Daily peaks in the incidence of sudden cardiac death and fatal stroke in Niigata Prefecture.

To clarify the circadian variation in sudden death (SD) in Japan, where the causes of sudden death differ from those in the USA, we examined all of the death certificates from 1984 to 1986 in Niigata Prefecture, Japan. We defined SD as death which occurred within 1 h from the onset of the underlying cause. A significant circadian variation, with a high incidence between 6 and 8 am and a secondary peak between 6 and 8 pm, was found in the occurrence of sudden cardiac death (SCD, n = 2953). Although the proportion of SCD due to acute myocardial infarction (AMI) was as low as 28% of SCD cases, the circadian variation of SCD was similar to that previously reported in the USA. In SCD due to AMI in males (n = 487), a significant circadian variation with 3 peaks, including a primary peak between 4 and 6 am, was evident. There was also a marked increase in the incidence of fatal stroke between 6 and 8 pm (n = 529). We concluded that 1) a circadian variation with two peak incidences, one between 6 and 8 am, and one between 6 and 8 pm, was characteristic of SCD in general, 2) there was a primary peak between 4 and 6 am for SCD due to AMI in males, and 3) there was a peak between 6 and 8 pm in the incidence of fatal stroke for both men and women.