Adults with Down syndrome face an inevitable cognitive challenge: virtually all develop Alzheimer's-like brain changes by age 40, yet the timing of actual dementia varies dramatically. This variability suggests lifestyle factors might influence when and how severely cognitive decline manifests in this population. A comprehensive European consortium review examined nearly 25,000 research articles to map what science knows about lifestyle interventions for cognitive protection in Down syndrome adults. The analysis identified just 44 qualifying studies across exercise, diet, cardiovascular health, social connections, and cognitive stimulation—revealing a stark research gap compared to general population dementia prevention. Most existing studies focused narrowly on exercise interventions, with limited exploration of multimodal approaches that combine multiple lifestyle factors. The findings highlight a critical disconnect: while robust evidence supports lifestyle interventions for typical aging adults, the Down syndrome population remains largely unstudied despite their universal Alzheimer's risk. This research desert is particularly concerning given that Down syndrome adults now live significantly longer due to medical advances, creating an urgent need for evidence-based cognitive protection strategies. The review establishes a foundation for future intervention trials but underscores how little guidance currently exists for the estimated 200,000+ adults with Down syndrome navigating their heightened dementia risk through lifestyle choices.