Aluminum and silica in drinking water and the risk of Alzheimer's disease or cognitive decline: findings from 15-year follow-up of the PAQUID cohort.

The authors examined associations between exposure to aluminum or silica from drinking water and risk of cognitive decline, dementia, and Alzheimer's disease among elderly subjects followed for 15 years (1988-2003). They actively searched for incident cases of dementia among persons aged 65 years or over living in 91 civil drinking-water areas in southern France. Two measures of exposure to aluminum were assessed: geographic exposure and individual exposure, taking into account daily consumption of tap water and bottled water. A total of 1,925 subjects who were free of dementia at baseline and had reliable water assessment data were analyzed. Using random-effects models, the authors found that cognitive decline with time was greater in subjects with a higher daily intake of aluminum from drinking water (>or=0.1 mg/day, P=0.005) or higher geographic exposure to aluminum. Using a Cox model, a high daily intake of aluminum was significantly associated with increased risk of dementia. Conversely, an increase of 10 mg/day in silica intake was associated with a reduced risk of dementia (adjusted relative risk =0.89, P=0.036). However, geographic exposure to aluminum or silica from tap water was not associated with dementia. High consumption of aluminum from drinking water may be a risk factor for Alzheimer's disease.