Temperature, Myocardial Infarction, and Mortality: Effect Modification by Individual and Area-Level Characteristics
Human activity is expected to result in a global increase in temperature, as well as differential changes by season and location. Additionally, the frequency of extreme temperature episodes is projected to rise. Many studies have linked increased mortality to changes in or extremes of temperature. While the association between temperature and cardiovascular mortality is important, fewer studies have investigated the association between the incidence of cardiovascular disease (CVD) and ambient temperature. Many of the studies that have examined the association between temperature and myocardial infarction (MI) have used MI mortality as an outcome rather than non-fatal events. Moreover, few of these studies have adjusted for potentially important confounders, including air pollution
While several studies have examined associations between temperature and cardiovascular-disease-related mortality, fewer have investigated the association between temperature and the development of acute myocardial infarction (MI). Moreover, little is known about who is most susceptible to the effects of temperature. We analyzed data from the Worcester Heart Attack Study, a community-wide investigation of acute MI in residents of the Worcester (MA) metropolitan area. We used a case-crossover approach to examine the association of apparent temperature with acute MI occurrence and with all-cause in-hospital and post-discharge mortality. We examined effect modification by sociodemographic characteristics, medical history, clinical complications, and physical environment. A decrease in an interquartile range (IQR) in apparent temperature was associated with an increased risk of acute MI on the same day (hazard ratio=1.15 [95% confidence interval= 1.01–1.31]). Extreme cold during the 2 days prior was associated with an increased risk of acute MI (1.36 [1.07–1.74]). Extreme heat during the two days prior was also associated with an increased risk of mortality (1.44 [1.06–1.96]). Persons living in areas with greater poverty were more susceptible to heat.