When Throughout the Year Is Coronary Death Most Likely to Occur?

Abstract

Background—Previous studies have suggested that there is an increase in cardiac events in the morning. Fewer data relate cardiac events to months of the year and season. Methods and Results—We analyzed all monthly death certificate data from Los Angeles County, California, for death caused by coronary artery disease from 1985 through 1996 (n=222 265). The mean number of deaths was highest in December at 1808 and January at 1925; the lowest rates were in June, July, August, and September at 1402, 1424, 1418, and 1371, respectively. December and January had significantly higher rates than would be expected from a uniform distribution of monthly deaths (P=0.00001). The percent of yearly coronary deaths was defined by the quadratic U-shaped equation [percent=13.1198−1.5238(month)+0.0952(month2), where January=1, February=2, etc]. When monthly deaths were plotted by year, there was a decrease from 1985 through 1996. Monthly mortality correlated inversely with temperature. During the months with the highest fre...