Subjects who were in the lowest and highest quintiles of serum magnesium had a higher risk of developing dementia during the eight-year follow-up period than those in the middle three quintiles.
Among the 9,500 elderly participants in the prospective study, incidence of dementia was 30% higher in the highest and lowest blood magnesium groups, found the research team from Erasmus University, Rotterdam.
"These results need to be confirmed with additional studies, but the results are intriguing," said first author Dr. Brenda Kieboom. "Since the current treatment and prevention options for dementia are limited, we urgently need to identify new risk factors for dementia that could potentially be adjusted. If people could reduce their risk for dementia through diet or supplements, that could be very beneficial."
Should the study findings be confirmed, Kieboom suggested that blood tests could be used as a screening tool for people at risk of dementia.
The study measured the serum magnesium content of subjects, average age 65 who did not have dementia. Participants were followed for eight years on average. During follow-up, 823 people developed dementia, of which 662 were diagnosed with Alzheimer’s disease.
Results were adjusted for adjusted for other variables which might affect magnesium levels and dementia risk such as kidney function, alcohol intake, body mass index and smoking status.
Subjects were divided into quintiles according to their blood levels of magnesium.
The researchers proposed that the findings of increased dementia risk in the lowest and highest quintiles suggested a U-shaped risk curve.
As an observational study, no causality can be determined from the findings. However, the researchers acknowledged two further limitations of the study.
Firstly, magnesium levels were only measured at the start of the study and could have changed in the follow-up period. Secondly, “serum magnesium levels do not necessarily represent total body magnesium. There can still be a magnesium deficiency if serum magnesium levels are normal; therefore, misclassification could have occurred,” wrote the researchers.
Thirdly, “serum magnesium levels in our study were virtually all within the clinically defined normal range; therefore, we are unable to study the effect of hypomagnesaemia,” they added.
Previous research suggests that simple, reliable measures of magnesium status remain lacking. Serum blood levels may only be reliable in identifying severe deficiency, due to the body’s magnesium homeostasis mechanism.
The researchers also acknowledged that the ability of serum magnesium to influence neuronal levels (and thus a possible mechanism for increased dementia risk) is still the subject of debate.
Given these limitations, further work is likely to be necessary to confirm the magnesium-dementia link, using measures which reflect whole-body magnesium status (e.g. ionised magnesium).
Published online ahead of print. DOI: 10.1212/WNL.0000000000004517
“Serum magnesium is associated with the risk of dementia”
Authors: Brenda C.T. Kieboom, M. Arfan Ikram et al