Tobacco reduces the ability of the immune system to deal with infections from viruses and bacteria, and these harmful effects persist for several years after a person stops smoking, although they decrease over time. This is clear from a study presented this Wednesday in the journal Nature, which suggests that this decrease is in some cases equivalent to that of natural factors such as age, sex or genetic predisposition.
“There is never a good time to start smoking, but if you are a smoker, the best time to stop is now,” Darragh Duffy, researcher at the Pasteur Institute in Paris and coordinator of the study, summarized in a press conference. The effects of tobacco on the immune system worsen as the number of cigarettes consumed per day increases and the years of smoking accumulate. Therefore, “reducing any amount is already something positive in terms of impact,” concludes the author.
The study, which investigated the effects of 136 environmental factors on the immune response of 1,000 healthy people, also points to body mass index (that is, weight) and latent infection with cytomegalovirus, a type of herpes, as factors that They influence the normal functioning of our defenses.
Even so, its effect is much less than that of tobacco. Smoking is the only habit that has consequences on both innate immunity (the body’s first line of defense, which produces a generic response against any infection) and adaptive immunity (a specific immune response against each pathogen).
Adaptive immunity is what is affected in the long term, even once the person has stopped smoking. Tobacco affects this specific response by altering the function of immune cells and causing changes in the smoker’s DNA, resulting in an altered immune response.
“This would indicate that there would be a persistent ‘memory of having smoked’ in the immune system,” González-Fernández, professor of Immunology at the University of Vigo, who did not participate in the study, told Science Media Center Africa. Consequently, the researcher points out, “smoking people can develop other diseases such as cancer, autoimmunity or allergies, or respond abnormally to infections.”
The nature of the study, carried out in healthy people, does not allow us to evaluate which specific diseases can be affected by these changes and which cannot, its authors acknowledge. It does allow, however, to draw a general idea, given that the results show that tobacco provokes a greater inflammatory response: “Smokers may have greater symptoms, more complications and greater chronicity” in the diseases, points out Duffy.
Population studies have repeatedly shown that smoking carries an increased risk of developing cancers and respiratory and cardiovascular diseases. The work presented this Wednesday in Nature lays the foundations for understanding the cellular and molecular processes behind these known epidemiological phenomena.
The research consisted of stimulating blood samples from 1,000 healthy people with agents such as viruses, bacteria and immunological signals. These simulated conditions activate an immune response that scientists have analyzed by measuring the concentration of some cytokines, proteins that coordinate the immune system when the body is threatened by a pathogen, and that are related to specific effects such as inflammation.
On the other hand, at the time of collecting the samples in 2013, each of the participants completed a form in which they were asked for details about their lifestyle, socioeconomic conditions, dietary habits and other similar factors. By crossing both databases, the immune responses and the written ones, the authors have been able to identify the key factors that most affect the immune system.
The next steps involve evaluating how the effects of each environmental factor on the immune response have been able to affect defenses against specific diseases. To do this, the team is recruiting again the volunteers who participated in the project 10 years ago, in order to get them to donate blood again to learn how each of them has experienced the covid-19 pandemic and other diseases with those that could have been found in this period.
Thus, researchers hope to be able to evaluate their results in the real world and observe concrete consequences of smoking on the progression of diseases. For now, the finding provides “a scientific basis to continue promoting a healthy, non-smoking lifestyle,” say Yang Luo and Simon Stent, researchers at the University of Oxford, in an analysis of the work also published in Nature.