Neurodegenerative disease and occupational magnetic field exposure: case control investigations and a biological marker study using the amyloid-beta protein

Abstract

Two studies were conducted to investigate recent epidemiological findings of an association between occupational exposure to magnetic fields and neurodegenerative diseases. The objective of the first study was to determine whether individuals whose death certificate indicated Alzheimer's disease, amyotrophic lateral sclerosis, Parkinson's disease, or brain cancer were more likely to have had occupations associated with magnetic field exposure. Three methods of exposure assessment were applied to each case-control group. Amyotrophic lateral sclerosis and Parkinson's disease were associated with history of electrical occupations: odds ratio (OR) and 95% confidence interval (CI) = 2.30 (1.29,4.09) and 1.55 (0.98, 1.76), respectively. A weak association was found for Alzheimer's disease [OR and 95% CI = 1.21 (0.83, 1.76)] using job title and industry to assess exposure. A weak association was found for brain cancer using a job exposure matrix [OR and 95% CI = 1.32 (0.92,1.89). Our findings suggest that associations between occupational exposure to magnetic fields and risk of neurological diseases are sensitive to methods of exposure assessment. The objective of the second study was to assess the relationship between occupational magnetic field exposure, melatonin, and concentrations of blood-borne soluble amyloid beta (Abeta), a protein associated with the pathological lesions of Alzheimer's disease. Blood and urine samples were obtained from male electric utility workers (n = 60) to quantify two lengths of the protein, Abeta(1-40) and Abeta(1-42), and the melatonin metabolite, 6-hydroxymelatonin sulfate (6-OHMS). Magnetic field exposure was assessed using personal data logging devices. There was no association between measures of magnetic field intensity and Abeta, but there was an inverse association between magnetic field variability and Abeta(1-42) and the ratio of Abeta(1-42) to Abeta(1-40). It was unclear whether variability was a magnetic field characteristic required to perturb Abeta concentrations or whether this exposure was a surrogate for other important factors such as physical activity. There was also suggestion of an inverse association between Abeta and post-workshift 6-OHMS. Overall, these two studies offer some support for an association between occupational magnetic field exposure and neurodegenerative disease. The potential for future investigations to more fully elucidate this relationship are discussed.