Influence of the great East Japan earthquake and tsunami 2011 on occurrence of cerebrovascular diseases in Iwate, Japan.

BACKGROUND AND PURPOSE Little information is available regarding the occurrence of cerebrovascular diseases after tsunamis. This study was performed to determine the influence of the tsunami damage caused by the Great East Japan earthquake on occurrence of cerebrovascular diseases. METHODS Subjects from the coastline and inland areas of Iwate Prefecture who developed cerebrovascular diseases before and after the disaster were included in the analysis. Standardized incidence ratios of 2011 against the previous 3 years were calculated in two 4-week periods before and four 4-week periods after the disaster, according to stroke subtype, sex, age group, and flood damage. RESULTS The standard incidence ratio for cerebrovascular diseases was 1.20 (1.00-1.40) in the first 4-week period after the disaster and was not significant in other periods. The standard incidence ratios in the first 4-week period for cerebral infarction, intracerebral hemorrhage, and subarachnoid hemorrhage were 1.22 (0.98-1.46), 1.15 (0.76-1.55), and 1.20 (0.52-1.88), respectively. These values were 1.51 (1.19-1.88) for men, 1.35 (1.06-1.64) for subjects aged ≥ 75 years, and 1.35 (1.06-1.64) for the high flooding areas. The standard incidence ratio of cerebral infarction in the first 4-week period for men aged ≥ 75 years in the high flooding areas was 2.34 (1.34-3.34). CONCLUSIONS In the areas highly flooded by the tsunami caused by the Great East Japan earthquake, the occurrence of cerebral infarction among elderly men more than doubled in the first 4 weeks after the disaster.