12/11/2008 - Living close to a power line can double your chance of dying from Alzheimer's Disease

A large new study from Switzerland^{[Huss 2008]} shows a significant dose-related increase in deaths from Alzheimer's Disease (AD) in people who have lived for a number of years within 50 metres of high-voltage overhead powerlines. The results of this new study considerably raises the stakes in the EMF-health debate by showing up a serious and wide-spread public ill health problem as being closely associated with power-frequency magnetic field exposure. The cost of dementia to the UK economy is estimated to be over £17 billion (GBP) per year.

Researchers at Bern University's Institute of Social and Preventative Medicine in Switzerland have found that people who have lived for least 5 years within 50 metres had an adjusted hazard ratio for dying of AD of 1.51, increasing to 1.78 after 10 years and to 2.0 (CI 1.21-3.33) after living there for at least 15 years. The pattern was similar for senile dementia.

The relation between where people live in relation to power lines and mortality from neurodegenerative conditions was analyzed within the data for 4.7 million people in the Swiss National (mortality and census) Cohort, covering the period 2000-2005. If anything this will have underestimated the risk as AD is often not entered as the prime or even underlying cause of death - so the actual incidence of the disease will almost certainly be higher.

Team member Professor Matthias Egger also warned that sleeping in power-frequency magnetic fields from any source probably presents a dementia risk. He said: "Anything that is plugged in and that is on all the time and that is near to your body is a source of EMF".

Magnetic fields from underground electricity cables, especially those that run under the pavements and supply our houses are another most significant source of higher-than-normal magnetic fields in homes, often up to several microtesla. This was highlighted in a report by the NRPB a few years ago ^{[Maslanyj 2005]}. Powerwatch has found it to be a common problem, especially in older areas of UK cities. The Department of Health SAGE Process will be investigating this matter during 2009 and hopefully reporting in early 2010.

Previous Research

The findings of this new Swiss study are consistent with the combined analyses of risk of Alzheimer's with occupational exposure to power-frequency magnetic fields by Ana Garcia^{[Garcia 2008]}, published earlier in 2008. Her study combined the results of 14 occupational studies (from 1995 to 2004) of EMF exposure and the later development of Alzheimer's disease. This resulted in an overall increased odds (risk) ratio of 2.03 (95% CI 1.38-3.00) from the case-control studies and 1.62 (CI 1.16-2.27) rising to 2.05 (95% CI 1.51-2.80) for men. They estimated that the effect occurred when the average magnetic field was over about 0.5 microtesla. Interestingly, this would agree well with the 50 metres distance from the powerlines in the new Swiss study.

The evidence for risk of Alzheimer's is now quantitatively comparable with that for childhood leukaemia, which is recognised as an IARC class 2B carcinogen.

For further detailed background information we suggest that you download and read Section 12 of the BioInitiative Report.

Alzheimer's Disease

The Alzheimer's Research Trust and Alzheimer's Society report that there are 700,000 people living with dementia in the UK today, a number forecast to double within a generation. 25 million people, or 42% of the UK population, are affected by dementia through knowing a close friend or family member with the condition. 1 in 3 over 65s will die with some form of dementia. Each year 39,400 more people are diagnosed with Alzheimer's Disease in England and Wales. That equates to one new case every 14 minutes.

In the UK, about 200,000 people live within 50 metres of a high-voltage overhead powerline^{[SAGE interim assessment]}. If "normally", 1 in 3 will develop AD before they die (see last paragraph) and exposure to the power-frequency magnetic fields doubles this, then that would be another 66,000 cases just due to living near to overhead powerlines. Extra cases will be due to underground net-current problems and fields from transformers and other high magnetic field sources within our homes.

Possible mechanisms

Several mechanisms have been proposed and studied in order to explain potential ELF-EMF actions on biological systems. Zecca expressed his concerns in 1998^{[Zecca 1998]} that "Should future epidemiological studies confirm an increased risk for neurological disorders, particularly for Alzheimer's disease, in chronic EMF exposed individuals, a study like the present one should be extended to rats exposed for the whole life span and to primates with a variety of exposure protocols". Habash, et al, wrote a useful over-view^{[Habash 2003]} as did the World Health Organisation in their Environmental Health Criteria EHC-238. One likely contender is the 'melatonin hypothesis', involving melatonin and biosynthetic enzymes in the pineal gland^{[Reiter 2001, Henshaw 2005]}. Others are oxidative stress or cellular Ca2+ efflux in immune system cells and neurons. Melatonin is a strong protector against oxidative stress. Other possibilities include apoptosis and necrosis in brain cells, effects on biomagnetic particles reported in the human brain or even differential levels of electrosensitivity among the general population.

Whatever the mechanism (or, more probably mixture of mechanisms), we now have a large general public epidemiological analysis whose results closely match those from 14 occupational studies that show a statistical doubling of Alzheimer's Disease associated with power-frequency magnetic fields above about 0.5 microtesla. This should be more that enough to trigger a more precautionary approach to EMF exposure that will better protect the public from harm. Currently the ICNIRP and UK public maximum exposure guidance levels are set 200-fold higher at 100 microtesla. Occupational levels are set even higher and this must be of concern to exposed occupations (such as railway workers), especially as the HPA has recently being saying that the occupational maximum guidance levels could probably be relaxed (i.e. made even higher, maybe up to 1800 microtesla).

Conclusions

If average background power-frequency magnetic fields above 0.5 microtesla do double the incidence of Alzheimer's Disease, then this represents a far more serious overall public health problem than the association with childhood leukaemia, serious though that is for the individuals involved. It would completely change the cost-benefit calculations that SAGE has been making and would almost certainly greatly strengthen their advice to Government set out in the first SAGE Report that was published last year (2007). The Goverment has not yet responded to the first SAGE Report, but has promised to do so by the end of 2008. There is a linked blog entry making some further comments.

References

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