Ambient particulate matter and frequency of outpatient visits for chronic rhinosinusitis in the United States.

Background: Emerging evidence has underscored the harmful effects of air pollution on the upper airway. We investigated the relationship between ambient particulate matter (PM) level and the frequency of outpatient visits for chronic rhinosinusitis (CRS).

Methods: We conducted an ecological cohort study of US adults enrolled in The Merative MarketScan outpatient database from 2007 to 2020. For each geographical subunit (core-based statistical area [CBSA]), we calculated the annual rate of CRS-related outpatient visits per 1000 well-patient checkup visits (CRS-OV). Using data from the Environmental Protection Agency's Air Quality System, we mapped the rolling statistical average of daily PM_2.5 and PM₁₀ over the preceding year onto each CBSA × year combination. We employed multivariable negative binomial regression modeling to estimate the association between PM levels and subsequent CRS-OV.

Results: Across 3933 observations (CBSA × year combinations), encompassing ∼4 billion visits, the median CRS-OV was 164 (interquartile range 110-267). The mean PM_2.5 level was 8.9 µg/m³ (SD 2.6) and the mean PM₁₀ level was 20.2 µg/m³ (SD 7.2). Adjusting for patient demographics and respiratory comorbidities, a compounded rise in subsequent CRS-OV was observed with increasing PM levels. Each µg/m³ rise in PM_2.5 independently predicted a 10% increase in CRS-OV (adjusted incidence rate ratio [aIRR]) 1.10, 95% confidence interval [CI] 1.08-1.13) and each µg/m³ rise in PM₁₀ independently predicted a 3% increase in CRS-OV (aIRR 1.03, 95% CI 1.02-1.04).

Conclusion: Elevated ambient PM_2.5 and PM₁₀ levels are associated with a subsequent compounded increase in the frequency of CRS-OV, with PM_2.5 predicting a more pronounced rise compared to PM₁₀.