Mobile phone use and risk of intracranial tumors

Sammanfattning: Mobile phones are today an integral part of many people's lives in western societies. The phones emit radiofrequency radiation when being used. Concerns have been raised about possible effects that the exposure may have on the health of the mobile phone user. If radiofrequency radiation has a carcinogenic potential the exposure might pose an important public health problem. The overall aim of this thesis was to study the association between radiofrequency exposure from mobile phone use and risk of intracranial tumors. The aim of Paper I was to describe the incidence trends of intracerebral tumors during a period with introduction of new diagnostic procedures and increasing prevalence of mobile phone users. Information about adult primary intracerebral tumors was obtained from national cancer registries in four Nordic countries for the years 1969-1998. Estimates of person-years at risk were calculated from the information obtained from national population registries. Annual age standardized incidence was calculated and time trends were analyzed. The result showed an increase in the incidence that was confined to the late 1970s and early 1980s and coincided with the introduction of improved diagnostic methods such as computerized tomography. After 1983, and during the period with increasing prevalence of mobile phone users, the incidence has remained relatively stable for both men and women. The purpose of Paper II was to analyze the distribution of power levels from mobile phones in four geographical areas with different population density to see whether region was a significant determinant of exposure. The output power for all mobile phone calls managed by the GSM operator Telia Mobile was recorded during one week in four defined areas in Sweden. In the rural area, the highest power level was used by mobile phones about 50% of the time, while the lowest power was used only 3% of the time. The corresponding numbers for the city area were approximately 25% in the highest and 22% in the lowest. Papers III and IV are based on a case-control study on intracranial tumors and radiofrequency exposure from mobile phone use. It includes all residents aged 20 to 69 years in geographical areas covered by four regional cancer registries in Sweden. Eligible cases were all subjects diagnosed with acoustic neuroma, glioma, meningioma, and parotid gland tumors. Cases were identified continuously during the study period at the clinics at all hospitals within the study area. Controls were randomly selected from the study base. Detailed information about mobile phone use and other environmental exposures was collected by personal interviews. The specific aim of Paper III was to test the hypothesis that radiofrequency exposure from mobile phones increases the risk of acoustic neuroma. The aim of Paper IV was to test the hypothesis that radiofrequency exposure from mobile phones increases the risk of glioma and meningiorna. The results displayed that ten or more years of mobile phone use increases the risk of acoustic neuroma and that the risk increase was confined to the side of the head where the phone was usually held. No indications of an increased risk for less than 10 years of mobile phone use were found. No increased risk was found for glioma or meningiorna related to mobile phone use. The results in this thesis are in accordance with results from most previous studies. The results do not support the hypothesis that radiofrequency exposure from mobile phone use increases the risk of glioma or meningioma. The results do not support the hypothesis that short-term mobile phone use increases the risk of acoustic neuroma, but the results indicate that long-term use increases the risk of acoustic neuroma. This result needs to be confirmed in other studies before firm conclusion could be drawn.