Prevalence and Risk Factors of Chronic Obstructive Pulmonary Disease (COPD) in an Urban Poor Locality of Bengaluru, South India – A Cross-sectional Study

Abstract

Background:

COPD is a worldwide public health problem; approximately 5% of all global deaths are attributed to COPD. Among chronic respiratory conditions, COPD contributes to 50% of the disease burden and 70% of DALYs in India. In India, it accounted for 9.5% of all deaths. There is limited community-based data on the prevalence of COPD and its risk factors in India.

Materials and Methods:

A community-based cross-sectional study was conducted in an urban poor locality of Bangalore. Sample size was calculated to be 1560. Population proportion to size (PPS) sampling technique was used. Information was collected from subjects aged >30 years through the interview method using a pretested semistructured questionnaire. A spirometry test was used to diagnose COPD.

Statistical Analysis:

Descriptive statistics such as mean, standard deviation, and percentages were used. A Chi-square test was used to assess the association between categorical variables. Multivariate logistic regression was done.

Results:

The prevalence of COPD among individuals aged above 30 years was 10.38%. The prevalence among males was 14.4% and among females was 7.1%. The majority (74.06% had a moderate to severe stage of COPD. On multivariate logistic regression analysis, the association of the risk factors for COPD was found to be statistically significant with age, history of tobacco smoke, smokeless tobacco, type of fuel used, biomass fuel exposure, ETS exposure, and indoor air pollution.

Conclusion:

The prevalence of COPD among the population aged more than 30 years in an urban poor locality of a metropolitan city is high, with males having a higher prevalence than females.

INTRODUCTION

Chronic obstructive pulmonary disease (COPD) is a major noncommunicable respiratory disorder characterized by persistent airflow limitation that is usually progressive and associated with an enhanced chronic inflammatory response of the airways and lungs to noxious particles and gases. Symptoms include cough, sometimes with phlegm, difficulty breathing, wheezing, and tiredness.[1] COPD is not curable, but symptoms can improve if one avoids smoking and exposure to air pollution and gets vaccines to prevent infections. It can also be treated with medicines, oxygen, and pulmonary rehabilitation. It is a progressive life-threatening disease that can lead to death if not diagnosed and treated on time.[2]

COPD is the fourth leading cause of death worldwide, causing 3.5 million deaths in 2021, approximately 5% of all global deaths. Nearly 90% of COPD deaths in those under 70 years of age occur in low- and middle-income countries (LMIC). COPD is the eighth leading cause of poor health worldwide. In LMIC, tobacco smoking accounts for 30–40% of COPD cases, and household air pollution is a major risk factor.[3]

India contributes substantially to the global COPD burden, accounting for a significant proportion of cases and deaths. Rapid urbanization, industrialization, increasing vehicular emissions, tobacco consumption, biomass fuel exposure, and poor living conditions amplify the risk, particularly in densely populated urban settlements. It is estimated that the overall prevalence of COPD among Indian adults aged ≥30 years is approximately 7–7.4%, with a higher prevalence observed in urban populations and among males.[4] Bengaluru, a rapidly expanding metropolitan city in South India, has witnessed marked growth in urban slums and low-income settlements. These areas are characterized by poor ventilation, use of solid fuels, overcrowding, and high exposure to environmental pollutants, creating a conducive environment for chronic respiratory illnesses. Despite this, there is limited community-based data on the actual prevalence of COPD and its associated risk factors in such vulnerable populations.[5]

COPD is a progressive disease associated with risk factors. Therefore, early identification of both the risk factors and the diagnosis of the disease helps in better management. Global Initiative for Chronic Obstructive Lung Disease (GOLD) recommends the use of spirometry for the diagnosis and identification of COPD.[6]

Based on the literature search, even though there are studies on prevalence and risk factors for COPD in the community both in urban and rural areas of India, the majority of them had used only questionnaires. There are very few studies on estimation of prevalence of COPD using spirometry with bronchodilator reversibility in the community from this geographical area in recent years. Hence, this cross-sectional study was undertaken to estimate the prevalence of COPD and to identify the associated risk factors in an urban poor locality of Bengaluru.

MATERIALS AND METHODS

A community-based cross-sectional study was conducted in an urban field practice area of a medical college, in south Bangalore, India, covering a population of 43,834. The study was conducted for a period of 1-year duration from July 2019 to June 2020. Institutional ethical committee clearance was obtained before the start of the study (Ref No. KIMS/IEC/D105/2018 dated 10^th November 2018). Ethical issues were discussed. Informed consent was taken from all study subjects.

Sample size was calculated based on the study by Saleem M et al.[7] Sample size was calculated using the formula 4PQ/d2. Sample size was calculated to be 1560, including the addition of 10% nonresponders.

