A case-crossover analysis of short-term PM_2.5 exposure and COVID19-related hospitalizations in the National Clinical Cohort Collaborative

Studies show associations between air pollution exposure and coronavirus 2019 (COVID19) hospitalizations, but have not substantially explored regional differences. In this study, we estimate associations between shorter-term exposure to fine particulate matter (PM_2.5) and hospitalization among individuals with SARS-CoV-2 infection.

This study utilized data from 72,385 patients (78,504 hospitalizations) with a hospital-confirmed SARS-CoV-2 infection between January 1, 2020 and December 31, 2020. Daily PM_2.5 concentrations from ground-based monitors were averaged to generate 2, 5, and 21-day average exposures prior to hospitalization. We used a time-stratified case-crossover approach to estimate associations between PM_2.5 and COVID19-related hospitalizations in 57 Core Based Statistical Areas (CBSAs) across the United States (US). We subsequently conducted nationwide and region-specific random effects meta-analysis.

In the random effects meta-analysis, a 1 µg/m³ increase in 2, 5, and 21-day average PM_2.5 are associated with a 0.61% (95% Confidence Interval [CI] = 0.12, 1.11); 0.91% (CI = 0.15, 1.67); and 0.04% (CI = -2.70, 2.85) increase in COVID19-related hospitalization risk, respectively. We observe substantial heterogeneity in the associations by region with the largest adverse associations in the South.

Higher concentrations of PM_2.5 are associated with higher risk of COVID19-related hospitalizations. Given the geographic heterogeneity observed, studies exploring factors, such as PM_2.5 exposure, that could explain differences in COVID19 risks may help to understand the COVID19 pandemic and aid in preparing for future ones.