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      Influence of country-level differences on COPD prevalence

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          Studies suggest that COPD prevalence may vary between countries. We conducted an ecological study of data from COPD prevalence articles to assess the influence of differences in country-level risk factors on COPD prevalence.

          Patients and methods

          Our study covered English language articles published during 2003–2014. Qualified articles used spirometry to assess COPD prevalence and used representative samples from national or subnational populations. Stepwise binomial regression was used to analyze associations between study- and country-level factors and COPD prevalence.


          Eighty articles provided 1,583 measures of COPD prevalence for subjects in different sex, age, and smoking categories for 112 districts in 41 countries. Adjusted prevalence rates for COPD were significantly lower for Australia/New Zealand and the Mediterranean and significantly higher for Latin America, compared to North America, Southeast Asia, and Northern Europe. Country-level socioeconomic development variables had an uneven and mixed association with COPD prevalence. High elevation above sea level was shown to be a protective factor for COPD. Study-level variables for the established risk factors of sex, age, and smoking explained 64% of variability in COPD prevalence. Country-level risk factors raised the explanatory power to 72%. Approximately 28% of worldwide variability in COPD prevalence remained unexplained.


          Our study suggests that COPD prevalence varies across world regions, even after adjustment for established risk factors. Major country-level risk factors contributing to the worldwide epidemic of COPD remain to be investigated.

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          Most cited references 7

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          Global strategy for the diagnosis, management and prevention of COPD

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            Prevalence of chronic obstructive pulmonary disease according to BTS, ERS, GOLD and ATS criteria in relation to doctor's diagnosis, symptoms, age, gender, and smoking habits.

            Guidelines and standards for diagnosis and management of chronic obstructive pulmonary disease (COPD) have been presented by different national and international societies, but the spirometric criteria for COPD differ between guidelines. To estimate prevalence of COPD using the guidelines of the British Thoracic Society (BTS), the European Respiratory Society (ERS), the Global Initiative for Chronic Obstructive Lung Disease (GOLD), and the American Thoracic Society (ATS). Further, to evaluate reported airway symptoms, contacts with health care providers, and physician diagnosis of COPD in relation to the respective criteria, and gender differences. In 1992 a postal questionnaire was sent to a random sample of adults aged 20-69 years, 4,851 (85%) out of 5,681 subjects responded. In 1994-1995 a random sample of the responders, 970 subjects, were invited to a structured interview and a lung function test; 666 (69%) participated. The prevalence of COPD was 7.6, 14.0, 14.1, 12.2 and 34.1% according to BTS, ERS, GOLD, clinical ATS (with symptoms or physician diagnosis), and spirometric ATS criteria, respectively. Prevalent COPD was related to age, smoking habits and family history of obstructive airway disease but not to gender. Physician diagnosis of chronic bronchitis or emphysema was only reported by 16.3, 12.2, 11.0, 23.4 and 8.2% of subjects fulfilling the respective criteria, though a majority reported airway symptoms. The main determinants for prevalent COPD were age, smoking habits and spirometric criteria of COPD. Though a majority reported airway symptoms and contact with health care providers due to respiratory complaints, only a minority was diagnosed as having COPD, indicating a large underdiagnosis. Copyright (c) 2005 S. Karger AG, Basel.
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              Occupational exposures and COPD: an ecological analysis of international data.

              The occupational contribution to chronic obstructive pulmonary disease (COPD) has yet to be put in a global perspective. In the present study, an ecological approach to this question was used, analysing group-level data from 90 sex-specific strata from 45 sites of the Burden of Obstructive Lung Disease study, the Latin American Project for the Investigation of Obstructive Lung Disease and the European Community Respiratory Health Survey follow-up. These data were used to study the association between occupational exposures and COPD Global Initiative for Chronic Obstructive Lung Disease (GOLD) stage II or above. Regression analysis of the sex-specific group-level prevalence rates of COPD at each site against the prevalence of occupational exposure and ever-smoking was performed, taking into account mean smoking pack-yrs and mean age by site, sex, study cohort and sample size. For the entire data set, the prevalence of exposures predicted COPD prevalence (0.8% increase in COPD prevalence per 10% increase in exposure prevalence). By comparison, for every 10% increase in the proportion of the ever-smoking population, the prevalence of COPD GOLD stage II or above increased by 1.3%. Given the observed median population COPD prevalence of 3.4%, the model predicted that a 20% relative reduction in the disease burden (i.e. to a COPD prevalence of 2.7%) could be achieved by a 5.4% reduction in overall smoking rates or an 8.8% reduction in the prevalence of occupational exposures. When the data set was analysed by sex-specific site data, among males, the occupational effect was a 0.8% COPD prevalence increase per 10% change in exposure prevalence; among females, a 1.0% increase in COPD per 10% change in exposure prevalence was observed. Within the limitations of an ecological analysis, these findings support a worldwide association between dusty trades and chronic obstructive pulmonary disease for both females and males, placing this within the context of the dominant role of cigarette smoking in chronic obstructive pulmonary disease causation.

                Author and article information

                Int J Chron Obstruct Pulmon Dis
                Int J Chron Obstruct Pulmon Dis
                International Journal of COPD
                International Journal of Chronic Obstructive Pulmonary Disease
                Dove Medical Press
                19 September 2016
                : 11
                : 2305-2313
                [1 ]Ottawa Hospital Research Institute, University of Ottawa, Ottawa
                [2 ]Sunnybrook Research Institute, University of Toronto, ON
                [3 ]Desautels Faculty of Management, McGill University, Montreal, QC, Canada
                Author notes
                Correspondence: Shawn D Aaron, The Ottawa Hospital, General Campus, 501 Smyth Road, Ottawa, ON K1H 8L6, Canada, Tel +1 613 739 6636, Fax +1 613 739 6807, Email saaron@
                © 2016 Aaron et al. This work is published and licensed by Dove Medical Press Limited

                The full terms of this license are available at and incorporate the Creative Commons Attribution – Non Commercial (unported, v3.0) License ( By accessing the work you hereby accept the Terms. Non-commercial uses of the work are permitted without any further permission from Dove Medical Press Limited, provided the work is properly attributed.

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