A Johns Hopkins Children's Center study challenged the long-running belief that living in the city caused more asthma attacks and found that income, ethnic origin and race were bigger factors in asthma risk compared to actual physical surroundings.

Published in the Journal of Allergy and Clinical Immunology, the study compared asthma rates in children living within and outside city limits and found no difference in their risk. Instead, a more powerful link was discovered when Puerto Rican ethnicity, the African-American race and poverty were involved.

The idea that urban living, which exposed children to pollution, pest allergens and indoor smoke, was causing higher incidences of asthma in inner-city children began over 50 years ago as public health experts tackled the asthma epidemic. However, while these factors continue to affect asthma risk, they are not exclusive to inner-city areas.

According to the study, cases of inner-city asthma widely varied depending on geographic regions. The highest prevalence was reported in Northeast urban areas where 17 percent of children suffered from asthma, while the lowest number of cases at 8 percent were recorded in western United States.

Elizabeth Matsui, M.D., M.H.S., a pediatrics and epidemiology associate professor and pediatric asthma specialist from the Johns Hopkins University School of Medicine and senior author for the study, however, cautions against focusing on inner cities as asthma epicenters as this may lead doctors as well as public health experts to overlook new asthma hot zones.

The study used data from the National Health Interview Survey between 2009 and 2011, involving 23,065 children from 6 to 17 years old. According to the survey, 13 percent of children from inner cities were diagnosed with asthma compared to the 11 percent represented by children living outside inner cities. However, the small statistical difference vanished when the researchers added variables like geographic region, race and ethnicity to their analysis.

Additionally, children from families living below the national poverty line were likelier to suffer from asthma as well as have an attack severe enough to call for emergency treatment compared to those from families living on higher incomes. And as annual incomes went down, risks for severe asthma attacks increased.

Researchers pointed out though that the study focused on baseline asthma risk. It was not meant to determine if children from inner cities experienced worse symptoms or needed more medical attention compared to children living elsewhere.

Other authors for the study include: Corinne Keet, M.D., Ph.D., Emily McGowan, M.D., Meredith McCormack, M.D., Roger Peng, Ph.D. And Craig Pollack, M.D., M.H.S.

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