Case-Control Study on Radiology Work, Medical X-ray Investigations, and Use of Cellular Telephones as Risk Factors for Brain Tumors

, Department of Oncology, Orebro Medical Center, SE-701 85 Orebro, Sweden email: , Department of Oncology, Orebro Medical Center, SE-701 85 Orebro, Sweden , Department of Neurology, Orebro Medical Center, SE-701 85 Orebro, Sweden , Department of Oncology, Karolinska Institute and Stockholms Sjukhem, Mariebergsgatan 22, SE-112 35 Stockholm, Sweden

In This Article

Results

In total, 270 cases that fulfilled these inclusion criteria were included. Of these, 37 patients were judged by their physicians not to be able to participate. Thus, 233 cases and 466 controls remained in the study. The questionnaire was answered by 217 cases and 439 controls. When scrutinizing medical reports, we discovered that 8 cases had recurrent brain tumors. These cases were excluded from further analysis together with their 14 responding matched controls. Thus, the analysis encompassed 209 cases (90%) and 425 controls (91%). The mean age of both cases and controls was 50 years (range, 21-80 years).

As displayed previously.[6] histopathologic reports were obtained for 197 patients, 136 with malignant and 62 with benign tumors (1 case had 2 benign tumors: ependymoma and acoustic neurinoma). Anatomic tumor localization was assessed for 198 patients: 99 with tumor in the right side of the brain, 78 in the left side of the brain, and 21 with no applicable side (eg, central tumor). The analysis of mobile telephone use and the risk for brain tumor according to anatomic localization was based on these 198 cases with corresponding controls. The whole material of 209 cases and 425 controls was used in the other calculations. The results are presented for all cases with either benign or malignant tumors.

Occupation

Occupation as a risk factor was analyzed ( Table 1 ). For physicians, an OR of 6.00 (95% CI, 0.62-57.7) was obtained. All 3 case patients had worked with x-ray investigations for some period, with tumor induction (latency) periods of 20, 28, and 31 years ( Table 2 ). On the contrary, the only control subject who was a physician had never worked with x-ray investigations.

Overall, work at a radiology department yielded an OR of 1.89 (95% CI, 0.61-5.89). Excluding the 3 physicians, the 4 cases and 6 controls with other job titles in radiology yielded an OR of 1.24 (95% CI, 0.35-4.43). No increased risk was found for other occupational categories in health services. These job titles were included among nurses or nurse assistants in Table 1 .

Electronics, telecommunication, or electrical work did not increase the risk for brain tumors. No subject had worked as a railway engine driver.

For laboratory work, an OR of 3.21 (95% CI, 1.16-8.85) was obtained. Also, work in the chemical industry yielded an increased risk (OR, 4.10; 95% CI, 1.25-13.4).

Eight cases and 11 controls reported previous radiotherapy for benign or malignant disease, yielding an OR of 1.58 (95% CI, 0.60-4.16). If only the head and neck region was considered, an OR of 3.61 (95% CI, 0.65-19.9) was obtained (4 cases, 2 controls).

Overall, no increased risk for brain tumors was found for medical diagnostic x-ray investigations. However, if previous x-ray investigations of the head and neck region were considered, an OR of 1.64 (95% CI, 1.04-2.58) was obtained. Using a tumor induction period of 5 years or more, the risk increased further to an OR of 2.10 (95% CI, 1.25-3.53) based on 36 exposed cases and 37 exposed controls. For the 13 cases with meningioma, an OR of 5.03 (95% CI, 1.60-15.8) was obtained with the 5-year or more induction period.

Agents

In Table 3 , exposure to different agents is presented. No association was found for exposure to asbestos, pesticides, organic solvents, smoking, or a video display unit. For low-calorie drinks taken as aspartame exposure, an OR of 1.24 (95% CI, 0.72-2.14) was found. The risk was further increased for malignant tumors, with an OR of 2.66 (95% CI, 1.01-7.04) in the highest-exposure group.

Cellular Telephones

Table 4 gives the results for use of cellular phones. Increased risk was only found for cases with tumors in the temporal, temporoparietal, or occipital lobe and ipsilateral use of a mobile phone (OR, 2.42; 95% CI, 0.97-6.05). This result was based on 13 exposed cases, 10 with malignant and 3 with benign tumors.[6] Nine cases were exposed to NMT only, 3 to both NMT and GSM and 1 to GSM only. For contralateral use, no increased risk was found. Only a few subjects reported both ipsilateral and contralateral use of a cellular telephone.

Multivariate Analysis

Exposure to cellular phones for subjects with brain tumors in the temporal, occipital, or temporoparietal anatomic areas and other exposures with significantly increased risk were included in a multivariate analysis. Work in the chemical industry was not included, since only 1 case with tumor in these lobes and no controls were exposed. Significantly increased risk was found for subjects with ipsilateral exposure to microwaves from a mobile phone (OR, 2.62; 95% CI, 1.02-6.71; Table 5 ). For laboratory work and medical diagnostic x-ray investigations of the head or neck, a nonsignificantly increased risk was calculated in the multivariate analysis. Similar results were found in the multivariate analysis as in univariate analyses for use of cellular telephone and the risk for brain tumor in other anatomic areas of the brain.

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