Could Mercury Play a Role in the Development of Alzheimer’s?

Aluminum is one of a number of environmental factors that have been suggested as possible contributory causes of Alzheimer's disease.  The idea was first mooted in the 1960s, but, despite some circumstantial evidence of an association, there is no proof of a role for aluminum exposure as a causative factor in Alzheimer’s, though this is a difficult task - it has proved to be difficult to design appropriate studies to resolve this problem one way or another.

Now a review of available literature on a possible role for mercury in causing Alzheimer’s has been published in the Journal of Alzheimer’s Disease.  Starting from the premise that Alzheimer’s might be in part caused or exacerbated by inorganic mercury, German researchers scrutinized 1,041 references in medical publications, and found 106 articles that met established criteria.  Most of the studies were case-control or comparative cohort studies.

In 40 studies that tested memory in individuals exposed to inorganic mercury, 32 reported significant memory defects.  Some autopsy studies also revealed increased mercury levels in the brains of Alzheimer patients.  However, measurement of mercury levels in blood and other body tissues were inconsistent.  Animal experiments show that administration of inorganic mercury produces pathologic changes that are ‘similar to those seen in Alzheimer’s disease’.

The authors of the review conclude that the evidence for a role of inorganic mercury in Alzheimer’s is ‘strongly suggestive’, but direct evidence is lacking.  This sounds very much like the situation with aluminum 10-20 years ago.  However, inorganic mercury is recognized as a toxic agent, with levels in fish and other foods carefully checked, so there is no need to panic.  A possible role of chronic mercury exposure in Alzheimer’s will be as difficult to establish as that for aluminum has proved to be; by that time, we may have better treatments for the disease . . .