title: Prevalence of chronic obstructive pulmonary disease in asymptomatic smokers.
abstract: BACKGROUND
  Physicians do not routinely recommend smokers to undergo spirometry unless they are symptomatic.
  
  
  OBJECTIVE
  To test the hypothesis that there are a significant number of asymptomatic smokers with chronic obstructive pulmonary disease (COPD), we estimated the prevalence of COPD in a group of asymptomatic smokers.
  
  
  METHODS
  Two thousand nine hundred and sixty-one smokers with a cumulative consumption history of at least 10 pack-years, either smokers with symptoms or smokers without symptoms (WOS) were invited to perform a spirometry and complete a symptom questionnaire.
  
  
  RESULTS
  Six hundred and thirty-seven (21.5%) smokers had no symptoms, whereas 2,324 (78.5%) had at least one symptom. The prevalence of COPD in subjects WOS was 1.5% when considering the whole group of smokers (45/2,961) and 7% when considering only the group WOS (45/637). From 329 smokers with COPD, 13.7% were WOS. Subjects WOS were younger, had better lung function and lower cumulative consumption of cigarettes, estimated as both cigarettes per day and pack-years. According to severity of airflow limitation, 69% vs 87% of subjects were classified as Global Initiative for Chronic Obstructive Lung Disease stages I-II in the WOS and smokers with symptoms groups, respectively (P<0.001). A multivariate analysis showed that forced expiratory volume in 1 second (mL) was the only predictive factor for COPD in asymptomatic smokers.
  
  
  CONCLUSIONS
  Prevalence of COPD in asymptomatic smokers is 1.5%. This number of asymptomatic smokers may be excluded from the benefit of an "early" intervention, not just pharmacological but also from smoking cessation counseling. The higher forced expiratory volume in 1 second may contribute to prevent early diagnosis.
authors.affiliation: Tobacco Smoking and COPD Research Department, National Institute of Respiratory Diseases, Ismael Cosio Villegas, Mexico City, Mexico.
authors.forename: Raúl H
authors.initials: RH
authors.lastname: Sansores
authors.affiliation: Tobacco Smoking and COPD Research Department, National Institute of Respiratory Diseases, Ismael Cosio Villegas, Mexico City, Mexico.
authors.forename: Mónica
authors.initials: M
authors.lastname: Velázquez-Uncal
authors.affiliation: Tobacco Smoking and COPD Research Department, National Institute of Respiratory Diseases, Ismael Cosio Villegas, Mexico City, Mexico.
authors.forename: Oliver
authors.initials: O
authors.lastname: Pérez-Bautista
authors.affiliation: Tobacco Smoking and COPD Research Department, National Institute of Respiratory Diseases, Ismael Cosio Villegas, Mexico City, Mexico.
authors.forename: Jaime
authors.initials: J
authors.lastname: Villalba-Caloca
authors.affiliation: Tobacco Smoking and COPD Research Department, National Institute of Respiratory Diseases, Ismael Cosio Villegas, Mexico City, Mexico.
authors.forename: Ramcés
authors.initials: R
authors.lastname: Falfán-Valencia
authors.affiliation: Tobacco Smoking and COPD Research Department, National Institute of Respiratory Diseases, Ismael Cosio Villegas, Mexico City, Mexico.
authors.forename: Alejandra
authors.initials: A
authors.lastname: Ramírez-Venegas
mesh_terms: D000328:Adult; D058070:Asymptomatic Diseases / Q000453:epidemiology*; D042241:Early Diagnosis; D005260:Female; D005541:Forced Expiratory Volume; D006801:Humans; D016015:Logistic Models; D008168:Lung / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D029424:Pulmonary Disease, Chronic Obstructive / Q000453:epidemiology*; D012907:Smoking / Q000503:physiopathology*; D013147:Spirometry; D011795:Surveys and Questionnaires; D014797:Vital Capacity
keywords: COPD; asymptomatic smokers; early diagnosis