The time of sunrise and the number of hours with daylight may influence the diurnal rhythm of acute heart attack mortality

We investigated whether the time of sunrise and the number of daylight hours have an effect on the seasonality, or the daily rhythm of heart attack mortality. We analyzed retrospectively data of patients admitted to hospitals with the diagnosis of heart attack (n=32,329) and patients who deceased of a heart attack (n=5142) between January 1, 2004 and December 31, 2005 in Hungary. Heart attack mortality was highest during winter, while lowest number of events was recorded during summer . The daily peak of diurnality was between 6:00 am and 12:00 pm (33.77%). A positive correlation was found between the time of sunrise, time of sunset and the mortality caused by myocardial infarction (p<0,01). In the analysis of the number of daylight hours and the heart attack mortality we found a negative correlation (r=-0.105, p<0.05). No significant difference was found between sexes and different age-groups in heart attack mortality. Our data suggest, that the occurrence and the mortality of heart attack may be related to the time of sunrise and the number of daylight hours.