key: cord-0713258-tiqbw9zp
authors: Jarhyan, Prashant; Hutchinson, Anastasia; Khaw, Damien; Prabhakaran, Dorairaj; Mohan, Sailesh
title: Prevalence of chronic obstructive pulmonary disease and chronic bronchitis in eight countries: a systematic review and meta-analysis
date: 2022-03-01
journal: Bull World Health Organ
DOI: 10.2471/blt.21.286870
sha: bbfc548ccb10678c999629478bd9753ff633a981
doc_id: 713258
cord_uid: tiqbw9zp

OBJECTIVE: To estimate the prevalence of chronic obstructive pulmonary disease (COPD) and chronic bronchitis in eight countries in South Asia through a systematic review and meta-analysis. METHODS: We searched MEDLINE® Complete, Web of Science, Embase®, Scopus, CINAHL and reference lists of screened studies for research on the prevalence of COPD and chronic bronchitis in South Asian countries published between January 1990 and February 2021. We used standardized diagnostic criteria for definitions of COPD and chronic bronchitis. Two reviewers undertook study screening, full-text review, quality appraisal and data extraction. FINDINGS: Of 1529 studies retrieved, 43 met the inclusion criteria: 32 provided data from India; four from Bangladesh; three from Nepal; two from Pakistan; and two from both India and Sri Lanka. Twenty-six studies used standardized diagnostic definitions and 19 were included in the meta-analysis. The estimated pooled prevalence of COPD was 11.1% (95% confidence interval, CI: 7.4–14.8%), using the Global Initiative for Chronic Obstructive Lung Disease fixed criteria and 8.0% (95% CI: 5.6–10.4%) using the lower limit of normal criteria. The prevalence of COPD was highest in north India (19.4%) and Bangladesh (13.5%) and in men. The estimated pooled prevalence of chronic bronchitis was 5.0% (95% CI: 4.1–6.0%) in India and 3.6% (95% CI: 3.1–4.0%) in Pakistan. CONCLUSION: Included countries have a high prevalence of COPD although it varied by geographical area and study characteristics. Future research in South Asia should use standardized diagnostic criteria to examine the contribution of setting-specific risk factors to inform prevention and control strategies.

Chronic obstructive pulmonary disease (COPD) is a common, preventable and treatable disease, with a worldwide prevalence of 10.1% in people aged 40 years or older. 1, 2 In 2019, COPD was the third leading cause of deaths globally, contributing to 3.23 million deaths, with most deaths (80%) occurring in low-and middle-income countries. 3, 4 A systematic review on COPD showed that estimates of the number of cases of COPD in countries of the World Health Organization South-East Asia Region had increased from 44.5 million to 75.1 million between 1990 and 2010, a 68.8% increase. 5 According to the World Bank, South Asia comprises Afghanistan, Bangladesh, Bhutan, India, Maldives, Nepal, Pakistan and Sri Lanka, and is home to a quarter of the global population. 6 The area is currently undergoing a demographic transition, because of ageing and increased life expectancy. 7 According to the 2017 Global Burden of Disease study, despite a lower prevalence of COPD in South Asia, the attributable morbidity and premature mortality due to chronic respiratory diseases was highest in South Asia with COPD being the most common cause of premature deaths among chronic respiratory diseases. 8 The area is also experiencing a change in the burden of risk factors with ambient air pollution becoming a greater risk due to rapid economic development. 8 While systematic reviews on the prevalence of COPD from Latin America 9 and sub-Saharan Africa 10 have been published previously, literature on current prevalence estimates of COPD and its common risk factors in South Asia is scarce. 11 Notably, few published data exist on the rural-urban, sex, and within and between country differences in the prevalence of COPD. Relevant and timely information on the prevalence of COPD in the area is crucial to inform, develop and implement context-appropriate policies and programmes for its prevention and control, in a setting where the burden is rising. 8 In COPD, airflow in and out of the lungs is limited due to chronic inflammation and narrowing of airways, which is a result of repeated and long-term exposure of the respiratory tract to noxious stimuli (tobacco smoke, indoor air pollution and repeated respiratory tract infections during childhood). 4 COPD presents as chronic bronchitis and emphysema. 4 However, variation in the underlying pathology and clinical presentation, and overlap with the symptoms of asthma and other chronic lung diseases often pose a challenge to making an accurate diagnosis of COPD. 12 Moreover, the gold standard diagnosis of COPD, which needs evaluation of lung air volumes using a spirometer, requires skilled personnel and quality assurance measures, which makes obtaining accurate data more challenging, especially in low-and middle-income countries where a skilled workforce is limited. 1, 12 A 2012 systematic review reported limitations in estimates of the prevalence of COPD in India due to a lack of data, concerns about the quality of studies, inconsistencies in study settings and population characteristics. 11 The availability of more recently published studies provides an opportunity to conduct a systematic review to obtain up-to-date estimates of the prevalence of COPD. These data can be used to inform policy-makers when planning and implementing populationlevel risk mitigation strategies to control the rising burden of COPD in South Asia.

