The National Institutes of Health- and many other organizations and individuals worldwide- are interested in the state of the science of preventing Alzheimer's disease, mild cognitive impairment, and age-related cognitive decline. To develop a better understanding of current scientific evidence, implications for public health messaging, and future research needs, the National Institute on Aging (NIA) turned to the Agency for Healthcare Research and Quality (AHRQ) and the National Academies of Sciences, Engineering, and Medicine (The Academies). NIA asked AHRQ to commission and oversee a systematic review of the evidence on interventions to decrease the risk of developing clinical Alzheimer's-type dementia and mild cognitive impairment, and delay or slow age-related cognitive decline. NIA also asked the Academies to convene an expert committee to provide input into the design of the AHRQ systematic review and, later, use the review to make recommendations that inform public health messaging on preventative interventions and recommendations for future research. This letter report summarizes the committee's input into the design of the AHRQ systematic review. The committee's full report, including its recommendations, is expected in 2017.