An epidemiologic study of cerebrovascular disease in western Japan: with special reference to transient ischemic attacks.

The prevalence and incidence ratios of cerebrovascular disease, with special reference to transient ischemic attack (TIA), were studied in the towns of Daisen and Ama in western Japan. There have been no previous reports on this subject in Japan. The prevalence ratios of TIA were estimated to be 4.4 in Daisen and 2.0 in Ama per 1,000 people over 40 years old. The ratio of carotid arterial system TIA to vertebrobasilar arterial system TIA was about 1 to 1. The incidence ratios of stroke were 319.6 in Daisen and 314.5 in Ama per 100,000 people of all ages. The prevalence ratios of stroke were estimated to be 14.8 in Daisen and 13.5 in Ama per 1,000 people of all ages. The prevalence ratio of TIA in Japan is about one-third to one-half of that in Western countries. However, the prevalence of complete stroke is much higher in Japan compared with that in Western countries. Therefore, the ratio of TIA to stroke is much lower in Japan than in Western countries. The obstruction of small intracranial arteries, in addition to heart disease, might play an important role in TIA in Japan, whereas in Western countries TIA might be mostly caused by heart disease or the atherosclerosis of extracranial arteries.