Abstract 16987: Increased Ischemic Heart Disease And Stroke-related Hospitalizations From Cold Temperature in Ontario, Canada: Population-based Study

Introduction: Experimental studies suggest that exposure to extreme ambient temperature, especially cold, can induce inflammatory reactions and a state of hypercoagulability which may in turn promote thrombosis and clot formation. However, epidemiological evidence relating cold temperature and cardiovascular-related morbidity is sparse. Even less is known about who is most susceptible to the effect of temperature. Methods: We obtained daily data on temperature and hospital admissions for any cardiovascular cause from all 14 health regions in Ontario, Canada in 1996-2013. A distributed lag non-linear model with 21 days of lag was applied to estimate the cumulative effect of temperature on selected cardiovascular conditions, controlling for air pollutants, influenza activity, relative humidity, long-term trends and day of the week. We estimated risks for cold and heat, defined as temperatures below and above the optimal temperature, which corresponded to the point with minimum cardiovascular morbidity, for each health region, and then pooled across Ontario. To identify potentially vulnerable subpopulations, we conducted stratified analyses by selected comorbidities and demographic characteristics. Results: Between 1996 and 2013, we identified 1.4 million hospitalizations from ischemic heart disease, 443,447 from myocardial infarction, 355,837 from stroke, and 237,979 from ischemic stroke across Ontario. The relationship of temperature and the selected cardiovascular conditions exhibited a U shape, with the minimum risk at ~60th percentile (12oC). For cold (at the 1st percentile temperature), the adjusted rate ratio was 1.12 (95% confidence interval (CI)=1.05-1.19) for ischemic heart disease, 1.28 (95%CI=1.13-1.44) for myocardial infarction, 1.15 (95%CI=1.02-1.30) for stroke, and 1.19 (95%CI=1.03-1.36) for ischemic stroke. Heat also exhibited elevated risks, albeit not significant, for these conditions. We found that the risk of ischemic heart disease from cold was highest among those with a history of conduction disorders, whereas the risk of stroke from cold was highest in those with arrhythmias. Conclusions: Acute exposure to cold temperature contributed to excess hospitalizations from cardiovascular disease in Ontario.