Application of the case-specular method to two studies of wire codes and childhood cancers.
Abstract
This paper presents the results of applying the case-specular method to two earlier studies of wire codes and childhood cancers (DA Savitz et al, Am J Epidemiol 1988;128:21-38, and SJ London et al, Am J Epidemiol 1991;9:923-937). The method compares the wire codes of case residences with the wire codes of specular residences constructed by switching the location of the case residence across the center of the street. The method was designed to discriminate between the magnetic field hypothesis, which postulates that childhood cancer is affected by magnetic fields and that wire codes are a proxy for magnetic fields, and the neighborhood hypothesis, which postulates that childhood cancer is affected by some characteristics of the neighborhood other than magnetic fields and that wire codes are a proxy for those characteristics. Although the results from the two applications of the method have limited precision, they support the results originally reported (odds ratios of around 2 for very high current configuration residences and childhood cancers) and do not support suggestions that the associations are due to confounding by socio-economic and neighborhood factors. The results leave open the question of whether or not control selection bias could have influenced the original associations, because there was no convincing evidence that the control-specular matrices were symmetric.
- PMID: 10401874
Location of gliomas in relation to mobile telephone use: a case-case and case-specular analysis.
Abstract
The energy absorbed from the radio-frequency fields of mobile telephones depends strongly on distance from the source. The authors' objective in this study was to evaluate whether gliomas occur preferentially in the areas of the brain having the highest radio-frequency exposure. The authors used 2 approaches: In a case-case analysis, tumor locations were compared with varying exposure levels; in a case-specular analysis, a hypothetical reference location was assigned for each glioma, and the distances from the actual and specular locations to the handset were compared. The study included 888 gliomas from 7 European countries (2000-2004), with tumor midpoints defined on a 3-dimensional grid based on radiologic images. The case-case analyses were carried out using unconditional logistic regression, whereas in the case-specular analysis, conditional logistic regression was used. In the case-case analyses, tumors were located closest to the source of exposure among never-regular and contralateral users, but not statistically significantly. In the case-specular analysis, the mean distances between exposure source and location were similar for cases and speculars. These results do not suggest that gliomas in mobile phone users are preferentially located in the parts of the brain with the highest radio-frequency fields from mobile phones.
- PMID: 21610117