according to a systematic review.
PhD candidate Sabria Khan and her colleagues at the Centre for Epidemiology and Biostatistics at the University of Melbourne said that the atopic march concept “asserts that allergic diseases start in early life with eczema, progress through food allergy, and culminate with hay fever and asthma.”
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This systematic review of ten twin and sibling studies looked at known, measured environmental and genetic influences on the associations between the atopic phenotypes of the atopic march.
The studies of asthma and hay fever suggested that the prevalence of having both conditions was high (32%) and that they were more likely to occur together in monozygotic twins than they were in dizygotic twins. Similarly, other studies found a high phenotypic overlap between eczema and asthma and between eczema and hay fever, which was more pronounced in monozygotic twins than in dizygotic twins.
“Asthma is linked to hay fever and eczema through intermediate phenotypes like clinical measures of lung function, physiological measures of airway responsiveness and the biomarker exhaled nitric oxide, all of which are influenced by hereditary factors,” the authors said.
Overall, they concluded that genetic factors account for 75% of eczema cases, 70%-91% of asthma cases, and 72%-84% of hay fever cases, making them all highly heritable diseases.
“Our study found that the contribution of shared environmental factors to the proportion of correlation are very low (from 4% to 18%) and does not explain the familial patterns seen for asthma and hay fever,” they reported. “This finding contradicts various analyses where smoking behavior, indoor-outdoor pollution, and house dust mites were found to be significant risk factor for asthma and hay fever that are shared by siblings.”
The authors commented that preventing the onset of the atopic march, or arresting its development, could have significant public health implications. They suggested that interventions such as oral antihistamines could be introduced either before a child gets eczema or before a child with eczema goes on to develop asthma or hay fever. “Two randomized controlled trials showed moisturizing the skin can prevent mild to moderate eczema, and long-term studies are needed to see whether such intervention will prevent development of asthma and hay fever,” they said.
No conflicts of interest were declared.
SOURCE: Khan SJ et al. Allergy. 2018 Jan;73(1):17-28.