The development of disease concepts for conditions such as Alzheimer's disease (AD) is an ongoing social process that evolves over time. The biomedical paradigm about AD that has informed our culture's understanding of brain aging for the past several decades is currently undergoing a major and timely renovation in the early 21st century. This evolution is reflected in new guidelines issued by the National Institute on Aging and Alzheimer's Association (NIA/AA) for the diagnosis of AD and related conditions that aim at helping researchers identify and eventually treat AD in its presymptomatic stages. The purpose of this article is to offer the scientific, clinical, and ethics communities a critical analysis of the implications of proposed guidelines and prompt deeper reflection about the lessons learned from these new efforts both in terms of their actual content and the cultural context in which they were issued and will be used. From a social-constructivist perspective, we explore the gradual 100-year evolution of AD and summarize the proposed NIA/AA guidelines within this historical context, enumerating what we see as their main benefits and limitations. We then consider the potential implications of these guidelines in the clinical setting, and explore shifts in our cultural paradigm about brain aging that might be engendered by the logic of the guidelines.