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. 2017 Jul;71(7):707-712.
doi: 10.1136/jech-2016-208025. Epub 2017 Apr 13.

Air pollution and the incidence of ischaemic and haemorrhagic stroke in the South London Stroke Register: a case-cross-over analysis

B K Butland  1 , R W Atkinson  1 , S Crichton  2 , B Barratt  3   4 , S Beevers  3 , A Spiridou  2   4 , U Hoang  2   4 , F J Kelly  3   4 , C D Wolfe  2   4
Affiliations

Air pollution and the incidence of ischaemic and haemorrhagic stroke in the South London Stroke Register: a case-cross-over analysis

B K Butland et al. J Epidemiol Community Health. 2017 Jul.

Abstract

Background: Few European studies investigating associations between short-term exposure to air pollution and incident stroke have considered stroke subtypes. Using information from the South London Stroke Register for 2005-2012, we investigated associations between daily concentrations of gaseous and particulate air pollutants and incident stroke subtypes in an ethnically diverse area of London, UK.

Methods: Modelled daily pollutant concentrations based on a combination of measurements and dispersion modelling were linked at postcode level to incident stroke events stratified by haemorrhagic and ischaemic subtypes. The data were analysed using a time-stratified case-cross-over approach. Conditional logistic regression models included natural cubic splines for daily mean temperature and daily mean relative humidity, a binary term for public holidays and a sine-cosine annual cycle. Of primary interest were same day mean concentrations of particulate matter <2.5 and <10 µm in diameter (PM2.5, PM10), ozone (O3), nitrogen dioxide (NO2) and NO2+nitrogen oxide (NOX).

Results: Our analysis was based on 1758 incident strokes (1311 were ischaemic and 256 were haemorrhagic). We found no evidence of an association between all stroke or ischaemic stroke and same day exposure to PM2.5, PM10, O3, NO2 or NOX. For haemorrhagic stroke, we found a negative association with PM10 suggestive of a 14.6% (95% CI 0.7% to 26.5%) fall in risk per 10 µg/m3 increase in pollutant.

Conclusions: Using data from the South London Stroke Register, we found no evidence of a positive association between outdoor air pollution and incident stroke or its subtypes. These results, though in contrast to recent meta-analyses, are not inconsistent with the mixed findings of other UK studies.

Keywords: AIR POLLUTION; Environmental epidemiology; STROKE.

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Conflict of interest statement

Competing interests: BKB owns shares in Royal Dutch Shell and Scottish and Southern Energy. Her work on this project was funded by King's College London. RWA reports grants from King's College London during the conduct of the study and personal fees from COMEAP outside the submitted work. FJK and AS report grants from NIHR during the conduct of the study.

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