Aerobic training may cool one smoking-linked inflammation marker

Smoking drives systemic inflammation, one of the pathways through which it damages the heart, lungs and blood vessels. Aerobic exercise training is thought to reduce systemic inflammation, but its effects on inflammatory markers specifically in adult tobacco smokers had never been systematically reviewed. If exercise could dampen inflammation in people who smoke, that would matter for a large population carrying elevated cardiovascular and respiratory risk. This review set out to pool the randomised evidence on two of the most studied markers, C-reactive protein and tumour necrosis factor-α.

The authors searched PubMed/Medline, Web of Science, EMBASE and Google Scholar, plus reference lists, for English or Persian randomised controlled trials up to August 2023. From 1641 articles identified, six trials met the predefined inclusion criteria. Four of those evaluated C-reactive protein and two evaluated TNF-α, and the TNF-α trials enrolled only males. Each trial tested aerobic exercise training in adult tobacco smokers, and the marker data were pooled in a meta-analysis.

Aerobic exercise training significantly decreased TNF-α concentrations in male smokers. C-reactive protein told a different story: when the four relevant trials were pooled, the reduction did not reach statistical significance. So the review supports an anti-inflammatory effect of aerobic training in smokers on one marker but not the other. The authors are explicit that these findings rest on a small number of studies, each enrolling exclusively male or exclusively female participants, and that further investigation is necessary to strengthen the statistical case.

Aerobic training's reputation for lowering inflammation comes largely from studies in other populations, and this is a first systematic attempt to test whether it holds in smokers. The mixed answer, movement in TNF-α but not CRP, mirrors a wider pattern in exercise research where different inflammatory markers respond differently. With only six trials available and sex-segregated samples, the evidence base is too thin to say whether women who smoke respond similarly or what training dose matters. Larger mixed-sex trials are the clear next step.

For smokers, or anyone who has recently quit, this is a modest reason to think aerobic exercise may be doing quiet anti-inflammatory work beneath the surface, at least on one measurable marker in men. It is not evidence that exercise offsets the harms of smoking, and the flat C-reactive protein result is a caution against reading too much into any single marker. The honest summary is a promising signal from a small evidence base, awaiting bigger trials.