Incidence of Aneurysmal Subarachnoid Hemorrhage in Shimokita, Japan, From 1989 to 1998

Abstract

Background and Purpose-The incidence of subarachnoid hemorrhage (SAH) has been investigated in many studies. A recent study in Izumo, Japan, indicates that the incidence of SAH is as high as that in Finland. The purpose of this study was to confirm the high incidence of SAH in Japan. Methods-The incidence rate of SAH was investigated from 1989 through 1998 in the Shimokita peninsula, which is a clearly defined closed-boundary area in northern Japan with a population of 89 991. The registration was based on the complete referral system of SAH patients. All cases suspected of SAH underwent CT scan, and the images were referred to stroke specialists. The moribund cases and dead-on-arrival cases suspected of SAH also underwent CT scan. Results-From 1989 through 1998, 198 cases were diagnosed as having aneurysmal SAH. Out of these, 26 cases were moribund or dead when the initial CT scan was performed. The age-adjusted annual incidence of SAH was 21 per 100 000 person-years. The age and sex distribution of the cases indicated that the incidence plateaued after age 45 in men and the incidence increased after age 45 and reached the peak after 75 years in women. Conclusions-The high incidence of SAH in Japan is confirmed. The incidence of SAH obtained in this study is near to that of the Izumo study, of which the size of the geographic region and denominator and diagnostic criteria were similar to this study. (Stroke. 2002;33:195-199.)

Risk Factors for Aneurysmal Subarachnoid Hemorrhage in Aomori, Japan

“…Our previous study 10 revealed that the annual incidence of aneurysmal SAH of 21.0 per 100 000 population in Shimokita did not change when adjusted to the Finnish population, but it was reduced to 12.1 per 100 000 population when adjusted to an age distribution similar to the world population. Although the incidence of SAH in Japan and Finland decreases after adjusting for age, it remains nearly twice as high as the incidence in other countries.…”

“…10 The incidence of aneurysmal SAH was investigated between 1989 and 1998 inclusively, and 198 cases of aneurysmal SAH were seen at the Department of Neurosurgery at Mutsu General Hospital, which is the sole institute treating aneurysmal SAH in Shimokita. 10 Another part of this study was performed by 7 neurosurgical institutes located throughout the whole of the Aomori prefecture (the Figure) in the 1 year between June 2000 and May 2001 as part of an epidemiological study of cerebrovascular disease in this prefecture. Institutional ethics committees in each institute approved the protocol.…”

“…[1][2][3] The incidence appears to be especially high in Finland. 1,2,4 -8 Recent studies, 9 -14 including our previous report, 10 suggest that Japan has as high an incidence of SAH as Finland. The reasons for the higher incidence of aneurysmal SAH in Japan and Finland have yet to be determined.…”

Distal Anterior Cerebral Artery Aneurysms

“…In most populations the incidence is 6-0 cases per 00 000 person-years [7,28]. For unknown reasons, probably genetic, in Finland, Japan and Northern Sweden the incidence is much higher with 6-20 cases per 00 000 person-years [84,8,277,69,8].…”

15 Distal Anterior Cerebral Artery Aneurysms

“…In most populations the incidence is 6-0 cases per 00 000 person-years [7,2 8]. For unknown reasons, probably genetic, in Finland, Japan and Northern Sweden the incidence is much higher with 6-20 cases per 00 000 person-years [84,8,277,69,8 ].…”