Chronobiology of acute myocardial infarction

ABSTRACT

The chronobiology of the Acute Myocardial Infarction [AMI] is an interesting matter for recognition of the biological mechanism that might trigger AMI. The present study was aimed to investigate the circadian, seasonal and circannual variation of the AMI occurrence with solar, lunar, and Christian months. A retrospective study of 1174 cases with diagnosis of AMI was conducted. All the cases were admitted to the coronary care unit of Shahid Beheshti and Yahyanejad Hospitals in Babol, north of Iran, between 1990 to 2000. The date was extracted by the day and months of diagnosis based on the solar, lunar and Christian calender from hospital charts. The Chi-squarc test was used to test the uniformity of the observed frequencies of AMI onset in the different months based on solar, lunar Christian and the days of the week. The result showed that there was a significant trend toward higher rate of MI at the beginning of the week, on Saturday [18.1%] and the least [12.3%] on Fridays. Although, the observed frequency of AMI has tendency to be higher in Ordibehesht of solar month and Shaban in lunar month than other months, the monthly variation was not statistically significant [P>0.05]. However, there was a significant difference in MI occurrence in Christian months with the highest peak in November [P<0.05]. Also, we did not find a significant seasonal variation of AMI where 26.2%, 32.1%, 26.8% and 23.9% of Ml occurred in spring, summer, fall, and winter respectively [P>0.05]. Our result indicated a significant day of week variation in AMI occurrence with higher peak on Saturdays and full moon phase of lunar months