Estimation of short-term effects of air pollution on stroke hospital admissions in southern Sweden.
BACKGROUND
Short-term exposure to high levels of air pollution can increase stroke risk. In this study we investigated the short-term effects of air pollution on hospital admissions for stroke in a setting where pollutant levels are rather low. We also addressed methodological issues in evaluating the short-term effects of air pollution.


METHODS
Daily admissions of ischemic (n = 11,267) and hemorrhagic (n =1,681) stroke were obtained from a Swedish quality register for stroke, Riks-Stroke. We used two types of exposure data: (1) daily measured background levels of ozone, temperature and particles with a diameter < 10 microm (PM(10)) and (2) modeled levels of a mixture of NO and NO2 (NOx) at the residential address of each individual.


RESULTS
We estimated a 13% (95% confidence interval, 4-22%) increased risk for hospital admissions for ischemic stroke for levels of PM 10 above 30 microg/m(3) compared to < 15 microg/m(3) , whereas temperature above 16 degrees C decreased the risk. No consistent associations were found for hemorrhagic stroke or for ischemic stroke and ozone or NOx .


CONCLUSIONS
Particulate air pollution and temperature seemed to be associated with ischemic stroke hospital admissions. Individual exposure modeling facilitates a detailed exposure assessment but may also be more prone to misclassification errors. The time series and case crossover approaches yielded similar effect estimates.
Oudin
Anna
A
Division of Occupational and Environmental Medicine, Lund University, Lund, Sweden. anna.oudin@med.lu.se
Strömberg
Ulf
U
Jakobsson
Kristina
K
Stroh
Emilie
E
Björk
Jonas
J
D000368:Aged; D000369:Aged, 80 and over; D000393:Air Pollutants / Q000009:adverse effects; D000397:Air Pollution / Q000009:adverse effects* / Q000706:statistics & numerical data; D018592:Cross-Over Studies; D005260:Female; D006760:Hospitalization / Q000706:statistics & numerical data / Q000639:trends; D006358:Hot Temperature / Q000009:adverse effects; D006801:Humans; D019570:Inhalation Exposure / Q000009:adverse effects; D008297:Male; D052638:Particulate Matter / Q000009:adverse effects*; D010343:Patient Admission / Q000706:statistics & numerical data / Q000639:trends*; D020521:Stroke / Q000453:epidemiology* / Q000209:etiology*; D013548:Sweden / Q000453:epidemiology; D013997:Time Factors
D000393:Air Pollutants; D052638:Particulate Matter