After a Major Earthquake, Stroke Death Occurs More Frequently Than Coronary Heart Disease Death in Very Old Subjects

To the Editor: A linkage has been recognized between many myocardial infarctions and specific physiological triggers such as psychological stress and physiological exertion.1 We reported recently that the frequency of coronary heart disease (CHD) death was increased after the 1995 Hanshin-Awaji earthquake, a catastrophic stress with a grade of 6 (maximum) according to the DSM-III-R.2 Previous reports on cardiovascular accidents related to major earthquakes have focused on CHD or sudden deaths.3,4 Some authors suggest that psychological stress may serve as a risk factor for stroke,5,6 but others do not agree.7 Earthquake-related stroke has not been studied thoroughly. To identify the characteristics of earthquake-induced stroke and of earthquake-induced coronary heart disease, we investigated the stroke mortality in the Tsuna region, including the epicenter and one of the areas most heavily damaged by the January 17, 1995, Hanshin-Awaji earthquake, where we had studied the CHD mortality. Earthquake-related stroke mortality was evaluated by direct inspection of the records kept by physicians who were able to continue to provide services for the earthquake victims, without interruption, during this disaster. This method was the same as that used in the CHD mortality study reported previously.2 The number of stroke deaths increased during the 3 months after the earthquake, and the total number from January 17 to April 30, 1995, was 58, which was significantly (1.9 times) greater than the 31 deaths that occurred during the same period of the previous year (1994) and was also greater (1.3 times) than the number of CHD deaths (45) that occurred during the 1995 period. The significant increase of stroke deaths was found in the population aged 70 years or more, whereas that of CHD deaths was found in the population aged 60 to 79 years (Figure 1). In regard to time of onset, stroke deaths occurred 2.0 times more often (P < .05) at night (11 p.m. - 5 am) and 1.6 times as often during the morning (5 a.m. - 11 a.m.), whereas their occurrence did not vary during the 12-hour period from 11 a.m. to 11 p.m. This tendency was the same as that of CHD deaths. . Prevalence of deaths from stroke and coronary heart disease in different age groups after the 1995 Hanshin-Awaji earthquake. * P < .05, ** P < .01, *** P < .001 The region studied has a large older community, with individuals 60 years of age or older constituting about 30% of the total population. For a few months after the earthquake, both CHD mortality and stroke mortality increased in the segment of the population aged 70 years or older. This persistent increase of stroke mortality might be affected by infections, such as upper or lower respiratory tract infections or urinary tract infections, which prevailed in the winter after the earthquake. A recent report shows that infection or inflammation, with or without fever, could be a trigger for stroke.7 The level of fibrinogen, an established risk factor not only for CHD but also for stroke,8 is increased by stress, minor infection, and normal aging in association with a low-grade inflammatory reaction.9 We found earthquake-induced stress in afebrile, hypertensive, older patients without any laboratory finding corresponding to infection. This earthquake-induced increase of fibrinogen level might have been augmented, leading to clinical cardiovascular accidents, in the older community on Awaji Island because fibrinogen has seasonal variations, with increase in the winter, in older individuals.10