Researchers, on the other hand, noted that the benefits of stopping tobacco appear after 3 years.
Two recent studies have shown that there are permanent effects of tobacco on the human body even after quitting smoking, as their results concluded that the subsequent health damage to the immune system continues for years after giving up cigarettes.
A study whose results were published in the journal Nature concluded that “smoking modulates adaptive immunity in a continuous manner.”
This research work represents an important advance in understanding the harmful health effects of smoking, which kills nearly 8 million people annually around the world, according to the World Health Organization. The research also highlights a hitherto overlooked element: damage to adaptive immunity, which builds over time with infection and persists years after smoking cessation.
These conclusions are based on a sample of a thousand people who were tested over a period of more than ten years, within a project led by the Pasteur Institute in Paris. After that, their immunity was regularly studied through various tests, especially blood tests.
This type of project, called a group project, is of great importance for evaluating how different factors affect health and metabolism over time.
In this case, it is smoking that highlights its effect more than other factors such as sleep time or degree of physical activity, according to researchers led by biologist Violin Santandre.
But these conclusions are not entirely new. It was known that smoking affects “innate” immunity—that is, that which is common to everyone—by exacerbating inflammatory responses.
The study confirms this, as it found that this effect disappears immediately after stopping smoking. But the most prominent new conclusion is that the same does not apply to acquired immunity.
In some individuals, this type of immunity remains damaged for years, or even decades, after stopping smoking, even if the sample that was tested was very small and the reactions were too variable to determine an accurate average duration.
“Epigenetic” effect
The researchers went further by showing that these disorders are linked to an “epigenetic” influence: people’s DNA, of course, remains the same, but exposure to tobacco affects the way certain genes are expressed in practice.
We should certainly not conclude from this that quitting smoking is of no benefit, as these effects eventually fade away.
But “to maintain your immunity in the long term, it is certainly better not to start smoking at all,” Santandre stressed during a press conference.
However, the study, which relies on biological tests, was unable to determine the health consequences of these immune differences.
According to the study's authors, there may be effects on the risk of infections, cancer, or autoimmune diseases. But at this point, it is still just a hypothesis.
Another study, the results of which were published last week, is trying to determine to what extent health risks actually persist when smoking is stopped.
The study results were published in NEJM Evidence and are based on data relating to about 1.5 million people in Canada, the United States, Norway, and the United Kingdom.
The researchers compared the death rate between several groups that include people who currently smoke, others who have never smoked, and people who have smoked for a long time in one way or another.
For individuals in the latter category, risks take a long time to dissipate completely. Once you stop smoking, you must wait ten years to regain a life expectancy comparable to that of someone who has never smoked.
Wrong conclusion
But it would be wrong to conclude that quitting smoking is not worth the effort. The researchers noted that “the benefits actually appear after three years,” with a five-year recovery in life expectancy among members of this group, which is halfway to a normal life expectancy.
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