The health benefits of smoking cessation.

Smoking is the main risk factor in the development of chronic obstructive pulmonary disease (COPD), and smoking cessation is the only effective treatment for avoiding or reducing the progression of this disease. Despite the fact that smoking cessation is a very important health issue, information about the underlying mechanisms of the effects of smoking cessation on the lungs is surprisingly scarce. It is likely that the reversibility of smoke-induced changes differs between smokers without chronic symptoms, smokers with nonobstructive chronic bronchitis and smokers with COPD. This review describes how these three groups differ regarding the effects of smoking cessation on respiratory symptoms, lung function (forced expiratory volume in one second), airway hyperresponsiveness, and pathological and inflammatory changes in the lung. Smoking cessation clearly improves respiratory symptoms and bronchial hyperresponsiveness, and prevents excessive decline in lung function in all three groups. Data from well-designed studies are lacking regarding the effects on inflammation and remodelling, and the few available studies show contradictory results. In chronic obstructive pulmonary disease, a few histopathological studies suggest that airway inflammation persists in exsmokers. Nevertheless, many studies have shown that smoking cessation improves the accelerated decline in forced expiratory volume in one second, which strongly indicates that important inflammatory and/or remodelling processes are positively affected.

https://erj.ersjournals.com/content/erj/23/3/464.full.pdf

The impact of smoking cessation on respiratory symptoms, lung function, airway hyperresponsiveness and inflammation

The Lung Health Study is a randomized clinical trial designed to determine whether a smoking intervention program and prescription of an inhaled bronchodilator can reduce the annual rate of decline of FEV1 (FEV1 slope) in cigarette smokers with mild to moderate airflow limitation. During the recruitment period, spirometry measurements were obtained during three screening visits from 5,887 cigarette smokers 35 to 60 yr of age. To improve the statistical power of the study to detect significant differences in the FEV1 slopes among study groups, the spirometry testing protocol carefully controls for multiple factors that are known to increase intraindividual variability of FEV1 and FVC results. These factors include participant preparation, maneuver acceptability and reproducibility, technician training and performance monitoring, equipment design and calibration, and result processing. The objective of this report is to describe the success of the spirometry quality control program in minimizing the short-term intraindividual FEV1 variability. The mean difference between the FEV1 values obtained at the second and third screening visits (mean 25 days apart) was +5.7 ml in women and -14.7 ml in men, with a mean intraindividual variability of 119 ml in women and 162 ml in men, with a coefficient of variation of 5.8% for both. During only 2.1% of the test sessions were participants unable to produce three acceptable FVC maneuvers with the two best FEV1 values matching within 5% or 100 ml. Institution of site visits and technician performance monitoring was associated with improved test session quality grades and maintenance of high quality grades thereafter.

Spirometry in the Lung Health Study. 1. Methods and quality control.

The authors investigated the association between changes in smoking habits and mortality by pooling data from three large cohort studies conducted in Copenhagen, Denmark. The study included a total of 19,732 persons who had been examined between 1967 and 1988, with reexaminations at 5- to 10-year intervals and a mean follow-up of 15.5 years. Date of death and cause of death were obtained by record linkage with nationwide registers. By means of Cox proportional hazards models, heavy smokers (>or=15 cigarettes/day) who reduced their daily tobacco intake by at least 50% without quitting between the first two examinations and participants who quit smoking were compared with persons who continued to smoke heavily. After exclusion of deaths occurring in the first 2 years of follow-up, the authors found the following adjusted hazard ratios for subjects who reduced their smoking: for cardiovascular diseases, hazard ratio (HR) = 1.01 (95% confidence interval (CI): 0.76, 1.35); for respiratory diseases, HR = 1.20 (95% CI: 0.70, 2.07); for tobacco-related cancers, HR = 0.91 (95% CI: 0.63, 1.31); and for all-cause mortality, HR = 1.02 (95% CI: 0.89, 1.17). In subjects who stopped smoking, most estimates were significantly lower than the heavy smokers'. These results suggest that smoking reduction is not associated with a decrease in mortality from tobacco-related diseases. The data confirm that smoking cessation reduces mortality risk.

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Smoking Reduction, Smoking Cessation, and Mortality: A 16-year Follow-up of 19,732 Men and Women from the Copenhagen Centre for Prospective Population Studies

Background: Early detection of airflow obstruction is particularly important among young adults because they are more likely to benefit from intervention. Using the forced expiratory volume in 1 s (FEV 1 ) to forced vital capacity (FVC) (FEV 1 /FVC) Methods: To evaluate the characteristics and longitudinal outcomes of subjects misidentified as normal by the fixed ratio with respect to the LLN, 6249 participants (aged 20–44 years) in the European Community Respiratory Health Survey were examined and divided into three groups (absence of airflow obstruction by the LLN and the fixed ratio; presence of airflow obstruction only by the LLN; presence of airflow obstruction by the two criteria) for 1991–1993. LLN equations were obtained from normal non-smoking participants. A set of clinical and functional outcomes was evaluated in 1999–2002. Results: The misidentified subjects were 318 (5.1%); only 45.6% of the subjects with airflow obstruction by the LLN were also identified by the fixed cut-off. At baseline, FEV 1 (107%, 97%, 85%) progressively decreased and bronchial hyperresponsiveness (slope 7.84, 6.32, 5.57) progressively increased across the three groups. During follow-up, misidentified subjects had a significantly higher risk of developing chronic obstructive pulmonary disease and a significantly higher use of health resources (medicines, emergency department visits/hospital admissions) because of breathing problems than subjects without airflow obstruction (p Conclusions: Our findings show the importance of using statistically derived spirometric criteria to identify airflow obstruction.

https://thorax.bmj.com/content/thoraxjnl/early/2008/05/20/thx.2008.095554.full.pdf

Underestimation of airflow obstruction among young adults using FEV1/FVC <70% as a fixed cut-off: a longitudinal evaluation of clinical and functional outcomes

Mary C. Townsend

Papers

Pulmonary function in relation to cigarette smoking and smoking cessation

Conflicting definitions of airways obstruction: Drawing the line between normal and abnormal.

Quality control aspects of pulmonary function testing in the multiple risk factor intervention trial