Feychting M, Kaune W T, Savitz D A, Ahlbom A
Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden.
Epidemiology. 1996 May;7(3):220-4. doi: 10.1097/00001648-199605000-00001.
Validity of exposure assessment methods has been a major concern in epidemiologic studies of magnetic field exposure and cancer. We conducted a study to evaluate the relative importance of distance to power lines and calculated historical magnetic fields when estimating past magnetic field exposure. Another goal was to compare results based on various estimates of magnetic field exposure, to assess the importance of short-term variability in magnetic fields, time between diagnosis and measurement, and sources of magnetic field exposure. We used data from a Swedish case-control study of residential exposure to magnetic fields and cancer. Childhood leukemia risk was associated with calculated historical annual average magnetic fields regardless of distance, and the association with distance disappeared when both variables were entered into the same logistic regression model. Relative risks for measurements at the time of the study (contemporary annual average fields, spot calculations, and spot measurements) were all close to or below unity. The results support the hypothesis that the difference between results using historical calculations and spot measurements is explained by the time interval between diagnosis and contemporary magnetic field estimates.
在磁场暴露与癌症的流行病学研究中，暴露评估方法的有效性一直是主要关注点。我们开展了一项研究，以评估在估计过去的磁场暴露时，与输电线的距离及计算得出的历史磁场的相对重要性。另一个目标是比较基于磁场暴露的各种估计结果，以评估磁场短期变化、诊断与测量之间的时间间隔以及磁场暴露源的重要性。我们使用了瑞典一项关于居住环境磁场暴露与癌症的病例对照研究的数据。儿童白血病风险与计算得出的历史年均磁场相关，与距离无关，并且当将这两个变量纳入同一逻辑回归模型时，与距离的关联消失了。研究时测量的相对风险（当代年均磁场、现场计算和现场测量）均接近或低于1。结果支持这样的假设，即使用历史计算结果与现场测量结果之间的差异可由诊断与当代磁场估计之间的时间间隔来解释。
