Estimating the season-specific percentage change in risk (95% CI) per 10 µg/m3 increase in pollutant: single pollutant regression models*†
| All stroke (number of cases=1758) | Ischaemic stroke (number of cases=1311) | Haemorrhagic stroke (number of cases=256) | |||||
|---|---|---|---|---|---|---|---|
| Daily mean pollutant | Per cent change (95% CI) | p Value | Per cent change (95% CI) | p Value | Per cent change (95% CI) | p Value | |
| PM2.5 | Autumn | 8.0 (−4.5 to 22.2) | 0.168 | 9.5 (−5.8 to 27.2) | 0.109 | −17.0 (−42.5 to 19.8) | 0.807 |
| Winter | −8.3 (−20.1 to 5.2) | −16.3 (−28.9 to −1.5) | −5.9 (−34.2 to 34.7) | ||||
| Spring | −10.2 (−22.4 to 3.9) | −6.8 (−20.8 to 9.8) | −29.2 (−54.1 to 9.3) | ||||
| Summer | −10.7 (−31.6 to 16.5) | −6.9 (−31.1 to 25.8) | −20.8 (−61.6 to 63.2) | ||||
| PM10 | Autumn | 2.8 (−6.4 to 13.0) | 0.413 | 3.3 (−7.6 to 15.6) | 0.300 | −14.8 (−35.0 to 11.7) | 0.780 |
| Winter | −4.8 (−14.0 to 5.4) | −10.6 (−20.8 to 0.9) | −5.4 (−26.9 to 22.4) | ||||
| Spring | −4.2 (−12.3 to 4.6) | −1.5 (−10.7 to 8.7) | −22.6 (−40.9 to 1.4) | ||||
| Summer | −12.1 (−26.7 to 5.5) | −9.6 (−26.3 to 10.8) | −15.7 (−49.6 to 40.9) | ||||
| O3 | Autumn | −11.8 (−19.1 to −3.9) | 0.019 | −10.6 (−19.1 to −1.2) | 0.053 | −17.8 (−34.7 to 3.4) | 0.135 |
| Winter | 1.5 (−5.6 to 9.1) | 4.9 (−3.5 to 14.0) | 5.9 (−13.6 to 29.7) | ||||
| Spring | −0.6 (−7.4 to 6.8) | −2.0 (−9.7 to 6.4) | 15.7 (−5.2 to 41.1) | ||||
| Summer | 5.4 (−3.8 to 15.6) | 4.2 (−6.4 to 16.0) | 6.9 (−17.0 to 37.5) | ||||
| NO2 | Autumn | 8.7 (−0.3 to 18.5) | 0.075 | 8.7 (−1.8 to 20.3) | 0.138 | 13.7 (−7.5 to 39.6) | 0.136 |
| Winter | −3.4 (−10.4 to 4.1) | −5.0 (−12.8 to 3.6) | −6.6 (−23.3 to 13.7) | ||||
| Spring | −6.0 (−14.3 to 3.1) | −4.8 (−14.4 to 5.8) | −20.5 (−37.5 to 1.2) | ||||
| Summer | −5.5 (−16.1 to 6.5) | −7.0 (−19.0 to 6.8) | 0.6 (−24.8 to 34.6) | ||||
| NOX | Autumn | 2.0 (−0.2 to 4.3) | 0.091 | 1.8 (−0.9 to 4.5) | 0.178 | 3.1 (−1.6 to 7.9) | 0.131 |
| Winter | −1.0 (−2.9 to 1.0) | −1.6 (−3.9 to 0.6) | −1.1 (−5.7 to 3.7) | ||||
| Spring | −2.2 (−6.3 to 2.1) | −2.0 (−6.7 to 3.0) | −9.7 (−19.7 to 1.5) | ||||
| Summer | −3.7 (−10.8 to 3.9) | −3.5 (−11.6 to 5.5) | −5.9 (−21.8 to 13.3) | ||||
*The conditional logistic regression model fits the pollutant at lag 0 and adjusts for two natural cubic splines (df=2) for temperature (lags 0–1 and 2–6), two natural cubic splines (df=2) for humidity (lags 0–1 and 2–6), public holidays and a sine/cosine annual cycle.
†The p values in the table correspond to likelihood ratio tests for season interaction.
NO2, nitrogen dioxide; NOX, NO2+nitrogen oxide; O3, ozone; PM10, particulate matter <10 µm in diameter; PM2.5, particulate matter <2.5 µm in diameter.