Childhood cancer in relation to a modified residential wire code.

Several studies have found associations between wire configuration codes, a proxy for historical residential magnetic field exposure, and childhood cancer. The Wertheimer-Leeper coding method was modified by eliminating the distinction between thick and thin primaries, distinguishing only between open and spun secondaries, and reducing the number of categories from five to three. The association between the modified code and measured magnetic fields was similar to the association with the original wire code. The modified code was used to reanalyze data from a case-control study of childhood cancer in the Denver metropolitan area. In the original study, cases were diagnosed from 1976 to 1983 among children under age 15 and compared to controls selected through random digit dialing. Wire codes for the residence at diagnosis yielded imprecise elevations of two and above for very high current configuration homes or modest 1.5-fold elevations for a dichotomous wire code. In contrast, the modified Wertheimer-Leeper code generated risk estimates that were both precise and markedly elevated for the high wire code (HWC) compared to low wire code (LWC) classifications, with medium wire code (MWC) showing little or no increase in risk. High wire code yielded odds ratios of 1.9 for total cancers (95% CI: 1.1-3.2), 2.9 for leukemias (95% CI: 1.5-5.5), and 2.5 for brain cancer (95% CI: 1.1-5.5) that were not confounded by measured potential risk factors for childhood cancer. These risk estimates are larger than the dichotomized results and more precise than those from the original five-level wire code, though limitations in the original study remain, particularly potential control selection bias.(ABSTRACT TRUNCATED AT 250 WORDS)