ABSTRACT
In Akita Prefecture, there are nine hospitals established by the Akita Prefectural Federation of Agricultural Cooperatives for Health and Welfare (Koseiren). Half of the stroke patients in the prefecture were treated in these Koseiren hospitals, and half of the mass screening projects for the prevention of cardio vascular diseases were undertaken by these hospitals. A retrospective cohort study was done using mass-screening data (age, sex, past history of diabetes mellitus, blood pressure, body mass index, smoking and drinking habits) of 175,033 cases stored at these hospitals from 1988 to 1999, and the prefecture-wide stroke data of 2,520 initial stroke events registered from 1988 to 2003. The number of stroke cases was broken down into 1,428 cases of cerebral infarction (57%, CI), 693 cases of cerebral hemorrhage (27%, CH) and 399 cases of subarachnoid hemorrhage (16%, SAH). The subjects were also divided into five age groups:30-49, 50-59, 60-69, 70-79 and 80-89. Blood pressure (BP) was classified into six categories according to the JNC 6 criteria. Risk factors were determined using the Cox analysis. The hazard ratio for CI and CH was increasing with advancing age. CI showed a higher hazard ratio in men than women (hazard ratio for men was 1.8). The hazard ratio was increasing as BP became higher in any of three stroke subtypes, and especially CH showed the strongest correlation with BP. Uncontrollable risk factors were very closely associated with the attack of CI. On the other hand, BP (controllable risk) was closely linked with the attack of CH. Our results showed the prevention of CI was not easy. Controlling BP may be the most effective strategy for preventing hemorrhagic stroke (CH and SAH).