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Doi:10.3402/gha.v4i0.7226

Prevalence of chronic obstructivepulmonary disease in rural women ofTamilnadu: implications for refiningdisease burden assessmentsattributable to household biomasscombustion Priscilla Johnson1Kalpana Balakrishnan2,Padmavathi Ramaswamy1, Santu Ghosh2,Muthukumar Sadhasivam3, Omprakash Abirami1,Bernard W. C. Sathiasekaran4, Kirk R. Smith5,Vijayalakshmi Thanasekaraan6 and Arcot S. Subhashini1 1Department of Physiology, Sri Ramachandra University, Chennai, India; 2Department ofEnvironmental Health Engineering, Sri Ramachandra University, Chennai, India; 3Department ofPhysiology, Muthukumaran Medical College, Chennai, India; 4Department of Community Medicine,Sri Ramachandra University, Chennai, India; 5School of Public Health, University of California,Berkeley, CA, USA; 6Department of Chest Medicine, Sri Ramachandra University, Chennai, India Background: Chronic obstructive pulmonary disease (COPD) is the 13th leading cause of burden of diseaseworldwide and is expected to become 5th by 2020. Biomass fuel combustion significantly contributes toCOPD, although smoking is recognized as the most important risk factor. Rural women in developingcountries bear the largest share of this burden resulting from chronic exposures to biomass fuelsmoke. Although there is considerable strength of evidence for the association between COPD and biomasssmoke exposure, limited information is available on the background prevalence of COPD in thesepopulations.
Objective: This study was conducted to estimate the prevalence of COPD and its associated factors amongnon-smoking rural women in Tiruvallur district of Tamilnadu in Southern India.
Design: This cross-sectional study was conducted among 900 non-smoking women aged above 30 years, from45 rural villages of Tiruvallur district of Tamilnadu in Southern India in the period between January and May2007. COPD assessments were done using a combination of clinical examination and spirometry. Logisticregression analysis was performed to examine the association between COPD and use of biomass for cooking.
R software was used for statistical analysis.
Results: The overall prevalence of COPD in this study was found to be 2.44% (95% CI: 1.43
3.45). COPDprevalence was higher in biomass fuel users than the clean fuel users 2.5 vs. 2%, (OR: 1.24; 95% CI: 0.36
6.64)and it was two times higher (3%) in women who spend
2 hours/day in the kitchen involved in cooking. Useof solid fuel was associated with higher risk for COPD, although no statistically significant results wereobtained in this study.
Conclusion: The estimates generated in this study will contribute significantly to the growing database ofavailable information on COPD prevalence in rural women. Moreover, with concomitant indoor air pollutionmeasurements, it may be possible to increase the resolution of the association between biomass use andCOPD prevalence and refine available attributable burden of disease estimates.
This paper was orally presented in the Annual conferenceInternational Society of Environmental Epidemiology held in Pasadena in 2008.
Global Health Action 2011. # 2011 Priscilla Johnson et al. This is an Open Access article distributed under the terms of the Creative Commons Attribution- Noncommercial 3.0 Unported License (http://creativecommons.org/licenses/by-nc/3.0/), permitting all non-commercial use, distribution, and reproductionin any medium, provided the original work is properly cited.
Citation: Global Health Action 2011, 4: 7226 - DOI: 10.3402/gha.v4i0.7226 (page number not for citation purpose) Priscilla Johnson et al.
