Chest ACCP Member Benefits
HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
QUICK SEARCH:   [advanced]


     

Guest Access | Sign In via User Name/Password
This Article
Right arrow Abstract Freely available
Right arrow Full Text (PDF) Free
Right arrow Submit a response
Right arrow Alert me when this article is cited
Right arrow Alert me when eLetters are posted
Right arrow Alert me if a correction is posted
Right arrow Citation Map
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in ISI Web of Science
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Add to My Personal Article Archive
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via ISI Web of Science (8)
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Heijdra, Y. F.
Right arrow Articles by Celli, B. R.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Heijdra, Y. F.
Right arrow Articles by Celli, B. R.
(Chest. 2002;121:1427-1433.)
© 2002 American College of Chest Physicians

Cough and Phlegm Are Important Predictors of Health Status in Smokers Without COPD*

Yvonne F. Heijdra, MD, PhD; Victor M. Pinto-Plata, MD; Lawrence A. Kenney, MD, FCCP; John Rassulo and Bartolome R. Celli, MD, FCCP

* From the Pulmonary Department (Dr. Heijdra), University Medical Center, St. Radboud, Nijmegen, The Netherlands; and Pulmonary and Critical Care Division (Drs. Pinto-Plata, Kenney, and Celli, and Mr. Rassulo), COPD Center at St. Elizabeth’s Medical Center, Tufts University School of Medicine, Boston, MA.

Correspondence to: Bartolome Celli, MD, FCCP, Pulmonary and Critical Care Division, COPD Center at St. Elizabeth’s Medical Center, 736 Cambridge St, Boston, MA 02135; e-mail: bcelli{at}cchcs.org


   Abstract
TOP
 Abstract
Introduction
 Materials and Methods
 Results
 Discussion
 References
 
Study objectives: The health-related quality of life of smokers without COPD and that of ex-smokers has not been defined. If abnormal, the role of small airways disease and that of cough and phlegm have never been evaluated. Therefore, the aim of the study was to explore whether the differences in quality of life between smokers and ex-smokers could be explained by cough and phlegm, differences in pulmonary function tests, or exercise capacity.

Design: Observational, prospective.

Setting: Pulmonary and Critical Care Division, COPD Center at St. Elizabeth’s Medical Center.

Population: In 36 smokers, 21 ex-smokers (stopped smoking for > 20 years), 19 never-smokers with normal FVC and FEV1 values, and 41 patients with COPD (FEV1 38 ± 11% predicted [mean ± SD]), the St. George’s Respiratory Questionnaire (SGRQ), pulmonary function tests, and a 6-min walk distance (6MWD) were performed.

Results: The total SGRQ scores were worse in current smokers (15 ± 15) than in ex-smokers (6 ± 4) or never-smokers (4 ± 3) [p < 0.05]. As expected, the worst score was seen in COPD (50 ± 15). After correcting for cough and phlegm, the difference in SGRQ scores between smokers and ex-smokers disappeared. In current and ex-smokers, the SGRQ score was associated with the exposure to pack-years smoking history (r = 0.45, p < 0.01, and r = 0.83, p < 0.0001, respectively) but independent of lung function or exercise parameters (6MWD).

Conclusions: In smokers without COPD, the abnormal SGRQ score is due to the noxious effect of cigarette smoke, resulting in cough and phlegm, independent of its physiologic effects.

Key Words: cough • quality of life • smoking • sputum


   Introduction
TOP
 Abstract
 Introduction
Materials and Methods
 Results
 Discussion
 References
 
The health-related quality of life scores in smokers and ex-smokers or never-smokers have only been studied twice1 2 using the generic Short Form-36.3 In both studies, worse scores were seen in smokers than in ex-smokers or never-smokers. However, no attempts were made to explain the difference. There have been no studies using disease-specific quality of life instruments.

Since smokers can have normal spirometry findings but may have mucus hypersecretion,4 a reduced diffusion capacity of the lung for carbon monoxide (DLCO),5 or peripheral airway obstruction,6 7 the differences between smokers and ex-smokers or never-smokers could be explained by cough and phlegm, differences in pulmonary function tests, or exercise capacity. This prospective study evaluated the quality-of-life scores measured with the St. George’s Respiratory Questionnaire (SGRQ),8 lung function, and the functional capacity in smokers and ex-smokers with normal FVC and FEV1 values, and compared them with the values obtained in patients with COPD.


