Cardiovascular emergency hospital visits and hourly changes in air pollution.

BACKGROUND AND PURPOSE Few studies have examined the effect of hourly changes in air pollution on cardiovascular disease morbidity. We evaluated the associations between hourly changes in air pollution and the risks of several types of cardiovascular disease. METHODS We used a time-stratified case-crossover design. Study participants were 10,949 residents of the city of Okayama, Japan, aged≥65 years who were taken to hospital emergency rooms between January 2006 and December 2010 for onset of cardiovascular disease. We calculated city representative hourly average concentrations of air pollutants from several monitoring stations and examined the associations between air pollution exposure before the case event, focusing mainly on suspended particulate matter, and disease onset. RESULTS Suspended particulate matter exposure 0 to <6 hours before the case events was associated with risks of onset of cardiovascular and cerebrovascular disease; odds ratios after 1 interquartile range increase in suspended particulate matter exposure were 1.04 (95% confidence interval, 1.01-1.06) for cardiovascular disease and 1.04 (95% confidence interval, 1.00-1.08) for cerebrovascular disease. We observed an elevated risk of hemorrhagic as well as ischemic stroke, but the risk was slightly higher for hemorrhagic stroke, and this elevation was persistent. Women tended to have higher effect estimates. CONCLUSIONS This study provides further evidence that particulate matter exposure increases the risks of onset of cardiovascular and cerebrovascular disease (including hemorrhagic stroke) shortly after exposure.