Abstract
BackgroundExposure to intermittent magnetic fields of 16 Hz has been shown to reduce heart rate variability, and decreased heart rate variability predicts cardiovascular mortality. We examined mortality from cardiovascular causes in railway workers exposed to varying degrees to intermittent 16.7 Hz magnetic fields.MethodsWe studied a cohort of 20,141 Swiss railway employees between 1972 and 2002, including highly exposed train drivers (median lifetime exposure 120.5 μT-years), and less or little exposed shunting yard engineers (42.1 μT-years), train attendants (13.3 μT-years) and station masters (5.7 μT-years). During 464,129 person-years of follow up, 5,413 deaths were recorded and 3,594 deaths were attributed to cardio-vascular diseases. We analyzed data using Cox proportional hazards models.ResultsFor all cardiovascular mortality the hazard ratio compared to station masters was 0.99 (95%CI: 0.91, 1.08) in train drivers, 1.13 (95%CI: 0.98, 1.30) in shunting yard engineers, and 1.09 (95%CI: 1.00, 1.19) in train attendants. Corresponding hazard ratios for arrhythmia related deaths were 1.04 (95%CI: 0.68, 1.59), 0.58 (95%CI: 0.24, 1.37) and 10 (95%CI: 0.87, 1.93) and for acute myocardial infarction 1.00 (95%CI: 0.73, 1.36), 1.56 (95%CI: 1.04, 2.32), and 1.14 (95%CI: 0.85, 1.53). The hazard ratio for arrhythmia related deaths per 100 μT-years of cumulative exposure was 0.94 (95%CI: 0.71, 1.24) and 0.91 (95%CI: 0.75, 1.11) for acute myocardial infarction.ConclusionThis study provides evidence against an association between long-term occupational exposure to intermittent 16.7 Hz magnetic fields and cardiovascular mortality.
Highlights
Exposure to intermittent magnetic fields of 16 Hz has been shown to reduce heart rate variability, and decreased heart rate variability predicts cardiovascular mortality
Based on a laboratory study [5], which showed that heart rate variability is reduced after nocturnal exposure to intermittent 60-Hz magnetic fields Sastre et al hypothesized that long-term exposure to low frequency magnetic fields (ELF-MF) might be associated
We considered deaths from cardiovascular diseases classified by the following four groups: arrhythmia related diseases, acute myocardial infarction, atherosclerosis related mortality as well as Sub-acute and chronic coronary heart diseases
Summary
Exposure to intermittent magnetic fields of 16 Hz has been shown to reduce heart rate variability, and decreased heart rate variability predicts cardiovascular mortality. We examined mortality from cardiovascular causes in railway workers exposed to varying degrees to intermittent 16.7 Hz magnetic fields. Based on a laboratory study [5], which showed that heart rate variability is reduced after nocturnal exposure to intermittent 60-Hz magnetic fields Sastre et al hypothesized that long-term exposure to low frequency magnetic fields (ELF-MF) might be associated (page number not for citation purposes). Since several cohort studies failed to confirm this finding [7], and a pooled analysis of laboratory studies did not show a consistent effect on heart rate variability [8]. Several doubleblind laboratory studies demonstrated changes in human brain electrical activity from ELF-MF exposure, in in the alpha frequency band [10]
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