Seasonal pattern in admissions and mortality from acute myocardial infarction in elderly patients in Isfahan, Iran

BACKGROUND: Seasonal variation in admissions and mortality due to acute myocardial infarction has been observed in different countries. Since there are scarce reports about this variation in Iran, this study was carried out to determine the existence of seasonal rhythms in hospital admissions for acute myocardial infarction, and in mortality due to acute myocardial infarction (AMI) in elderly patients in Isfahan city. METHODS: This prospective hospital-based study included a total of ۳۹۹۰ consecutive patients with acute myocardial infarction admitted to ۱۳ hospitals from January ۲۰۰۲ to December ۲۰۰۷. Seasonal variations were analyzed with the Kaplan-Meier table, log rank test, and Cox regression model. RESULTS: There was a statistically significant relationship between the occurrence of heart disease based on season and type of acute myocardial infarction anatomical (P < ۰.۰۰۱). The relationship between the occurrence of death and season and type of AMI according to International Classification of Diseases code ۱۰ (ICD) was also observed and it was statistically significant (P = ۰.۰۲۶). Hazard ratio for death from acute myocardial infarction were ۰.۹۶ [Confidence interval of ۹۵% (۹۵% CI) = ۰.۷۸-۱.۱۸], ۰.۹ (۹۵%CI = ۰.۷۳-۱.۱۱), and ۱.۰۴ (۹۵%CI = ۰.۸۵-۱.۲۶) during spring, summer, and winter, respectively. CONCLUSION: There is seasonal variation in hospital admission and mortality due to AMI; however, after adjusting in the model only gender and age were significant predictor factors.   Keywords: Acute Myocardial Infarction, Season, Admission in Hospital, Mortality, Isfahan