Daily, Monthly, and Seasonal Pattern of ST-Segment Elevation Myocardial Infarction (STEMI) Occurrence in Western Iran; a Cross-Sectional Study

Acute myocardial infarction (AMI) is a leading cause of death and disability worldwide. Determining seasonal pattern of AMI may contribute to disease prevention and better treatment. 

The present study was conducted to investigate daily, monthly, and seasonal pattern for symptoms҆ onset in the patients with ST-segment elevation myocardial infarction (STEMI), and also other possible associated factors. 

This cross-sectional study was conducted on 777 patients diagnosed with STEMI admitted at the Imam Ali Cardiovascular Hospital affiliated with Kermanshah University of Medical Sciences (KUMS), Kermanshah province, Iran from March 2018 to February 2019. Data were collected using a checklist developed based on the study's objectives. Differences between subgroups were assessed using one-way analysis of variance (ANOVA) followed by Tukeys҆ post‐hoc test and Chi-Square test (or Fishers҆ exact test). 

Out of 777 patients, 616 (79.3%) of them were male. Mean age of the patients was (mean±SD) equal to 60.93±12.86 years old. Occurrence of STEMI was most common in winter (38.4%), followed by autumn (27.8%), spring (22.9%), and summer (10.9%), respectively. Monthly occurrence of AMI was at the highest level in January (10.8%) and December (9.9%), and it was at the lowest level in July (4.9 %). Most patients were admitted on Fridays (15.8%) and Wednesdays (15.6%). Hypercholesterolemia, prior congestive heart failure (CHF), prior MI, prior stroke, prior atrial fibrillation (AF), low-density lipoprotein (LDL), high-density lipoprotein (HDL), triglycerides, total cholesterol, creatine phosphokinase (CPK), and creatine kinase myocardial band (CK-MB) were significantly associated with seasonal pattern of STEMI (p-value<0.05). 

Results of the present study on Iranian patients with STEMI revealed that AMI occurred more frequently on Wednesdays and Fridays and during winter from December to January compared to the other days of the week, months, and seasons.