We conducted a systematic review and meta-analysis of peer-reviewed literature to estimate the prevalence of COPD and chronic bronchitis in South Asia, according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. 13 We used the World Bank's classification of countries of the South Asia area: Afghanistan, Bhutan, Bangladesh, India, Maldives, Nepal, Pakistan and Sri Lanka. 6 We used standardized diagnostic criteria for definitions of COPD and chronic bronchitis. We defined COPD as the presence of persistent airflow limitation according to the Global Initiative for Chronic Obstructive Lung Disease, i.e. a post-bronchodilator ratio of forced expiratory volume in one second (FEV1) to the forced vital capacity (FVC), FEV1/FVC < 0.70 (fixed criteria), 1 or post-bronchodilator FEV1/FVC below the lower limit of normal, i.e. the lower fifth centile of values from a reference population. 14 We defined chronic bronchitis as the presence of chronic cough and phlegm according to the criteria of the Medical Research Council in the United Kingdom of Great Britain and Northern Ireland, i.e. cough and sputum production on most days continuously for 3 months for more than 2 consecutive years. 15 We registered the protocol for this systematic review in the international prospective register of systematic reviews (CRD42020206189).

We searched MEDLINE® Complete, Web of Science, Embase®, Scopus and CINAHL databases using keywords: chronic obstructive pulmonary disease; COPD; obstructive airway disease; obstructive lung disease; airflow obstruction; chronic bronchitis; emphysema; prevalence; and other related terms. These keywords were combined with terms for individual countries and demonyms: Afghan*; Bangladesh*; Bhutan*; India*; Maldiv*; Nepal*; Pakistan*; Sri Lanka*; and associated global areas -South Asia*; Central Asia* (see data repository for search terms). 16 The study inclusion criteria were (i) community-based studies reporting the prevalence of COPD or chronic bronchitis; (ii) cross-sectional, cohort and case-control design; and (iii) publication date between 1 January 1990 and 28 February 2021. We had no language restrictions. We hand-searched the reference lists of screened studies for additional relevant citations.

We used Covidence for management of systematic review citations. 17 Two authors independently screened the study titles and abstracts using the inclusion criteria to identify studies for full-text review. These authors undertook an independent full-text review of shortlisted articles, made the final decision to include or exclude studies from the review, independently assessed the methodological quality of included studies using the Joanna Briggs Institute checklist for prevalence studies, 18 and extracted data from all included studies into a structured data extraction sheet. The following data were extracted from the studies: authors' names; year of publication and data collection; study title and area; method of disease ascertainment; sample size; sampling technique; study participants; residence; sex; age group; prevalence of COPD and/or chronic bronchitis with their 95% confidence intervals (CIs); and associations between risk factors for and prevalence of COPD and/or chronic bronchitis.

We resolved inconsistencies between reviewers in screening, inclusion and exclusion of studies, quality appraisal and data extraction decisions through discussion. In cases of disagreement, the third reviewer made the final decision. Where necessary, we also contacted the authors of some publications for further information about the methods and data.

We included studies that used probability sampling techniques and standard definitions for disease ascertainment for the meta-analyses. We did not include studies conducted before 2000 in the meta-analyses. If more than one published study reported the prevalence from the same data set, we included the prevalence from the most recently published study. However, if the older studies provided more details on prevalence data compared with recently published studies, we included the older study data. In the qualitative summary we described characteristics of the studies and charted patterns of the prevalence data according to area, sex and criteria for COPD diagnosis.

