[Brain tumors in Yamaguchi Prefecture--incidence through 4 years]

The incidence of brain tumors was studied in Yamaguchi prefecture of about 1,600,000 population. All of the brain tumor patients admitted to the neurosurgical hospitals in Yamaguchi prefecture were registered. Cases of osteoma, lipoma, scalp tumor and spinal tumor were excluded. From 1986 through 1989, 726 cases were registered. 135 recurrent cases were included. Therefore first-diagnosed primary brain tumors were selected to calculate the true incidence. The number of cases of primary brain tumor was 478 and showed female preponderance (male/female: 207/271). The incidence of primary brain tumor was 7.5/100,000/year (male/female: 6.8/8. 1). No difference was present between the incidence in cities and that in rural districts. Percentages of representative tumors were 28.2% for glioma, 32.8% for meningioma, 13.0% for pituitary adenoma and 10.7% for neurinoma. Age-adjusted incidence was 2.1/100,000/year for glioma and 2.1/100,000/year for meningioma. The incidence of glioma was lower and that of meningioma was higher in Yamaguchi prefecture than those in other reports. Compared with the Brain Tumor Registry of Japan (1969-1983), the percentage of meningioma cases was large in Yamaguchi prefecture. This difference owed partly to the increased number of population over age of 40's in Yamaguchi prefecture. The peak of age distribution was present in age of 50's in Yamaguchi prefecture and in age of 30's and 40's in Brain Tumor Registry of Japan. The peak of age distribution shifted to older ages in Yamaguchi and the difference was conspicuous in age of 60's. This peak consisted of mainly cases of meningioma and partly those of glioma.(ABSTRACT TRUNCATED AT 250 WORDS)