   Materials and Methods
TOP
 Abstract
 Introduction
 Materials and Methods
Results
 Discussion
 References
 
Subjects
One hundred seventeen subjects (66 men and 51 women) were studied: 36 subjects were smokers, 21 were ex-smokers, 19 were never-smokers, and 41 had COPD. They are all participants in a cohort longitudinal study of patients with COPD and appropriate control subjects. The study was approved by the Institutional Review Board at St. Elizabeth’s Medical Center. All subjects signed the informed consent. Smokers were defined as subjects who were still active smokers. Ex-smokers were subjects who had not smoked for the past 20 years, and never-smokers were subjects who never smoked a cigarette. Smokers, ex-smokers, and never-smokers were recruited by advertisement. Inclusion criteria were: FEV1 and/or FEV1/FVC > 70% predicted value, age > 55 years, and the ability to complete the SGRQ. Exclusion criteria were myocardial infarction within 6 months, ventilator dependency, malignancy, congestive heart failure, hepatic cirrhosis, end-stage renal disease, orthopedic conditions precluding performance of the 6-min walk distance (6MWD), and a history of psychiatric or neurologic illness that interfered with participation in the study. All subjects were free of any disease thought to cause death within 5 years of initiation of the study, and were in a clinically stable state for at least 6 months prior to inclusion.

COPD was defined using standards of the American Thoracic Society.9 Inclusion criteria were age > 55 years, FEV1 < 55% predicted, stable disease on medical treatment, and the ability to understand and complete the SGRQ. They were recruited from our outpatient pulmonary clinic. The exclusion criteria were the same as mentioned earlier.

Measurements
Pulmonary Function Testing: Spirometry was performed with a dry seal spirometer (Vmax; SensorMedics; Yorba Linda, CA) calibrated according to American Thoracic Society recommendations.10 Functional residual capacity was measured in a body plethysmograph as described by Dubois et al11 in COPD patients and by N2 uptake in the normal spirometry groups.

Health-Related Quality of Life: A prepublished, translated, and validated version of the original SGRQ was used.8 12 The questionnaire contains 50 questions and is divided in three sections (symptoms, activity, impact). The symptom component consists of eight items that assess the frequency over the last year of such symptoms as coughing, sputum production, dyspnea, and wheezing, as well as the numbers of attacks. Responses to the symptom items are selected from four or five possible levels of frequency or occurrence. The 16 items of the impact component identify physical activities that induce breathlessness (eg, getting washed, walking up a flight of stairs) or that affect breathlessness (eg, taking a long time to get washed because of breathlessness). The 26 items of the impact component broadly assess the impact of the disease on different aspects of social and emotional functions, such as employment, self-efficacy, medication use, and expectations for health (eg, cough hurts, cough is embarrassing in public, medication interferes with life). The items of the activity and impact components are scored in a true/false format. A detailed description of the questionnaire has been published by Barr et al.12 Each section of the questionnaire is scored separately with a range from 0 to 100%. Zero indicates no impairment of life quality. A summary score utilizing responses to all items is the total SGRQ, also ranging from 0 to 100%. The SGRQ scores are calculated using weights attached to each item in the questionnaire.13

To see if the difference in quality-of-life scores between smokers and ex-smokers and never-smokers is caused by sputum production and cough, the first two questions of the SGRQ, which address those items, were scored separately. The first question was, "How much cough did you have over the last year?" The second question was, "How much phlegm or sputum did you bring up over the last year?" The five possible answers for these questions were as follows: (1) not at all, (2) only with chest infections, (3) a few days a month, (4) several days a week, and (5) most days a week. They were scored from 0 (not at all) to 4 (most days a week) on both questions, and the scores were added together to provide a value that ranged from 0 to 8. The SGRQ scores were analyzed between smokers, ex-smokers, and never-smokers with the same score on cough and phlegm production. The correlation between the added cough and sputum score and the impact SGRQ score was calculated.

6MWD: The subjects were asked to cover as much distance as possible in 6 min.14 At each 30-s interval, they are given a standard encouragement, "You are doing well." The highest 6MWD value was used, which was the result of two tests separated by 20 min completed in a 50-m corridor. With oxygen desaturation < 88%, oxygen was added up to 5 L/min to keep oxygen saturation > 88% in the subsequent walks.

