Aluminum, silica in water affect Alzheimer's risk

NEW YORK (Reuters Health) - Higher levels of aluminum in drinking water appear to increase people's risk of developing Alzheimer's disease, whereas higher levels of silica appear to decrease the risk, according to French investigators.

"Alzheimer's disease is a multifactorial disease, and aluminum concentrations in drinking water may have an effect on cognitive decline and Alzheimer's disease," Dr. Virginie Rondeau told Reuters Health.

The results of some studies suggest that silica reduces the oral absorption of aluminum or increases the excretion of this metal.

Rondeau, at the Institut National de la Sante et de la Recherche Medicale in Bordeaux, and her colleagues examined associations between exposure to aluminum or silica from drinking water and the risk of cognitive decline, dementia, and Alzheimer's disease among elderly subjects followed for 15 years.

Daily aluminum intake of at least 0.1 milligram was associated with greater cognitive decline during the course of the study, the team reports in the American Journal of Epidemiology.

Subjects with a high daily aluminum intake had a 2.26-fold increased risk of dementia, the researchers note. On the other hand, for every 10 milligram-per-day intake of silica, the odds of developing dementia dropped by 11 percent.

"Further studies are needed to settle the debate over the link between aluminum or silica in drinking water and neurologic disorders and cognitive impairment," the investigators conclude.

SOURCE: American Journal of Epidemiology, February 15, 2009.