SILICA AND ALUMINUM IN DRINKING-WATER AND COGNITIVE IMPAIRMENT IN THEELDERLY

We studied the relation between silica and aluminum levels in drinking water and the risk of cognitive impairment using data from a populati on-based survey of 3,777 French subjects age 65 years and older. We al so studied the effect of pH and the concentrations of calcium, magnesi um, fluorine, zinc, copper, and iron. We used a mixed effects logistic regression adjusting for age, sex, educational level, and occupation of the subjects. We confirmed the inverse relation previously found be tween calcium level and cognitive impairment. We found no important as sociation between cognitive impairment and fluorine, magnesium, iron, copper, or:inc. The association between cognitive impairment and alumi num depended on the pH and the concentration of silica: high levels of aluminum appeared to have a deleterious effect when the silica concen tration was low, but there was a protective effect when the pH and the silica level were high. The threshold for an aluminum effect, however , was very low (3.5 mu g per liter) and did not support the hypothesis of a deleterious effect for only high levels of aluminum.