E-Cigarette Vapor Causes Airway Inflammation in Just 1-3 Years, Study

E-Cigarette Vapor Triggers Airway Inflammation Within Just 1–3 Years, Karolinska Study Finds

People who had used e-cigarettes for only one to three years already showed elevated inflammatory markers in both their airways and bloodstream — changes comparable to, and in some measures exceeding, those seen in cigarette smokers. That is the central finding of a 2025 clinical study from Karolinska Institutet published in Respiratory Research, which compared 20 e-cigarette users, 20 cigarette smokers, 20 dual users, and 22 healthy non-smokers.

How the Study Measured Breathing, Immune Function, and Inflammation

Researchers led by Shanzina Islam Sompa and Lena Palmberg at Karolinska Institutet’s Integrative Toxicology unit recruited 82 participants matched by age and body mass index, all with normal baseline lung function and no allergies. This design matters: it isolates the biological effects of inhaled products from the confounders of existing disease.

Each participant underwent a battery of measurements. Exhaled fractional nitric oxide (FeNO) quantifies airway inflammation — nitric oxide is produced by inflamed airway lining cells. Bronchial responsiveness testing measured how easily the airways constrict under provocation. Sputum and blood samples were analyzed for reactive oxygen species, expression of toll-like receptors (TLR2 and TLR4) on immune cells, and cytokine-producing T cells.

Cytokines, TLR Receptors, and ROS: The Inflammatory Signature of Vaping

Three findings deserve close attention, because they reveal mechanism rather than just correlation.

Reactive oxygen species. E-cigarette users and dual users showed elevated ROS in both blood (p = 0.005 and p = 0.003) and sputum (both p = 0.04). ROS are unstable oxygen molecules that damage cell membranes, proteins, and DNA. Vaporized solvents like propylene glycol and glycerol, plus heated flavoring compounds, generate oxidative byproducts the lungs must neutralize.

Toll-like receptors. TLR2 rose on blood granulocytes across all exposed groups (p = 0.001). In sputum, e-cigarette users showed elevated TLR2 (p = 0.04) and TLR4 (p = 0.03), and dual users showed even stronger increases (p < 0.0001 and p = 0.004). TLRs are the innate immune system's early-warning sensors — they recognize microbial patterns and danger signals and trigger cascades of inflammatory cytokines. Their upregulation means the immune system is being chronically primed, which relates to how breathing and immune defense interact in lung disease.

Cytokine-producing T cells. The proportion of T cells producing IL-13 (p = 0.0001 in e-cigarette users) and IFNγ (p < 0.0001) rose sharply. IL-13 drives allergic-type airway inflammation — the same pathway central to asthma. IFNγ marks antiviral-type Th1 activation. Elevated FeNO in vapers (14 ppb, p = 0.04) fits this picture, since IL-13 induces nitric oxide production in airway epithelium. Cigarette smokers, in contrast, showed lower FeNO (9 ppb), reflecting combustion byproducts’ different effect on nitric oxide chemistry.

What These Immune Changes Mean for Respiratory Health

Bronchial responsiveness increased in both e-cigarette users and cigarette smokers (1.9 mg vs. 2.9 mg in non-smokers, p = 0.01) — their airways constricted at roughly two-thirds the provocation dose needed in never-smokers. Inflammation without symptoms is not benign; it is the substrate from which chronic respiratory disease develops. The results echo what we covered on how breathing patterns influence immune cell health and how slow, nasal breathing can lower inflammation — but the reverse also holds: inhaling vaporized chemicals raises it.

Dual users fared worst in several measures, supporting the concern that combining products multiplies rather than averages exposure risks. A limitation worth noting: with 20 participants per group, this cross-sectional study detects associations, not causal progression, and it cannot rule out selection differences between groups.

Practical Applications: Protecting Airway Immunity

• If you vape to quit smoking, treat e-cigarettes as a short-term bridge, not a permanent replacement — inflammatory changes appeared within 1–3 years in this study.
• Avoid dual use. Combined vaping and smoking produced the most pronounced immune activation.
• Support antioxidant defenses through diet — fruits and vegetables rich in vitamin C, flavonoids, and polyphenols help counter oxidative stress from inhaled chemicals.
• Consider anti-inflammatory breathing practices. Evidence suggests slow breathing and techniques like paced breathing can reduce inflammatory signaling, though they cannot substitute for removing the exposure itself.
• Ask your physician about FeNO testing if you vape and experience cough, wheeze, or shortness of breath — inflammation can precede measurable lung function decline.

Frequently Asked Questions

Is vaping safer than smoking for inflammation?

This study found e-cigarette users had equal or greater inflammatory and immune activation than cigarette smokers in several measures, including ROS and T cell cytokines — though the groups differed in specific markers like FeNO.

How quickly does vaping cause inflammation in the airways?

Remarkably fast. Participants had used e-cigarettes for only 1 to 3 years and already showed elevated airway inflammation, oxidative stress, and primed innate immunity despite normal lung function tests.

What are IL-13 and IFNγ, and why do they matter?

IL-13 is a cytokine that drives allergic-type airway inflammation (as in asthma), while IFNγ activates antiviral immune responses. Elevated levels of both indicate the immune system is being persistently switched on by vapor exposure.

Does quitting vaping reverse these immune changes?

The study did not follow participants over time, so reversal could not be tested. However, since lung function was still normal, early cessation may plausibly prevent progression before permanent damage sets in.

Conclusion

Breathing is the frontline of immune defense, and this Karolinska study shows e-cigarette vapor activates it on multiple fronts: oxidative stress, innate immune receptors, and allergy- and antiviral-linked cytokines — within just a few years and before symptoms appear. The evidence argues against long-term vaping as a harmless habit, especially when combined with cigarettes.

Sources:
https://pubmed.ncbi.nlm.nih.gov/40468357/
https://pubmed.ncbi.nlm.nih.gov/40388789/
https://pubmed.ncbi.nlm.nih.gov/40330457/
https://pubmed.ncbi.nlm.nih.gov/40260245/
https://pubmed.ncbi.nlm.nih.gov/40142058/