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Blue Zone BS: The Longevity Cluster Myth

We need to be reminded how much real science has done for us and how real science is done.

I recently tried to watch the television series, “Live to 100: Secrets of the Blue Zones,” which Netflix promotes as “an insightful adventure through longevity hotspots around the world.” The enthusiastic host, Dan Buettner, seems to be genuinely driven to help us all live to 100. I alternated between laughing and groaning, and then gave up.

Real science is currently under siege, pummeled by conspiracy nuts and undermined internally by a replication crisis created by sloppy science. We need to be reminded how much real science has done for us and how real science is done.

The Blue Zone BS is not helpful. To the contrary, it promotes sloppy science.

In 2004 a team led by Michel Poulain and Gianni Pes identified a mountainous area in central Sardinia, an Italian island in the Mediterranean Sea, characterized by exceptional male longevity. They characterized this longevity hot spot as a “Blue Zone.” They noted that the reasons “remains unknown,” but they speculated that it might be due to living in a mountainous geographical area or to a high rate of inbreeding that nourished genetic defenses against some fatal diseases.

Buettner evidently recognized the commercial appeal of Blue Zones and identified four more longevity hot spots: Okinawa, Japan; Nicoya, Costa Rica; Loma Linda, California; and Ikaria, Greece. Americans have a seemingly insatiable appetite for self-improvement — how to lose weight, how to get rich, how to make friends, how to have a happy marriage — but few people will buy books or watch television shows on how to live to 100 if the answer is to move to a remote mountain. The audience wants easy life hacks — simple, painless tricks to become lighter, stronger, smarter, more productive, or whatever. As discredited weight-loss guru Brian Wansink quipped, “The best diet is one you don’t know you’re on.”

So Buettner went to these five Blue Zones and returned with seductive ideas for articles, cookbooks, and television shows. I didn’t watch the entire show but I found a 2018 interview with Time magazine where he listed several characteristics, including these:

  • People in Sardinia engage in daily physical activity; people in Okinawa have strong social support groups; people in Nicoya eat plenty of beans; people in Seventh-Day Adventists in Loma Linda observe the Sabbath; and people in Ikaria take daily naps.

There was some overlap (for example, in eating beans and having religious beliefs) and some differences (for example, many Sardinians drink alcohol daily; Seventh-day Adventists abstain) but it seems that people should eat beans and go to church, not necessarily in that order.

All in all, the conclusions seem sensible — engage in regular physical activity, have a healthy diet, don’t stress out. Who could disagree? So, why did I alternate between groaning and laughing?

One problem is the reliability of the data — people do misreport and misrecord ages — but my reaction was due to something much more fundamental. There are two huge problems with this kind of sloppy science. The first is the cancer-cluster myth; the second is data-mining.

The cancer-cluster myth refers to the fact that even if cancer is randomly distributed in the population, there will, more likely than not, be geographic clusters of cancer victims. To demonstrate this, I created a fictitious city with ten thousand residents living in homes evenly spaced throughout the city, each having a one-in-a-hundred chance of cancer. (I ignored the fact that people live in families and that cancer is related to age.) I used computerized coin flips to determine the cancer victims in this imaginary town. Each black dot in the resulting cancer map represents a home with a cancer victim.

There is clearly a cancer cluster in the lower part of the map and a cancer fortress in the eastern part, but both are utterly meaningless.

Unfortunately, we seem to be hard-wired to see statistical patterns as meaningful. The National Institutes of Health website has cancer rates for twenty-two different types of cancer, two sexes, four age groups, six races and ethnicities, and more than three thousand counties. Some places, by chance alone, have above-average cancer rates. The curious and fearful scrutinize these cancer maps and the Center for Disease Control has a web page where people can report the cancer clusters that they discover. More than a thousand cancer clusters are reported and investigated each year even though the CDC cautions that, “Follow-up investigations can be done, but can take years to complete and the results are generally inconclusive (i.e., usually, no cause is found).”

In the same way, finding five geographic locations in the world with an unusual number of centenarians may be nothing more than chance longevity-clusters.

