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This study highlighted the strong effects of environmental factors on eczema, especially given the higher prevalence of the skin condition in industrialized countries.
Air pollutant exposure—specifically NO2, SO2, and particulate matter—is linked to medical visit increases for those with atopic dermatitis, according to recent findings, showing that greater air pollution may lead to more flares.1
These findings were the results of a systematic review of air pollution and use of health care by eczema patients, specifically including information on emergency department and clinic visits as well as hospitalizations.
The research was authored by Maria L. Wei, MD, PhD, from the Department of Dermatology at the University of California, San Francisco. The investigators sought to expand the body of research around the effects of pollution on atopic dermatitis, given that the condition has been increasing in industrialized nations and affects around 15% - 20% of children and up to 10% of adults around the world.2
“Our aims were to comprehensively synthesize and interpret data from studies performed around the world that examined the associations of outdoor air pollutants and AD-related health care use, to increase understanding of how air pollution may increase risk for AD activity and affect health care utilization for skin disease,” Wei and colleagues wrote.
The investigators performed a systematic review of the relationship between air pollution and healthcare use for atopic dermatitis utilizing Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) recommendations. The review protocol was registered with PROSPERO, and a comprehensive literature search was performed using four databases (PubMed, MEDLINE, Web of Science, and EMBASE).
The research team searched for relevant articles that had been published prior to January 15 of 2022. The determined inclusion criteria for their analysis required the studies to have a cross-sectional, longitudinal, case-crossover, or time-series design, with the study outcome being medical visits for eczema/atopic dermatitis.
Additionally, exposure to a minimum of a single outdoor air pollutant had to be assessed. The investigators added that studies without primary epidemiologic data, without a focus on healthcare use for atopic dermatitis, that were conference abstracts, or that assessed air pollution exposure were excluded.
The research team did not apply language restrictions, and one non-English article meeting the criteria was translated. Following their removal of duplicates, the titles and abstracts of 327 studies were independently screened, and the full-text versions of the remaining articles were assessed.
The investigators had the data extraction, screening, and assessment of quality done by multiple team members, with discrepancies resolved through later discussion. The research team categorized the studies based on the air pollutants measured, including the following:
Each studies’ findings were labeled by the investigators as positive, negative, or inconclusive associations for each type of pollutant and then further analyzed by sex, age, and temperature/season if it was reported.
Given the heterogeneity in air pollution exposures, as well as the variety of measures of association reported, pooled effects were not calculated as in other air pollution reviews. Following a review of 390 studies, the research team selected 18 studies from several different locations across the world, which accounted for at least 5,197,643 total medical visits related to atopic dermatitis/eczema.
The investigators’ assessment showed that exposure to particulate matter with a diameter less than 2.5 micrometers showed a positive association with visits in 10 out of 11 studies, and for matter with a diameter less than 10 micrometers, there was a positive association in 11 of 13.
They also added that nitrogen dioxide showed a positive association in 12 of 14 studies, and sulfur dioxide in 10 of 13 studies. The research team noted that their results regarding ozone were inconclusive, with 4 out of 8 studies showing a positive association.
Limited evidence was found to be available for carbon monoxide as well. Further analysis of patients’ age, sex, and seasonal weather, showed that the associations between particulate matter, ozone, and nitrogen dioxide could be influenced by temperature.
Overall, the team’s findings indicate that exposure to specific air pollutants was found to be associated with an increased number of atopic dermatitis medical visits. Moreover, deteriorating air quality may help lead to rises in global healthcare utilization for this skin condition.
“These results can assist clinicians and public health practitioners to recognize the roles of environmental pollution when counseling patients and the public on the prevention and management of AD,” they wrote. “More studies assessing the effectiveness of preventative and treatment strategies are needed.”