Fri. Apr 12th, 2024

The body takes time

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Smoking persistently alters adaptive immunity, concludes a study.

Agence France-Presse

When you stop smoking, the counters take a long time to return to zero. Two recent studies demonstrate the lasting effects of smoking on health. Our immunity, in particular, seems even more damaged than expected.

Smoking modifies adaptive immunity in a persistent manner, concludes a published study in the journal Nature (New window) (in English).

This work marks an important breakthrough in understanding the deleterious health effects of smoking which, according to the World Health Organization (WHO), kills some eight million people per year worldwide.

It highlights an element hitherto ignored: adaptive immunity, which is built over time with infections, remains damaged for years after smoking cessation.

These conclusions are based on a sample of one thousand people. These were selected more than ten years ago, as part of a project carried out by the Pasteur Institute in Paris, and their immunity was then regularly studied using different tests, particularly blood tests. .

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This type of project, called a cohort project, is very reliable for assessing the number of different factors that influence health and metabolism over time. And, in this case, it is smoking that stands out for its influence, more than other factors such as sleep time or the amount of physical activity, according to researchers recruited by the biologist Violaine Saint-André.

This is not completely new. It was known that smoking harms innate immunity – that which is common to all – by aggravating inflammatory responses.

The study confirms this, finding that this effect disappears immediately after stopping smoking. But, and this is the big news, it is not the same thing for acquired immunity. This remains, for certain individuals, affected for years, even decades, after stopping smoking even if the sample is too small and the reactions too variable to put forward a precise average duration. p>

The researchers went further by showing that these disturbances are linked to an epigenetic effect: 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 useless. These effects eventually subside. But to preserve your long-term immunity, it is surely better never to start smoking, Ms. Saint-André emphasized during a press conference.

This study, which is based on biological examinations, cannot however say what the consequences of these immune variations are for health.

According to the authors , there could be effects on the risk of infections, cancers or autoimmune diseases. But this is, at this stage, a hypothesis.

Another study, published the previous week, attempts to determine to what extent the health risks really persist when you have stopped smoking.

Published in NEJM Evidence (New window), it is based on data on some 1.5 million people in Canada, the United States, Norway and the United Kingdom. Plain.

The researchers compared the mortality rate between several groups: active smokers, people who have never smoked and former smokers.

And, for the latter, the risks take time to fully resolve. Once you have stopped smoking, you have to wait ten years to regain a life expectancy comparable to someone who has not smoked at all.

But, here again, we must avoid concluding that a shutdown is not quickly worth it: benefits are already appearing three years later, note the researchers, including five years of survival regained on average in this group, or half the way towards normal life expectancy.

And the effect is notable, whatever the age at which we stop, even if it is more marked in those under 40.

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