Keywords: chronic obstructive pulmonary disease; prevalence; biomass fuel users; rural women; disease burden Received: 25 April 2011; Revised: 7 August 2011; Accepted: 29 September 2011; Published: 3 November 2011 Chronicobstructivepulmonarydisease(COPD)is Baseline information on prevalence of COPD is an the fourth leading cause of death and 13th important input for disease burden estimations as well as leading cause of burden of diseases worldwide for estimations of attributable disease burdens for im- with projected increases in its contributions over the next portant risk factors. Most previous studies have focused decade (1). The global initiative for chronic obstructive on prevalence of COPD in men addressing primarily lung disease (GOLD) has classified COPD as ‘a disease smoking as a risk factor. Few studies have attempted to state characterized by airflow limitation that is not fully assess prevalence among non-smoking rural women in reversible. The airflow limitation is usually both progres- developing countries using primarily biomass for cook- sive and associated with an abnormal inflammatory ing. Estimates based on health care resource utilization in response of the lungs to noxious particles or gases' (2, 3).
this setting may underestimate true prevalence and Active smoking is the major risk factor for COPD probably be biased toward the more severe and sympto- worldwide, and the risk attributable to active smoking in matic cases. Hospital-based estimates of COPD preva-lence are also often hindered by unavailability of health COPD varies from 40 to 70% according to the country care data, inaccuracies in coding as well as inconsistent (4). Although smoking remains the predominant risk physician recognition of early disease.
factor (5
7), it needs to be emphasized that prevalence of With this background, we report here results of a COPD in non-smokers suggests the existence of other community-based cross-sectional assessment for COPD risk factors such as passive smoking, occupational that included physician diagnosis for COPD using exposure, and indoor air pollution (8
10).
pulmonary function testing with bronchodilatation, Recently, exposure to biomass smoke resulting from among rural women of Southern India.
household combustion of solid fuels has been identifiedas an important risk factor for COPD, with rural womenin developing countries bearing most of this disease Materials and methods burden (11). In addition to respirable particulate matter, This cross-sectional study was conducted in Tiruvallur, a biomass combustion results in high levels of pollutants district that has 605,866 households comprising a popu- such as carbon monoxide, oxides of nitrogen and sulphur, lation of 2,738,866 persons with approximately an equal formaldehyde, benzo(a)pyrene, and benzene that are a distribution of males and females in the southern India major source of respiratory irritants in the etiopathogen- state of Tamilnadu in India (16). The study was approved esis of COPD (12).
by the Institutional Ethics committee of Sri Ramachan- Although COPD affects twice as many males as dra University on 24 August 2006 (MEC/06/52/44) andthe study was conducted between January and May 2007.
females, this difference will diminish, given the fact that Sample size of 900 subjects was calculated for the study more and more females throughout the world have taken based on the following factors: an expected 2.55% up smoking in the past few years in developed countries, prevalence of COPD for women in South India; and non-smoking females are exposed to biomass desired confidence level of (a) of 0.05; power of the combustion products in developing countries.
study (1 b) 0.80: and design effect 2.
Recent studies have made important contributions in The study subjects were selected through cluster examining temporal, spatial, or multipollutant patterns, in sampling using probability proportion to size criteria.
addition to day-to-day or seasonal variability in house- This approach resulted in the selection of 45 rural villages hold concentrations and exposures in biomass using out of 612 small villages with population less than 10,000 homes (13
15). Collectively, the evidence from these in Tiruvallur district (Census 2001). In each village that studies shows that rural women, children in solid fuel was selected by cluster sampling method, the center of the using settings experience extremely high levels of air village was located by spinning a pencil and seeing the pollutants often at least an order of magnitude higher direction in which it stopped, the street in that particular than what is commonly considered as safe levels of direction comprising various households was selected.
exposure. WHO's Comparative Risk Assessment (15) Twenty females from that particular street of that village estimated that about 950,000 children die each year from were selected for study, so that a total of 900 female acute lower respiratory infections as a result of these subjects were recruited.
exposures worldwide along with about 650,000 premature The selection criteria included women aged 30 years deaths of women from COPD and lung cancer (10).
