Numerous studies have provided evidence supporting the hypothesis that AD neuropathology develops slowly over time, with the deposition of amyloid in the brain beginning as much as two decades before cognitive impairment. Intervening before pathology begins to develop — primary prevention — would thus require identifying those individual who are clinically normal but at risk of developing the disease. Once the pathological process has begun, secondary prevention measures would aim to prevent or delay the emergence of symptoms in those with preclinical AD or slow progression of symptoms in those with mild cognitive impairment (prodromal AD). As clinical trials for Alzheimer’s disease (AD) have shifted, in large part, towards preclinical and prodromal stages of the disease, the need for novel recruitment, randomization, and retention strategies has emerged see more R.C Petersen et all Jour Prev Alz Dis 2016