Smoking and Lung Function of Lung Health Study Participants after 11 Years
Abstract & Commentary
Synopsis: Continuing smokers from the Lung Health Study 1 followed for a period of 11 years demonstrated a greater decline in lung function when compared to sustained quitters.
Source: Anthonisen NR, et al. Am J Respir Crit Care Med. 2002;166: 675-679.
The Lung Health Study 3 (LHS 3) was developed as an extension of the Lung Health Study 1 (LHS 1). The LHS 1 was a randomized, clinical trial of smoking cessation and regular administration of an inhaled bronchodilator (ipratropium bromide) conducted for a period of 5 years. The study was conducted in 5887 middle-aged smokers (35-60 years of age at study entry) who had airway obstruction (FEV1/FVC ratio less than 70%), but who were otherwise healthy. The follow-up rate in LHS 1 was very high, with more than 90% of participants attending each of the 5 annual visits to evaluate pulmonary function, and thus an extension of the LHS 1 was thought to be feasible. The original participants were asked to return to their original clinical centers for reassessment approximately 11 years after their enrollment.
The objective of the LHS 3 was to assess whether differences in pulmonary function and smoking habits persisted between the 2 groups after 1 year and to determine if the profound effect of smoking cessation on lung function decline noted in LHS 1 persisted.
LHS 1 participants who were not deceased were enrolled in the LHS 3. They were asked to return for spirometry and to answer smoking questionnaires. Some participants were visited to obtain data. Smoking issues were addressed through questionnaires, which included the modified American Thoracic Society-Division of Lung Diseases questionnaire and a detailed smoking history. Smoking status was checked by measuring expired carbon monoxide. Results of 10 ppm or higher were considered indicative of smoking.
Spirometry was performed with the same type of spirometer used in the LHS 1. FEV1 and FVC were measured before and after 2 puffs (200 µg) of albuterol from a metered dose inhaler.
Patients continued to be grouped in the same 2 groups as in LHS 1. This consisted of usual care and smoking intervention. The smoking intervention group received smoking cessation counseling. They were also assigned to either active bronchodilator or placebo therapy during the original LHS 1. Smoking outcome was categorized as sustained quitter, intermittent quitter, or continuing smoker.
There were 4517 participants enrolled for LHS 3. Enrollment ranged from 77.1% to 91.0% at the various clinical centers. Younger, male patients who still continued to smoke were more likely to refuse enrollment in LHS 3. Nonenrollees were also less likely to be married. There were no significant differences in employment rate, alcohol consumption, and years of education between groups.
At LHS 3 enrollment, 16.7% of the participants were sustained quitters, 57.4% were intermittent quitters, and 25.9% were continuing smokers. There were major differences between treatment groups in smoking habit with 21.9% of the smoking intervention group being sustained quitters compared with 6.0% of the usual care group, and 23.4% of the smoking intervention group being continuous smokers in contrast to 31.3% of the usual care group (P = 0.001). At the LHS 3 visit, 48.8% of all participants were not smoking, with 51.7% of the smoking intervention group and 42.9% of the usual care group in this category.
For the 11 years, the FEV1 of the usual care group declined by 587 mL (12.3% of predicted normal value), whereas that of the smoking intervention group declined by 502 mL (9.3% of predicted normal value). There was a strong relationship between smoking history and decline in pulmonary function. For smoking intervention and usual care participants combined, sustained quitters lost less than 27 mL/y (0.22% of predicted normal value), intermittent quitters lost approximately 48mL/year (approximately 0.91% of predicted normal), continuing smokers lost 60 mL/y (1.3% of predicted normal value). Over the 11 years of observation, the mean difference in FEV1 between continuing smokers and sustained quitters was approximately 0.5 L, or 14% of the predicted normal value.
Comment by David Ost, MD, and Najma Usmani, MD
Chronic obstructive pulmonary disease (COPD) is a major and growing health problem throughout the world. The principal etiologic factor, and by far the most potent one, cigarette smoking, has been associated with this disease for decades. Classic studies by Fletcher and associates1 have shown that smoking cessation usually mitigates the rate of decline of lung function. The LHS 1, which was a landmark study in COPD research, documented the decline in lung function related to smoking.2
The LHS 3 documents and further emphasizes the deleterious effect that smoking has on lung function. Differences in lung function between participants who quit smoking and those who did not increased progressively over 11 years, resulting in substantial differences in FEV1 values.
Sustained quitters had a rate of decline in lung function similar to never smokers, which were significantly lower than in continuing smokers. LHS 3 also demonstrated that loss of lung function in continuing smokers is similar between the sexes as has been noted in other studies.3 This emphasizes that smoking cessation is the first and most important clinical intervention in smokers with mild airway obstruction.
Dr. Ost is Assistant Professor of Medicine at NYU School of Medicine and Director of Interventional Pulmonology, Division of Pulmonary and Critical Care Medicine at Northshore University Hospital, Manhasset, NY. Dr. Usmani is a Fellow, Pulmonary and Critical Care, North Shore University Hospital and Nassau University Medical Center, East Meadow, NY.
References
1. Fletcher C, et al. The Natural History of Chronic Bronchitis and Emphysema. Oxford, England:Oxford University Press; 1976.
2. Anthonisen NR, et al. JAMA. 1994;272:1497-1505.
3. Peat JK, et al. Thorax. 1990;45:32-37.
Continuing smokers from the Lung Health Study 1 followed for a period of 11 years demonstrated a greater decline in lung function when compared to sustained quitters.
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