Prevention of Alzheimer disease.

The prevention of Alzheimer disease (AD) remains an important goal because of its high prevalence in our society and its associated costs. Two types of primary prevention trials have been conducted in AD to date: trials in independent cohorts specifically recruited for an AD primary prevention trial and cohorts in other studies randomized to a drug of interest where appropriate cognitive measures can be added. There have been numerous difficulties in conducting primary prevention trials in AD because of the need for a large sample size, long length of poor follow up, and adverse event profile or toxicity of the agents being studied. Many primary prevention trials are ongoing. However, to date, no primary prevention trial has successfully delayed the development of AD. Future primary prevention trials for AD will need to carefully consider issues of safety, tolerability, ability to follow subjects over long periods of time, methods of collecting data, and strategies to enhance recruitment to carry out such trials.