Whether mercury plays any role in the development of Alzheimer's disease is unclear.  It appears that it may play a very minor role at most.

Mercury Vapor Damages Rats: Rats exposed 4 hours/day to mercury vapor similar to humans with many fillings developed lesions similar to AD. The authors conclude that mercury fillings can inhibit microtubular polymerization necessary for proper development. U Kentucky, Neurotox ’97;18:315

Mercury: Increases Blood Mercury (Hg): This study found that blood mercury is twice as high in AD patients, three times as high in early onset AD patients, but is unrelated to dental status. The controls in the study were one group of psychiatric depressive patients and one group of medical patients without psychiatric difficulties. Hock, U Basel, J Neural Trans ’98;105:59

Mercury: No Increase Blood Mercury: A study of nursing home patients found no difference in plasma mercury or the mercury:selenium ratio in AD patients vs. other patients. Fung, J Toxicol Clin Toxicol ’95;33:243-7

Mercury: No Difference in Mercury Levels in AD or MS: Fung of the University of Nebraska in J Toxicol Clin Toxicol ’97:35:49 says that he found no difference in mercury in MS or AD vs. controls.

Mercury: Increased Hair Mercury in Ill in Japan: Regular medical patients had definitely higher average mercury levels in their hair than did healthy controls. Nakagawa, Chiba U, Chemosphere 1/95;30:135

Mercury: No Increase Urine Mercury: Fung of the Dental School at the University of Nebraska found no difference in urinary mercury in nursing home AD patients vs. controls and doubts amalgam plays any role. Gen Dent 1/96;44-74

Mercury in Fish Low Toxic Form: Rather than bound to hydrogen and carbon atoms, it has formed tight bonds with sulphur atoms, which, in principle, should make it far harder for the mercury to be taken up by the human body. This found is much less toxic than methyl mercury. Dr Graham George, Stanford University. Science 8/30/03

Heavy Metals: No Increase in Blood Mercury, Aluminum, Selenium, Cadmium: No increase was found in cerebral spinal fluid. Basum, J Neural Trans Park ‘91

Heavy Metals: No Increase with Mercury, Iron, Zinc, Rubidium in Alzheimer's Pituitary: The author reports that pituitary gland concentrations are a good indicator of environmental exposure. He found no increase in Alzheimer's vs. controls. Selenium detoxifies Mercury. Cornett, U Kentucky, Biol Trace Elem Res 4/98;62:107; Cornett did find increased iron and zinc in another ’98 study noted elsewhere.

Heavy Metals: No Difference in Occupational Background: 170 AD vs. 170 controls showed no difference in occupational exposure to heavy metals, etc. Gun, U Adelaide, Alzheim Dis Assoc Disord 3/97;11:21-7