Statistical Analysis
Data are expressed as mean ± SD. Differences among the groups were evaluated using analysis of variance. The t test for independent samples was used to test differences between groups. Pearson correlation coefficients or, if not normally distributed, Spearman correlation coefficients were calculated between the different items of the SGRQ and the FEV1, the 6MWD, the number of smoking pack-years, the DLCO, the forced expiratory flows, and the total cough and sputum score. A p value < 0.05 was considered significant. For all analyses, Statistica software (StatSoft; Tulsa, OK) was used.


   Results
TOP
 Abstract
 Introduction
 Materials and Methods
 Results
Discussion
 References
 
General Characteristics
The characteristics of smokers, ex-smokers, never-smokers, and COPD patients are shown in Table 1 . The age in the smoker group was slightly lower than in the other three groups. The four groups had the same anthropometric values.


View this table:
[in this window]
[in a new window]

  		Table 1.. Subject Characteristics*

 
Pulmonary Function
The pulmonary function test results are shown in Table 1 . The smokers, ex-smokers, and never-smokers had similar FVC and static lung volumes. However, the DLCO was lower in current smokers (89 ± 16% predicted). The FEV1 percent predicted, although normal, was lower in ex-smokers (83 ± 12% predicted) compared to never-smokers (93 ± 16% predicted). The FEV1/FVC, however, was exactly the same and normal in smokers, ex-smokers, and never-smokers. The forced expiratory flow, midexpiratory phase (FEF25–75) percent predicted, and the forced expiratory flow at 50% of vital capacity (FEF50) percent predicted values were lower in ex-smokers compared to never-smokers. As expected, the patients with COPD were obstructed (FEV1 0.97 ± 0.3 L or 38 ± 11% predicted), had increased static lung volumes, and had decreased DLCO. Only 4 of the 41 patients with COPD were current smokers.

SGRQ
The symptom, impact, and total SGRQ scores were significantly higher in smokers than in ex-smokers. The scores between ex-smokers and never-smokers were the same. As expected, the SGRQ scores were the highest in COPD patients (Fig 1 ).



View larger version (18K):
[in this window]
[in a new window]
[Download PPT slide]
  		Figure 1.. SGRQ scores for symptoms (top left, A), activity (bottom left, B), impact (top right, C), and total (bottom right, D) in COPD patients, smokers, ex-smokers, and never-smokers. There were significant differences between smokers and ex-smokers in symptom, impact, and total scores. The scores were significantly higher for patients with COPD; *p < 0.05; ***p < 0.001.

 
The combined cough and sputum score in the smokers ranged from 0 to 8, in the ex-smokers from 0 to 5, and in the never-smokers from 0 to 4. The total SGRQ scores of smokers, ex-smokers, and never-smokers were similar when corrected for cough and phlegm score (Table 2 ). The correlation between the phlegm and cough score and the impact SGRQ score was 0.64 (p < 0.0001; Fig 2 ). The impact score was used because it was different between smokers and ex-smokers and because cough and phlegm are no part of it, in contrast to the symptom and total score, where cough and phlegm are included in the score.


View this table:
[in this window]
[in a new window]

  		Table 2.. Comparison of the Total SGRQ Scores in Smokers, Ex-Smokers, and Never-Smokers With the Same Cough and Phlegm Score*

 


View larger version (11K):
[in this window]
[in a new window]
[Download PPT slide]
  		Figure 2.. Correlation between the added cough and phlegm score and the impact SGRQ score in smokers, ex-smokers, and never-smokers. Data represent the number of subjects with the same score.

 
6MWD
The 6MWD was not different between smokers (539 ± 74 m), ex-smokers (528 ± 81 m), and never-smokers (559 ± 100 m). The distance in COPD patients was shorter (370 ± 95 m; p < 0.001) compared to the other groups.

Correlations
In smokers, ex-smokers, and never-smokers, no correlations were seen between SGRQ items and FEV1 percent predicted and 6MWD (Table 3 ). Because the FEV1, DLCO, FEF25–75, and the FEF50 (all expressed as percentage of predicted) were different among those groups, correlations were evaluated among those parameters and the different items of the SGRQ in smokers, ex-smokers, and never-smokers separately and also taken as one group. However, no significant correlations were found. In contrast, there were high correlations between the SGRQ scores and the number of pack-years in smokers and even higher correlations in ex-smokers (Table 3) . The correlation between the total cough and phlegm score and the amount of pack-years in smokers and ex-smokers was 0.49 (p < 0.001).


View this table:
[in this window]
[in a new window]

  		Table 3.. Correlations Between SGRQ Scores, FEV1 Percent Predicted, and 6MWD*

 
In COPD patients, significant correlations were found between SGRQ scores and FEV1 and 6MWD. No correlations were found between SGRQ scores and the amount of smoking pack-years.