The area was divided into 8 localities, and the number of subjects from each locality was selected using the population proportion to size (PPS) technique. In each locality, the first house was randomly selected, and a house-to-house survey was done to complete the estimated sample size.

Individuals aged >30 years who are residents of the locality for a minimum duration of 6 months and willing to participate and cooperate in the study were included. Those with acute respiratory infections, severely ill patients and, in case of spirometry, individuals not able to perform the procedure despite repeated instructions and individuals with contraindications to spirometry were excluded from the study. A household survey was done by interview method using a pretested semistructured questionnaire. Information regarding sociodemographic profile and respiratory symptoms like cough, phlegm, difficulty in breathing, wheezing, and other history, if any, were collected. Information on risk factors of COPD like tobacco smoke, usage of smokeless tobacco, ETS exposure, and type of fuel used for cooking was recorded. Ventilation, smoke outlet, dampness on wall, and signs of indoor air pollution were assessed by the investigator during the household survey.

Spirometry was done for those who were having symptoms suggestive of COPD based on the questionnaire. Spirometry was performed at an urban primary health center. Spirometry is considered to be the gold standard for the diagnosis of COPD [Figure 1]. Spirometry was done using EasyOne^® Air portable spirometer. The EasyOne had a sensitivity of 80-95% and a specificity of 85-98%. The investigator performed the spirometry test after the training. Subjects were screened for contraindications to spirometry. They were informed about the procedure as per ATS guidelines. Four hundred micrograms of salbutamol was given through a spacer, and the spirometry was repeated after 20 minutes to assess the bronchodilator reversibility.

Figure 1.

Flow chart showing stepwise selection of study participants

Operational definitions used in the study

1. Questionnaire definition for screening of COPD – Those with the presence of cough with expectoration for three or more months in a year for two or more consecutive years.

2. Spirometry criteria for diagnosis of COPD – postbronchodilator ratio of FEV1/FVC less than 0.70.

3. ETS (environmental tobacco smoke) exposure: regular exposure to others’ smoke in the household/workplace.

4. Signs of indoor air pollution: presence of soot on the indoor walls of the house on visual inspection.

5. Ventilation: ventilation is inadequate when the total area of doors and windows is less than 20% of the floor area.

6. Dampness in the wall: presence of visible indicators of moisture, like peeling of paint, white powdery deposits on the wall, or visible mould growth.

Those who were having symptoms suggestive of COPD were given free medications and referred to a higher center for further management. Health education was given regarding prevention and control of COPD.

Statistical analysis

Descriptive statistics such as mean, standard deviation, frequency, and percentages were used to summarize data. Chi-square test was used to assess the association between categorical variables. Multivariate logistic regression analysis was done after adjusting for confounding factors. P value of <0.05 was considered statistically significant.

RESULTS

Out of 1560 study subjects, males were 44.94% (n = 701) and females were 859 (55.06%). The mean age was 44.44 ± 12.98 (mean ± SD). 69.55% belonged to the upper-lower middle class as per the modified Kuppuswamy classification. Two hundred and fifty-two subjects had symptoms suggestive of COPD as per the questionnaire. All 252 were advised to do a spirometry test. After applying inclusion and exclusion criteria and acceptability criteria, 182 subjects had acceptable spirometry reports. One hundred and sixty-two subjects showed a postbronchodilator FEV1/FVC ratio <0.7, indicating persistent airflow obstruction. Hence, the prevalence of COPD is 10.38% (n = 162). The prevalence of COPD among males was 14.4% (n = 101) and among females was 7.1% (n = 61). The prevalence of COPD increases with increasing age. Severity of COPD was graded using GOLD’s criteria for diagnosis of COPD.[8] The majority, 74.06%, had moderate to severe forms of COPD, followed by 18.54% with very severe COPD [Table 1]. Only 7.4% had the mild form of COPD [Graph 1].

Table 1.

Baseline characteristics of study subjects (n=1560)

Parameters		Number	Percentages
Sex	Male	701	44.94
	Female	859	55.06
Age	31 – 40	592	37.94
Mean±SD	Male	48.50±13.34
	Female	48.20±13.34
	Overall	48.33+12.98
SES status*	Upper lower	1085	69.55

*Modified Kuppuswamy classification

Graph 1.

Pie chart showing the classification of severity of COPD based on GOLD guidelines (n = 162)

Association for various factors like age, sex, tobacco smoke, smokeless tobacco, ventilation, type of fuel used, smoke outlet, dampness in the wall, ETS exposure, and biomass fuel exposure was assessed. Statistically significant associations were found with respect to age, sex, tobacco smoke, smokeless tobacco, type of fuel used, ETS exposure, and biomass fuel exposure (P < 0.05) [Table 2].

