Scientific truth or false hope? Understanding Alzheimer's disease from an aging perspective

In this paper, we argue that the current official definition for Alzheimer's disease is misleading, since it defines senile dementia (SD), a long-known incurable senile/geriatric condition, as a discrete/curable disease. This overly optimistic definition was incepted in the 1970s amid the public's fear of the upcoming SD crisis and desperate hope for a cure. Scientifically, however, it has overturned Alois Alzheimer's age-based concept for disease classification-the essence of modern Geriatric Medicine and the National Institute of Aging. Thus, the current definition for SD, though socially and politically appealing, would be scientifically flawed. As an authoritative study guideline, it has caused profound and far-reaching confusions in research by misleading attention to the presumptive pathogenic/erroneous factors as drug targets for "silver bullets". Such well-intentioned studies would generate numerous data, but render SD a scientific and logical enigma. In this context we discuss: 1) why and how senile conditions including SD differ from discrete diseases by origin, thus also by study paradigm and intervention strategy; 2) why senile conditions may not be explained by abnormal/pathogenic factors, but logically should be explained by "normal" elements in life, perhaps advanced aging plus risk factors; and 3) why the "amyloid-β toxicity" controversy, a simple scientific issue, has lasted for so long. Finally, we ask: can scientific inquiry preserve its integrity and objectivity under social pressure? It appears that these fundamental questions warrant serious attention if the scientific nature of SD is to be eventually understood.