Advanced biomarker detection now enables identification of Alzheimer pathology decades before cognitive symptoms appear, creating an unprecedented opportunity to deploy disease-modifying therapies as preventive interventions. Anti-amyloid agents like aducanumab and lecanemab, alongside emerging anti-tau compounds, are being repositioned from treatment to prevention protocols targeting high-risk individuals with detectable brain amyloid but intact cognition. This paradigm shift from reactive treatment to proactive prevention represents a fundamental evolution in Alzheimer therapeutic strategy, potentially transforming the condition from an inevitable cognitive decline into a manageable chronic disease. The preventive approach faces substantial implementation challenges including the need for population-scale biomarker screening, managing treatment risks in asymptomatic individuals, and designing trials that may require decades of follow-up. However, mathematical modeling suggests even modest delays in disease onset could dramatically reduce dementia prevalence globally. The success of cardiovascular prevention with statins provides a compelling precedent for widespread pharmacological prevention in neurodegenerative disease, though the complexity of brain pathology and higher treatment risks demand more sophisticated patient selection algorithms.