and above who have been residents of the villages in Citation: Global Health Action 2011, 4: 7226 - DOI: 10.3402/gha.v4i0.7226 (page number not for citation purpose) Prevalence of COPD in rural women of Tamilnadu Tiruvallur district for a minimum period of 5 years who no more air can be expelled while maintaining an upright did not report a history of bronchial asthma, pulmonary posture. The subjects were verbally encouraged to con- tuberculosis, cardiac diseases, pregnancy, diabetes, and tinue to exhale the air at the end of the maneuver to cancer. Only one female member from each household obtain optimal effort, for example, by saying ‘keep who fulfilled the selection criteria was finally recruited. In going.' The same was repeated for a minimum of three certain occasional households with more than one eligible maneuvers and not more than eight was done for member, a random selection was done. Ten (0.92%) acceptability and repeatability. Spirobank is a spirometer subjects refused consent. About 1,016 households includ- that is designed to facilitate the total valuation of lung ing approximately 1,087 members were contacted to function such as forced vital capacity (FVC), vital reach the desired sample size of 900 participants.
capacity (VC), and maximal voluntary ventilation Informed written consent was obtained before recruiting (MVV) tests with pre and post comparison. FVC, forced any person into the study. Once the persons gave informed expiratory volume in 1 second (FEV1), peak expiratory consent, to be part of the study, questionnaire was flow rate peak expiratory flow rate (PEFR), and mid administered that collected information on known risk expiratory volume (FEF 25
75%) values were recorded.
factors for COPD, details on type of fuel (biomass, clean), A complete flow volume loop was obtained from the duration of cooking involvement in years (time interval spirometer. The values of the largest FVC and the largest between start and stop of cooking/till the date of inter- FEV1 were taken from all of the three reproducible and view), average total hours involved in cooking in a day, usable curves (acceptable start of test and free from kitchen configuration, and so on (kitchen indoor/outdoor, artifact). The data were compared with individual pre- with or without windows/openings). A detailed clinical dictive values based on age, sex, body weight, standing history on respiratory symptoms was also obtained. All height, and ethnic group and were interpreted to arrive at symptomatic women were then subjected to pulmonary the diagnosis (18). Most of the sources of variation in function tests. COPD cases were diagnosed based on the pulmonary function assessment such as motivation and three criteria: (1) cough with expectoration on most days of effort and body position were controlled by following the week for 3 months of the year for at least 2 consecutive American thoracic society (ATS) guidelines and using years, (2) forced expiratory volume in 1 second (FEV standardized verbal encouragement phrases (17, 19, 20).
Spirometry with bronchodilation testing after inhala- 1)/FVC value lower than 80% predicted as diagnosed by spirometry, and (3) reversibility test result of B15% tion of 200 mg of Salbutamol was carried out in order to or B200 ml improvement in FEV confirm COPD (21). COPD cases were defined as 1 compared to pre- bronchodilator FEV follows: reversibility test result of B15% improvement in 1. All the three criteria were consid- ered as essential for diagnosis of COPD.
FEV1 compared to prebronchodilator FEV1, or post- Subjects were instructed to avoid the activities such as bronchodilator improvement of FEV1B200 mL, and performing vigorous exercise within 30 min of testing, FEV1/FVCB70% and no history of atopy or pattern of wearing clothing that substantially restricts full chest and disease suggestive of asthma. Data collectors were trained abdominal expansion, and eating a large meal within on questionnaire administration, Anthropometry mea- 2 hours of testing, and these requirements were given to surement, Pulmonary Function Tests (PFT) assessment the patient at the time of making the recruitment (17).
as per ATS guidelines and the same set of investigators The patient's age, height, and weight (wearing indoor were involved in the collection of information from the clothes without footwears) were recorded for use in the study population to avoid the information bias and to calculation of reference values basically to arrive at the minimize the interobserver variability. All the data classification of the derived values with respect to a recorded on data forms were stored in locked cabinets reference population. Body mass index was calculated as to maintain confidentiality. Questionnaire data were kilogram per meter square. The height was measured entered in Microsoft Access for data analysis. Statistical without footwear, with the feet together, standing as tall analysis was performed using ‘R' Version 2. Prevalence as possible with the eyes level and looking straight ahead was expressed in terms of percentage. Logistic regression using a stadiometer.
analysis was performed to examine the association Pulmonary function test was performed following between selected risk factors and COPD. The odds ratios American Thoracic Society guidelines using a portable were calculated.
data logging Spirometer (MIR Spirobank) (17). This testwas performed in a sitting position with nose closed by nose clips and a mouthpiece placed in mouth making Table 1 provides important descriptive characteristics of sure that the lips were sealed around the mouthpiece and the study population. Most study subjects (66%) were that the tongue did not occlude it. The subject was then under the age of 50 while only a third of the subjects were asked to inhale completely and rapidly with a pause of 1 above 50. Majority of the women were illiterate and of second at total lung capacity and exhale maximally until low socioeconomic status (with household income BRs.