We used Stata, version 16.1 (Stata Corp, College Station, United States of America) for all meta-analyses. We used the Stata metaprop command to estimate the pooled prevalence and generate forest plots of COPD (total, men and women) according to fixed criteria and lower limit of normal criteria. 19 We assessed statistical heterogeneity using the χ 2 test, percentage of variance due to heterogeneity using the I 2 test and estimated standard deviation of prevalence using the τ 2 test. Due to the considerable heterogeneity across studies, we used random-effects models to calculate the pooled prevalence estimates.

Our search of electronic databases and reference lists yielded a total of 1529 studies. After removing 493 duplicates, we screened 1036 titles and abstracts for inclusion and reviewed the full texts of 127 studies. Of these studies, 43 met the inclusion criteria and were included in the qualitative summary and 19 were included in the meta-analysis: 11 studies on COPD with the most recent or detailed data on prevalence of COPD and eight on chronic bronchitis that reported the overall prevalence ( Fig. 1) .

Of the studies included, 32 were undertaken in India, four in Bangladesh, three in Nepal, two in Pakistan and two in both India and Sri Lanka. Five of the studies were part of the multinational Burden of Obstructive Lung Disease study. [20] [21] [22] [23] [24] No studies from Afghanistan, Bhutan and Maldives met the inclusion criteria. We judged 16 of the included studies had acceptable quality in all appraisal criteria (data repository). 16, [20] [21] [22] [23] [24] [25] [26] [27] [28] [29] [30] [31] [32] [33] [34] [35] Only three studies (two from India and one from Nepal) collected the data on COPD prevalence in the past 5 years ( Table 1) .

Overall, 15 studies reported the prevalence of COPD using the standard diagnostic criteria and post-bronchodilation spirometry (Table 1) . Four studies reported data from Bangladesh, eight studies reported data from India, two from both India and Sri Lanka and one from Nepal. [20] [21] [22] [23] [24] [25] [26] [27] [28] [29] [30] [36] [37] [38] [39] Four studies with data from India 20,22-24 and two from Sri Systematic reviews Prevalence of COPD, eight countries Prashant Jarhyan et al.

Lanka 22, 23 reported the overall prevalence of COPD using the lower limit of normal criteria, six studies used the fixed criteria 26, 29, [36] [37] [38] [39] and four studies (two from India and one each from Bangladesh and Nepal) 21,25,28,30 used a combination of both the fixed and lower limit of normal criteria (Table 1) . Three studies, two from India 29,37 and one from Bangladesh, 36 reported the prevalence using the fixed criteria among women only ( Table 1) . The estimated pooled prevalence of COPD in the South Asian countries included in our study was 11.1% (95% CI: 7.4-14.8%) using the fixed criteria 21, 25, 26, 28, 30, 38 (Fig. 2 ) and 8.0% (95% CI: 5.6-10.4%) using the lower limit of normal criteria (Fig. 3) . 21, 22, 25, 28, 30 The study outcomes had considerable and statistically significant heterogeneity across South Asia (fixed criteria I 2 : 96.83%, P < 0.001; lower limit of normal criteria I 2 : 94.16%, P < 0.01), and within India with lower limit of normal criteria I 2 : 94.84%, P < 0.001.

The estimated pooled prevalence of COPD was highest in Bangladesh (13.1%; 95% CI: 12.1-14.0%) followed by India (11.1%; 95% CI: 3.5-18.7) and Nepal (8.5%; 95% CI: 7.2-10.0%; Fig. 2 ).

