Impact of Exposure to Environmental Particulate Matter on the Onset of Giant Cell Arteritis.

Objective: The aim of this study was to investigate the association between exposure to particulate matter with an aerodynamic diameter ≤10 μm (PM₁₀) and the development of giant cell arteritis (GCA) and its ischemic complications.

Methods: This was case-crossover study on consecutive patients who received a diagnosis of GCA in three hospitals in northern Italy between 2013 and 2021. The PM₁₀ hourly and daily average concentrations, collected in the Italian monitoring network and archived by Istituto Superiore per la Protezione e la Ricerca Ambientale, were determined using European reference. We used a Bayesian hierarchical model to determine patients' daily exposures to them. We employed conditional logistic regression to estimate the effect of exposure on GCA symptoms onset or ischemic complications.

Results: We included 232 patients. A positive association was observed between exposure to PM₁₀ and GCA risk, with an incremental odd of 27.1% (95% confidence interval 5.8-52.6) for every 10-μg/m³ increase in PM₁₀ concentration within a 60-day period. We did not find any significant association for shorter periods or with ischemic complications. Subgroup analysis found a significantly higher incremental risk at a 60-day lag for patients ≥70 years old. Comparing patients who were chronically exposed to high PM₁₀ levels (26.9 ± 13.8 μg/m³) to those who were not (11.9 ± 7.9 μg/m³) revealed that only in the former group was there an association between GCA onset and increased PM₁₀ levels in the preceding 60 days.

Conclusion: Exposure to environmental PM₁₀ in the preceding 60 days seems to be associated with an increased risk of developing GCA, especially in older individuals with prolonged exposure to high levels of air pollution.