Relationship between the seismic scale of the 2011 northeast Japan earthquake and the incidence of acute myocardial infarction: A population-based study

Background Previous studies have reported a relationship between large earthquakes and acute coronary events, but have yielded conflicting results. On March 11, 2011, a massive magnitude 9.0 earthquake hit the northeastern coast of Japan and generated repeated aftershocks. The aim of this study is to clarify the influence of this earthquake on the risk of acute myocardial infarction (AMI) including sudden cardiac death based on the data from a population-based analysis. Methods The study subjects were residents in the northeast of Iwate prefecture, Japan. Cases corresponding to the definition of AMI according to the criteria of the World Health Organization MONICA project were registered from 4 weeks before to 8 weeks after the disaster and in the corresponding periods in 2009 and 2010. Results The relative risk of AMI was 2.03 (95% CI 1.55-2.66) for the 4-week period after the disaster compared with the corresponding periods in the preceding years. The number of events peaked within the first week after the earthquake decreased to levels seen in the preceding years and then increased again after high-magnitude aftershocks. The incidence of AMI was positively correlated with the seismic scale of the earthquake (r = 0.75, P < .01). Conclusions This population-based study suggests that the increase in AMI events after a major earthquake varies depending on the seismic scale of the initial shock and each aftershock.