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Epidemiology and Risk Factors
COPD is primarily a disease of the adult. The prevalence of COPD reported in different population based studies from India is highly variable (Table 1)5-16.The prevalence rates in male subjects of 2.12% to 9.4% in studies reported from North are generally higher than 1.4% to 4.08% reported from South India. The respective range for female subjects vary from 1.33% to 4.9% from North and from 2.55% to 2.7% from South India. For epidemiological assessment, the rounded-off median prevalence rates were assessed as 5 percent for male and 2.7 percent for female subjects of over 30 years of age.
The disease is distinctly more common in males. The male to female ratio had varied from 1.32:1 to 2.6:1 in different studies with a median ratio of 1.6:1.
COPD results from chronic inhalational exposure to various smokes, noxious particles and gases.
Tobacco smoke
Tobacco smoke, which is a mixture of over 4000 chemical constituents, is the most important cause. Amongst males, tobacco smoking is responsible for more than 80% of patients5,17. Both cigarette and ‘bidi’ smoking are equally responsible.18 Pipe and ‘hookah’ smoking are also important in causing COPD. There is no reliable information on smoking associated COPD in women in whom the overall prevalence of smoking is very low. Besides active tobacco smoking, exposure to smoking from others i.e. passive smoking, better termed as Environmental Tobacco Smoke (ETS) exposure, may also play a contributory role especially in nonsmoker individuals including women.19,20
Solid fuel combustion
The smoke from combustion of solid fuels such as dried dung, wood and crop residue used for cooking and heating, especially in villages, semi urban and slum areas, is an important cause of pollution of the indoor air. It is responsible for a large number of COPD in the rural inhabitants in general and women in particular.20-23
Air pollution
Exhausts from vehicles and industrial units; dusts, fumes and smoke from burning of crop residues in the field constitute important sources of air pollution. Chronic exposure to polluted air is an important cause of chronic respiratory diseases such as the COPD.24-27