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- Special isolation: loneliness dangerously "hits" the brain in hypertension and depression
Special isolation: loneliness dangerously "hits" the brain in hypertension and depression
Scientists have found that social isolation affects the brain and memory in different ways, depending on genetic characteristics and concomitant diseases such as hypertension and depression. Experiments on rats have shown that healthy animals tolerate loneliness relatively easily, while individuals with hypertension and a tendency to depression develop severe memory impairments and inflammation in the brain. The study shows that the reason probably lies in the different reactions of the brain's immune cells to social isolation. Experts interviewed by Izvestia noted that not all data obtained from animal models can be directly transferred to humans. However, a number of described mechanisms are also observed in humans. For more information about the dangers of lack of social contacts— see the Izvestia article.
The harm of loneliness for the nervous system
Researchers from the Institute of Higher Nervous Activity and Neurophysiology of the Russian Academy of Sciences (Moscow) studied how prolonged social isolation affects cognitive functions and brain condition in three lines of laboratory rats. The first group was healthy, the second had normal blood pressure, but was prone to depressive behavior, and the third suffered from congenital hypertension. The results of the work will help to better understand the mechanisms of the negative impact of social isolation, including on humans.
The participant of the study is PhD student Diana Mammadova with the object of the study
Prolonged loneliness affects not only a person's mood and psychological state, but also their physical health, scientists say. However, it can affect people in different ways: according to clinical observations, elderly people, as well as patients with hypertension or depression, are at increased risk. However, it is still unclear why some people tolerate isolation more easily than others. To understand this, experts are studying changes in the behavior and condition of laboratory animals.
According to the WHO, social isolation increases the risk of dementia, cardiovascular diseases and mental disorders. The elderly are particularly vulnerable: about one in four people over the age of 65 feels lonely, as if they live in isolation. The COVID-19 pandemic, during which millions of people were trapped at home, has made this problem particularly acute.
A total of 110 animals participated in the study. The scientists divided them into two equal groups: control and experimental. 55 "control" animals lived in groups, while 55 "experimental" animals were housed alone in small cages for almost four months.
Two weeks before the end of the isolation, all the rats were trained in the Barnes maze. This is a large round table with holes, under one of which is hidden a house where animals can hide from bright light and noise. On the walls of the room where the maze stood, black and white geometric shapes - a square, a triangle and a cross —were fixed, which served as landmarks. After that, the experts checked whether the rats remembered where the shelter was located. To do this, all the holes were covered with plugs and we looked at how much time the animal spends in the area where the house used to be. This is how the authors assessed the spatial memory of rats — the ability to remember the location of the shelter.
Then the house was moved to another part of the maze and the rats were taught to find it again — in a new place. A day after that, a second memory test was performed.: We looked at whether the rats remembered the new location, that is, whether they are able to relearn when conditions change.
After behavioral tests, the researchers examined the structure of nervous tissue in the rat hippocampus, the brain region responsible for memory and spatial orientation, and assessed the activity of genes associated with inflammation.
Astrocytes from the rat hippocampus. Double immunofluorescence labeling for reactive astrocyte marker GFAP (orange) and nuclear dye DAPI (blue)
It turned out that healthy rats endured isolation the best of all: they had no inflammation in the brain, no loss of neurons. However, they still did not form long—term memory - scientists suggest that these animals either simply did not have the motivation to seek shelter, or they used a different strategy.
Rats with congenital hypertension suffered the most: they lost about 10% weight due to isolation, performed the worst on memory tasks, and the activity of genes involved in inflammation increased two to four times in their brains.
"Our data show that the genetic background plays a significant role in how social isolation affects brain aging. We observe a spectrum of vulnerability: from the resistance of rats of one lineage to physiological sensitivity and neuroinflammation in another and structural degradation in a third. In the future, we plan to find out whether these changes can be reversed if the animal is returned to the group, and whether the treatment of neuroinflammation will be effective for different genetic features of the body," said Mikhail Stepanichev, project leader, Doctor of Biological Sciences, leading researcher at the Laboratory of Functional Biochemistry of the Nervous System at the Institute of Higher Nervous Activity and Neurophysiology of the Russian Academy of Sciences.
The biopsychosocial factor of well-being
There is an important confirmation in this study: loneliness is not just an emotional background, but a biopsychosocial factor, Olga Valaeva, head of the NPC Virtual Clinic at the Moscow Institute of Psychoanalysis, told Izvestia. Direct transfer of data obtained in animal experiments to humans is limited, but common mechanisms such as chronic stress, inflammation, and memory impairment are quite likely.
— Our country has accumulated considerable experience in studying the consequences of isolation and loneliness. In the USSR, isolation was studied in practice: mental asthenization (exhaustion), sensory deprivation, and "polar disease" are described in the sign language cameras of Fyodor Gorbov, the founder of Russian space psychology, and at polar stations. Today it is important to distinguish between social isolation (objectively few contacts) and loneliness (subjective feeling of isolation). Many studies of the last decade show that both factors are associated with the loss of several years of life free from chronic diseases. Gender differences are also significant: Mental health suffers more in women when they are alone, and in men when they are socially isolated," the specialist said.
Microglia in the rat brain. Double immunofluorescence labeling for marker microglia protein Iba-1 (green) and nuclear dye DAPI (blue)
From the point of view of efforts aimed at prolonging human life and improving its quality, the study is another contribution to understanding the importance of platforms for social contacts, especially for the elderly and people with disabilities. Such platforms are not limited to leisure: They perform preventive and rehabilitative functions, reducing the risk of loneliness, social isolation and the development of destructive states, Olga Valaeva noted.
Loneliness in humans is largely subjective: a person can suffer from it surrounded by family or live peacefully alone without harm to health, said Marina Chumakova, a leading market expert at NTI Helsnet.
— A rat in a solitary cage has been experiencing a completely different state for almost four months. This is a complete social and sensory deprivation, which is extremely rare in human life. Therefore, the model describes the brain's response to severe chronic stress rather than the usual feeling of loneliness. Nevertheless, the results of the study rhyme well with clinical observations that people with hypertension and depression suffer isolation more severely," said Marina Chumakova.
The results of the study, supported by a grant from the Russian Science Foundation, are published in the journal of Neurochemical Research.
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