The effect of smoking on the severity, and mechanisms of acute exacerbations of chronic obstructive pulmonary disease (COPD)

COPD (Chronic Obstructive Pulmonary Disease) worldwide has a prevalence of10% in men and 8.5% in women. Exacerbations of COPD account forapproximately 10% of all acute medical admissions. Projected prevalencefigures suggest that by 2020 COPD will be the third leading cause of mortalityworldwide thus imposing a significant burden on healthcare resources in thefuture. Acute exacerbations are not only responsible for a decline in thepatient’s quality of life, but have a major socioeconomic impact. Following apilot study that showed current smokers recover lung function much moreslowly from their exacerbation than ex smokers, I initiated a properly poweredprospective study to investigate the difference between the two groups.A total of 58 patients admitted with acute infectious exacerbations of COPDwere recruited to the study to determine the effect of smoking status on theirexacerbation. Throughout the admission lung function was measured. Sputumwas cultured for bacteria, and PCR used to detect viral infection. Blood andsputum cells were analyzed by flow cytometry. Serum was collected for CRPlevels.Ex-smokers recovered significantly more quickly than current smokers in allspirometric parameters (P<0.01), and were discharged sooner (mean 3.08 vs5.59 days, P<0.001). Sputum culture was positive for more pathogenic bacteriain current smokers, especially H. influenzae, which was associated with asignificantly higher CRP rise (p<0.05) than any other organism. CD8+ T cellspredominated in the sputum of ex-smokers while CD4+ T cells were thedominant cell type in current smokers (p<0.01).Current smoking is a risk factor for more severe exacerbations, delayedrecovery and prolonged hospitalization. This may result from a variety of factorsincluding bacterial, immune mediated responses and systemic inflammation