Looking Beyond the Cigarette in COPD
2008; Elsevier BV; Volume: 133; Issue: 2 Linguagem: Inglês
10.1378/chest.07-2485
ISSN1931-3543
Autores Tópico(s)Pediatric health and respiratory diseases
ResumoOur understanding of COPD has improved with standardized definitions of disease state and recent population-based surveys. Variability in disease prevalence has been noted across a series of studies,1Halbert RJ Natoli JL Gano A et al.Global burden of COPD: systematic review and meta-analysis.Eur Respir J. 2006; 528: 523-532Crossref Scopus (1048) Google Scholar2Halbert RJ Isonaka S George D et al.Interpreting COPD prevalence estimates: what is the true burden of disease?.Chest. 2003; 123: 1684-1692Abstract Full Text Full Text PDF PubMed Scopus (353) Google Scholar although much of this variability has been attributed to varying definitions or study methodologies. Two recent multisite studies, the PLATINO (Proyecto Latino-Americano de Investigación en Obstrucción Pulmonar) study3Menezes AM Perez-Padilla R Jardim JR et al.Chronic obstructive pulmonary disease in five Latin American cities (the PLATINO study): a prevalence study.Lancet. 2005; 366: 1875-1881Abstract Full Text Full Text PDF PubMed Scopus (704) Google Scholar and the Burden of Lung Disease (BOLD) study,4Buist AS McBurnie MA Vollmer WM et al.International variation in the prevalence of COPD (the BOLD study): a population-based prevalence study.Lancet. 2007; 370: 741-750Abstract Full Text Full Text PDF PubMed Scopus (1611) Google Scholar which used a uniform definition and methodology, have also found variability in disease prevalence across sites. With this increased understanding, however, comes additional questions. Tobacco smoking remains the overwhelming risk factor for COPD in the world. Additional factors are probably important. The BOLD and PLATINO studies3Menezes AM Perez-Padilla R Jardim JR et al.Chronic obstructive pulmonary disease in five Latin American cities (the PLATINO study): a prevalence study.Lancet. 2005; 366: 1875-1881Abstract Full Text Full Text PDF PubMed Scopus (704) Google Scholar4Buist AS McBurnie MA Vollmer WM et al.International variation in the prevalence of COPD (the BOLD study): a population-based prevalence study.Lancet. 2007; 370: 741-750Abstract Full Text Full Text PDF PubMed Scopus (1611) Google Scholar demonstrated that smoking and aging were risk factors for disease, and indoor air pollution is a risk factor for disease prevalence in China.5Liu S Zhou Y Wang X et al.Biomass fuels are the probable risk factor for chronic obstructive pulmonary disease in rural South China.Thorax. 2007; 62: 889-897Crossref PubMed Scopus (220) Google Scholar The PLATINO study3Menezes AM Perez-Padilla R Jardim JR et al.Chronic obstructive pulmonary disease in five Latin American cities (the PLATINO study): a prevalence study.Lancet. 2005; 366: 1875-1881Abstract Full Text Full Text PDF PubMed Scopus (704) Google Scholar also found higher prevalence was associated with residence at a lower altitude. The study in this issue of CHEST (see page 343) by Caballaro et al6Caballero A Torres-Duque CA Jaramillo C et al.Prevalence of chronic obstructive pulmonary disease in five Columbian cities situated at low, medium and high altitude (PREPOCOL study).Chest. 2008; 133: 343-349Abstract Full Text Full Text PDF PubMed Scopus (190) Google Scholar looked at some of these same factors, with some results similar to those previously reported, and others different. It is of no surprise that both aging and tobacco smoking predicted COPD, as these risk factors have been documented in multiple studies.1Halbert RJ Natoli JL Gano A et al.Global burden of COPD: systematic review and meta-analysis.Eur Respir J. 2006; 528: 523-532Crossref Scopus (1048) Google Scholar7Schirnhofer L Lamprecht B Vollmer WM et al.COPD prevalence in Salzburg, Austria: results from the Burden of Obstructive Lung Disease study.Chest. 