Table 2.

Association of various risk factors for COPD (n=1560)

Variables	COPD		Odds ratio	95 % CI		P**
	Yes (n=162)	No (n=1398)		Lower	Upper
Sex			2.20	1.57	3.07	<0.001
Males (n=701)	101 (14.4)	600 (85.6)
Female (n=859)	61 (7.1)	798 (92.9)
Age (in yrs)			2.4	1.66	3.45	<0.001
≥60 (n=263)	49 (18.6)	214 (81.4)
<60 (n=1297)	113 (8.7)	1184 (91.3)
Tobacco smoke
Yes (n=259)	66 (25.4)	193 (74.6)	4.3	3.03	6.08	<0.001
No (n=1301)	96 (7.4)	1205 (92.6)
Smokeless tobacco
Yes (n=66)	22 (33.3)	44(66.7)	4.84	2.81	8..30	<0.001
No (n=1494)	140 (9.4)	1354 (90.6)
Ventilation
Inadequate (n=301)	39 (13.0)	262 (87.0)	1.37	0.93	2.01	0.10
Adequate (n=1259)	123 (9.8)	1398 (89.6)
Type of fuel used
Smoke forming (n=802)	138 (17.2)	664(82.8)	4.34	2.96	6.3	<0.001
Smokeless (n=758)	30 (4.0)	728(96.0)
Smoke outlet			0.78	0.57	1.09	0.15
Absent (n=736)	77 (9.3)	1398 (90.7)
Present (n=824)	85 (11.5)	951 (88.5)
Dampness in the wall
Present (n=247)	34 (13.8)	213 (86.2)	1.47	0.98	2.21	0.58
Absent (n=1313)	128 (9.7)	1185 (90.3)
ETS exposure
Yes (n=242)	57 (23.55)	185 (76.45)	2.95	2.48	5.08	<0.001
No (n=1318)	105 (7.97)	1213 (92.03)
Biomass fuel exposure			2.11	1.54	2.91	<0.001
Present (n=802)	112 13.97	690 86.03
Absent (n=758)	50 (6.60)	708 (93.40)
Indoor air pollution			2.52	1.76	3.63	<0.001
Present (n=266)	51 (19.2)	215 (80.8)
Absent (n=1294)	111 (8.6)	1183 (91.4)

*Figures in parenthesis indicate percentages; **chi-square test was used

On multivariate logistic regression analysis after adjusting for the confounding factors, the association of the risk factors for COPD was found to be statistically significant with age, History of tobacco smoke, smokeless tobacco, type of fuel used, biomass fuel exposure, ETS exposure, and indoor air pollution [Table 3].

Table 3.

Multivariate logistic regression of risk factors for COPD

Risk factors	Adjusted Odds Ratio	95% CI		P
		Lower	Upper
Age	2.57	1.74	3.80	<001
Sex	1.28	0.83	1.98	0.25
History of tobacco smoking	3.74	2.37	5.89	<001
Smokeless tobacco	3.23	1.8	5.7	<0.001
Type of fuel used	1.88	1.30	2.70	0.001
Indoor air pollution	2.12	1.44	3.13	<001
ETS exposure	2.2	1.6	3.44	<0.05
Biomass fuel exposure	1.68	1.3	2.90	<0.05

DISCUSSION

This study was done in an urban poor locality of a metropolitan city in South India using standard definitions and diagnostic procedures. Hence, the findings of this study can be generalized to a similar study population.

COPD is one of the leading causes of death in LMICs. Globally, there were more than 3 million deaths due to COPD in 2019 alone, making it the 3^rd leading cause of death. COPD is a multifactorial disease with varying contributions of personal habits, infections, environmental exposures, etc., The outcomes of this unattended public health problem have resulted in DALYs burdening the health care system.[9]

The present study primarily intended to estimate the prevalence of COPD in an urban poor locality. The study showed the prevalence to be 10.38%. A systematic review by Roy Arokiam Daniel et al.[10] showed the prevalence of COPD ranged from 2.4% in a study from South India to 16.1% in the north. The pooled estimate gives a prevalence of 7.4% (95% CI: 5.0%–9.8%), which is less than our study. Similarly, a study by Salvi et al.,[11] showing a trend of COPD between 1990 and 2016 in India, shows COPD prevalence to be 4.2% (95% CI: 4.0–4.4) in 2016. The difference is due to differences in the study setting and the method employed for diagnosis of COPD. We see that the questionnaire method picks up more cases of COPD than the spirometry method. It also does not need a tool/expertise to diagnose COPD. Hence, it is advisable to screen the community first with a questionnaire and then confirm the diagnosis with spirometry.

