Association between short- and medium-term air pollution exposure and risk of mortality after intravenous thrombolysis for stroke

The exposure to air pollutants may increase both incidence and mortality of stroke. We aimed to investigate the association of short- and medium-term exposure to particulate matter (PM) and nitrogen dioxide (NO2) with the outcome of intravenous thrombolysis (IVT) for stroke. We conducted a retrospective analysis based on data prospectively collected from 944 consecutive IVT-treated stroke patients. The main outcome measure was 3-month mortality. The secondary outcome measures were causes of neurological deterioration (≥ 1 NIHSS point from baseline or death < 7 days), including intracerebral hemorrhage, cerebral edema (CED), and persistence or new appearance of hyperdense cerebral artery sign. In the adjusted model, higher PM2.5 and PM10 values in the last 3 days and 4 weeks before stroke were independently associated with higher mortality rate [hazard ratio (HR) 1.014, 95% confidence intervals (CI) 1.005–1.024, p = 0.003; HR 1.079, 95% CI 1.055–1.103, p = 0.001; HR 1.019, 95% CI 1.005–1.032, p = 0.008; and HR 1.015, 95% CI 1.004–1.027, p = 0.007; respectively]. Higher PM2.5 and PM10 values in the last 4 weeks were associated with higher CED rate [odd ratio (OR) 1.023, 95% CI 1.007–1.040, p = 0.006; and OR 1.017, 95% CI 1.003–1.032, p = 0.021; respectively]. No significant association between PM or NO2 and other causes of neurological deterioration was observed. Higher exposure to PM in the last 3 days and 4 weeks before stroke may be independently associated with 3-month mortality after IVT. Higher exposure to PM in the last 4 weeks before stroke may also be independently associated with CED after IVT.