A Cross-sectional Study of the Socio-demographic and Other Determinants of Chronic Obstructive Pulmonary Disease (COPD) Among Those Who Smoke, Quit Smoking and Never-smoking Cigarettes

Chronic obstructive pulmonary disease (COPD) is the fourth leading cause of death worldwide. An estimated 0.5 million individuals in Kazakhstan may be affected by COPD, and the number of affected individuals and of deaths from COPD are expected to increase as the population ages. A better understanding of the epidemiology, causes, and social and other determinants of the disease is needed in order to develop effective treatments and prevention strategies.

Although COPD is traditionally defined by airflow obstruction in a spirometry test, smoking-associated effects on the lungs related to COPD also include emphysema, gas trapping, and chronic bronchitis. Symptoms such as productive cough, dyspnea, and exercise intolerance may be dismissed as normal aging, especially in older former smokers. Information is sparse about effects of smoking on individuals not diagnosed as having COPD (based on spirometry), and data from high-resolution computed tomography (CT) scanning in these individuals are limited.

COPD is strongly associated with smoking, but not all smokers will develop COPD. Cigarette smoking continues to be a common addiction in Kazakhstan despite efforts to reduce its prevalence. The study objectives are to assess true prevalence of COPD based on pulmonary function assessment and structural changes (emphysema and large and small airway inflammation with thickening) identified by high-resolution computer tomography (CT-scan) in addition to standard spirometric criteria and symptoms of dyspnea, exercise limitations, and chronic bronchitis. Such comprehensive approach will allow for objective comparisons of (1) current smokers of conventional cigarettes - 500 participants, (2) those subjects who quit smoking within the past 1 - 5 years - 200 participants, and (3) those subjects who never smoked cigarettes - 200 participants.

Using high resolution CT in addition to spirometry and other types of lung function assessment will help to determine COPD prevalence among non-smokers, smokers of conventional cigarettes and those who quit smoking. COPD prevalence will be defined based on abnormal respiratory function assessed by standard spirometric tests and by using COPD assessment test (CAT) questionnaire, 6-minute walk test and a high-resolution computed tomographic (HRCT) scan of the chest of those patients with preserved pulmonary functions but with clinical symptoms.

The cross-sectional study is retrospective in a sense, as it will allow to collect historical data on smoking, smoking cessation, address socio-demographic and other differentials of smoking. The investigators will also address the relationship of liver disease with COPD. This will be determined based on presence of hepatitis B and C tests (antigens and antibodies), liver enzyme levels and concentration of alpha-1-antitripsine, which is related to the development of COPD. Current or former smokers who had a concomitant diagnosis of asthma will not be excluded in the cross-sectional study. Instead, historical data on whether the participant had been diagnosed with asthma will be collected.