"I would be cautious about evaluating the results of single studies on the effects of various fine particles on the human brain"

Recently, foreign media reported on the work of a group of researchers at the University of Rhode Island (USA), who allegedly established a link between microplastics and Alzheimer's disease. However, many scientists and medical practitioners reacted cautiously to the sensation. Mikhail Sinkin, MD, Acting Head of the Department of Medical Neurotechnology at Pirogov University Medical Institute, told Izvestia about the real state of affairs with the diagnosis and treatment of Alzheimer's disease and the connection of this disease with the influence of external factors.

— What are the main mechanisms of the genesis of Alzheimer's disease and related diseases recognized by science today?

— Today, it is believed that the development of Alzheimer's disease and other neurodegenerative diseases is a consequence of impaired protein synthesis and generally normal cell functioning. There is no strictly scientific evidence that any external influences can lead to the development of Alzheimer's disease and dementia.

Another question is to what extent the development of such diseases is related to external factors. I repeat, it is impossible to say unequivocally that there is a connection between such factors and Alzheimer's disease. The entire scientific community now recognizes that these are purely internal causes, and it is difficult to say what they are related to: it has not yet been fully studied. There may be genetic factors and other disorders, but it is impossible to identify any external factors, physical effects.: they cannot lead to the development of neurodegenerative diseases.

— To what extent is the growth of such diseases related to external factors?

— The growth of neurocognitive diseases is primarily associated with an improvement in the quality of diagnosis, with a deepening of knowledge about the features of these diseases, with the training of doctors and the development of new neuroimaging technologies, in particular magnetic resonance imaging, etc. Most likely, such patients had simply not been seen before and did not understand what was wrong with them. Previously, an old term was used, senile dementia. Now the conditions are strictly classified, which creates the feeling that the incidence has increased. In fact, the very evidence of an increase in the incidence requires large population-based studies.

— In a recent meta-analysis by researchers from Canada and the United States, solid fine microparticles associated with the combustion of organic fuels and forest fires were identified as the first of the most noticeable factors influencing the development of neurocognitive disorders. Is it possible to estimate the contribution of microplastics to this effect (weight factor) as a derivative of its quantity among other solid particles?

— I would be cautious about evaluating the results of single studies on the effects of various fine particles on the human brain. The journal in which he is published is generally devoted to the effects of the external environment, and such research has been conducted for quite a long time, and very often it is overgrown with various speculative arguments.

First of all, you need to understand that plastic has been used by mankind for a very long time. I would draw an analogy with the use of mobile phones — until recently, everyone was afraid that they caused brain tumors, and there were also some isolated publications in scientific journals. No one is even discussing it now. We must remember that there is so much plastic that if it really somehow harmed the brain, then our people would not live longer, as we actually see, but would become massively ill with dementia. So I would be very cautious about this kind of article. I repeat, if this were a mass phenomenon, there would be many articles, not one where they found some kind of correlation. You might be surprised, but there is even a special website for comic correlations, where you can use statistical methods to find a connection between anything and anything.

— Do polymer particles really have a higher ability to penetrate the blood-brain barrier compared to other particles of similar size?

— The question of whether polymer particles really have a higher ability to penetrate the blood-brain barrier requires a separate study. I have not seen such publications, and it is completely unclear why they should have a higher penetration ability compared to others.

So far, it looks like another urban horror story — I repeat that plastic has been used for more than 60 years in civilization, there is a huge amount of it, but we doctors do not see that there is an explosive increase in the number of people with dementia. On the contrary, the use of modern drugs that lower blood pressure, cholesterol, and blood sugar levels has an effect on reducing the risk of dementia. Moreover, there is a feeling that there are fewer such patients and often people live to a ripe old age with fully preserved cognitive health. Despite the widespread use of plastic by the population.

— Is it possible to assess which is primary: do particles accumulated in the brain lead to the development of pathological conditions or do pathological conditions contribute to the accumulation of foreign particles?

— There is no evidence that any solid particles accumulate in the brain at all, and even more so that they lead to any pathological conditions. There are diseases that have long been described, associated with, for example, the appearance of calcium salts in the nuclei of the brain, but this is in no way related to either microplastics or solid particles that affect the brain and lead to any problems. So I urge you not to be afraid of microplastics.

You should monitor your cognitive health in a completely different way: early detection and treatment of risk factors, diabetes, thyroid diseases, other endocrine disorders, hypertension, and so on.