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 3990 consecutive patients with acute myocardial infarction admitted to 13 hospitals from January 2002 to December 2007. 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 < 0.001). The relationship between the occurrence of death and season and type of AMI according to International Classification of Diseases code 10 (ICD) was also observed and it was statistically significant (P = 0.026). Hazard ratio for death from acute myocardial infarction were 0.96 [Confidence interval of 95% (95% CI) = 0.78-1.18], 0.9 (95% CI = 0.73-1.11), and 1.04 (95% CI = 0.85-1.26) 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.