In India, the prevalence of COPD varied, with rural Srinagar in northern India having the highest overall prevalence reported in adults aged 40 years or older (19.3% according to the fixed criteria; 16.1% according to the lower limit of normal criteria) 21 and the lowest prevalence reported in south India (4.1% according to the fixed criteria; Table 1 ). 28 A higher prevalence of COPD was also reported in Bangladeshi men from rural Matlab and suburban Kamlapur (22.0% based on fixed criteria; 16.2% based on lower limit of normal criteria; Table 1 ). 25 COPD prevalence was found to be significantly higher in men than women in four studies, in Delhi 38 and Srinagar 21 according to the fixed criteria, and in Nepal 30 and rural Matlab, Bangladesh 25 according to both spirometry criteria. Only one study in Bangladesh compared rural versus non-rural samples and reported a significantly higher prevalence of COPD in rural dwellers (17.0% by fixed criteria and 12.5% by lower limit of normal criteria) than suburban dwellers (9.9% by fixed criteria and 8.0% by lower limit of normal criteria). 25

Thirteen studies reported the prevalence of chronic bronchitis and overall prevalence ranged from 2.9% to 9.1% ( Table 2) . [31] [32] [33] [34] [35] 43, 47, [51] [52] [53] [54] [55] [56] Studies varied according to residence (three both in rural and urban areas, 32, 33, 51 nine in rural areas only, 31, 34, 35, 43, 47, [52] [53] [54] [55] and one was unspecified) 56 and sex, with eight studies conducted among both men and women, 32, 33, 47, 51, 52, [54] [55] [56] four studies restricted to women 31, 34, 43, 53 and one study was restricted to men. 35 In two multicentre studies in India, the overall prevalence of chronic bronchitis was 4.1% (5.0% in men and 3.2% in women) in 2006 32 and 3.5% in 2012. 33 The prevalence of chronic bronchitis was higher in men 32,47,51,54 and rural dwellers ( Table 2 ). 32, 51 Eight studies (six from India and two from Pakistan), which diagnosed chronic bronchitis using standardized criteria and provided the overall prevalence of chronic bronchitis, were used in the meta-analysis (Table 2) . 32, 33, 47, 51, 52, [54] [55] [56] The overall estimated pooled prevalence of chronic bronchitis was 4.8% (95% CI: 4.0-5.5%): 5.0% (95% CI: 4.1-6.0%) in India and 3.6% (95% CI: 3.1-4.0) in Pakistan (Fig. 4) . Statistical heterogeneity was very high and statistically significant for all the studies included (I 2 : 96.93%; P < 0.001) and for studies undertaken in India (I 2 : 97.59%; P < 0.01). There was an insufficient number of relevant studies to calculate statistical heterogeneity in Pakistan.

Common risk factors associated with COPD and chronic bronchitis were age, smoking, lower socioeconomic status, exposure to environmental tobacco smoke, exposure to biomass fuel, exposure to dust, history of tuberculosis and history of allergy and/or asthma. 20 

Here we report on the prevalence of COPD and chronic bronchitis in South Asia. A substantial regional variation was seen in the prevalence of COPD and chronic bronchitis, with higher prevalence estimates reported by studies in north India 21 and Bangladesh. 25 While tobacco smoking and indoor air pollution were the most common risk factors assessed for their association with COPD, no population-based studies were found in the area that determined (. . .continued)

Prevalence of COPD, eight countries Prashant Jarhyan et al.

