Prevention trials in Alzheimer disease: one step forward?

Finding strategies that prevent or delay the onset of dementia in Alzheimer disease (AD) will be a challenge for the years to come. Prevention trials in AD pose several unresolved questions, including methodologic, scientific, medical, regulatory, and ethical issues. A critical concern is the benefit and relative risk of giving a treatment to non-demented patients or to asymptomatic subjects. Some trials are under way and will perhaps move the field of prevention of dementia one big step forward.