Short-term effects of air pollution and weather on reversible cerebral vasoconstriction syndrome: a retrospective bicenter study.

Background: Reversible cerebral vasoconstriction syndrome (RCVS) is characterized by thunderclap headaches and transient cerebral vasoconstriction. The influence of environmental factors, particularly air pollution and weather conditions, on RCVS remains poorly understood.

Methods: From 2010 to 2022, clinical data from two hospitals were analyzed alongside air pollution and meteorological data provided by Air Pays de la Loire and Météo-France. A time-stratified case-crossover design was used to evaluate the association between RCVS onset and daily mean concentrations of O₃, PM₁₀, PM_2.5, and NO₂, using spatial modeling of residential exposure. Pollutant effects were examined over lag periods of up to three days, with adjustments for temperature and atmospheric pressure.

Results: A total of 216 patients were included (mean age: 39.9 years; SD: 12.3; sex ratio: 1:1). In the three days preceding RCVS onset, only PM₁₀ concentrations remained significantly higher compared to the day of onset (19.03 vs. 17.99 µg/m³, P = 0.0029). A significant downward trend in PM₁₀ levels was observed over this period (slope -0.735, P = 0.0286), whereas no significant changes were found for PM_2.5, O₃, or NO₂. PM₁₀ was the only pollutant significantly associated with RCVS onset across lag days (Lag 0: OR 0.747, 95% CI: 0.579-0.962, P = 0.024; Lag 1: OR 0.770, 95% CI: 0.599-0.989, P = 0.041; Lag 2: OR 0.776, 95% CI: 0.604-0.997, P = 0.047; Lag 3: OR 0.768, 95% CI: 0.599-0.984, P = 0.037). After adjusting for atmospheric pressure and temperature, these associations were no longer statistically significant.

Conclusion: This study suggests a short-term decrease in PM₁₀ levels prior to RCVS onset and a negative association between PM₁₀ concentration and occurrence. These findings contribute to understanding the potential environmental triggers of RCVS in the context of changing air quality and climate.