LYON, France — A new analysis trying to quantify the impact of the 2011 East Japan earthquake suggests that the incidence of sudden death and acute MI across a single Japanese community was closely aligned with seismic activity. For these acute events, say the authors, the original quake and aftershocks were likely more important than the tsunami and the displacement it caused.

A previous paper, reported by Aoki et al during the European Society of Cardiology 2012 Congress, showed a strong correlation between all types of cardiovascular disease, including heart failure, as well as pneumonia, in the two months following the earthquake. In that paper, however, many of the health effects and their time course likely also related to the subsequent tsunami and refugee migration.

Dr Motoyuki Nakamura

In the current study, Dr Motoyuki Nakamura (Uchimaru, Morioka, Iwate, Japan) and colleagues reviewed hospital charts for the six hospitals in the region of Iwate, Japan, presenting their findings as a poster here at the European Atherosclerosis Society 2013 Congress .

Investigators then also obtained records of seismic activity before and after the earthquake, capturing the aftershocks that continued to rock the community for several weeks, as well as the different seismic recordings from different parts of the community.

Nakamura et al were then able to show a direct correlation between levels of seismic activity and number of acute-MI and sudden-death cases. The two peaked together in the week of the earthquake, with a seismic intensity of 5.6 and 28 cases. But additional seismic peaks, at week 4 (seismic intensity 5.5, 20 cases) and again at week 8 (seismic intensity approximately 3.2, 16 cases) also correlated closely with acute MI and sudden death. Plotted in terms of weekly changes in seismic activity and case number, the line was absolutely linear, with cases and seismic activity rising in unison.

For comparison, investigators also looked at cases of acute MI and sudden death during the same weeks in 2009 and 2010, and no such pattern was seen.

"The concordance of sudden increases in the incidence of AMI/sudden death and the sequential quake shocks suggests that acute physical and emotional stress is an important trigger of ACS," the authors conclude.

Of note, there were no differences in the incidence of ACS and sudden death between inland and coastal regions, "suggesting that acute psychosomatic stress, rather than environmental deterioration by the tsunami, is an important trigger of acute coronary syndrome," the authors concluded.

The finding is important because large aftershocks are to be expected after a major quake. To heartwire , Nakamura added that other regions that have suffered major quakes have also looked at whether CV events are increased during and after this kind of natural disaster. Those results have not necessarily been consistent, he noted.

"The strength of our study is that this was a community-based study. There are only six hospitals in this area, so we can check all the data and all the hospital charts" to capture the full effects on the community. "This is the first report like this. Other reports were from just one hospital, or from several hospitals but in a larger area. Our study covered a very small area, a small population, and a small number of hospitals" treating the entire population."

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