Association between short-term exposure to ultrafine particles and hospital admissions for stroke in Copenhagen, Denmark.
OBJECTIVE
The relevance of ultrafine particles (UFPs, particles <0.1 microm diameter), the smallest fraction of ambient particulate matter, on stroke morbidity has not been documented. We studied the effects of short-term changes in exposure to these particles on stroke, separately for ischaemic and haemorrhagic strokes, mild and severe strokes, and ischaemic strokes with (likely embolic) and without (likely thrombotic) atrial fibrillation (AF).


RESULTS
We used a time-stratified case-crossover design to study the association between short-term exposure to UFPs, particulate matter <10 microm in diameter (PM(10)), nitrogen oxides (NO(x)) and carbon monoxide (CO) (measured at single background station) and hospital admissions for stroke in Copenhagen (2003-2006). Of 7485 stroke admissions, 6798 were ischaemic and 687 haemorrhagic, 3485 mild, and 2248 severe. Of the ischaemic stroke cases, 1204 had AF and 5273 did not. We found significant positive association with exposure to UFPs, NO(x) and CO, and ischaemic strokes, and UFPs and NO(x) and mild strokes, 4 days before admission. The strongest associations were with UFPs. Exposure to UFPs lead to a 21% increase in hospital admissions (per interquartile range of 5-day averages; 95% confidence interval 4-41%) for mild ischaemic stroke of without AF (likely thrombotic origin).


CONCLUSIONS
Our results indicate possible effects of traffic-related air pollution, mainly UFPs, on hospital admissions for ischaemic stroke, especially for mild ischaemic stroke of likely thrombotic origin (without AF). These are novel findings regarding the relevance of UFPs and the heterogeneous effect of air pollution on the severity and origin of stroke, and need confirmation by other data.
The Danish Cancer Society, Institute of Cancer Epidemiology, Strandboulevarden 49, 2100 Copenhagen, Denmark. zorana@cancer.dk
Zorana Jovanovic
ZJ
Andersen
Tom Skyhøj
TS
Olsen
Klaus Kaae
KK
Andersen
Steffen
S
Loft
Matthias
M
Ketzel
Ole
O
Raaschou-Nielsen
D000368:Aged; D000393:Air Pollutants / Q000633:toxicity*; D001281:Atrial Fibrillation / Q000209:etiology; D002545:Brain Ischemia / Q000453:epidemiology; D002248:Carbon Monoxide / Q000633:toxicity; D002543:Cerebral Hemorrhage / Q000453:epidemiology; D003430:Cross-Sectional Studies; D003718:Denmark / Q000453:epidemiology; D004781:Environmental Exposure / Q000009:adverse effects; D005260:Female; D006801:Humans; D008297:Male; D009569:Nitric Oxide / Q000633:toxicity; D052638:Particulate Matter / Q000633:toxicity*; D020521:Stroke / Q000453:epidemiology*
D000393:Air Pollutants; D052638:Particulate Matter; D009569:Nitric Oxide; D002248:Carbon Monoxide