Research shows long-term damage from smoking to the immune system of former smokers
Paris (AFP) – According to two scientific studies, the harmful effects of tobacco are long-lasting even for those who quit smoking, and above all, the immune system appears to be much more damaged than previously thought.
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“Smoking permanently alters the adaptive system,” says a study published this Wednesday in the journal Nature about the harm caused by smoking, which kills about 8 million people a year worldwide, according to the World Health Organization (WHO).
The study highlights a factor that has been ignored until now: the adaptive immune system created by infections remains damaged for years in those who quit smoking.
These findings are based on a sample of one thousand people. They were selected more than ten years ago as part of a project at the Pasteur Institute in Paris, and their immunity was regularly examined using various tests, in particular blood.
This type of design, called a cohort, is very reliable for assessing how different factors affect health and metabolism over time.
According to researchers led by biologist Violaine Saint-André, in this case, it is smoking that stands out for its influence more than other factors, such as sleep time or the degree of physical activity.
This is not entirely new. It was known that smoking affects the “innate” immunity inherent in everyone, exacerbating inflammatory reactions.
The study confirms this by testing that this effect disappears immediately after tobacco use is stopped. But, and this is good news, with acquired immunity the situation is different.
Some people experience this for years or even decades after quitting, although the sample is too small and the responses too variable to determine an exact average duration.
Effects that disappear
The researchers went further and showed that these disturbances are associated with an “epigenetic” effect. People’s DNA remains the same, but exposure to tobacco affects how certain genes are actually expressed.
This does not mean that quitting smoking is useless. These effects disappear over time. But “to maintain long-term immunity, it is better to never start smoking,” Saint-André emphasized at a press conference.
This study, based on biological data, cannot say what the health consequences of these immune changes are. According to the authors, this may affect the risk of infections, cancer or autoimmune diseases.
But at the moment this is just a hypothesis.
Another study, published last week, aims to pinpoint the extent to which health risks actually persist after smoking cessation.
Published in NEJM Evidence, it is based on data covering approximately 1.5 million people in Canada, the US, Norway and the UK.
The researchers compared mortality rates between several groups: active smokers, people who had never smoked, and older smokers. In the latter case, it takes time for the risks to completely disappear.
Once you quit smoking, you will have to wait ten years to regain a life expectancy comparable to that of someone who never smoked.
But “benefit appears as early as three years,” the researchers note, with an average of five years of survival restored, halfway to normal life expectancy.
The effect is noticeable regardless of the age at which it stops, even if it is more pronounced in those under 40 years of age.
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