the association of COPD with other important risk factors such as ambient air pollution and occupational hazards. Within-country and betweencountry variations in the prevalence of COPD have been reported previously due to differences in the prevalence of risk factors, especially tobacco smoking. 63, 64 The higher prevalence of COPD in north India (Kashmir) was mainly ascribed to tobacco smoking using traditional hookahs and higher exposure to indoor air pollution. 21 The high prevalence of COPD in Bangladesh was also attributed to the high prevalence of tobacco smoking, particularly among men. 25 Traditional norms of offering smoking products, low awareness of the harmful effects of smoking among low-income groups and people living in rural areas, suboptimal implementation of tobacco control measures and limited access to cessation services may account for high prevalence estimates in these areas. 65 Thus, these relevant regional, sociocultural and economic factors need to be considered while planning strategies to reduce smoking, decrease the COPD burden and improve population lung health. 65 Indoor air pollution is one of the main causes of COPD, especially in South Asian women. 66 Although many governments have scaled up access to cleaner cooking fuels, the reach and change to cleaner fuels is suboptimal. Furthermore, the effect of this transition on the COPD burden, especially among women in South Asia, remains unclear and warrants further evaluation. 67 More specific approaches are required to understand the role of various indoor air pollutants, such as particulate matter, nitrogen dioxide, carbon monoxide, sulfur oxides, polycyclic organic matter and formaldehyde which are produced by combustion of biomass fuels, in the development of COPD and chronic bronchitis. 68, 69 Ambient air pollution is one of the main risk factors for COPD mortality and disability-adjusted life years lost, with the highest burden reported in South Asia. 8, 70 In 2015, Bangladesh, India and Nepal had the highest burden of particulate matter 2.5 (PM 2.5 ) and Bangladesh, India and Pakistan had the highest increase in the ozone levels and the highest mortality due to ambient PM 2.5 observed. 71 Increased air pollution aggravates COPD symptoms, known as COPD exacerbations, and in- creases hospitalizations and mortality. 72 Although a few studies from large cities in India have shown the short-term effect of increased ambient air pollution and increased hospital visits due to respiratory problems, 73,74 the long-term effects of extended exposure to ambient air pollution and its effects on lung function, morbidity and mortality need to be studied. 69, 75 Educating health-care providers and patients about the adverse health effects of ambient air pollution and simple measures that can be taken to reduce exposure, such as avoiding going out during periods of high pollution and wearing masks outdoors, is needed. 76 Few studies have assessed the association between COPD and respiratory infections in South Asia, such as lower respiratory tract infections and tuberculosis. 21, 24, 30 Given that many people in the area have been affected by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), 77 the long-term effects of this virus on the burden of COPD and other chronic respiratory diseases need to be assessed. Poor lung function associated with SARS-COV-2 and respiratory infections also requires monitoring to assess their long-term effects and the attributable risk for the development of COPD.

We also found that none of the included studies had assessed the presence of chronic bronchitis with airway obstruction in COPD. Chronic bronchitis in people with airway obstruction is associated with more severe disease, poor general health status, greater limitations on physical activity and higher mortality. 78 Therefore, COPD should be assessed together with the presence of chronic bronchitis in both clinical and research settings.

In our study, we tried to assess the current prevalence of COPD in South Asian countries. The strengths of our study include selection of recent studies, a comprehensive literature search using explicit definitions for COPD and chronic bronchitis according to international guidelines and a comprehensive quality assessment of studies selected for the review.

Our study has some limitations. First, because few studies in the area were available, our pooled prevalence estimates of COPD cannot be generalized to all South Asian countries. Only one study each from Bangladesh and India assessed the prevalence of COPD in urban areas and the only study from Nepal 80 while the ambient air pollution has increased in South Asia. 81 These limitations highlight the lack of research to determine the accurate burden of COPD in the area and the need for large population-based studies with rigorous methods to generate accurate prevalence estimates in various population subgroups as well as attributable risks of common risk factors, including outdoor air pollution, occupational exposure and infections. Such data are important to inform the development and implementation of context-relevant policies and programmes for reducing the increasing burden of COPD and its risk factors. Estimation of the prevalence of COPD is challenging for researchers in low-and middle-income countries. As a result, there is likely a large burden of undetected COPD. COPD is a complex disease with varied presentations and new phenotypes being identified. 82, 83 Conducting post-bronchodilation spirometry, which is required for the confirmation of a diagnosis of COPD, is resource intensive and requires a high Some studies have suggested screening strategies for early detection of COPD. 84, 85 However, COPD screening needs further evaluation and feasibil-ity studies and should be supported by strengthening of public health infrastructure for the confirmation of diagnosis, early initiation of pharmacological and non-pharmacological treatment including pulmonary rehabilitation. 85 In conclusion, given the paucity of studies on the current burden of COPD and its risk factors in most South Asian countries, future research in these countries should ensure that standardized diagnostic criteria are used to examine the contribution of exposure to contextrelevant risk factors to inform COPD prevention and control policies. 