Citation: Global Health Action 2011, 4: 7226 - DOI: 10.3402/gha.v4i0.7226 (page number not for citation purpose) Priscilla Johnson et al.
Table 1. Descriptive characteristics and prevalence of were cooking outdoors most part of the year. The years COPD of the study population of Tiruvallur district, of cooking ranged from 5 to 55 years with an average of 29.3911.2 years per woman. The mean time spent incooking was 3.191.2 hours per day. 40.3% were exposed Prevalence (%) with to other particle sources such as mosquito coils and incense smoke. Although 5% of participants reported tohave positive symptoms such as chronic cough with 2.44 (1.43, 3.45) phlegm, only 2.4% turned out to be COPD positive clinically and spirometrically. Distribution of the study population in the several descriptive categories such as age, religion, literacy status, house type, kitchen type, and so on was similar to the distribution given in census data indicating the robustness of the data (16).
Prevalence of COPD Overall, 2.44% (1.43, 3.45) of the study participants 1.5 ( 0.19, 3.19) (22 of 900 subjects) were diagnosed with COPD. Table 1 also provides the prevalence of COPD among several subcategories within the study population. Although the difference in prevalence of COPD across subcategories was not statistically significant, we describe the differ- ential prevalence across select subcategories to illustrate Kitchen type Outdoor possible contributions from risks related to biomass fuel use. Prevalence of COPD was higher among the elderly 2.0 ( 0.26, 4.26)
50 years), biomass users, women exposed to Environmental tobacco smoke (ETS), women who spent
2 hours/day in the kitchen for cooking, and women who have been involved in cooking for more than 15 years. As seen in Table 1, the majority of women were biomass users with greater than 15 years of cooking experience. Thus, although the observed differences in 1.2 ( 0.17, 2.57) prevalence were all in the direction indicating an effect of biomass use, the sample lacked adequate power to detect statistically significant differences.
Table 2 shows the univariate odds ratio and the adjusted effects of type of cooking fuel and other variables on prevalence of COPD. The odds ratio for the use of solid fuels and COPD was 1.43 with 95% 2.25 (0.87, 3.63) confidence interval of 0.36
5.73. Similarly, the odds ratio calculated for other related variables such as age (OR: 1.4; 95% CI: 0.49, 4.01), indoor kitchen type (OR: 1.1; aPucca
house with cemented walls and roof; bKutcha
crude, 95% CI: 0.43, 2.8), cooking duration (OR: 2.05; 95% CI: imperfect, temporary house with walls and roof made of mud or 0.73, 5.72), and history of passive smoking (OR: 1.16; 95% CI: 0.44, 3.05) also showed increased risk, althoughnot statistically significant.
2,000 or $40 per month). Although the study subjectswere all non-smokers, 25% reported exposure to passivesmoking from male smokers within their household.
