Environmental temperature and mortality from acute myocardial infarction.

Mortality from acute myocardial infarction (MI) over the 5 year period 1982-1987 in Brown County, Wisconsin, was analyzed to assess the relationship with environmental temperature. Deaths occurring on the day of and the day following a significant snowfall as well as deaths occurring in health care facilities were eliminated from consideration because the focus was upon temperature, not snowfall or events within a hospital. These criteria resulted in the inclusion of 1,802 days and 926 cases of acute MI. The mean temperature on the day of death was obtained from climatological data and were grouped into six categories covering a range of temperatures from less than -17.8 degrees C (0 degrees F) to 16.1 degrees C (61 degrees F). The number of deaths in each category was tabulated. The effect of temperature, sex, and age were analyzed by regression analysis. The results indicated a linear increase in mortality as mean daily temperature decreased over the temperature range. The inverse temperature effect was most pronounced in males over the age of 60. These results indicate that cold temperatures appear to be associated with an increased mortality from myocardial infarction.