   Discussion
TOP
 Abstract
 Introduction
 Materials and Methods
 Results
 Discussion
References
 
The present study had several important findings. First, the health status measured with the disease-specific SGRQ was worse in current smokers vs ex-smokers and never-smokers. Second, in current and ex-smokers, the intensity of overall exposure to cigarettes (number of pack-years) was associated with worse health status independent of lung function. This is due to the presence and intensity of cough and sputum production. Third, exercise capacity, as represented by the 6MWD, was the same in smokers, ex-smokers, and never-smokers, and therefore cannot explain the differences in SGRQ scores. Fourth, the SGRQ scores did not differ between never-smokers and ex-smokers even though the latter had lower FEV1 percent predicted, FEF25–75 percent predicted, and FEF50 percent predicted, minimizing the role of physiologic changes as the cause of worse quality of life in smokers.

The first important finding in this study is that the health status of smokers was worse than that of ex-smokers and never-smokers in spite of normal FVC and FEV1 values. In addition, we found that ex-smokers and never-smokers had the same SGRQ scores, a finding that underscores the benefit of smoking cessation independent of changes in lung function.

To our knowledge, neither the SGRQ nor any other disease-specific questionnaire has been used to evaluate health status in smokers, ex-smokers, and never-smokers. Interestingly, smokers had worse scores than ex-smokers and never-smokers in spite of similar FVC and FEV1 values. The largest difference was seen in the symptom score, with lesser difference in the impact and activity scores. Although no disease-specific questionnaire has been used, there are data utilizing generic health-related quality of life instruments. Wilson et al1 reported significant differences in mean Short Form-36 health status scores between never-smokers, ex-smokers, and current smokers, but they did not compare it with COPD. In another study,2 1,500 smokers and 1,500 ex-smokers (having stopped for at least 5 years) were sent the Short Form-36, Euroqol, and a set of condition-specific and sociodemographic questions. This study showed that ex-smokers reported less respiratory symptoms and a better health-related quality of life than current smokers. However, there was no attempt to identify the reasons for these differences. It is appealing to speculate that the reason is the prevalence of a lower FEF25–75, FEV1 percent predicted, and DLCO in smokers. However, this is not the case because the health status was similar between never-smokers and ex-smokers even though the later also had lower FEV1 percent predicted and FEF25–75. Furthermore, the fact that the differences in SGRQ scores among smokers, ex-smokers, and never-smokers are not due to the physiologic impairment caused by cigarette smoking is also supported by the 6MWD findings, which were identical for the three groups.

The best explanation for the observed differences in SGRQ scores between smokers and nonsmokers is derived from a careful analysis of the different components of the questionnaire. As shown in Figure 1 , the main difference between groups occurred in the symptom component. Further analyses indicate that this was due to the presence and intensity of cough and phlegm production (Fig 2) . After normalizing for cough and sputum production, there were no differences in scores among the three groups. Our findings also indicate that small airways dysfunction has very little impact on health status unless associated with cough and phlegm. Interestingly, Jones and coworkers8 also observed that patients with COPD manifested worse health status if they had cough and phlegm production. However, the association of these symptoms and the degree of physiologic impairment was not explored.

It could be argued that the reason why the SGRQ scores of smokers are worse than those of nonsmokers is the presence of comorbidity induced by cigarette use. However, we observed no difference in comorbidity in the three groups (Table 4 ). As expected, the health status score was worst in the patients with COPD and was within the range reported in the literature.8 12 15 16 17 18 19 20 21 22 23 24 Similarly, the average 6MWD in our COPD group was 370 m, which equals the distance seen in other studies8 12 19 20 25 26 in patients with a comparable degree of airflow obstruction.


View this table:
[in this window]
[in a new window]

  		Table 4.. Comorbidity in Smokers, Ex-Smokers, and Never-Smokers*

 
We found no correlations between SGRQ scores and 6MWD in smokers, ex-smokers, or never-smokers. This is not surprising because we did not find differences in 6MWD among these groups. We also correlated SGRQ scores in these groups with FEV1, DLCO, and forced expiratory flow values, which were different among these groups, but again no correlations were found. Therefore, it seemed that factors other than simple pulmonary function are responsible for the differences in quality of life among smokers, ex-smokers, and never-smokers. This statement is further supported by the high correlation observed between the SGRQ items and the amount of pack-years in smokers and ex-smokers. It would appear that once cough and phlegm develop in patients exposed to cigarette smoke, the health status worsens and that the relation is proportional to the intensity and length of exposure, as was supported by the correlation between the amount of smoking pack-years and the total cough and phlegm score. Interestingly, smoking cessation results in improvement of health status independent of improvement of lung function. We believe that this is important, and that it should be added to the list of benefits associated with smoking cessation.