Nearly 50% reported spending most of their time indoors This population-based epidemiological study was carried on household chores and the rest reported working out for estimating the prevalence of COPD as there have outdoor during the day. A high proportion of study been few community-based prevalence assessments for participants used biomass as their primary fuel (83.7%) in COPD in India, especially among non-smoking rural unimproved stoves with only 16.3% using cleaner fuels women and men, and potential contributions from other such as kerosene and LPG. Nearly 50% of study house- risk factors such as biomass combustion and ETS have not holds had indoor kitchens and the rest of the households been extensively studied. In a recent multicentric study in Citation: Global Health Action 2011, 4: 7226 - DOI: 10.3402/gha.v4i0.7226 (page number not for citation purpose) Prevalence of COPD in rural women of Tamilnadu Table 2. Univariate OR and adjusted effects of type of cooking fuel and other variables on prevalence of chronic obstructivepulmonary disease Univariate OR with 95% CI Adjusted OR with 95% CI 2.02 (0.86, 4.71) 0.52 (0.19, 1.44) 0.55 (0.19, 1.54) 0.55 (0.23, 1.31) 0.72 (0.27, 1.95) 0.55 (0.16, 1.89) 1.06 (0.45, 2.52) 1.01 (0.41, 2.49) 1.03 (0.44, 2.41) 1.24 (0.36, 4.25) 1.43 (0.36, 5.73) 1.16 (0.44, 3.05) 0.63 (0.24, 1.62) 0.52 (0.19, 1.47) 2.36 (0.69, 8.03) 1.76 (0.45, 6.83) 2.05 (0.73, 5.72) 1.02 (0.41, 2.54) aPucca
house with cemented walls and roof; bKutcha
crude, imperfect, temporary house with walls and roof made of mud or thatch.
India, prevalence of smoking in women was found to be multicentric study] (22, 25
27) albeit slightly lower, where only 2% with most of them residing in urban areas (22).
PEFR and sets of questions were used for the diagnosis of In this study, a meticulous diagnostic approach was COPD. The estimate is higher than what has been chosen for identification of the COPD cases, including a reported for an urban population in the neighboring complete clinical evaluation with spirometry before and urban area in Chennai (25).
after bronchodilation, to minimize misclassification of However, because most studies were hospital-based asthmatics as COPD cases. Few community-based studies studies and as prevalence estimates were done using have used such rigorous criteria. The prevalence estimate smoking rates in the study population, results were likely of COPD of 2.44% obtained in this study population to bias estimates toward higher prevalence (28
30).
of Indian, rural, and primarily biomass-using women of Moreover, insufficient information on biomass use was
30 years of age is higher than the world prevalence of available in most of the previous studies to make detailed 0.8% (as reported by WHO). The prevalence in developed comparisons. Furthermore, biases resulting from the use countries assessed mostly on smokers ranges from 4% to of alternative diagnostic protocols such as self-reporting as high as 57% and prevalence tended to vary by the and evaluation without spirometry or without broncho- method used to estimate prevalence, namely spirometry dilation that could all contribute to the differences in the (11 studies), respiratory symptoms (14 studies), patient- prevalence observed between the studies could not be reported disease (10 studies), or expert opinion. The sufficiently examined (23, 24). Prevalence of COPD in lowest prevalence was based on expert opinion (23, 24).
subjects aged ]50 years in the study sample was 3.6% Prevalence estimates obtained in this study are similar to (1.49
5.7) as compared to subjects B50 years (1.8%).
what has been reported in other Indian studies [1.2% by Although prevalence of COPD in younger subjects is Thiruvengadam et al. in Chennai urban, 2.5% by Ray lower than in older individuals, it is of public health et al. in rural South India, 3.9% by Jindal et al.in rural importance as the younger population with a long life North India, 3.2% by Jindal et al. in rural India, a expectancy will continue to be exposed to several risk Citation: Global Health Action 2011, 4: 7226 - DOI: 10.3402/gha.v4i0.7226 (page number not for citation purpose) Priscilla Johnson et al.