With respect to severity of COPD according to GOLD criteria, the majority had (74.06%) moderate and severe COPD, followed by 18.54% very severe, and only 7.4% had mild. The severity prevalence varies with the population, their exposures and risk factors. This can be supported by findings of a population-based study conducted by Asif Jeelani Hanga et al.[12] wherein of the 1025 subjects who performed spirometry properly, the overall prevalence of COPD was 15.90%, and the prevalence of Grades 1, 2, 3 and 4 COPD was 8.8%, 5.2%, 1.4%, and 0.6%, respectively. Unlike our study, the prevalence of mild grade of COPD was more than moderate and severe forms.

The prevalence among males (14.4%) was higher than females (7.1%), but the difference was not statistically significant. The findings of the present study are comparable with the community-based cross-sectional study conducted by Saleem M et al.[7] (2017) done in Kallendri block of Madurai district, which showed males (39.2%) had higher prevalence of COPD than females (12.2%). Similarly, a study conducted by Sundeep Salvi et al.[11] reports that among 2699 subjects, males (6.5%) had higher COPD prevalence than females (3.4%). Male gender, with adjusted OR 1.93, was strongly associated with COPD. All the study settings show higher prevalence among men because of more exposure to risk factors like tobacco smoking or environmental tobacco exposure, and also occupation-related exposures in the case of factory workers, daily commuters in traffic, etc.

The prevalence increases with increasing age. This finding was in accordance with the observation made by a field survey conducted by B. G. Parasuramalu et al.[13] reported increasing prevalence of COPD with an increase in age. The odds of having COPD were significantly associated with advancing age [AOR = 1.07]. Many other studies done in different geographical regions of India, like Asif Jeelani Hanga et al., Salvi et al., and Vinod Sharma et al., also state that the prevalence of COPD increases with age, making it a nonmodifiable and predictable risk factor.[11,12,14]

Those with a history of tobacco smoking were 3.74 times higher. This observation was similar to a study by BG Parasuramalu et al.[13] where it was observed that tobacco smoke was significantly associated with higher odds of COPD [AOR = 2.97]. In a study by Salvi et al.[11] among the rural population in India, tobacco smoking alone was significantly associated with COPD [OR: 2.34 (CI: 1.2-4.3); P = 0.006]; however, after adjustment, the risk reduced [Adj OR: 1.88 (CI: 0.96-3.7); P = 0.06]. Also, a systematic review by Ailsa J McKay et al.[15] positively supports the risk of tobacco smoking in the causation of COPD.

Study subjects with a history of environmental tobacco smoke (ETS) exposure 2.2 times higher risk of developing COPD. Similar findings were documented by B G Parasuramalu et al.[13] wherein exposure to ETS was significantly associated with and had higher odds of COPD (AOR = 2.67, 95% CI: 1.31, 5.42). A community-based study in Delhi by B Sinha et al.[16] reported a proportion of COPD to be statistically higher (P < 0.05) in those exposed to ETS or having an occupational exposure to dust/fumes/smoke for a longer duration.

Those who are using smoke-forming fuel were 1.88 times more at risk of developing COPD. A meta-analysis by Utkarsha Pathak et al.,[17] of a total of 35 studies with 73,122 participants, showed that exposure to indoor air pollution due to solid biomass fuels increased the risk of COPD by 2.65 (95% CI: 2.13-3.31; n = 73,122) and chronic bronchitis by 2.89 (95% CI: 2.18-3.82) times more compared to nonbiomass fuels.

Those with indoor air pollution were at a 2.12 times higher risk of developing COPD. This finding is backed by a systematic review by Wimalasena et al.,[18] which analyzed data from 360 article and studied 19 risk factors of COPD. Of these, poor housing conditions with inadequate ventilation and biomass fuel exposure were reported to be significantly associated risk factors for COPD.

CONCLUSIONS AND RECOMMENDATIONS

The prevalence of COPD among people aged 30 years and above was high in the urban poor locality. The prevalence is higher in males compared to females. The common risk factors were age, History of tobacco smoke, smokeless tobacco, type of fuel used, biomass fuel exposure, ETS exposure, and indoor air pollution.

Periodic assessment of prevalence and risk factors for COPD across different parts of the country is needed. Health education should be given to the community on the importance of avoiding exposure to risk factors such as tobacco consumption, indoor air pollution, environmental tobacco smoke, biomass fuel exposure, and housing conditions. Appropriate actions are needed from regulatory authorities to reduce risk factors such as tobacco consumption, biomass fuel exposure, environmental tobacco smoke, and others.

Limitations of the study

Spirometry was done only for those subjects who had symptoms suggestive of COPD-based questionnaire and not for all study subjects because of the feasibility of conducting spirometry in the community and cost.

Conflicts of interest

There are no conflicts of interest.

Funding Statement

Nil.