By Steven Reinberg
In a study of more than 9,500 men and women, the highest or lowest levels of magnesium appeared to increase the chances for dementia by as much as 30 percent.
"At this moment, magnesium levels are not routinely measured in daily clinical practice," said lead researcher Dr. Brenda Kieboom, of Erasmus University Medical Center in Rotterdam. "If our study results are replicated, magnesium levels could be used to screen for dementia, especially in people at risk for low magnesium levels."
But she cautioned that "we cannot prove that low or high magnesium causes dementia on the basis of our data. For that, we need studies to see if supplements will reduce the risk."
Kieboom said she also wants to study whether low magnesium levels also associate with a decline in mental function over time.
"Mental function can be seen as a precursor stage of dementia, and if we find similar associations with dementia this will support our theory for a causal association," she said.
"We already found that proton pump inhibitors [acid reflux drugs such as Nexium and Prilosec] are associated with a higher risk for abnormally low magnesium levels, but we continue looking into other drugs," she said.
Those at risk for low levels of magnesium include people who use proton pump inhibitors or diuretics, or people who have a diet low in magnesium, Kieboom said.
The report was published online Sept. 20 in the journal Neurology.
For the study, Kieboom and colleagues collected data on 9,569 people, average age 65, who took part in the Rotterdam Study and who didn't have dementia. Participants had their blood levels of magnesium tested.
Over an average of eight years of follow-up, 823 participants developed dementia. Of those, 662 were diagnosed with Alzheimer's disease.
The researchers divided the participants into five groups based on their magnesium levels.
Those with the highest and the lowest levels of magnesium had an increased risk of dementia, compared with those in the middle groups, the researchers found.
Of the nearly 1,800 people in the low magnesium group, 160 developed dementia, as did nearly 180 in the high magnesium group.
Among the nearly 1,400 whose magnesium levels fell in between the highest and lowest levels, 102 developed dementia.
The findings held even after the researchers took into account other factors that could affect the risk for dementia. These included weight, smoking, alcohol use and kidney function.
Kieboom said that the study results have limitations, including that magnesium levels were measured only once, so they could have changed, and magnesium levels in the blood do not always show the total level of magnesium in the body.
One U.S. expert expressed caution over the findings.
"In general, I would worry most about low magnesium in the malnourished, for example, those suffering from alcoholism or starvation, and not so much in the general well-nourished population," said Dr. Sam Gandy. He's director of the Center for Cognitive Health at Mount Sinai Hospital in New York City.
Gandy, however, isn't convinced by this study alone that magnesium levels boost the risk for dementia.
"I am willing to be persuaded otherwise if several independent studies turn up magnesium disturbances related to dementia diagnoses," he said.
"But as someone who lived through the 1970s 'Throw away your pots and pans and antiperspirants' purge [from the belief that aluminum is linked to Alzheimer's], I would like to see more and larger independent studies before getting married to the idea," Gandy said.