One possible limitation of our study is that the smokers were, on average, 4 years younger than the other groups. Lung function parameters would have been lower after correcting for age. However, this would have made the difference in DLCO between smokers and ex-smokers even bigger. In addition, it would not have affected the other lung function parameters because they are in general a little higher in the smoker group.

This study shows for the first time that cough and sputum production negatively affects health status independent of lung physiology and systemic function. It also suggests that smoking cessation is important not only because it improves lung function but because it may improve health status by helping decrease cough and sputum production.


   Footnotes
 
Abbreviations: DLCO = diffusion capacity of the lung for carbon monoxide; FEF25–75 = forced expiratory flow, midexpiratory phase; FEF50 = forced expiratory flow at 50% of vital capacity; 6MWD = 6-min walk distance; SGRQ = St. George’s Respiratory Questionnaire

Supported in part by a grant from GlaxoSmithKline.

Received for publication July 16, 2001. Accepted for publication November 14, 2001.


   References
TOP
 Abstract
 Introduction
 Materials and Methods
 Results
 Discussion
 References
 

  1. Wilson, D, Parsons, J, Wakefield, M (1999) The health related quality of life of never smokers, ex-smokers, and light, moderate, and heavy smokers. Prev Med 29,139-144[CrossRef][ISI][Medline]
  2. Tillmann, M, Silcock, J (1997) A comparison of smokers’ and ex-smokers’ health related quality of life. J Public Health Med 19,268-273[Abstract/Free Full Text]
  3. Mahler, DA, Mackowiak, JI (1995) Evaluation of the Short-Form 36-item questionnaire to measure health-related quality of life in patients with COPD. Chest 107,1585-1589[Abstract/Free Full Text]
  4. Fletcher, CM, Peto, R, Tinker, CM (1974) A comparison of the assessment of simple bronchitis (chronic mucus hypersecretion) by measurement of sputum volume and by standardized questions on phlegm production. Int J Epidemiol 3,315-319[Abstract/Free Full Text]
  5. Watson, A, Joyce, H, Hopper, L, et al (1993) Influence of smoking habits on change in carbon monoxide transfer factor over 10 years in middle aged men. Thorax 48,119-124[Abstract]
  6. Teculescu, DB, Pino, J, Sadoul, P (1980) Cigarette smoking and density-dependence of maximal expiratory flow in asymptomatic men. Am Rev Respir Dis 122,651-656[ISI][Medline]
  7. Bode, FR, Dosman, J, Martin, RR, et al (1975) Reversibility of pulmonary function abnormalities in smokers: a prospective study of early diagnostic tests of small airways disease. Am J Med 59,43-52[CrossRef][ISI][Medline]
  8. Jones, PW, Quirk, FH, Baveystock, CM, et al (1992) A self-complete measure of health status for chronic airflow limitation: the St. George’s Respiratory Questionnaire. Am Rev Respir Dis 145,1321-1327[ISI][Medline]
  9. Standards for the diagnosis and care of patients with chronic obstructive pulmonary disease. American Thoracic Society Am J Respir Crit Care Med 1995;152,S77-S121
  10. Standardization of spirometry 1987 update. American Thoracic Society. Am Rev Respir Dis 1987;36,1285-1298
  11. Dubois, A, Bothelho, S, Bedell, G, et al (1956) A rapid plethysmographic method for measuring thoracic gas volume: a comparison with a nitrogen washout method for measuring functional residual capacity in normal subjects. J Clin Invest 35,322-326
  12. Barr, JT, Schumacher, GE, Freeman, S, et al (2000) American translation, modification, and validation of the St. George’s Respiratory Questionnaire. Clin Ther 22,1121-1145[CrossRef][ISI][Medline]
  13. Quirk, FH, Jones, PW (1990) Patients’ perception of distress due to symptoms and effects of asthma on daily living and investigation of possible influential factors. Clin Sci 79,7-21
  14. Guyatt, GH, Pugsley, SQ, Sullivan, MJ, et al (1984) Effect on encouragement on walking test performance. Thorax 39,818-822[Abstract]
  15. Hajiro, T, Nishimura, K, Jones, PW, et al (1999) A novel, short, and simple questionnaire to measure health-related quality of life in patients with chronic obstructive pulmonary disease. Am J Respir Crit Care Med 159,1874-1878[Abstract/Free Full Text]
  16. Hajiro, T, Nishimura, K, Tsukino, M, et al (1998) Comparison of discriminative properties among disease-specific questionnaires for measuring health-related quality of life in patients with chronic obstructive pulmonary disease. Am J Respir Crit Care Med 157,785-790[Abstract/Free Full Text]
  17. Rutten-van Molken, M, Roos, B, Van Noord, JA (1999) An empirical comparison of the St. George’s Respiratory Questionnaire (SGRQ) and the Chronic Respiratory Disease Questionnaire (CRQ) in a clinical trial setting. Thorax 54,995-1003[Abstract/Free Full Text]
  18. Gallefoss, F, Bakke, PS (2000) Impact of patient education and self-management on morbidity in asthmatics and patients with chronic obstructive pulmonary disease. Respir Med 94,279-287[CrossRef][ISI][Medline]
  19. Foglio, K, Bianchi, L, Bruletti, G, et al (1999) Long-term effectiveness of pulmonary rehabilitation in patients with chronic airway obstruction. Eur Respir J 13,125-132[Abstract]
  20. Engstrom, CP, Persson, LO, Larsson, S, et al (1998) Reliability and validity of a Swedish version of the St. George’s Respiratory Questionnaire. Eur Respir J 11,61-66[Abstract/Free Full Text]
  21. Harper, R, Brazier, JE, Waterhouse, JC, et al (1997) Comparison of outcome measures for patients with chronic obstructive pulmonary disease (COPD) in an outpatient setting. Thorax 52,879-887[Abstract]
  22. Hajiro, T, Nishimura, K, Tsukino, M, et al (1999) A comparison of the level of dyspnea vs disease severity in indicating the health-related quality of life of patients with COPD. Chest 116,1632-1637[Abstract/Free Full Text]
  23. Jones, PW, Bosh, TK (1997) Quality of life changes in COPD patients treated with salmeterol. Am J Respir Crit Care Med 155,1283-1289[Abstract]
  24. Ketelaars, CA, Schlosser, MA, Mostert, R, et al (1996) Determinants of health-related quality of life in patients with chronic obstructive pulmonary disease. Thorax 51,39-43[Abstract]
  25. Redelmeier, DA, Bayoumi, AM, Goldstein, RS, et al (1997) Interpreting small differences in functional status: the six minute walk test in chronic lung disease patients. Am J Respir Crit Care Med 155,1278-1282[Abstract]
  26. Ringbaek, TJ, Broendum, E, Hemmingsen, L, et al (2000) Rehabilitation of patients with chronic obstructive pulmonary disease: exercise twice a week is not sufficient! Respir Med 94,150-154[CrossRef][ISI][Medline]



