Short-Term Exposure to Air Pollution and Incidence of Stroke and Acute Myocardial Infarction in a Japanese Population

Abstract

Background: Exposure to high levels of air pollution can increase the risk of cardiovascular events. However, there is no clear information in Japan on the effect of pollution on the incidence of stroke and acute myocardial infarction (AMI). Therefore, we investigated the effects of air pollution on the incidence of stroke and AMI in a setting where pollutant levels are rather low. Methods: Data were obtained from the Takashima Stroke and AMI Registry, which covers a population of approximately 55,000 in Takashima County in central Japan. We applied a time-stratified, bidirectional, case-crossover design to estimate the effects of air pollutants, which included suspended particulate matter (SPM), sulfur dioxide (SO₂), nitrogen dioxide (NO₂) and photochemical oxidants (Ox). We used the distributed lag model to estimate the effect of pollutant exposure 0-3 days before the day of event onset and controlled for meteorological covariates in all of the models. Results: There were 2,038 first-ever strokes (1,083 men, 955 women) and 429 first-ever AMI cases (281 men, 148 women) during 1988-2004. The mean pollutant levels were as follows: SPM 26.9 µg/m³; SO₂ 3.9 ppb; NO₂ 16.0 ppb, and Ox 28.4 ppb. In single-pollutant and two-pollutant models, SO₂ was associated with the risk of cerebral hemorrhage. Other stroke subtypes and AMI were not associated with air pollutant levels. Conclusions: We observed an association between SO₂ and hemorrhagic stroke; however, we found inconclusive evidence for a short-term effect of air pollution on the incidence of other stroke types and AMI.

Cardiovascular Emergency Hospital Visits and Hourly Changes in Air Pollution

“…Peters et al 14 found that PM 2.5 concentrations 1 and 2 hours before onset were associated with an elevated risk of myocardial infarction in the United States. Bhaskaran et al 1 also demonstrated that PM 10 and NO 2 levels were associated with transiently increased risk of myocardial infarction 1 to 6 hours after exposure in England and Wales. Moreover, the effect of hourly changes in PM 2.5 in the United States on ischemic stroke was evaluated by Wellenius et al, 6 and the risk of stroke onset increased immediately after exposure and peaked 12 to 14 hours before onset.…”

“…[4][5][6] Several studies in Asian countries, where the incidence of hemorrhagic stroke is high, 7 have suggested an association between air pollutant levels and this type of stroke. [8][9][10][11][12][13] In addition, most studies to date have evaluated the association between daily time scale of air pollution and cardiovascular outcomes. Only a small number of epidemiological studies have examined the effect of hourly variations in air pollution on ischemic heart disease, 1,14 cardiac arrest, 3 or ischemic stroke 5,6 and demonstrated possible adverse effects.…”

Impact of Particulate Matter Exposition on the Risk of Ischemic Stroke: Epidemiologic Evidence and Putative Mechanisms

“…20 However, a considerable number of studies did not find a correlation between PM levels and cerebrovascular diseases. 20,27,28 Only three results reached the level of significance. 14,16,25 This reveals limitations of comparing air pollution and its influence on health outcomes globally.…”

“…We have identified 18 studies, which fulfilled these criteria (Table 4). [13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31] ACUTE EFFECTS OF PARTICULATE MATTER EXPOSURE Although most studies on PM and cardiovascular diseases have been conducted in developed western countries, first impulses for epidemiologic research on IS came from South Korea and Taiwan. 15,22,25 An increase in PM by an interquartile range in Seoul was associated with a 3% higher IS mortality.…”

“…In contrast, there was no increase in IS risk for people with first-ever stroke. 27 Taken together, there is accumulating evidence for a considerable relationship between PM exposure and IS risk even in moderately polluted regions, in particular for people with preexisting illnesses. However, post hoc analyses limited to the acute risk over a few days cannot reveal the entire relevance of air pollution.…”