Cross-Sectional Study of COPD Prevalence Among Smokers, Ex-smokers and Never-Smokers in Almaty, Kazakhstan

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.

The cross-sectional study has several study groups based on the exposure (smoking behavior) status. Combinations of paired associations are as follows: smokers vs. never-smokers; smokers vs. ex-smokers; never-smokers vs. ex-smokers. Therefore, it bears some feature of a retrospective cohort study, specifically; it provides an opportunity to make comparisons between the groups. While calculating the required sample size, the investigators considered this opportunity as the most important one. In addition to calculating prevalence ratio of COPD for exposure statuses, the cross-sectional study will allow for assessment of prevalence of these conditions and other characteristics in different study groups.

Data to be collected

• Spirometry (FEV / FVC), bronchodilation test
• COPD assessment test (CAT) questionnaire,
• 6-minute walk test
• Electrocardiography
• High-resolution computed tomographic (HRCT) scan of the chest
• Blood pressure
• Body mass index (BMI)
• Smoking status and history
• Passive smoking status
• Occupational exposure
• Exposure to indoor biofuel pollution
• Patient-reported comorbidities
• Laboratory testing for: blood cholesterol level, HDL (high-density lipoprotein), LDL (low-density lipoproteins), triglycerides, C-reactive protein, fibrinogen, glucose, Hepatitis B and C IgM and IgG antigens and antibodies, liver enzymes (ALT and AST), and alpha-1-antitrypsine.

The investigators plan to recruit subjects by using the following mechanisms, namely, through social media, a network of medical referral sites (polyclinics and ambulatory centers), and from large corporations, i.e. with more than 500 employees.

Information about current smoking behavior and very detailed historic information on smoking behavior will be used to for adjustments during the data analysis phase.