Prolonged sulfur dioxide exposure after discharge raises the risk of recurrent stroke [Health Check]

[Financial News] The longer patients with acute ischemic stroke were continuously exposed to sulfur dioxide (SO2) after discharge, the higher their risk of recurrent stroke, a study found. Of six major air pollutants, including fine particulate matter, ultrafine particulate matter and ozone, sulfur dioxide was the only one significantly associated with recurrence.
A research team comprising Professors Lee Geon-ju of the Department of Neurology at Korea University Guro Hospital, Hwang Jeong-eun of the Department of Medical IT Engineering at Soonchunhyang University, and Kim Seong-eun and Bae Hee-jun of the Department of Neurology at Seoul National University Bundang Hospital said it had identified an association between post-discharge sulfur dioxide exposure in patients with acute ischemic stroke and their risk of recurrent stroke.
Air pollution is considered a major environmental risk factor for cardiovascular and cerebrovascular diseases, including stroke. Associations between air pollutants such as fine particulate matter, nitrogen dioxide and sulfur dioxide and the occurrence of stroke have been consistently reported, but the effects of exposure to air pollution after discharge on recurrence have not been sufficiently established. Since recurrent stroke can increase the risk of disability and death, the need to identify environmental factors that affect recurrence has been raised.
The research team analyzed 27,340 patients with acute ischemic stroke—a stroke caused by the sudden blockage of a cerebral blood vessel—registered in the Korean prospective multicenter stroke cohort (CRCS-K-NIH) from March 2014 to April 2021. Using data from air-monitoring stations nationwide, they estimated average concentrations of six air pollutants in the patients’ residential areas during the three months after discharge: fine particulate matter (PM10), ultrafine particulate matter (PM2.5), nitrogen dioxide (NO2), sulfur dioxide (SO2), carbon monoxide (CO) and ozone (O3). They then followed the patients for one year to track whether their stroke recurred.
The analysis found that the risk of recurrence tended to increase as sulfur dioxide concentrations rose. No significant association was found for the other five pollutants. The team said the significance of the study lies in being the first to identify an association between post-discharge sulfur dioxide exposure and recurrent stroke, which had not previously been established.
The association became clearer as the exposure period grew longer. The average concentration over the first month after discharge was not significantly associated with recurrence, but the association strengthened at two months and reached statistical significance at three months. This suggests that sustained exposure, rather than short-term exposure, may be linked to recurrence.
Sulfur dioxide concentrations were relatively high in major port areas, including Incheon, Ulsan Metropolitan City and Busan. However, an additional analysis excluding all residents of the three cities still found an association with recurrence, indicating that the finding was not limited to specific port areas.
Professor Lee Geon-ju said, “Secondary stroke prevention has mainly focused on managing blood pressure, blood sugar and lipids, as well as medication. This study shows that the air quality in the area where patients live after discharge also needs to be considered when assessing the risk of recurrence.” He added, “Because this is an observational study, we cannot conclude that sulfur dioxide is a direct cause of recurrence, and it is not yet time to propose a specific concentration as a clinical threshold. Patients can consult air-quality information while continuing their existing secondary-prevention treatment as prescribed.”
The study was supported by the National Research Foundation of Korea (NRF) Creative Challenge Research Support Program and was published in the Korean Stroke Society’s international journal, Journal of Stroke.
 


[email protected] Jeong Myeong-jin, medical correspondent Reporter