The Circadian Variation of the Onset of Myocardial Infarction / 日本農村医学会雑誌

ABSTRACT

We have studied the circadian variation of the onset of myocardial infarction (MI). The subject were taken from the cases with MI, the onset of which was registered as the Saku Public Health Center, from April 1989 to March 1997, in accordance with the clinical criteria of the WHOMONICA Project. The number of subjects were 309 cases in which the onset time could be associated with circadian disturbance. We classified them into three groups, the <I>midnight and dawn</I> (00 00-07 59 hours), the <I>daytime</I> (08 00-17 59 hours) and the <I>nighttime</I> (18 00-23 59 hours), and the factors which had influenced the onset time were studied. The cases with sudden deaths (deaths out of hospitals and in the emergency room or deaths from post-resuscitation hypoxic encephalopathy) were also included, if autopsy found coronary occlusion or narrowing, and tissue signs suggestive of fresh MI. The t test was used to check the significant differences.<BR>From the circadian variation of 309 cases of MI, circadian rhythm was observed in a dual-peak pattern - morning and evening (morning < evening). As the sharpest peak had appeared in males at a relative young age (69 or under), it was suggested that there existed relations between the onset time of MI and the engagement in work. However, it was considered necessary to further study the impacts of farming work on the onset of ML In a study of deaths in acute phase, no difference was observed in mortality by onset time, but many deaths from cardiogenic shock were witnessed among cases at night. There is the need for the circulatory management of those cases.