2007; 131: 29-36Abstract Full Text Full Text PDF PubMed Scopus (120) Google Scholar8Lindberg A Bjerg-Backlund A Ronmark E et al.Prevalence and underdiagnosis of COPD by disease severity and the attributable fraction of smoking: report from the Obstructive Lung Disease in Northern Sweden studies.Respir Med. 2006; 100: 264-272Abstract Full Text Full Text PDF PubMed Scopus (205) Google Scholar Other factors that one might expect to be associated with COPD that Caballaro et al6Caballero A Torres-Duque CA Jaramillo C et al.Prevalence of chronic obstructive pulmonary disease in five Columbian cities situated at low, medium and high altitude (PREPOCOL study).Chest. 2008; 133: 343-349Abstract Full Text Full Text PDF PubMed Scopus (190) Google Scholar also found included a lower education level (as a reflection of socioeconomic status) and male gender. Both of these risks are thought to be related to factors that are associated with socioeconomic status and gender, such as occupational exposures, diet, or access to health care.9Walda IC Tabak C Smit HA et al.Diet and 20-year chronic obstructive pulmonary disease mortality in middle-aged men from three European countries.Eur J Clin Nutr. 2002; 56: 638-643Crossref PubMed Scopus (104) Google Scholar10Trupin L Earnest G San Pedro M et al.The occupational burden of chronic obstructive pulmonary disease.Eur Respir J. 2003; 22: 462-469Crossref PubMed Scopus (241) Google Scholar The role of indoor air pollutants in the development of COPD has received increasing attention in recent years, and the World Health Organization estimates that 35% of COPD in low- and medium-income countries is from indoor smoke from solid fuels.11Lopez AD Mathers CD Ezzati M et al.Global burden of disease and risk factors. The World Bank, Washington, DC2006Crossref Google Scholar The estimate in Caballaro et al6Caballero A Torres-Duque CA Jaramillo C et al.Prevalence of chronic obstructive pulmonary disease in five Columbian cities situated at low, medium and high altitude (PREPOCOL study).Chest. 2008; 133: 343-349Abstract Full Text Full Text PDF PubMed Scopus (190) Google Scholar was that the prevalence of COPD was approximately 50% higher in people with a longer history of exposure to wood smoke (≥ 10 years vs < 10 years).6Caballero A Torres-Duque CA Jaramillo C et al.Prevalence of chronic obstructive pulmonary disease in five Columbian cities situated at low, medium and high altitude (PREPOCOL study).Chest. 2008; 133: 343-349Abstract Full Text Full Text PDF PubMed Scopus (190) Google Scholar They also found that exposure to passive smoke was associated with a higher risk of COPD among neversmokers. This finding in supported by other studies.12Yin P Jiang CQ Cheng KK et al.Passive smoking exposure and risk of COPD among adults in China: the Guangzhou Biobank Cohort Study.Lancet. 2007; 370: 751-757Abstract Full Text Full Text PDF PubMed Scopus (215) Google Scholar13Eisner MD Balmes J Katz PP et al.Lifetime environmental tobacco smoke exposure and the risk of chronic obstructive pulmonary disease.Environ Health. 2005; 4: 7Crossref PubMed Scopus (193) Google Scholar The effects of particulate air pollutants are similar to those seen in passive smoking, so this is a finding that is also expected. One recently identified factor in the prevalence of COPD is a history of tuberculosis.4Buist AS McBurnie MA Vollmer WM et al.International variation in the prevalence of COPD (the BOLD study): a population-based prevalence study.Lancet. 2007; 370: 741-750Abstract Full Text Full Text PDF PubMed Scopus (1611) Google Scholar Overall, Caballero et al6Caballero A Torres-Duque CA Jaramillo C et al.Prevalence of chronic obstructive pulmonary disease in five Columbian cities situated at low, medium and high altitude (PREPOCOL study).Chest. 2008; 133: 343-349Abstract Full Text Full Text PDF PubMed Scopus (190) Google Scholar found that 25.8% of subjects with a history of tuberculosis had evidence of COPD on spirometry. This relation could inform us as to additional factors in the etiology and pathogenesis of COPD. One can speculate that patients with tuberculosis have a higher rate of bronchiectasis, and that this interacts with other risk factors to increase airway obstruction. By extension, other processes that increase the risk of infections, such as infections early in life, could also increase the risk of COPD. Although bronchiectasis is a condition that is in the differential diagnosis of COPD, it is likely that many patients with well-documented COPD have some degree of bronchiectasis that contributes to the severity and morbidity in COPD. The final risk factor of interest in the study by Caballero et al6Caballero A Torres-Duque CA Jaramillo C et al.Prevalence of chronic obstructive pulmonary disease in five Columbian cities situated at low, medium and high altitude (PREPOCOL study).Chest. 