Epidemiologic clues to the causes and routes to prevention of Alzheimer disease

Identification of epidemiologic risk factors serves many purposes. These include 1) identification of high risk groups as potential targets for interventions; 2) identification of the candidate interventions (when the risk factor is susceptible to modification); and 3) suggestion of previously unsuspected causal mechanisms (when the risk relationship is unexpected and not readily explained by current causal theories). Two possible risk relationships will be discussed - one now well known and the other novel - that may provide a means of reducing the risk of Alzheimer's disease (AD). I will also suggest a causal theory that encompasses these epidemiologic observations and other recent data.