Editor,—It has regularly been noted that familial cases of Alzheimer's disease (AD) tend to be of relatively early onset. This implies that there must be at least one further aetiological class, comprising sporadic cases that share some common exposure, and that tend to develop later in life than the familial cases. It can now be reported that cases of AD attributable to residence in areas where the public water supply has a relatively high content of aluminum do constitute such a class.

The largest data set so far studied in relation to waterborne aluminum comprises records of 2258 age …