long term damage to immune system

Smokers are left with effects on their body’s defence systems for years after kicking the habit, scientists have found.

Scientists at the Institut Pasteur studied 1,000 healthy volunteers aged 20 to 70. While certain factors such as age, sex and genetics are known to have a significant impact on the immune system, the aim of this new study was to identify which other factors had the most influence.

The scientists exposed blood samples taken from people in the study to a wide variety of viruses and bacteria and observed their immune response by measuring levels of secreted cytokines, which are proteins that allow a person’s immune system to mount a defence if germs or other substances enter your body.


The team then determined which of the 136 investigated variables, which included body mass index, smoking, number of hours’ sleep, exercise, childhood illnesses, vaccinations and living environment had the most influence on the immune responses studied.

Three stood out – smoking, body size and latent cytomegalovirus infection (a common, but usually harmless virus). But with smoking, both innate immune mechanisms and some adaptive immune mechanisms were disrupted.

A comparison of responses between smokers and ex-smokers revealed that the inflammatory response returned to normal levels quickly after smoking cessation, while the impact on adaptive immunity persisted for 10 to 15 years.

The study is the first to demonstrate the long-term influence of smoking on immune responses. 

Violaine Saint-André, a bioinformatician in the Institut Pasteur’s Translational Immunology Unit and first author of the study said: “This is a major discovery elucidating the impact of smoking on healthy individuals’ immunity and also, by comparison, on the immunity of individuals suffering from various diseases.”

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Catherine Early is a freelance environmental journalist and chief reporter for The Ecologist. She tweets at @Cat_Early76.


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