Dating Mining is a Problem

The second reason why Blue Zones are BS is data mining, also known as HARKing (Hypothesizing After the Results are Known). In any reasonably large database, there are bound to be coincidental correlations. A visit to a cancer cluster-location might find that people living there eat rice, play pickleball, and grow daylilies. That doesn’t mean that any of those things cause cancer. All it demonstrates is that when we look for patterns, we will inevitably find some.

Hey, I can find silly things that all five Blue Zones have in common. Every location has at least one a and one i in its name: Sardinia, Okinawa, Nicoya, Loma Linda, Ikaria. If you want to live to 100, move to Indianapolis! This pattern is obviously meaningless and other discovered commonalities may be meaningless too.

The Feynman trap is a memorable example of why HARKing is perilous. Nobel Laureate Richard Feynman once told an audience,

You know, the most amazing thing happened to me tonight. I was coming here, on the way to the lecture, and I came in through the parking lot. And you won’t believe what happened. I saw a car with the license plate ARW 357! Can you imagine? Of all the millions of license plates in the state, what was the chance that I would see that particular one tonight? Amazing!

If Feynman had predicted that he would see this license plate before he entered the parking lot, that would have been truly amazing. Not so, seeing some license plate after entering the lot. Something extremely unlikely is not unlikely at all if it has already happened.

Buettner leaped into this trap. The fact that a 100-year-old man eats beans doesn’t prove that eating beans is why he is 100 years old. A real scientist has a research hypothesis in mind before looking at the data, not afterward. If there are good reasons for thinking that beans promote longevity, then collect worldwide data on longevity and how much and how often beans are consumed.

The Blue Zone studies are the most extreme form of HARKing. Not only are the traits identified after visiting the Blue Zones, no attempt is made to compare bean consumption and longevity inside or outside the Blue Zones or to consider confounding factors.

Science Under Siege

Suppose a persistent researcher visits a Blue Zone and notices that many of the men wear hats. What does it mean? Who knows? Plenty of men around the world wear hats. Without looking elsewhere, we have no idea whether men who wear hats tend to live longer than men who do not wear hats. Even if we had such data, these would be observational data, which are subject to self-selection bias and confounding effects. Perhaps ethnic groups with good longevity genes also have a cultural preference for wearing hats. Perhaps men wear hats in sunny climates and sunshine is good for longevity. Perhaps balding men prefer hats and there are genes related to baldness that are also related to longevity.

The only way to know for certain is to do a randomized controlled trial in which a randomly selected treatment group is compelled to wear hats for decades while those in the control group are not allowed to wear hats. Fortunately for all involved, researchers are seldom allowed to do such experiments with hat-wearing, bean-eating, church attendance, and other activities.

In the same way, casual observation of centenarians may suggest research hypotheses that can be rigorously tested but such observations are not real science, and claims to the contrary can only mislead audiences about how real science is done.

As I said, Buettner’s recommendations seem sensible. We will likely be healthier if we avoid junk food, engage in regular physical activity, and try not to be stressed. Buettner most likely had these recommendations in mind before he visited any of the Blue Zones and he should be thanked for trying to persuade people to adopt healthier lifestyles.

So, why did I chuckle and cringe when I watched him in action?

My discomfort is with the promotion of the idea that HARKing is credible scientific research. HARKing is in, in fact, one of the primary reasons for the replication crisis that is undermining the credibility of science. A more informative television show would warn us about the dangers of HARKing and give us examples (like Wansink’s discredited studies), not pretend that sloppy science is real science.

Gary N. Smith

Senior Fellow, Walter Bradley Center for Natural and Artificial Intelligence
Gary N. Smith is the Fletcher Jones Professor of Economics at Pomona College. His research on financial markets statistical reasoning, and artificial intelligence, often involves stock market anomalies, statistical fallacies, and the misuse of data have been widely cited. He is the author of dozens of research articles and 16 books, most recently, The Power of Modern Value Investing: Beyond Indexing, Algos, and Alpha, co-authored with Margaret Smith (Palgrave Macmillan, 2023).

Blue Zone BS: The Longevity Cluster Myth