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 In fact, the wrong amount may actually increase dementia risk,
researchers report in JAMA Psychiatry.
Lithium, used for years in drugs to treat depression and bipolar
disorder, is a naturally-occurring element in drinking water in
Denmark but levels vary by location. The team compared the estimated
amount found in the water supplies of 275 municipalities to the
rates of dementia, including Alzheimer's, in those areas.
Residents who had been diagnosed with dementia from 1995 through
2013 tended to consume lower levels of lithium in their water than
residents whose water had higher levels. However, there was a middle
level of consumption where dementia risk was elevated or unchanged.
Compared to those whose water contained lithium concentrations of 2
to 5 micrograms of lithium per liter, which served as the baseline,
the rate of dementia was 22 percent higher when the drinking water
concentration was 5 to 10 micrograms.
Levels of 10.1 to 15 micrograms had no effect on the risk.
But at levels of 15.1 to 27 micrograms per liter, the dementia risk
seemed to drop by 17 percent compared to places where the levels
were 2 to 5 micrograms.
"It's a really interesting study but you have to be careful about
inferring cause and effect," said Dr. Brent Forester, head of the
geriatric division of McLean Hospital, a psychiatric hospital in
Belmont, Massachusetts affiliated with Harvard Medical School, who
wasn’t involved in the research.
In a telephone interview with Reuters Health, he called the fact
that the effect didn't strictly increase or decrease based on the
lithium dose "a worrisome sign" and said the non-linear trend "could
be a warning that there's another confounding variable. It may not
be the lithium itself but something about the mechanism of action
might be protecting against developing dementia. The biology of
lithium is worth exploring, for sure."
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The chief author of the study, Dr. Lars Vedel Kessing of the
University of Copenhagen, did not respond to requests for an
interview. But the researchers cautioned in their paper that "it
cannot be excluded that other, unobserved environmental or social
care factors related to individuals’ municipality of residence might
have confounded the association between lithium exposure and
dementia rate."
The idea of a link between lithium and Alzheimer's has been around
for years, Forester said.
"Over a decade ago, a pathology study that looked at the brains of
patients who had a lifelong history of bipolar disorder and were
treated with lithium versus those with a lifelong history of bipolar
disorder who were not on lithium showed that those exposed to
lithium had about one sixth the rate of Alzheimer's pathology," he
said. "It raised a lot of interesting questions and eyebrows about
the mechanism."
Other research has shown that low doses - but doses far higher than
found in the drinking water in the Denmark trial - may reduce the
odds of Alzheimer's. But research has been limited because drug
companies don't stand to make a lot of money from lithium therapy.
Forester said he would not advise people to try using lithium to
ward off Alzheimer's because the drug can harm the kidneys, although
the levels seen in the drinking water in Denmark are too low to pose
a serious risk.
SOURCE: http://bit.ly/2voKL7m and http://bit.ly/2xsCHUN JAMA
Psychiatry, online August 23, 2017.
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