Diabetes Mellitus Modifies the Association Between Particulate Air Pollution and Acute Ischemic Stroke: Results from the Registry of the Canadian Stroke Network

Abstract

ISEE-0529 Background and Objective: Previous studies have reported an association between short-term exposure to ambient fine particulate matter (PM2.5) and the risk of hospitalization for ischemic stroke. Patients with diabetes mellitus have been shown to have enhanced sensitivity to the vascular effects of ambient particles and thus may be at increased risk of ischemic stroke, but this hypothesis has not been previously evaluated. Methods: We analyzed data from 8882 patients hospitalized between 2003 and 2008 with acute ischemic stroke, having a documented date and time of stroke symptom onset, and residing ≤50 km from a PM2.5 monitor in one of 8 major metropolitan regions in Ontario, Canada. All patients were admitted to a Regional Stroke Center participating in the Registry of the Canadian Stroke Network. We applied the time-stratified case-crossover design to estimate the effect of mean PM2.5 in each city 0–47 hr prior to time of stroke symptom onset, controlling for meteorological variables, and used random-effects meta-analytic techniques to combine the city-specific estimates. Separate analyses were performed according to the presence or absence of a history of diabetes mellitus, atrial fibrillation, and hypertension. Results: Overall, there was no consistent association between PM2.5 levels and risk of ischemic stroke 0–47 hr later. However, we found significant effect modification by diabetes mellitus (P = 0.033). Among patients with diabetes we observed a 9.5% (95% CI: −0.1%, 20.1%; P = 0.052) increased risk of ischemic stroke per 10 μg/m3 increase in PM2.5. We did not find evidence of statistically significant effect modification by a history of hypertension (P = 0.82) or atrial fibrillation (P = 0.73). Conclusion: Patients with diabetes mellitus may be especially susceptible to the cerebrovascular effects of particulate air pollution. This observation is consistent with prior studies suggesting that patients with diabetes may be at greater risk of particulate-related cardiac events.