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