Survival time in Alzheimer's disease: An overlooked measure of safety and efficacy of disease-modifying therapies.

It is of vital importance to patients and physicians, as well as administrators and drug regulators, that the treatment for a disease has been shown to be safe and clinically meaningful in long-term use. Recent literature has highlighted 3 major categories of arguments for and against modification of the underlying disease process in Alzheimer's disease (AD): pathophysiology, biomarkers and data from clinical trials. We argue that the Alzheimer's arena is over-reliant on theories of disease modification based solely on brain positron emission tomography (PET) imaging and blood biomarkers of tau and Aβ peptides. Here, we instead focus on a historically-grounded empirical criterion from other fields of medicine to overcome the weak interpretations of short Alzheimer's trials: survival time (ST). Our analysis has identified 3 key points. First, if anti-amyloid therapies are AD-modifying treatments, then we argue that they should increase ST more than the standard "symptomatic" care with memantine and acetylcholinesterase inhibitors. Second, we question memantine and cholinesterase inhibitors being labeled simply as "symptomatic" Alzheimer's drugs since long-term use of them can produce disease modification, that is, increase ST. Third, we make a case for memantine or cholinesterase inhibitors being used as controls in clinical trials with amyloid-lowering and other drugs, and argue against their current under-use in care of Alzheimer's patients.