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The consequences of smoking and excessive alcohol consumption have been known for a long time, and smokers have for some time been portrayed quite strikingly on every box of cigarettes. Fitness studios, on the other hand, like to advertise with lists of various advantages of sport and emphasize how healthy regular exercise is. So it is widely known what is healthy and what is unhealthy. However, two researchers from Jülich have now shown how “unhealthy” it can be to have no or only a few social contacts.

Professor Svenja Caspers from the Jülich Institute for Neurosciences and Medicine and the young scientist Nora Bittner, together with colleagues from Jülich, Düsseldorf, Essen and Basel, analysed the data of 248 women and 301 men aged 55 to 85 in a study. The factors social environment, alcohol and tobacco consumption, as well as physical activity, were included. The researchers used extensive information and data on the life of the test persons from the Jülich 1,000-brain study and the Heinz-Nixdorf-Recall study in Essen as well as magnetic resonance imaging of the brains as a basis.

“For example, whether sport in a group – i.e. in a social context – has a different effect on mental performance and healthy ageing than the lonely forest run.”

“In previous studies, only one of these aspects has generally been examined,” says Prof. Svenja Caspers. “However, our data set allows us to look at all four aspects simultaneously in each individual subject and also to uncover effects that can only be achieved through the interaction of the various factors.”

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Sports, social contacts and alcohol had a direct effect on the brain structure after the results, explains Nora Bittner. “The grey matter in certain regions of the brain, for example, is better preserved in people who live in a busy social environment than in people who have few social contacts. Further studies show that people who are active in sports also show a lower volume loss of the brain in old age than inactive contemporaries. A high alcohol consumption, on the other hand, has a negative effect on the brain structure, i.e. it is associated with brain breakdown and the loss of nerve cells.” The decrease of nerve cells, as well as the decrease of brain volume, are generally responsible for the decrease of mental performance and flexibility in old age.

Different consequences of alcohol and smoking

In contrast to alcohol consumption, smoking affects brain function rather than brain structure, says Nora Bittner. “We found that the so-called functional connectivity, i.e. the targeted cooperation between brain regions, is higher in the resting brain of smokers than in non-smokers,” said Bittner explaining that “we assume that this reduces the cognitive reserve of smokers because the regions in question are already running at full speed in their resting state and thus no performance buffer is available.”

Cognitive reserve is the brain’s ability to activate additional capacities or areas in order to solve problems, for example. However, if these capacities are already used elsewhere, the mental capacity is reduced. “Our research results impressively show that generally valid statements about a healthy lifestyle are also reflected anatomically and functionally in the brain,” stresses Svenja Caspers.

It is not possible to express the difference between the brains of people with “healthy” and “unhealthy” lifestyles in percentages. “Such a clear quantification would, of course, be very interesting and helpful, but it would be impossible to describe this without further clarification. The kind of analysis does not make this possible, according to Caspers. “In our analysis, we tried to search the entire brain for areas that might be modified by lifestyle. This gives a statement in the form that a particular area of the brain is significantly correlated with lifestyle factors across the entire group of people. A direct comparison between people with healthy or unhealthy lifestyles would be a different issue and would require a different kind of analysis.”

Prof. Svenja Caspers ©: Research Centre Jülich / Sascha Kreklau

Genetic predispositions negligible

The team also investigated genetic predispositions associated with increased smoking behavior or alcohol consumption. “Together with our colleagues from genetics, we were able to prove that genetic information obviously plays a secondary role. The actual behavior is therefore more important than the pure predisposition,” emphasizes Nora Bittner.

In addition to the factors of smoking, alcohol and physical activity, the social environment apparently also leaves traces in the brain. “The positive relationship between physical activity and mental performance has been known and well documented for some time. The fact that now an intensive or small social life leaves equally clear traces in the brain opens a multiplicity of new research questions”, says Caspers. “For example, whether sport in a group – i.e. in a social context – has a different effect on mental performance and healthy ageing than the lonely forest run.”

Questions such as the difference between people who have never smoked and former smokers and whether or to what extent the brain “regenerates” when people quit smoking or start exercising were not part of the study, but according to Svenja Caspers they are “incredibly exciting for future analyses”.

The results of the current study were published at the beginning of February in the renowned journal Nature Communications.

Cover photo: Have a negative effect on the brain structure: Alcohol and lack of sporting activity (left) and lack of social interaction (right) ©: Research Centre Jülich, vector illustration from