Seasonal variation in case fatality rate in Korean patients with acute myocardial infarction using the 1997-2006 Korean National Health Insurance Claims Database

Abstract

Objective Seasonal and monthly variation in the occurrence and case fatality rate (CFR) of acute myocardial infarction (AMI) have been reported. We examined the seasonal variation in hospital admissions and CFR in Korean patients with AMI, and analysed the influence of season on fatality risk for AMI.

Methods We used the 10-year administrative database of the Korean National Health Insurance covering the entire population of Korea. The data included 265,935 AMI events that occurred in 228,601 patients who were admitted to hospitals across Korea from 1997-2006.

Results Hospital admissions and CFR for AMI were highest in winter and lowest in summer. The fatality risk for AMI was significantly higher in spring (odds ratio [OR]: 1.06, confidence interval [CI]: 1.02-1.10), autumn (OR: 1.08, CI: 1.04-1.12), and winter (OR: 1.11, CI: 1.07-1.15) than in summer. Interestingly, among the summer months, the fatality risk for men was higher in August (OR: 1.10, CI: 1.01-1.19) than in June.

Conclusions Our findings support the hypothesis that AMI may be triggered by events external to atherosclerotic plaques. This seasonal evidence supports the idea that a disease forecast system may be developed using temperature information in Korea.

• Acute myocardial infarction
• case-fatality rate
• seasonal variation