Smoking can alter your immune system long after you quit, say French scientists...
A large study from the Institut Pasteur, in Paris, has found that cigarettes play havoc with the way the immune system fights off infections as well as making smokers more prone to cancer and other diseases.
“A smoker has a stronger inflammatory response, so they might have more symptomatic disease, more complications, more chronicity because they are going to have a response that is sort of overactive compared to non-smokers,” explains Dr Darragh Duffy, one of the study’s co-authors.
The team studied the effects of 136 environmental factors on the immune responses of 1000 individuals. They found that smoking causes changes in an individual’s epigenetics; these are the molecular tags that attach to your DNA and tell genes when to turn on or off.
Smoking reduces the number of these tags at specific sites in the DNA, the new study shows. The part of the DNA code that are affected are involved in controlling how the immune system communicates with the different arms of its defences, and how the body fights off infection in general.
The researchers identified a strong link between the number of cigarettes smoked and changes in these tags. Heavier smokers, they found, including those who had been smoking for the longest time, showed the greatest tag loss, indicating a potentially greater degree of immune disruption, and a longer recovery period after smoking cessation.
There are two components to the immune system, a rapid response, more generalised "innate" component, as well as a more specialised and targeted "adaptive" response that we generate in response to exposure to specific threats.
Cigarette smoking seems to affect both, although, when a person stops smoking, the innate response can reset itself rapidly but the impact on the adaptive response can take years to return to normal.
There is no difference in the inflammatory response of a non-smoker or a smoker after they quit, indicating that the effect on innate immunity is transient and short-lived. However, there is a significant difference between the amount of genetic tags present in a non-smoker and a smoker long after they have quit. These epigenetic tags are thus shown to be associated with adaptive immunity. While these tags do return to normal over time, the longer you smoke for, the longer it takes for this specialised immunity to recover.
Body weight and viral infections also affect how well the immune system works, but the study nevertheless shows that smoking seems to be the biggest factor in altering the tuning of the adaptive immune response.
The scientists accept there are limitations with their study - including being unable to double check their results and a lack of diversity in the sample. But, overall, their findings suggest it is vital to stop smoking at the earliest opportunity in a bid to promote a much healthier lifestyle and stronger immune system.
“We know smoking is bad in multiple ways. We have added a new layer of understanding of how it can have negative health consequences so the message is still clear, it’s never a good time to start smoking, but if you’re a smoker, the best time to stop is now,” Duffy adds.
