Supplementary file 1_Association of air pollution and prior COVID-19 with atopic dermatitis risk: an interaction analysis in the UK biobank.docx

Background and objectiveLong-term air pollution is an established risk factor for atopic dermatitis (AD), but modifiers of this risk, particularly following post-COVID-19 immune alterations, are poorly understood. We investigated whether prior COVID-19 infection modifies the association between air pollution and incident AD.
MethodsFrom an initial cohort of 502,357 UK Biobank (UKB) participants, a final analytic sample of 173,766 individuals was included after excluding those with missing data or indeterminate COVID-19 status. Incident AD was identified via ICD-10 code L20. Multivariable logistic regression was used to examine associations between long-term PM2.5, NO2, and NOx exposure and AD risk, adjusting for age, sex, Townsend Deprivation Index, BMI, and lifestyle factors. The synergistic interaction between PM2.5 and COVID-19 was evaluated on both multiplicative and additive scales.
ResultsA significant association was identified between long-term PM2.5 exposure and a higher likelihood of AD (OR = 1.04, 95% CI 1.01–1.07). While prior COVID-19 infection was not an independent risk factor (OR = 0.98, 95% CI 0.91–1.05), it significantly modified the effect of PM2.5, with a synergistic interaction observed (P for interaction = 0.018). A synergistic interaction was observed, meaning the combined effect of air pollution and COVID-19 history exceeded the sum of their individual risks.
ConclusionChronic PM2.5 exposure is linked to a heightened AD risk, which is then markedly amplified in individuals with a prior history of COVID-19 infection. Our findings suggest that prior viral infections can sensitize individuals to the dermatological effects of air pollution, defining a vulnerable subgroup that may benefit from targeted environmental health strategies.