2008; 133: 343-349Abstract Full Text Full Text PDF PubMed Scopus (190) Google Scholar is altitude, with the suggestion that higher altitude was associated with a higher COPD prevalence. This contrasts with the findings from the PLATINO study,3Menezes AM Perez-Padilla R Jardim JR et al.Chronic obstructive pulmonary disease in five Latin American cities (the PLATINO study): a prevalence study.Lancet. 2005; 366: 1875-1881Abstract Full Text Full Text PDF PubMed Scopus (704) Google Scholar in which the data suggest that lower altitude had a higher prevalence of COPD. Which of these studies may be more correct? In the PLATINO study,3Menezes AM Perez-Padilla R Jardim JR et al.Chronic obstructive pulmonary disease in five Latin American cities (the PLATINO study): a prevalence study.Lancet. 2005; 366: 1875-1881Abstract Full Text Full Text PDF PubMed Scopus (704) Google Scholar the five sites were in five different countries3Menezes AM Perez-Padilla R Jardim JR et al.Chronic obstructive pulmonary disease in five Latin American cities (the PLATINO study): a prevalence study.Lancet. 2005; 366: 1875-1881Abstract Full Text Full Text PDF PubMed Scopus (704) Google Scholar; whereas in the study by Caballero et al,6Caballero A Torres-Duque CA Jaramillo C et al.Prevalence of chronic obstructive pulmonary disease in five Columbian cities situated at low, medium and high altitude (PREPOCOL study).Chest. 2008; 133: 343-349Abstract Full Text Full Text PDF PubMed Scopus (190) Google Scholar all sites were in the same country. Thus, there is the potential that intercountry differences in the PLATINO study3Menezes AM Perez-Padilla R Jardim JR et al.Chronic obstructive pulmonary disease in five Latin American cities (the PLATINO study): a prevalence study.Lancet. 2005; 366: 1875-1881Abstract Full Text Full Text PDF PubMed Scopus (704) Google Scholar may have been partially responsible for what was perceived as a difference related to altitude. There is some evidence that the lower density of air at higher altitudes in subjects studied at different altitudes might alter pulmonary function; researchers found that the FVC is slightly lower and FEV1 is slightly higher.14Welsh CH Wagner PD Reeves JT et al.Operation Everest: II. Spirometric and radiographic changes in acclimatized humans at simulated high altitudes.Am Rev Respir Dis. 1993; 147: 1239-1244Crossref PubMed Scopus (58) Google Scholar This would have the net effect of increasing the FEV1/FVC at altitude with the net result of a lower rate of COPD at altitude. Another study15Vargas MH Sienra-Monge JJ Diaz-Mejia G et al.Asthma and geographical altitude: an inverse relationship in Mexico.J Asthma. 1999; 36: 511-517Crossref PubMed Scopus (30) Google Scholar suggests that asthma rates are lower at higher altitude. On the other hand, it is also possible that lower atmospheric pressure and relative hypoxemia may contribute to more comorbid disease, such as pulmonary hypertension and congestive heart failure, in patients living at altitude,16Cote TR Stroup DF Dwyer DM et al.Chronic obstructive pulmonary disease mortality: a role for altitude.Chest. 1993; 103: 1194-1197Abstract Full Text Full Text PDF PubMed Scopus (38) Google Scholar with a possible result of earlier mortality in this population. Thus, the role of altitude in the development of COPD and subsequent outcomes is an area that could benefit from further investigation. Cigarette smoking is undeniably the main preventable risk factor for the development and progression of COPD. Comprehensive prevention and treatment efforts, however, require us to look beyond the burning cigarette at factors such as air pollutant exposures, infections, comorbid disease, and even altitude. Better understanding will, hopefully, leading to better interventions and outcomes for our patients.
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