Over the past few decades there have been numerous studies investigating whether proximity to high-voltage power lines and exposure to electromagnetic fields (EMF) contributes to the development of neurodegenerative diseases. The most recent epidemiological study reports that living near a power line does not increase the risk of developing dementia, Parkinson’s disease or motor neuron disease (Frei et al. Am J Epidemiol 2013; epublished April 9, 2013).
The study included all patients diagnosed with a neurodegenerative disease in Denmark in the period 1994-2010. The risk of Alzheimer’s disease for individuals ever living within 50 m of a power line was not increased (hazard ratio 1.04). No association was seen between the development of PD, MS or motor neuron disease and living near a power line. An earlier study in Denmark found an increased risk of MS with EMF exposure but the association was not significant (Johansen. Scan J Work Environ Health 2004;30 Suppl 1:1-30; free full text at http://www.sjweh.fi/show_abstract.php?abstract_id=792).
In contrast, the Swiss National Cohort Study reported a modest association between AD and living within 50 m of a 220-380 kV power line (adjusted HR 1.24) compared to individuals living >600 m from a power line (Huss et al. Am J Epidemiol 2009;169:167-175; free full text at http://aje.oxfordjournals.org/content/169/2/167.full.pdf+html). AD risk increased with increasing duration of exposure of >5 years (HR 1.51), >10 years (HR 1.78) and >15 years (HR 2.00). There was little evidence of an association between exposure to high-voltage power lines and PD, MS or amyotrophic lateral sclerosis.
A previous review of 10 epidemiological studies concluded that there was a moderate to strong association between ALS and occupational EMF exposure (Li & Sung. Am J Ind Med 2003;43:212-220), although the authors noted that there are a number of possible confounders, such as electric shocks and welding on the job (Hug et al. Soz Praventivmed 2006;51:210-220).
A further concern is that methodological weaknesses of studies have resulted in inconsistent conclusions. A decade ago, an international panel recommended a multinational study with more rigorous data collection to investigate the possible association of EMF exposure and neurological diseases (Kheifets et al. Occup Environ Med 2009;66:72-80).
A Canadian review concluded that there is little evidence of health effects with EMF exposure (Habash et al. Crit Rev Biomed Eng 2003;31:141-195). The same authors also reviewed the limited data on radiofrequency radiation exposure (e.g. cell phones, microwaves) and possible health effects (Habash et al. Crit Rev Biomed Eng 2003;31:197-254).
Comment
Dr. Daniel Selchen: The alleged causative links to neurodegenerative diseases have been a major epidemiological (and medico-legal) “industry” for a number of years. Various viruses and trauma have been linked to MS, occupational categories to parkinsonism, and there is a court case in Canada linking ALS to an isolated episode of physical trauma. Most of these theories have lacked real evidence. There have been a number studies with regard to high-voltage power lines, EMF and neurodegenerative diseases which have demonstrated inconsistent results suggestive of methodological challenges. On the basis of the currently available information, it appears that if there is any effect it is probably very small and of doubtful clinical significance.