Associations between exhaust and non-exhaust particulate matter and stroke incidence by stroke subtype in South London.
BACKGROUND
Airborne particulate matter (PM) consists of particles from diverse sources, including vehicle exhausts. Associations between short-term PM changes and stroke incidence have been shown. Cumulative exposures over several months, or years, are less well studied; few studies examined ischaemic subtypes or PM source.


OBJECTIVE
This study combines a high resolution urban air quality model with a population-based stroke register to explore associations between long-term exposure to PM and stroke incidence.


METHODS
Data from the South London Stroke Register from 2005-2012 were included. Poisson regression explored association between stroke incidence and long-term (averaged across the study period) exposure to PM2.5(PM<2.5μm diameter) and PM10(PM<10μm), nitric oxide, nitrogen dioxide, nitrogen oxides and ozone, at the output area level (average population=309). Estimates were standardised for age and sex and adjusted for socio-economic deprivation. Models were stratified for ischaemic and haemorrhagic strokes and further broken down by Oxford Community Stroke Project classification and Trial of ORG 10172 in Acute Stroke Treatment (TOAST) classification.


RESULTS
1800 strokes were recorded (incidence=42.6/100,000 person-years). No associations were observed between PM and overall ischaemic or haemorrhagic incidence. For an interquartile range increase in PM2.5, there was a 23% increase in incidence (Incidence rate ratio=1.23 (95%CI: 1.03-1.44)) of total anterior circulation infarcts (TACI) and 20% increase for PM2.5 from exhausts (1.20(1.01-1.41)). There were similar associations with PM10, overall (1.21(1.01-1.44)) and from exhausts (1.20(1.01-1.41)). TACI incidence was not associated with non-exhaust sources. There were no associations with other stroke subtypes or pollutants.


CONCLUSIONS
Outdoor air pollution, particularly that arising from vehicle exhausts, may increase risk of TACI but not other stroke subtypes.
Division of Health and Social Care Research, King's College London, London, UK; National Institute of Health Research Collaboration for Leadership in Applied Health Research and Care (CLAHRC) South London, London, UK.
Siobhan
S
Crichton
Analytical and Environmental Sciences Division and MRC-PHE Centre for Environment and Health, King's College London, UK; NIHR Biomedical Research Centre, Guy's & St. Thomas' NHS Foundation Trust and King's College London, London, UK.
Benjamin
B
Barratt
NIHR Biomedical Research Centre, Guy's & St. Thomas' NHS Foundation Trust and King's College London, London, UK.
Anastassia
A
Spiridou
Division of Health and Social Care Research, King's College London, London, UK; National Institute of Health Research Collaboration for Leadership in Applied Health Research and Care (CLAHRC) South London, London, UK; NIHR Biomedical Research Centre, Guy's & St. Thomas' NHS Foundation Trust and King's College London, London, UK.
Uy
U
Hoang
Division of Health and Social Care Research, King's College London, London, UK; NIHR Biomedical Research Centre, Guy's & St. Thomas' NHS Foundation Trust and King's College London, London, UK.
Shao Fen
SF
Liang
NIHR Biomedical Research Centre for Mental Health & Biomedical Research Unit for Dementia, King's College London, UK.
Yevgeniya
Y
Kovalchuk
Analytical and Environmental Sciences Division and MRC-PHE Centre for Environment and Health, King's College London, UK.
Sean D
SD
Beevers
Analytical and Environmental Sciences Division and MRC-PHE Centre for Environment and Health, King's College London, UK; NIHR Biomedical Research Centre, Guy's & St. Thomas' NHS Foundation Trust and King's College London, London, UK.
Frank J
FJ
Kelly
Department of Cancer and Surgery, Imperial College, London, UK.
Brendan
B
Delaney
Division of Health and Social Care Research, King's College London, London, UK; National Institute of Health Research Collaboration for Leadership in Applied Health Research and Care (CLAHRC) South London, London, UK; NIHR Biomedical Research Centre, Guy's & St. Thomas' NHS Foundation Trust and King's College London, London, UK.
Charles DA
CD
Wolfe
D000368:Aged; D000369:Aged, 80 and over; D000393:Air Pollutants / Q000032:analysis*; D000397:Air Pollution; D004781:Environmental Exposure / Q000032:analysis*; D004784:Environmental Monitoring; D005260:Female; D006801:Humans; D015994:Incidence; D008131:London / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D009585:Nitrogen Dioxide / Q000032:analysis; D052638:Particulate Matter / Q000032:analysis*; D020521:Stroke / Q000139:chemically induced / Q000453:epidemiology*; D001335:Vehicle Emissions / Q000032:analysis*
D000393:Air Pollutants; D052638:Particulate Matter; D001335:Vehicle Emissions; D009585:Nitrogen Dioxide
Air pollution; Incidence; Stroke