Increased occurrence of out-of-hospital cardiac arrest on Mondays in a community-based study.

Acute myocardial infarction and sudden cardiac death are more common on Mondays than other days of the week. The stress of returning to work at the beginning of the week has been postulated as a possible trigger factor. This project examined the weekly variation of out-of-hospital cardiac arrests of nontraumatic origin for the entire case series as well as for selected subgroups. A retrospective analysis of 1,498 incidences between January 1, 1995 and December 31, 1996 revealed a distinct Monday peak in occurrence irrespective of age, gender, presence of witnesses, primary survival, or primary ECG. This finding, however, was most pronounced in retired patients, subjects living alone, and persons found unconscious outside buildings or in public places. One important trigger of cardiac arrest is going to work after weekends; however, resumption of social and other activities on Mondays is another possible trigger. Other factors, such as endogenous biological rhythms, may contribute to an increased risk at this particular time even in elderly.