up the upper limit.