EMF Database abstract: USE OF CELLULAR TELEPHONES AND THE RISK FOR BRAIN TUMOURS: A CASE-CONTROL STUDY.

EMF Database sample abstract

Last modified on: Monday, July 31, 2000
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USE OF CELLULAR TELEPHONES AND THE RISK FOR BRAIN TUMOURS: A CASE-CONTROL STUDY.
(Eng.) Hardell, L.; Nasman, A.; Pahlson, A.; Hallquist, A.; Mild, K. H. [Dept. of Oncology, Orebro Medical Centre, SE-701 85 Orebro, Sweden (RR/L.H., A.N.); Dept. of Neurology, Orebro Medical Centre, SE-701 85 Orebro, Sweden (A.P.); Dept. of Oncology, Karolinska Inst. and Stockholms Sjukhem, Mariebergsgatan 22, SE-112 35 Stockholm, Sweden (A.H.); Natl. Inst. for Working Life, SE-907 13 Umea, Sweden (K.H.M.)]
Int J Oncol 15(1):113-116; 1999
Funding: Swedish Medical Res. Council; Orebro Cancer Fund

A case-control study examining associations between use of cellular telephones and brain tumor risk among Swedish residents was conducted. Persons diagnosed with brain tumors when 20-80 yr of age and who were still alive were identified from the records of the Oncological Center in Uppsala-Orebro (for 1994 through 1996) and the Stockholm region (for 1995 and 1996). A total of 270 histopathologically verified cases were identified. After exclusion of 37 patients for medical reasons, such as being too ill to participate, 233 cases remained for analysis. Two controls matched by sex, age, and study region were selected for each case from the Swedish population registry. The subjects were interviewed by postal questionnaire, supplemented by telephone contacts, to obtain complete occupational histories including information on chemical exposures and information on cellular telephone use. All subjects who said they used cellular phones were contacted by the interviewer to confirm this and, if necessary, to qualify the answers. The type of cellular phone system used, digital GSM system or analogue NMT system, was also determined based on the first 3 digits of the cell phone number. Detailed information on the specifics of cellular telephone use such as whether used during leisure time or occupationally, average minutes of use per day, years of use, specific type of phone, use of hands-free devices, and use in a car with a fixed antenna on the car were assessed from questionnaire and interview responses. All cellular phone use (exposures) with hands-free devices or an automobile antenna, or occurring within 1 yr prior to diagnosis were disregarded for exposure analysis. The same timing was used for the matched controls. Cumulative exposure in hours was calculated, and a minimum cumulative exposure time of 8 hr was used for both cases and controls. Conditional logistic regression analysis was used to calculate odds ratios (ORs) and their 95% confidence intervals (CIs). Analyses were also performed using minimum tumor induction times of 5 or 10 yr. A total of 217 questionnaires were returned from the cases and 439 from the controls. Eight cases with recurrent brain tumors and their 14 matched controls were excluded leaving 209 cases and 425 controls for analysis. The mean age of the cases and controls was 50 yr with approximately equal numbers of men and women in both groups. Seventy eight cases (37.3%) and 161 controls (37.9%) reported using cellular phones. The mean number of hr of use was 511 for the cases (median 136, range 8-9000) and 428 (median 136, range 8-6304) for the controls. No overall increased risk for brain tumors was found, the OR being 0.98 (CI 0.69-1.41). No change in the results and no dose-response effect (based on median hours of cellular telephone use) could be seen when the different tumor induction periods were used. Separate analyses of use of GSM or NMT telephones also indicated no increased brain tumor risk. When examined by tumor type, no increased risk was found for malignant or benign tumors. A suggestion of increased risk was seen based on tumor site. There was a marginal increased risk for cases with right brain tumors who used the phone at their right ear (OR 1.28, CI 0.68-2.38, 25 cases) which was stronger for temporal or occipital localization of the tumor on the right side (OR 2.45, CI 0.78-7.76, 8 cases) and increased somewhat more when only NMT phones were considered (OR 2.56, CI 0.72-9.12, 7 cases). An indication of elevated risk was seen for temporal or occipital localization of the tumor on the same side as phone use for the left side use as well (OR 2.40, CI 0.52-10.9, 5 cases), again attributed to ever using NMT phones (OR 2.10, CI 0.46-9.57, 5 cases). All CIs, however, included 1.0 so these ORs were not statistically significant. Thirteen cases were diagnosed with acoustic neurinoma, yielding an OR for cellular phone use of 0.78 (CI 0.14-4.20, 5 cases). Of these, only 1 case had the tumor on the same side that the telephone was held. The authors conclude that a nonsignificantly increased risk for brain tumors located in the temporal or occipital lobe was found for people who had used a NMT cellular phone on the same side of the head (that is, the tumor was in the area with the highest radiofrequency radiation exposure). This finding, however, is based on small numbers and must be interpreted with caution. Most of these cases had used NMT phones and an increased risk was found only for such use, but GSM phones were only introduced in the early 1990s so the observation time is too short for definite conclusions to be drawn. Future research should be directed at the risk, if any, for brain tumors in the anatomical region closest to the ear used for cellular phones. (4 Refs). [Copyright 2000, Information Ventures, Inc.]
AUTHOR KEY WORDS: Brain tumors, Analogue telephones, Digital telephones, Microwave radiation

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