Daily and seasonal variation in sudden cardiac death, Rochester, Minnesota, 1950-1975.

Incidence cases of coronary heart disease that occurred in Rochester, Minnesota, during the years 1950 through 1975 were used for a study of the distribution of sudden cardiac death (1,054 cases) by day of the week and season of the year. Overall, sudden cardiac death--that is, death within 24 hours of onset of symptoms--occurred with greater frequency on Saturdays than on other days of the week. The frequency of occurrence of sudden cardiac death by season varied somewhat--the highest frequency was in winter and the lowest in summer-- but no more than expected by chance. Among males, there was a decreasing trend by day of the week from Saturday to Friday, and this was so for those with and those without a history of coronary heart disease (P less than 0.01).