Editorial: Aluminum – Alzheimer's Smoking Gun?

It is becoming apparent that with an aging population comes an increase in the incidence of mental impairment. In death certificates of people over 75 years of age, the number listed as having dementia has increased by a factor of 20 in the last 15 years (Forbes, Lessard, & Gentleman, 1995, appearing in the present issue). Most of this increase is probably the result of heightened diagnostic sensitivity to clinical dementia, although the demographic shift to an older population likely contributes as well. The importance of uncovering possible links between cognitive impairment and environmental exposure to putative toxins is of particular concern in older people, since normal protective mechanisms preventing toxicity may decline with age. Into the field stride our epidemiological colleagues whose job it is to mine the data base for correlations. In a series of papers in this journal, Forbes et al. examine the relationship between mental function and certain geochemical aspects, notably aluminum, in drinking water. The principal hypothesis under investigation is that aluminum in drinking water is a causal factor for the onset of Alzheimer's disease (AD). The approach they have taken is to use data obtained from the Ontario Longitudinal Study of Aging (LSA), and correlate them with the levels of Al and other pertinent factors in the drinking water to which the individuals in the study were exposed. The first four papers do not assess AD directly in the subjects, but rather the presence or absence of normal cognitive function, based on questionnaires. This is reasonable, given that AD was under-recognized during most of the study, which commenced in 1959 with a cohort of 2000 45 year old men. In the fifth paper, the LSA data are compared with death certificates of individuals in which the underlying cause of death was either AD or presenile dementia. The water quality data were obtained from the Drinking Water Surveillance Program of the Ontario Ministry of the Environment, which started in 1986. Water quality variables examined included drinking water levels of Al, fluoride (F), silica, turbidity, dissolved organic content (DOC), and the pH. Alzheimer's disease was first described in 1907 by the neurologist Alois Alzheimer. Public awareness of AD has increased enormously in the last few years, and it is now recognized as a major public health problem with devastating effects on afflicted individuals and their families. Historically, there are only three confirmed risk factors for AD (Berg, 1994): old age, familial history, and Down's syndrome (virtually all individuals with Down's syndrome develop AD by age 40) (Jorm, 1990). AD is defined as progressive clinical dementia with characteristic abnormalities in brain tissue. Dementia in AD begins subtly with gradual and increasing memory loss, typically