Worldwide incidence of primary nervous system neoplasms. Geographical, racial and sex differences, 1960-1977.

International and interregional comparisons of average annual age-adjusted incidence rates for primary tumours of the nervous system showed marked variations. The highest rates were observed in those areas having high socioeconomic levels. In communities with multiple racial groups the highest rates were in Caucasians. Migrant populations retained rates close to those found in the country of origin. The majority of populations showed modest increases only while about one-third showed a decrease in the incidence rates during a period of approximately 15 years. Overall, there was a male excess. It is suggested that differences in medical practices (including availability of specialist expertise), diagnostic facilities and individual registry practices account for some of the variations observed. However, the possible aetiological roles of genetic, racial, hormonal and environmental factors need to be evaluated to explain the consistently higher incidence rates in Caucasians and in males of all races.