Influence of circadian rhythms and seasonal and annual variations on acute myocardial infarction incidence

Background/Aim: Acute myocardial infarction (AMI) is a consequence of complete coronary artery occlusion. There is a considerable seasonal variation in the incidence of AMI. The aim of the study was to establish a circadian and seasonal pattern of AMI. Methods: A retrospective observational study was conducted, using the database of the Institute of Emergency Medical Service of the City of Novi Sad. The study included 982 patients, both male and female, diagnosed with AMI (I.21 - ICD-10 code) in the period between 15 March 2018 and 14 March 2022. Data were classified according to the time of the day, days of the week, quarters and months. Data were analysed by using descriptive statistical methods, Mann-Whitney U test, Chi-squared test and Fisher's exact test. Results: AMI most frequently occurred between 6 am and 2 pm (389; 39.6 %). A statistically significant incidence of AMI was calculated for the periods between 6 am and 2 pm (ch2 = 39.69; p < 0.001) and between 2 pm and 10 pm (ch2 = 28.06; p < 0.001). Most cases of AMI were noted on Monday (153; 15.6 %) and in January (93; 9.5 %). The highest incidence of AMI was in the period between 15 March 2021 and 14 March 2022 (304; 31.0 %), while the lowest incidence was noted between 15 March 2019 and 14 March 2020 (190; 19.3 %). Conclusion: Circadian, seasonal and annual rhythm may have a significant impact on the incidence of AMI. This fact can have an important role in the prevention, timely recognition and adequate treatment of acute coronary disease.