Association between week of the month and death from acute myocardial infarction in Washington state, 1988 to 1997

Background Deaths caused by substance abuse, circulatory disorders, and ext ernal causes such as suicide, homicide, and accidents are more likely to oc cur during the first week of the month than the last week of the preceding month. The purpose of this report is to determine if death caused by acute myocardial infarction occurs more often in the first 7 days of the month th an in the last 7 days of the preceding month. Methods and Results This study used computerized death records for Washingt on state from 1988 to 1997. There were 401,314 deaths, of which 33,436 (8.3 %) had an underlying cause of acute myocardial infarction. The week of the month during which death occurred was defined as occurring during the first 7 days of the month or the last 7 days of the preceding month. R, the rati o of the number of deaths during the first 7 days of the month to the numbe r of deaths in the last 7 days of the preceding month multiplied by 100, wa s calculated, as were 95% confidence intervals. R values For other cardiac causes and substance abuse-related causes were also calculated. Deaths caus ed by acute myocardial infarction occurred more often in the first week of the month than in the lost week of the previous month (R = 104.4, 95% confi dence interval 101.7-107.8). This pattern of death was most apparent for in dividuals greater than or equal to 75 years of age (R = 107.3, 95% confiden ce interval 102.1-111.1) and was not evident for other cardiac causes, incl uding congestive heart failure or myocardial ischemia. By comparison, subst ance abuse-related deaths occurred much more frequently during the first we ek of the month (R = 117.6, 95% confidence interval 110.0-125.8). Conclusions This pattern of death for acute myocardial infarction may be in part caused by stressful events associated with the first week of the mont h.