Are you familiar with the “blue zones,” those regions of the world where people live exceptionally long lives?

In certain regions of the world, people seem to have exceptional longevity. These places are called "Blue Zones." What do we know about them?

Officially, there are only four, or maybe five, of them in the world. The "Blue Zones" are regions where people live exceptionally long lives and where being a centenarian is almost normal. Myth or reality?

It all began in the late 1990s, when a team of researchers began studying longevity in Sardinia. With its relatively isolated population, low immigration rate, and low genetic diversity, the island seemed ideal for studying genes and habits that might influence life expectancy. But once there, they realized that centenarians were not evenly distributed. They concentrated in the province of Ogliastra, a central mountainous region. Even more intriguing, this province has almost as many centenarian men as women.

Gianni Pes and Giovanella Baggio, doctors at the University of Sassari, presented the results of this work in 1999 at a conference in Montpellier. The demographers present were confused. Some questioned their data, suggesting that they came from poorly maintained, erroneous, or even nonexistent records, and that the centenarians they were talking about might not actually be centenarians.

No matter, Michel Poulain, a Belgian demographer from the Catholic University of Louvain and an expert in age validation, accompanied him to verify the records. For six months, he spoke with residents, checked documents, and validated the ages of all centenarians. And each time he encountered one in a village, he made a mark with a blue pen on a map. Little by little, the map began to color in. Thus, the term "blue zone" was born, starting in the spring of 2020. But what lies behind it?

"There are two criteria, and they are purely demographic," explains Michel Poulain, who is currently finalizing an article on the subject for the journal " American Lifestyle Medicine ." He first calculates what is known as the extreme longevity index, which is the number of centenarians born in the region 100 years ago divided by the total number of births recorded over the same period. If this longevity index is at least equal to what was observed in Sardinia in 2000, a figure that has become the benchmark, and is significantly higher in this region than in the country as a whole, then the region can be declared a blue zone.

Accompanied by American explorer and adventurer Dan Buettner, Gianni Pes and Michel Poulain explored many areas of the world they suspected were Blue Zones. But they didn't always find sufficiently robust data, and ultimately, they only validated a handful: Sardinia, Okinawa (Japan), Nicoya (Costa Rica), and Ikaria (Greece).

Having distanced himself from Dan Buettner since the latter created the "Blue Zones LLC" brand, turning it into a business empire that has produced books, diets, a multimillion-dollar company, and a controversial Netflix documentary, Michel Poulain approved a fifth blue zone in 2023: Martinique. "Basically, a Martinican born in Martinique has a 50% greater chance of reaching 100 years old than a French citizen from mainland France," the researcher summarizes. He also points out that, "when a Martinican migrates to Paris, he has a lower chance of becoming a centenarian than when he stays in Martinique..." Is this due to living conditions and habits? Partly.

The causes of the exceptional longevity observed in the Blue Zones are multifactorial. Unsurprisingly, genetics plays a role, given that in more isolated populations, such as those in Sardinia, relatively rare genetic variants can become more common, a phenomenon known as the "founder effect."

The lifestyle of Blue Zone residents also plays a significant role. By surveying them and collecting data as diverse as their eating habits, blood sugar levels, relationship status, and more, researchers were able to identify a set of lifestyle principles that could partly explain this longevity. A balanced diet, moderate alcohol consumption, low-intensity but daily physical activity, stress reduction, community belonging, family relationships, and a positive attitude: "We observe seven lifestyle principles in the 'Blue Zones'. They are inseparable," says Michel Poulain. "And at the intersection of all this, there is a component of epigenetics," these reversible and hereditary modifications induced by our environment in the broadest sense.

These are hypotheses that Saul Newman, an Australian researcher at University College London, challenges. He argues that these blue zones are located in poor, remote areas where record-keeping is uneven. In short, that they don't exist . Arguments that Michel Poulain dismisses: "I spend my life validating centenarians, but also invalidating those who aren't. Newman is simply stating well-known generalities." As for the question of living standards, "I'm happy to learn that wealth doesn't bring longevity," the researcher smiles, pointing out that while "the inhabitants of the 'blue zones' do indeed have a low standard of living, they don't live in poverty either."

Saul Newman also argues that the healthy lifestyles of Blue Zone residents are not always supported. He cites Okinawa and its obesity rate in particular. This is not denied by Michel Poulain, who published an article on the subject in 2024. "From the moment the United States took possession of the island in 1947, obesity exploded among the generations born thereafter and longevity is in decline."A trend also observed in Nicoya .

Are Blue Zones disappearing? For Michel Poulain, they are in any case threatened by Western lifestyles that encourage people to swap walking for cars, a balanced diet for ultra-processed foods, and rural communities for urban life in cities with degraded air quality.