Распространенность хронической обструктивной болезни легких и хронического бронхита в восьми странах: систематический обзор и метаанализ Цель Оценить распространенность хронической обструктивной болезни легких (ХОБЛ) и хронического бронхита в восьми странах Южной Азии посредством систематического обзора и метаанализа. Методы Авторы провели поиск по базам данных MEDLINE® Complete, Web of Science, Embase®, Scopus, CINAHL и по спискам литературы отобранных исследований, опубликованных в период с января 1990 года по февраль 2021 года, для определения распространенности ХОБЛ и хронического бронхита в странах Южной Азии. Для определения ХОБЛ и хронического бронхита авторы использовали стандартизированные диагностические критерии. Два рецензента провели скрининг исследования, обзор полного текста, оценку качества и выборку данных. Ре з у л ьт а т ы И з 1 5 2 9 п о л у ч е н н ы х и с с л е д о в а н и й 43 соответствовали критериям включения: 32 исследования предоставили данные из Индии; четыре -из Бангладеш; три -из Непала; два -из Пакистана и два -из Индии и Шри-Ланки вместе.. В 26 исследованиях использовались стандартизированные диагностические определения, а 19 исследований были включены в метаанализ. Показатель объединенной распространенности ХОБЛ составил 11,1% (95%й доверительный интервал, ДИ: 7,4-14,8%) при использовании фиксированных критериев Глобальной инициативы по хронической обструктивной болезни легких, и 8,0% (95%-й ДИ: 5,6-10,4%) при использовании нижней границы нормы критериев. Распространенность ХОБЛ была самой высокой среди мужчин в северной Индии (19,4%) и Бангладеш (13,5%). Показатель объединенной распространенности хронического бронхита составил 5,0% (95%-й ДИ: 4,1-6,0%) в Индии и 3,6% (95%й ДИ: 3,1-4,0%) в Пакистане. Вывод Включенные страны имеют высокую распространенность ХОБЛ, хотя она варьировалась в зависимости от географического региона и характеристик исследования. Чтобы разработать стратегии по профилактике и борьбе с заболеванием, в будущих исследованиях в Южной Азии следует использовать стандартизированные диагностические критерии для изучения вклада факторов риска, зависимых от условий.

Prevalence of COPD, eight countries Prashant Jarhyan et al.

Objetivo Estimar la prevalencia de las enfermedades pulmonares obstructivas crónicas (EPOC) y de la bronquitis crónica en ocho países del sur de Asia mediante una revisión sistemática y un metanálisis. Métodos Se realizaron búsquedas en MEDLINE® Complete, Web of Science, Embase®, Scopus, CINAHL y en las listas de referencias de los estudios seleccionados en busca de investigaciones sobre la prevalencia de las EPOC y de la bronquitis crónica en los países del sur de Asia publicadas entre enero de 1990 y febrero de 2021. Se utilizaron criterios de diagnóstico estandarizados para las definiciones de EPOC y bronquitis crónica. Dos revisores realizaron la selección de los estudios, la revisión del texto completo, la valoración de la calidad y la extracción de los datos. Resultados De los 1529 estudios recuperados, 43 cumplían los criterios de inclusión: 32 proporcionaron datos de la India; cuatro de Bangladesh; tres de Nepal; dos de Pakistán; y dos tanto de la India como de Sri Lanka. Veintiséis estudios utilizaron definiciones diagnósticas estandarizadas y 19 se incluyeron en el metanálisis. La prevalencia conjunta estimada de las EPOC fue del 11,1 % (intervalo de confianza del 95 %, IC: 7,4-14,8 %), utilizando los criterios fijos de la Iniciativa Mundial para las Enfermedades Pulmonares Obstructivas Crónicas y del 8,0 % (IC del 95 %: 5,6-10,4 %) utilizando los criterios del límite inferior de la normalidad. La prevalencia de las EPOC fue mayor en el norte de la India (19,4 %) y en Bangladesh (13,5 %) y en los varones. La prevalencia conjunta estimada de bronquitis crónica fue del 5,0 % (IC del 95 %: 4,1-6,0 %) en la India y del 3,6 % (IC del 95 %: 3,1-4,0 %) en Pakistán. Conclusión Los países incluidos tienen una alta prevalencia de EPOC, aunque esta varía según la zona geográfica y las características del estudio. Las investigaciones futuras en el sur de Asia deberían utilizar criterios de diagnóstico estandarizados para analizar la contribución de los factores de riesgo específicos del entorno con el fin de fundamentar las estrategias de prevención y control.

