Associations of air pollution with COVID-19 test positivity, hospitalisations, and mortality: observational evidence from UK Biobank

Abstract

Background and aim: Individual-level studies with adjustment for COVID-19 risk factors suggest a weak positive association of long-term air pollution exposure (particulate matter and nitrogen dioxide) with COVID-19 positive test, hospitalisation, and mortality. The evidence, however, remains limited and mechanisms remain unclear. We aimed to investigate these associations within UK Biobank, and to examine the role of underlying chronic disease as a potential mechanism. Methods: UK Biobank COVID-19 positive test results were ascertained via Public Health England and general practitioner record linkage, COVID-19 hospitalisations via Hospital Episode Statistics, and COVID-19 mortality via Office for National Statistics mortality records from March – December 2020. We used annual average outdoor air pollution from a 2010 land-use regression model at residential addresses within England of UK Biobank participants (n = 424,721) and obtained important COVID-19 risk factors from baseline UK Biobank questionnaire responses (2006-2010) and general practitioner record linkage. We used logistic regression models to assess associations of air pollution with COVID-19 outcomes after adjustment for relevant confounders and conducted multiple sensitivity analyses. Results: We found positive associations of fine particulate matter (PM2.5) and nitrogen dioxide (NO2) with COVID-19 positive test result after adjustment for confounders, with odds ratio of 1.06 (95% confidence intervals (CI) = 1.03, 1.09), and 1.06 (95% CI = 1.02, 1.09) per interquartile range increase, respectively. PM2.5 and NO2 were positively associated with COVID-19 hospitalisations and deaths in minimally adjusted models but not in fully adjusted models. No associations for PM10 were found. In analyses with additional adjustment for pre-existing chronic disease, effect estimates were not substantially attenuated, indicating that underlying chronic disease may not fully explain associations. Conclusion: We found some evidence that long-term exposure to PM2.5 and NO2 was associated with a COVID-19 positive test, though not with COVID-19 hospitalisations or deaths. Keywords: PM2.5, NO2, coronavirus