Eloy Rodríguez Rodríguez
Head of the Neurology Department at the Marqués de Valdecilla-IDIVAL University Hospital and Associate Professor of Medicine in the Department of Medicine and Psychiatry at the University of Cantabria
This is a systematic review of epidemiological studies that study the association between different drugs and the risk of dementia. Methodologically it seems to be well conducted, and the team is made up of high-level experts in this field.
The main conclusions of the study are that, putting together all the data from the studies analyzed, there are several groups of drugs (antimicrobials, vaccines and anti-inflammatory drugs) that are associated with a lower risk of dementia. These studies are interesting as hypothesis generators, but conclusions should not be drawn from them, because the data, in general, are of low quality (taken from large registries, with very limited clinical information, and not always available) and are subject to finding erroneous relationships (for example, you can associate the use of antidepressants with dementia, but it is really the early stages of dementia that cause more antidepressants to be prescribed; or treatments for cerebrovascular events, when it is the stroke that predisposes to dementia). These points are correctly analyzed in the discussion.
The issue of anti-inflammatory drugs is not new; in fact, there have been directed clinical studies in Alzheimer's disease with some NSAIDs [non-steroidal anti-inflammatory drugs], but without results in the search for a direct relationship. The subject of antimicrobials and vaccines is interesting, since there has been talk for some time about the possible relationship of certain infections, mainly viral, with the etiology of Alzheimer's disease, and the possible protective action of some vaccines by 'training' our brain immune system, either to better fight against these harmful infectious events, or to have a more adequate immune response to other events that may influence the risk of developing the disease.
In short, for me, no significant conclusions of causal/protective relationships can be drawn, but it is interesting to keep the research focus (or increase it) on the role of viral infections and the regulation of immunity/inflammation as factors involved in the origin of Alzheimer's disease and other neurodegenerative diseases.