NEW YORK (Reuters Health) - Older people living within 50 meters of major power lines are at increased risk of dying from Alzheimer’s disease or senile dementia, research from Switzerland shows.

The risk increased steadily with the amount of time a person had been living in close proximity to a 220-380 kV power line, Dr. Anke Huss of the University of Bern and colleagues found. These are extra-high voltage lines used for long-distance transmission of large amounts of electricity.

Huss and colleagues were able to look at census and mortality data for over 95% of the Swiss population, which strengthens the power of the findings. Nevertheless, the researcher told Reuters Health, the results should be interpreted with caution because this is the first study to link residential magnetic field exposure to Alzheimer’s mortality. Huss said she would like to see other research teams, preferably in other countries, look into the issue.

Extremely low-frequency magnetic fields are produced by electrical appliances and wiring as well as by power lines. The World Health Organization has stated that these magnetic fields are possible human carcinogens. In 2007, WHO concluded that there was not enough evidence to link extremely low-frequency magnetic fields to Alzheimer’s disease, but called for the relationship to be a “key research priority,” Huss and her team note in the American Journal of Epidemiology.

To investigate the relationship between residential exposure to power lines and risk of neurodegenerative disease, the researchers looked at 1990 and 2000 census data and 2000-2005 mortality data for 4.7 million people 30 and older.

Overall, Huss and her colleagues found, people living within 50 meters of a 220-380 kV power line were 1.24 times more likely to die of Alzheimer’s disease than those living at least 600 meters away from these power lines.

People who lived for at least 5 years near a 220-380 kV power line were at a 1.51-fold increased risk. For people who lived close to a large power line for at least a decade, risk increased by a factor of 1.78, while it was doubled for those who had been living near a power line for at least 15 years. Results were similar when the researchers looked at deaths from senile dementia.

While 9.2% of the Swiss population lives within 600 meters of an extra-high voltage power line, only 0.3% live within 50 meters of one, Huss noted. “It’s not a huge amount of people.”

People are much more likely to be exposed to extremely low-frequency magnetic fields at home, but such exposure can easily be controlled, according to Huss. While household appliances such as radio alarm clocks can produce magnetic fields similar to those emitted by power lines, the researcher pointed out, reducing risk is a simple matter of avoiding being very close to such devices for long periods of time; for example, not sleeping with one’s head close to a radio alarm clock or keeping an electric blanket on all night long.

At present, the researcher added, there is no accepted biological mechanism to explain why magnetic fields might increase Alzheimer’s risk. Given the consistency of the findings, she added, “There might be something going on even if we don’t know what it is.”

SOURCE: American Journal of Epidemiology, January 15, 2009.