Risk of asthmatic attack on US children is directly related to their low social economic status (SES) and exposure to pests. Foreign born children do not develop asthma despite these risks. The finding from this study is doubly unique because it confirms the reason for asthma in US children and relates asthma prevalence in the Unites States to its absence outside US. This study is a continuation of previous result wherein the child’s native country had an influence on asthma risk.

According to the authors, this study was conducted on a large sample size that enabled them to conduct additional data analysis. This result accrues upon the previously determined association of asthma with country of birth in children. Authors find that exposure to pathogens absent in US develops immunity to asthma in foreign-born children. But they acknowledge that it is still difficult to establish causation criteria for this condition.

The hygiene hypothesis and vitamin D hypothesis can explain the differences in prevalence of asthma among US children. The hygiene hypothesis developed by authors from this study explains that children from less-developed countries exposed to pathogens end up being more resistant to an asthmatic attack. Vitamin D hypothesis relates to effect of Vitamin D in children. When Vitamin D was produced by the body upon exposure to sunlight from the child’s country of origin, it makes the child more immune to asthma.

All the five independent epidemiological studies were conducted and published from 2002 to 2007. In all 962 children between 4-18 years of age were studied for prevalence of asthma by analyzing data from all the 5 studies. Children were from Chinatown and Dorchester in Boston. Although causation could not be explained, this study provides further key insights that give an in-depth understanding of asthma in relation to birth country. For instance, the initially non evident relationship between asthma and pest exposure in US children is actually 60%. Similarly low SES US children are more likely to develop asthma unlike from lesser developed nations.

This work was done by Brugge group at Tufts University and will come out in Journal of Immigrant and Minority Health.