factors such as biomass fuel use, passive smoking, and exposure across geographical regions (12, 13, 38). With an increasing body of prevalence information across Logistic regression analysis has shown increased risk of regions (states), where concomitant indoor pollution COPD in women using biomass fuel for cooking, in older measurements are being made, it may be possible to women, in women involved in cooking for longer increase the resolution of the association between bio- duration, in women living in kutcha houses, and in mass use and COPD prevalence across a continuum of women with history of passive smoking, although population exposures. The study has contributed by statistically not significant. The lack of statistical sig- providing large scientific database of health data and nificance is probably due to the sample size and power of has also developed methods and protocols for large-scale the sample size. The sample size for this study was health assessments related to COPD for future applica- calculated for generating the prevalence of COPD, and tions in similar areas of research. Biomass will remain the the study design and the sampling frame work were also principal cooking fuel for a large majority of rural chosen for the same. Hence, this study is not adequately households for many years to come. Hence, an effective powered to examine the association between COPD and mitigation strategy should employ a variety of options, its risk factors, although the direction of the association from improvements in fuels and cooking technologies to of the select risk factors is similar to what is reported in housing improvements. Epidemiological studies such as the literature.
what has been accomplished in this study pave the way As studies have demonstrated that improved cook for understanding opportunities for intervention design stoves reduce considerably the smoke, either by having as well as in monitoring and evaluation of intervention a far better combustion or by having an excess of air or with a combination of both, the health impacts of smoke Moreover, it is difficult to estimate the effectiveness of from open fires inside dwellings can be reduced using an intervention in situations where preintervention esti- such improved cook stoves, changes to the environment mates of health parameter are inadequate, which requires (e.g. use of a chimney), and changes to user behavior (e.g.
a demanding study design and analysis to examine or drying fuel wood before use, using a lid during cooking) quantify causal associations (39). Such baseline preva- (31). Hence, young adults have to be targeted early by the lence information in biomass using populations is also health authorities to promote awareness of the disease useful for future cross-sectional assessments that may be and its risk factors and thereby reduce the morbidity and used to assess intervention efficacy or for making mortality due to COPD.
comparisons with other populations to frame an inter-vention.
Implications for refining disease burdenassessments attributable to biomass combustionThis prevalence estimate can also be used for calculation of global burden of COPD as COPD is the 13th leading In conclusion, this cross-sectional population-based cause of global burden of disease worldwide with study has estimated the COPD prevalence in a non- projected increase in its contribution over the next smoking, primarily biomass-using rural women popula- tion, using objective lung function measurements in The association between household biomass combus- addition to clinical criteria. The burden of disease tion and increased risk of COPD in rural women has been attributable to indoor air pollution has only been recently documented in many studies (32, 33) and has been used in recognized as an important contributor to national the WHO lead comparative risk assessments (CRA) and burden of disease. Integration of the results from this burden of disease calculations in 2002 (34, 35). An study with exposure studies will help in refining disease increasing body of animal studies also lend mechanistic burden estimates that are attributable to indoor air support for this association (36, 37). Most disease burden pollution. It is hoped that the baseline prevalence calculations have to rely on routinely collected secondary estimate for COPD generated in Tiruvallur district of health data to estimate baseline prevalence. These esti- Tamilnadu can be used by the researchers as well as local mates are often aggregated at the national level, masking public health officials in future for the implementation of differences that may exist across states in India both in interventions to reduce the morbidity, mortality, and terms of exposures and outcomes.
economic burden due to COPD.
An increasing body of exposure information now available on solid fuel-using households across multiplestates in India show that 24-hour household concentra- tions of respirable suspended particulate matter (RSPM)from biomass combustion may range from 200 to 2000 The authors would like to thank Sri Ramachandra University, Prof.
mg/m3 resulting in substantial differences in individual Michael Bates of University of California, Berkeley, the research Citation: Global Health Action 2011, 4: 7226 - DOI: 10.3402/gha.v4i0.7226 (page number not for citation purpose) Prevalence of COPD in rural women of Tamilnadu team, and the subjects. This study was approved by the Institutional use in Andhra Pradesh, India. J Expo Anal Environ 2004; 14: Ethics committee on 24 August 2006 (MEC/06/52/44).
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Citation: Global Health Action 2011, 4: 7226 - DOI: 10.3402/gha.v4i0.7226 (page number not for citation purpose)

Source: http://ehsdiv.sph.berkeley.edu/krsmith/publications/2011/gha_copd_2011.pdf