By Andrea Hargraves 
“Smoking modifies the adaptive immune system in a continuous manner,” as indicated by the study published by the journal “Nature” on Wednesday about the harms of smoking, which kills about 8 million people annually in the world, according to the World Health Organization. from).
The research highlights a previously overlooked factor: the adaptive immune system, built up by infection, remains damaged for years in those who stop smoking.
The conclusions were drawn from a sample of one thousand people. The participants were selected more than ten years ago, within the framework of a project implemented by the Pasteur Institute in Paris, and their immunity was regularly studied through various tests, especially blood tests.
It's a very powerful type of project to evaluate how different factors affect health and metabolism over time.
In this case, more than other factors, such as sleep time or degree of physical activity, smoking stands out for its effect, as indicated by the researchers led by biologist Violene Saint-André.
The information is not entirely new, as smoking has already been reported to affect “innate” immunity, common to all people, and exacerbate inflammatory responses.
The study confirmed the previous result, as it found that the effect disappears immediately after stopping smoking, but it revealed that the process is not the same for acquired immunity.
For some people, acquired immunity is affected for years, or even decades, after they stop smoking, although the sample size is small and reactions are too variable to give an accurate average duration.
Effects that disappear
The researchers went further to show that these disorders are linked to an “epigenetic” influence. Human DNA remains the same, but exposure to tobacco affects how certain genes are expressed in practice.
This does not mean that quitting smoking is useless: its effects eventually wear off. But “to maintain your immunity in the long term, it is better to never start smoking,” Saint-André stressed in a press conference.
Based on biological evidence, the study cannot determine the health consequences of these immune differences. It likely has effects on the risk of infections, cancer or autoimmune diseases, according to the authors.
But so far, this is just a hypothesis.
Last week, another study sought to determine how much health risks actually persist when you quit smoking.
Published in NEJM Evidence, it was based on data from about 1.5 million people in Canada, the United States, Norway and the United Kingdom.
The researchers compared mortality rates between several groups: active smokers, people who have never smoked, and older smokers – in the latter case, the risks take time to disappear completely.
After stopping smoking, an individual must wait ten years to regain a life expectancy that is comparable to someone who has never smoked.
However, the researchers noted that “benefits actually appear after three years,” with an average of five years of life, halfway to normal life expectancy.
The effect is noticeable regardless of the age at which smoking is stopped, even if it is more pronounced in people under 40 years of age.