Asthma-Inducing Changes to the Lungs Could Be Reversed by Quitting Smoking

Additionally, lung function, exhaled nitric oxide (NO) levels, and symptom questionnaires were assessed. The researchers found that the smokers with asthma had epithelial changes associated with increased asthma symptoms, such as shortness of breath and phlegm production. Smokers with asthma also had lower forced expiratory volume in one second (FEV1) and alveolar and bronchial NO levels than never-smokers. Smokers also had more goblet cells and mucus-positive epithelium, increased epithelial thickness, and a higher proliferation rate of intact and basal epithelium than ex-smokers and never-smokers, as well as higher numbers of mast cells and lower numbers of eosinophils than never-smokers. Ex-smokers, however, had similar goblet cell numbers, and mucus-positive epithelium, epithelial thickness, epithelial proliferation rate, and mast cell numbers as never-smokers.

To determine the role of exposure length on asthmatic lungs, the scientists divided the ex-smokers into two groups: those with fewer than the median 3.4 pack-year exposure and those with more than 3.4 pack-years. Interestingly, while they expected to find evidence of a dose-response effect between smoking and epithelial remodeling, no such association was apparent between the number of pack-years or duration of smoking cessation and epithelial remodeling. The researchers concluded, therefore that the smoke-induced changes can be reversed by smoking cessation. The study was published in the December 15, 2009 issue of the Journal of Respiratory and Critical Care Medicine.

"The amount of smoke exposure in the past does not influence our outcome measures,” said lead author Martine Broekema, Ph.D., of the department of pathology. "This study shows again how important smoking cessation is for pulmonary health, and this appears to be especially true for asthmatic patients. The good news is that quitting appears to have a measurable benefit in these individuals.”

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