Snowfall and Risk of Myocardial Infarction Death: A Case-Crossover Study

Previous research has associated snowfall with risk of myocardial infarction (MI). Most studies have been conducted in regions with harsh winters, it remains unclear whether snowfall is associated with risk of MI in regions with milder or more varied climates. This study used a case-crossover design to investigate the association between snowfall and MI mortality in British Columbia, Canada. MI deaths in British Columbia residents between October 15 and March 31 from 2009 to 2017 were identified. The day of each MI death was treated as the case day, and each case day was matched to control days drawn from the same day of week during the same month. Daily snowfall amount was assigned to case and control days at the residential address using weather stations within 15 kilometers distance and 100 meters of elevation. In total, 3300 MI case days were matched to 10,441 control days. Compared with days that had no snowfall, odds (95% confidence interval) of MI mortality increased 34% (0%, 80%) on days with heavy snowfall (>/= 5 cm). In stratified analysis of MI mortality as a function of both maximum temperature and snowfall, risk was significantly increased on snowfall days when the temperature was warmer.