• Posted February 15, 2024

Smoking Harms Immune System Years After Quitting

The harms of smoking are many, but new research delivers evidence of another troubling type of damage: Lighting up alters your immune system, leaving you more vulnerable to disease and infections even years after quitting.

“Stop smoking as soon as possible,” study co-author Dr. Violaine Saint-André, a specialist in computational biology at Institut Pasteur in Paris, told CNN. “The key message of our study, especially to the youth, is that there seems to be a significant interest for long-term immunity to never start smoking.”

The findings, published Feb. 14 in the journal Nature, show just how smoking lowers the body's ability to fight off infection, and that it may also raise the risk of autoimmune diseases such as rheumatoid arthritis and lupus.

“The major discovery of our study is that smoking has short-term but also long-term effects on adaptive immunity associated with B-cells and regulatory T-cells and with epigenetic changes,” Saint-André noted.

To arrive at that conclusion, the French scientists looked at blood samples gathered over time from a group of 1,000 healthy people ages 20 to 69.

The researchers wanted to see how numerous variables, including lifestyle, socioeconomic status, eating habits, age, sex and genetics, affected immune response. During the study, they exposed the blood samples to common germs like E. coli bacteria and the flu virus while also measuring immune response.

What did they discover?

Smoking, body-mass index and a latent infection caused by the herpes virus had the most impact on the immune system, with smoking showing the greatest effect of all.

Even when smokers in the study quit, their immune response didn't fully recover for years, study co-author Dr. Darragh Duffy, who leads the Translational Immunology unit at the Institut Pasteur, told CNN.

“The good news is, it does begin to reset,” he said. “It's never a good time to start smoking, but if you're a smoker, the best time to stop is now.”

The study also found that the more people smoked, the more it altered their immune response.

Smoking seemed to have long-term effects on the immune system's two main fronts of defense: the innate response and the adaptive response. The effect on the innate response quickly went away when someone stopped smoking, but the effect on the adaptive response persisted even after quitting.

The innate immune response is the general and immediate way you fight germs. When the body determines the innate response isn't enough, the adaptive immune system moves into action. Composed of antibodies, B-cells and T-cells, the adaptive immune system can remember a threat and better target threats it's seen before.

Dr. Albert Rizzo, chief medical officer of the American Medical Association, told CNN the findings seem to explain why even smokers who have quit can still develop conditions like chronic obstructive pulmonary disease (COPD).

“This study is helpful since it tells us what we've always thought, but now starts to explain the why,” Rizzo said.

More information

The U.S. Centers for Disease Control and Prevention has more on the harms of smoking.

SOURCE: Nature, Feb. 14, 2024; CNN