Prevalence of COPD, eight countries Prashant Jarhyan et al.

Global strategy for the diagnosis, management, and prevention of chronic obstructive pulmonary disease: 2021 report

Global Initiative for Chronic Obstructive Lung Disease

BOLD Collaborative Research Group. International variation in the prevalence of COPD (the BOLD Study): a population-based prevalence study

Chronic obstructive pulmonary disease (COPD) in Vietnam

World Health Organization

Geneva: World Health Organization

Global and regional estimates of COPD prevalence: systematic review and meta-analysis

World Bank Group

Non-communicable diseases in South Asia: contemporary perspectives

GBD Chronic Respiratory Disease Collaborators. Prevalence and attributable health burden of chronic respiratory diseases, 1990-2017: a systematic analysis for the Global Burden of Disease Study

The epidemiology and burden of COPD in Latin America and the Caribbean: systematic review and meta-analysis

Chronic obstructive pulmonary disease in sub-Saharan Africa: a systematic review

Prevalence of COPD in India: a systematic review

Epidemiology and costs of chronic obstructive pulmonary disease

Preferred reporting items for systematic reviews and meta-analyses: the PRISMA statement

Lower limit of normal or FEV1/FVC < 0.70 in diagnosing COPD: an evidence-based review

Definition and classification of chronic bronchitis for clinical and epidemiological purposes. A report to the Medical Research Council by their Committee on the Aetiology of Chronic Bronchitis

Supplementary material. London: figshare

Melbourne: Veritas Health Innovation; 2021. Available from: www .covidence .org

The development of a critical appraisal tool for use in systematic reviews addressing questions of prevalence

Metaprop: a Stata command to perform meta-analysis of binomial data

Burden of Obstructive Lung Disease (BOLD) Study. Chronic obstructive pulmonary disease mortality and prevalence: the associations with smoking and poverty-a BOLD analysis

Prevalence of chronic airflow limitation in Kashmir, North India: results from the BOLD study

Airflow obstruction and cardio-metabolic comorbidities

The association between chronic airflow obstruction and poverty in 12 sites of the multinational BOLD study

Prevalence and population-attributable risk for chronic airflow obstruction in a large multinational study

Prevalence and determinants of chronic obstructive pulmonary disease (COPD) in Bangladesh

Prevalence and risk factors of chronic obstructive pulmonary disease (COPD) in Dhaka city population

Socioeconomic status and COPD among low-and middle-income countries

Prevalence of airflow obstruction as measured by spirometry, in rural southern Indian adults

Prevalence of chronic obstructive pulmonary disease in rural women of Tamilnadu: implications for refining disease burden assessments attributable to household biomass combustion

Prevalence of chronic obstructive pulmonary disease and its associated factors in Nepal: findings from a community-based household survey

Prevalence and determinants of self-reported chronic bronchitis among women in rural central India

Asthma Epidemiology Study Group. A multicentric study on epidemiology of chronic obstructive pulmonary disease and its relationship with tobacco smoking and environmental tobacco smoke exposure

Indian study on epidemiology of asthma, respiratory symptoms and chronic bronchitis in adults (INSEARCH)

Identification of a threshold for biomass exposure index for chronic bronchitis in rural women of Mysore district

Variation in the prevalence of chronic bronchitis among smokers: a crosssectional study

Indoor biomass fuel smoke exposure as a risk factor for chronic obstructive pulmonary disease (COPD) for women of rural Bangladesh. Chattagram Maa-O-Shishu Hospital Med Coll J

COPDprevalence and risk study among females of rural area, district Ambala, Haryana, India

An epidemiological profile of chronic obstructive pulmonary disease: a community-based study in Delhi

The Mysuru studies of determinants of health in rural adults (MUDHRA), India. Epidemiol Health

Air pollution and environmental risk factors for altered lung function among adult women of an urban slum area of Delhi: a prevalence study

Prevalence of COPD in rural population

Respiratory symptoms, lung function decrement and chronic obstructive pulmonary disease in pre-menopausal Indian women exposed to biomass smoke

Chronic bronchitis and airflow obstruction is associated with household cooking fuel use among never-smoking women: a community-based cross-sectional study in Odisha, India

