(Bloomberg) -- Does being poor mean being less healthy?

In the United States, the answer is generally yes: Income and health are intertwined, and the richer you are, the healthier you’re likely to be.

But the link between poverty and poor health isn't ironclad.

Take Costa Rica, where the poorest 25 percent of people actually live longer than their counterparts in the U.S., according to an analysis published this week in the Proceedings of the National Academy of Sciences.

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Costa Rica punches above its weight on many measures of health and social welfare. It’s a middle-income democracy with a population of 4.8 million—about the size of Alabama—and a per-capita GDP about one-fifth of the United States.

In other words, it's much less wealthy than America—and, as you would expect, the rich in America have lower mortality than the rich in Costa Rica.

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But when you look at the other end of the socio-economic scale, the reverse is true.

Why are the poor in one of the world’s wealthiest countries more likely to die than the poor in a small, middle-income country? Lifestyle factors have a lot to do with it.

In the U.S., smoking and obesity are far more common at the bottom of the income scale. That's not the case in Costa Rica.

“Poor people or lower socioeconomic-status people are thinner and less prone to obesity than rich people, while in the U.S. the inverse of that situation is true,” says Luis Rosero-Bixby, a demographer at the Universidad de Costa Rica and lead author of the study.

Costa Ricans are more likely to adhere to traditional diets and lifestyles that don’t include junk food or cigarettes.

Costa Rica’s health care system is not better than the U.S.’s, according to Rosero-Bixby, but it manages to ensure that "the very basic needs are covered."

While Costa Rica outperforms the U.S. on the health of its poorest, it’s not because the country has greater equality than America.

The income distribution in Costa Rica is actually more skewed to concentrate wealth at the top, according to the paper. Somehow, though, that skewed income doesn’t translate to skewed health outcomes.

The analysis linked census records with death registries from the 1990s in both countries. Matching that kind of data isn’t possible in many places, Rosero-Bixby says, so it’s hard to tell whether the pattern is similar in elsewhere.

The explanation might be because both countries are, to some extent, outliers.

While Costa Ricans are generally healthier and live longer than the country’s income and health spending would predict, the reverse is true in the United States.

Instant Insights /

A longevity puzzle: Why do poor Costa Ricans outlive poor Americans?

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