Abstract
046: Associations between exhaust and non-exhaust related components of particulate matter and stroke incidence by stroke subtype in South London
Crichton S1, Barratt B2, Hoang U1, Kelly F2, Wolfe C1
1 Division of Health & Social Care Research, Department of Primary Care and Public Health Sciences, King's College London, London, UK
2 Analytical and Environmental Sciences Division and MRC-PHE Centre for Environment and Health, King's College London, London, UK
Introduction: Particulate matter (PM) consists of particles from diverse sources. Associations between short-term changes in PM and ischaemic but not haemorrhagic stroke incidence have been shown. Long-term exposures have been less well studied, few studies looked at ischaemic subtypes and none at source of the PM. This study utilised improved modelling methods and a stroke register to explore associations between sources of PM and stroke subtypes.
Method: Incident stroke from the South London Stroke Register, registered from 2005–2011 were included. Poisson regression explored association between stroke incidence and average PM2.5 (PM < 2.5μm diameter)and PM10 (PM < 10μm) at residential postcode. Estimates were standardised for age and sex and adjusted for area level derivation. Models were fitted separately for ischaemic and haemorrhagic strokes and were then further broken down using the Oxford Community Stroke Project classification.
Results: 1,837 strokes were recorded with an incidence of 42.6 per 100,000 person-years. No associations were observed between PM and overall ischaemic or haemorrhagic incidence. However, for a one interquartile range increase in PM2.5, there was a 21.7% increase in incidence (IRR 1.217(95% CI 1.027–1.443), p = 0.023) of total anterior circulation infarcts (TACI) and a 19.6% increase for PM2.5 from exhausts (1.196(95% CI 1.013–1.411), p = 0.034). There were similar associations with PM10, overall (1.206 (95% CI 1.011–1.435), p = 0.034) and from exhausts (1.197(95% CI 1.014–1.412), p = 0.033). Risk of TACI was not associated with non-exhaust sources. There were no associations for other subtypes.
Discussion: Outdoor air pollution, particularly that arising from vehicle exhausts, was associated with an increased risk of TACI but not with any other subtype.
047: Thrombophilia screening in young ischaemic strokes
Duncan S, Simister R
Hyper Acute Stroke Unit, University College London Hospital, London, UK
Introduction: There is no agreed set of investigations that should be performed in young patients presenting with ischaemic stroke. We follow a local protocol for patients with cryptogenic ischaemic stroke aged <55 years, this includes a formal thrombophilia screen. We assessed whether this protocol is being followed and the outcome of these tests when completed.
Method: We identified all patients aged <55 years admitted with an ischaemic infarct between 1 January – 30 June 2014 and determined if a thrombophilia screen had been performed and what the results were.
Results: 67 patients were identified (total of 564 ischaemic strokes during this period). A full thrombophilia screen was performed on 22 patients (33%), of whom 12 patients (55%) had abnormal results. A partial screen was performed on 6 patients (9%), of whom 2 (33%) had abnormal results. In 21 patients, an alternative cause for the stroke was identified and 7 of these had a full thrombophilia screen. In total, 14 patients had abnormal results which included abnormal Protein C/S levels as well as Factor V Leiden and Prothrombin gene mutations. There was evidence only 1 of these abnormal results had been noted.
Discussion: Our findings indicate that despite a clear protocol investigations were not performed in 66% of cases. These tests take some time to be returned and this may explain why abnormal results were not noted. On the basis of this evaluation, detailed investigation should be tailored to the individual case and systems must be in place for following up results.