Leonard Bacharier, MD, right, examines Tristan Norris, 11, a participant in an ongoing study aimed at understanding what factors may increase or decrease the risk of developing asthma in childhood.
A new study of children living in inner-city areas and at high risk of developing asthma suggests that exposure to certain pet and pest allergens in infancy lowers the risk of developing asthma by age 7. The research also provides evidence that the type of bacteria hitching a ride on the allergen particles is an important factor in determining asthma risk.
The study also linked the mental health of the mother to a child's asthma risk, with higher risk associated with mothers scoring higher on measures of depression and stress. As in past studies, maternal smoking during pregnancy also increased the risk of a child being diagnosed with asthma.
The research, published Sept. 19 in The Journal of Allergy and Clinical Immunology, included children living in inner-city St. Louis, Baltimore, Boston and New York City. The Urban Environment and Childhood Asthma study (URECA) is funded by the National Institute of Allergy and Infectious Diseases, of the National Institutes of Health (NIH), through its inner-city asthma consortium. The study was conducted by Washington University School of Medicine in St. Louis, the Boston University School of Medicine, Columbia University, The Johns Hopkins University School of Medicine, the University of California San Francisco, and the University of Wisconsin-Madison.
Of the 442 children with complete data, 130 (29 percent) had an asthma diagnosis by age 7. The study found that higher amounts of cockroach, mouse and cat allergens measured in house dust during a child's first three years of life were associated with lower risk of developing asthma.
Children at high risk of asthma included those whose mothers reported having the condition and those with higher levels of a chemical called cotinine measured in umbilical cord blood at birth. A product of the breakdown of nicotine, cotinine measured in umbilical cord blood is a marker of tobacco use during pregnancy. However, smoking before pregnancy or after birth — by the mother or other household members — was not associated with increased risk of asthma in this study. Maternal stress and depression, measured via questionnaires, was significantly associated with increased asthma risk.
Of particular interest, according to Bacharier, was the analysis of the bacteria associated with the allergens, especially the counterintuitive finding that more cockroach exposure was beneficial. According to the data on household dust, high levels of cockroach allergen was the most protective against the development of asthma, followed by mouse and then cat allergens.
In households where children developed asthma, the bacteria associated with house dust tended to be microbes that cause disease, or their close relatives. In contrast, households where children did not develop asthma tended to have bacteria that have shown evidence of protecting against respiratory problems.
Because this study was observational, Bacharier said researchers can't say whether certain bacteria or allergens cause or prevent asthma. But the data do point to new areas of research to pursue in determining what leads to the development of asthma in early life and what can be done to prevent it.
This work was supported by the National Institutes of Health (NIH), including the National Institute of Allergy and Infectious Diseases, contract numbers NO1-AI-25496, NO1-AI-25482, HHSN272200900052C, HHSN272201000052I, 1UM1AI114271-01 and UM2AI117870; the National Center for Research Resources, grant numbers RR00052, M01RR00533, 1UL1RR025771, M01RR00071, 1UL1RR024156 and 5UL1RR024992-02; and the National Center for the Advancement of Translational Research, grant numbers UL1TR001079 and UL1TR000040.
O'Connor GT, Lynch SV, Bloomberg GR, Kattan M, Wood RA, Gergen PJ, Jaffee KF, Calatroni A, Bacharier LB, Beigelman A, Sandel MT, Johnson CC, Faruqi A, Santee C, Fujimura K, Fadrosh D, Boushey H, Visness CM, Gern JE. Early-life home environment and risk of asthma among inner-city children. The Journal of Allergy and Clinical Immunology. Sept. 19, 2017.