This article has been cited by other articles:


Home page
 ChestHome page
C. Shin, S. Lee, R. D. Abbott, J. H. Kim, S. Y. Lee, K. H. In, and K. Kimm
Respiratory Symptoms and Undiagnosed Airflow Obstruction in Middle-Aged Adults: The Korean Health and Genome Study
Chest, October 1, 2004; 126(4): 1234 - 1240.
[Abstract] [Full Text] [PDF]

Home page
 ChestHome page
J. A. B. Martinez, G. A. Mota, E. S. O. Vianna, J. T. Filho, G. A. Silva, and A. L. Rodrigues Jr.
Impaired Quality of Life of Healthy Young Smokers
Chest, February 1, 2004; 125(2): 425 - 428.
[Abstract] [Full Text] [PDF]

Home page
 JAMAHome page
B. R. Celli
A 62-Year-Old Woman With Chronic Obstructive Pulmonary Disease
JAMA, November 26, 2003; 290(20): 2721 - 2729.
[Full Text] [PDF]

This Article
Right arrow Abstract Freely available
Right arrow Full Text (PDF) Free
Right arrow Submit a response
Right arrow Alert me when this article is cited
Right arrow Alert me when eLetters are posted
Right arrow Alert me if a correction is posted
Right arrow Citation Map
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in ISI Web of Science
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Add to My Personal Article Archive
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via ISI Web of Science (8)
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Heijdra, Y. F.
Right arrow Articles by Celli, B. R.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Heijdra, Y. F.
Right arrow Articles by Celli, B. R.

HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS