Chronobiology of cardiac sudden death in men.

Daily variation in occurrence of sudden cardiac death was examined in 3,983 men observed since 1948. For men without previous clinical evidence of ischemic heart disease, an excess proportion of sudden cardiac deaths occurred on Mondays. For men with previous clinical evidence of ischemic heart disease, sudden cardiac death occurred more uniformly throughout the week. By comparison there was no significant daily variation in cancer mortality or in day of occurrence of myocardial infarction. Thus, for men without clinically manifest heart disease, the warning "beware on Monday" should stimulate further investigation.