The basic overview of the 19 included articles.

NM indicates not mentioned; PM10, particular matter with aerodynamic diameter ≤10 µm; PM2.5, particular matter with aerodynamic diameter ≤2.5 µm; UK, the United Kingdom; US, the United States; F, female; M, male; HS, hemorrhagic stroke; IS, ischemic stroke.*lag was the timing of the exposure; Lag0, the same day exposure; Lag1, exposure the day before; Lag2, exposure the 2 days before; Lag3, exposure the 3 days before; Lag4, exposure the 4 days before; Lag5, exposure the 5 days before; Lag0–3, mean exposure of previous 3 days and the same day; Lag0–4, mean exposure of previous 4 days and the same day.