COPD Prevalence among Women due To Indoor Air Pollution: South India

Author(s): Priscilla Johnson1, Padmavathi Ramaswamy2, Kalpana Balakrishnan2, Santu Ghosh2
Affiliation(s): 1Department of Physiology, Sri Ramachandra University, Chennai, India, 2Department of Environmental Health Engineering, Sri Ramachandra University, Chennai, India
1st country of focus: India
Relevant to the conference theme: Non-communicable chronic diseases
Summary (max 100 words): Chronic obstructive pulmonary disease (COPD) is the 4th leading cause of death and 13th leading cause of burden of diseases worldwide. Although smoking remains the predominant risk factor, exposure to solid fuel smoke has also been identified as a risk factor for COPD, with rural women in developing countries bearing most of this disease burden.  Despite the importance of this disease, the fact is that the prevalence of COPD is not well measured due to the uncertainties in the prevalence estimation. Most of the previous studies have focused on prevalence of COPD in men and primarily addressing smoking as a risk factor and relatively few studies have attempted to assess prevalence amongst non-smoking rural women. Moreover, estimates of COPD prevalence were diverse either due to variation in the type of assessment or due to inconsistent physician recognition of COPD. In this study a meticulous diagnostic approach was chosen for identification of the COPD cases, including a complete clinical evaluation with spirometry before and after bronchodilation. Further, a previously developed predicted equation using  a log linear multiple regression model was used for understanding the likely household concentrations experienced by the women dwelling in different type of rural household which may be applied in future to generate exposure response for the development of COPD.
Background (max 200 words): COPD is the 4th leading cause of death and 13th leading cause of burden of diseases worldwide with projected increases in its contributions over the next decade. Active smoking is the major risk factor for COPD. Other risk factors include air pollution, passive smoking, heredity etc., More recently exposure to biomass smoke resulting from household combustion of solid fuels has also been identified as a risk factor for COPD. Solid fuel combustion results in high levels of pollutants like respirable particulate matter, carbon monoxide, oxides of nitrogen and sulphur, formaldehyde, benzo(a)pyrene and benzene which are a  major source of  respiratory irritants in the etiopathogenesis of COPD. Evidence from recent studies which have made contributions to examining temporal, spatial, or multi-pollutant patterns, in addition to day-to-day or seasonal variability in household concentrations,  show that persons in solid fuel using settings experience extremely high levels of noxious pollutants. Moreover, WHO’s Comparative Risk Assessment estimated that about 650,000 premature deaths of women from COPD and lung cancer occurred as a result of these exposures. Despite the importance of this disease, the fact is that the prevalence of COPD is not well measured is due to the uncertainties in the prevalence estimation.
Objectives (max 100 words): The primary aim of this cross sectional study was to estimate the prevalence of COPD among the rural women above 30 years through a primary household level, clinical and spirometric assessment. The secondary objective was to explore the different household level variables that may influence the development of COPD. The additional objective was focused at understanding the likely household concentrations experienced by the women dwelling in different type of rural household which may be applied in future to generate a exposure response for the development of COPD.
Methodology (max 400 words): This cross sectional study was conducted among 900 women from 45 different rural villages in Tiruvallur, a rural district in the state of Tamilnadu in India. The study was approved by the Institutional Ethics committee and was conducted between January and May 2007. The study subjects were selected through cluster sampling using probability proportion to size criteria.  This approach resulted in the selection of 45 out of 612 small villages with populations less than 10,000 in Tiruvallur district. The selection criteria included women aged 30 yrs and above who have been residents of the villages in Tiruvallur District for a minimum period of five years who did not report a history of bronchial asthma, pulmonary tuberculosis, cardiac diseases, pregnancy, diabetes and cancer. Informed written consent was obtained before recruiting any person into the study.  Then, the questionnaire was administered that collected information on known risk factors for COPD, details on type of fuel, duration of cooking etc. A detailed clinical history on respiratory symptoms was also obtained.  All symptomatic women were then subjected to pulmonary function tests. COPD cases were diagnosed based on the three criteria given by the GOLD diagnostic guidelines. Pulmonary function test was performed following American Thoracic Society guidelines using a portable data logging Spiro meter (MIR Spirobank).  This test was performed in a sitting position and the subject was then asked to inhale completely and rapidly and exhale maximally until no more air can be expelled while maintaining an upright posture. The same was repeated for a minimum of three manoeuvres and not more than eight was done for acceptability and repeatability. A complete flow-volume loop was obtained from the Spiro meter. The data were compared with individual predictive values based on age, sex, body weight, standing height and interpreted to arrive at the diagnosis. Spirometry with broncho dilation testing after inhalation of 200 µg of Salbutamol, was carried out in order to confirm COPD. Statistical analysis was performed using “R” Version 2. Prevalence was expressed in terms of percentage. Logistic regression analysis was performed to examine the association between selected risk factors and COPD. The Odds Ratios were calculated. Further, a previously developed predicted equation using  a log linear multiple regression model by Santu Ghosh  et al 2011 that predicts household level concentrations in relation to the household level determinants was assigned to the solid fuel and the clean fuel using households of the study population.
Results (max 400 words): The overall prevalence of COPD in this study was found to be 2.44% (95% CI 1.43- 3.45). COPD prevalence was higher in solid 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 2hours/day in the kitchen involved in cooking. Logistic regression analysis was performed to examine the association between COPD and use of solid fuel for cooking. Logistic regression analysis has shown increased risk of COPD in women using solid fuel for cooking, in older women, in women involved in cooking for longer duration, in women living in kutcha houses, and in women with history of passive smoking, though not significant. The concentration of particulate matter (PM2.5 ) of solid fuel using households was found to be 237.4 µg/m3 which was significantly higher than the households using clean fuel (50 µg/m3)
Conclusion (max 400 words): Accurate prevalence information is vital for several reasons such as documentation of COPD’s impact on the morbidity, mortality and economic burden and also for public health planning. This population based cross-sectional study used a meticulous diagnostic approach for the identification of the COPD cases, including a complete clinical evaluation with spirometry before and after bronchodilation, and estimated the COPD prevalence in a non-smoking rural women population primarily using solid fuel. The estimates generated in this study will contribute significantly to the growing database of available information on COPD prevalence and to refine the attributable burden of disease estimates. Besides, this information will help researchers to monitor trends, including the success or failure of control efforts. Moreover, this study has incorporated a previously developed model to assign exposure status in terms of quantitative value for  the categorical variables namely solid fuel and clean fuel using households of the study population which in turn may be applied to generate exposure response relationship with relevant to the development of COPD.

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