Incidence trends of adult primary intracerebral tumors in four Nordic countries

Brain tumors are some of the most lethal adult cancers and there is a concern that the incidence is increasing. It has been suggested that the reported increased incidence can be explained by improvements in diagnostic procedures, although this has not been totally resolved. The aim of our study was to describe the incidence trends of adult primary intracerebral tumors in four Nordic countries during a period with introduction of new diagnostic procedures and increasing prevalence of mobile phone users. Information about benign and malignant primary intracerebral tumor cases 20-79 years of age was obtained from the national cancer registries in Denmark, Finland, Norway and Sweden for the years 1969-98 and estimates of person-years at risk were calculated from the information obtained from national population registries. Annual age standardized incidence rates per 100,000 person-years were calculated and time trends analyses were carried out using Poisson regression. The overall incidence of all intracerebral tumors ranged from 8.4-11.8 for men and 5.8-9.3 for women, corresponding to an average annual increase of 0.6% for men (95% confidence interval [CI] = 0.4, 0.7) and 0.9% for women (95% CI = 0.7, 1.0). The increase in the incidence was confined to the late 1970s and early 1980s and coinciding with introduction of improved diagnostic methods. This increase was largely confined to the oldest age group. After 1983 and during the period with increasing prevalence of mobile phone users, the incidence has remained relatively stable for both men and women.