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Asthma affects children regardless of where they live and whether they're rich or poor. But scientists have long thought that living in low-income urban neighborhoods adds a big additional risk. A new study suggests that that's not exactly the case, as NPR's Richard Harris reports.
RICHARD HARRIS, BYLINE: Asthma is an inflammation of the lungs, and it is often triggered by something in the environment. So in the 1960s, scientists started looking for places where asthma was especially bad.
CORINNE KEET: Researchers started noting that people living in inner cities like New York, Chicago and Baltimore had high rates of asthma in general and that they seemed to have very high rates of hospitalizations and emergency room visits.
HARRIS: Dr. Corinne Keet and her colleagues at Johns Hopkins realized that nobody had ever taken a sweeping survey to see if what was true in those cities applied nationwide, so they did a study to check those assumptions. Their findings appear in the Journal of Allergy and Clinical Immunology.
KEET: We found that living in an inner-city area was actually not a big risk factor for having asthma itself.
HARRIS: Absolutely, lots of children in those poor neighborhoods had asthma.
KEET: But we also found that even more children had asthma in some poor suburban and medium-sized towns in other regions of the country. And even other areas, like in the West, living in the inner city didn't seem to be a risk factor at all for having asthma.
HARRIS: When they dived into isolate the actual risks, they found that poverty itself was an overwhelming factor, along with African-American or Puerto Rican heritage. There's apparently a genetic component to asthma, though it's tough to tease out. That may help explain why Hispanics from places other than Puerto Rico generally have lower rates of asthma, regardless of their income levels. Part of what's going on here is that poor people have been moving out of the inner city.
KEET: Where we used to conflate inner city with poverty, now we see even more concentrated poverty in suburban areas and smaller towns.
HARRIS: So this means that the environment right outside your door doesn't matter nearly as much as what life is like in your home. Dr. Rosalind Wright at Mount Sinai in New York says there's plenty of evidence that bad housing with cockroaches and mold can increase the risk for asthma.
ROSALIND WRIGHT: This can also be true in non-urban areas, of course. If you live in lower quality housing, you may have similar types of risk.
HARRIS: Second-hand smoke is also a risk for children, and poor people are more likely to smoke. People in poverty, no matter where they live, also experience day-to-day stress.
WRIGHT: Certainly, people who live with lower income have many more challenges to deal with and psychological stress, and this can affect your immune system.
HARRIS: Scientists really want to track down the root causes of asthma, so it's helpful to replace a fuzzy observation about life in the inner city with more specific factors that can trigger asthma attacks. Wright has been chipping away at this problem for years, but she doesn't think we'll end up zeroing in on a few things that are common in all circumstances.
WRIGHT: The problem is it's not the same environmental factors that might be the most relevant or important if you're talking about the Upper East side of New York City versus East Harlem versus rural Michigan or something like this.
HARRIS: Wright says what's needed now are studies that don't simply survey the landscape but get down to the nitty-gritty so scientists can understand how environmental factors and genes interact to trigger this common and occasionally deadly disease. Richard Harris, NPR News.