Prevalence of chronic obstructive pulmonary disease and its association with tobacco smoking and environmental tobacco smoke exposure among rural population

Impact of biomass fuel exposure from traditional stoves on lung functions in adult women of a rural Indian village

Prevalence of chronic obstructive pulmonary disease (COPD) among Indian population

Prevalence of chronic respiratory disorders in a rural area of North West India: a population-based study

Pilot study of chronic obstructive pulmonary disease in an industrial town in India

Prevalence of selected chronic non-communicable diseases in Nepal

Reduced lung function due to biomass smoke exposure in young adults in rural Nepal

Epidemiological aspects of chronic bronchitis in Shimla hills

Prevalence of chronic bronchitis in selected districts of Kashmir Valley

Indoor air pollution from biomass combustion and its adverse health effects in central India: an exposureresponse study

Prevalence of chronic respiratory diseases from a rural area in Kerala, southern India

Chronic bronchitis in women using solid biomass fuel in rural Peshawar

BREATHE Study Group. Distribution of COPD-related symptoms in the Middle East and North Africa: results of the BREATHE study

Prevalence of chronic bronchitis in urban population of Kashmir

Ambient air pollution and chronic respiratory morbidity in Delhi

A field study on follow up at 10 years of prevalence of chronic obstructive pulmonary disease & peak expiratory flow rate

Validation of a structured questionnaire for COPD and prevalence of COPD in rural area of Mysore: A pilot study

A study on morbidity pattern among geriatric population of an urban slum

Domestic smoke pollution and prevalence of chronic bronchitis/asthma in a rural area of Kashmir

CRONICAS Cohort Study Group. Prevalence of chronic obstructive pulmonary disease and variation in risk factors across four geographically diverse resource-limited settings in Peru

CanCOLD Collaborative Research Group. The prevalence of chronic obstructive pulmonary disease (COPD) and the heterogeneity of risk factors in the Canadian population: results from the Canadian Obstructive Lung Disease (COLD) Study. Int J Chron Obstruct Pulmon Dis

Smoking cessation interventions in South Asian countries: protocol for scoping review

Effect of indoor air pollution on chronic obstructive pulmonary disease (COPD) deaths in southern Asia -a systematic review and meta-analysis. Toxics

Energy challenges for clean cooking in Asia, the background, and possible policy solutions. ADBI working paper 1007. Tokyo: Asian Development Bank Institute

Indoor air pollution, related human diseases, and recent trends in the control and improvement of indoor air quality

Environmental and health impacts of air pollution: a review. Front Public Health

Global burden of COPD attributable to ambient PM2.5 in 204 countries and territories, 1990 to 2019: a systematic analysis for the Global Burden of Disease Study

Estimates and 25-year trends of the global burden of disease attributable to ambient air pollution: an analysis of data from the Global Burden of Diseases Study

Air pollution and chronic airway diseases: what should people know and do? J Thorac Dis

Association of air quality with respiratory and cardiovascular morbidity rate in Delhi, India

Ambient air pollution and chronic respiratory morbidity in Delhi

Contribution of air pollution to COPD and small airway dysfunction

Perng DW; on behalf the COPD Assembly of the APSR. Management of COPD in Asia: a position statement of the Asian Pacific Society of Respirology

Pandemic preparedness and response to COVID-19 in South Asian countries

The chronic bronchitis phenotype in chronic obstructive pulmonary disease: features and implications

India State-Level Disease Burden Initiative CRD Collaborators. The burden of chronic respiratory diseases and their heterogeneity across the states of India: the Global Burden of Disease Study 1990-2016. Lancet Glob Health

New Delhi: Ministry of Health and Family Welfare, Government of India

Half the world's population are exposed to increasing air pollution

Changes in definition lead to changes in the clinical characteristics across COPD categories according to GOLD 2017: a national cross-sectional survey in China

Chronic obstructive pulmonary disease and phenotypes: a state-of-the-art

Effectiveness of case finding strategies for COPD in primary care: a systematic review and metaanalysis. NPJ Prim Care Respir Med

Diagnostic accuracy of a two-stage sequential screening strategy implemented by community health workers (CHWs) to identify individuals with COPD in rural India