Children born in the United States are about two times more likely to suffer from allergies and asthma than children who were born abroad, according to a study published this week in Pediatrics.
For the study, researchers from Beth Israel Medical Center and St Luke's-Roosevelt Hospital Center surveyed the parents of 80,000 children from 2007 to 2008. They determined the prevalence of physician-diagnosed asthma, eczema, hay fever, or food allergies and found that, overall:
- 20.3% of foreign-born children who live in the United States suffer from at least one of the conditions; versus
- 34.5% of U.S.-born children suffer from at least one of the conditions.
Moreover, the risk of suffering from allergies increases when foreign-born children spend more time in the United States, the study says. Researchers found that 27% of foreign-born children who had lived in the United States for 10 years had allergies, compared with 17% to 18% of foreign-born children who had immigrated within the last two years.
In addition, children born outside the United States were less likely to develop allergies or asthma if their parents were also born outside the United States.
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According to lead researcher Jonathan Silverberg, the study is the first to show that living in the United States increases the chances that a person will develop allergies. "The results of the study suggest that there are environmental factors in the U.S. that trigger allergic disease," Silverberg told Reuters, adding, "Children born outside the U.S. are likely not exposed to these factors early in life and are therefore less likely to develop allergic diseases."
He notes that the relatively sterile environment in the United States may make children more prone to allergies. Meanwhile, foreign-born children benefited from early-life exposure to toxins, although those benefits are not life-long. "You acclimate to wherever you are and you pick up whatever is going on there," explained Ruchi Gupta, who studies allergies at the Northwestern University Feinberg School of Medicine but was not involved in the study.
Silverberg also notes that climate, obesity, and infections may play their parts. According to CBS News, studies have linked diet to allergy risk. Earlier this year, a study in BMJ suggested that children who consumed fast food are more likely to have asthma, eczema, or hay fever. (Pittman, Reuters, 4/29; Abrams, The Atlantic, 4/30; Jaslow, CBS News, 4/30).