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In 2004, an earthquake with M6.8 on the Richter scale hit mid Niigata Prefecture (Chuetsu region) in Japan. This earthquake was one of the strongest ever recorded in Japan with its near-epicentre maximum seismic intensity of 7 on the Japan Meteorological Agency's Intensity (JMAI) scale, which was comparable to that of the 1995 Great Hanshin-Awaji earthquake in Japan. The Niigata-Chuetsu earthquake caused a great deal of damage; 68 dead, 4795 wounded and 121 495 destroyed homes (3175 completely destroyed). 1 Direct and indirect socioeconomic losses from destroyed infrastructure after the Niigata-Chuetsu earthquake was estimated at 3 trillion yen ($30 billion). 2
Large earthquakes are recognised as acute stressors. 3 A short-term increase in mortality from acute myocardial infarction (AMI), one of the prevalent stress-related diseases, following an earthquake has been reported worldwide. 4 5 6 7 8 For example, the Great Hanshin-Awaji earthquake (5480 total deaths) in Japan resulted in an increased mortality from AMI for eight weeks after the earthquake. 7 Although human casualties from the Niigata-Chuetsu earthquake were much fewer than those of the Great Hanshin-Awaji earthquake, a short-term increase in cardiovascular events from the Niigata-Chuetsu earthquake has been reported. 8
An interesting characteristic of the Niigata-Chuetsu earthquake was that it occurred in a rural, mountainous area, and thereby caused remarkable ground disaster, traffic and communication network disruption and further isolated the mountainous villages. 2 These factors delayed reconstruction of community lifelines such that approximately 9000 people lived in temporary housing provided by the local government one year after the earthquake, and 5000 people even two years after the earthquake. 9 Although temporary housing ended in December 2007, a number of people continued to struggle to reconstruct their lives owing to financial losses. 9
We hypothesised that the residents of Chuetsu experienced stress from living in an unfavourable environment, resulting in high risk of AMI death. To our knowledge, however, very few epidemiological studies have investigated long-term effects of an earthquake on AMI mortality. The aim of this study was to determine if the Niigata-Chuetsu earthquake increased mortality from AMI three years after the earthquake in comparison to the control area.
Methods
The Niigata-Chuetsu earthquake occurred on 23 October 2004, with its epicentre located at 37 degrees latitude, 29 minutes North, and 138...