Cross-Sectional Study of COPD Prevalence Among Smokers, Ex-smokers and Never-Smokers in Almaty, Kazakhstan
Condition: Chronic Obstructive Pulmonary Disease (COPD)
MeSH terms: Lung Diseases; Lung Diseases, Obstructive; Pulmonary Disease, Chronic Obstructive
Study type: Observational

Summary: 
      The purpose of this study is to assess the prevalence of COPD among individuals aged 35 - 59
      years based results of spirometry before and after bronchodilator, presence of structural
      changes in lungs (emphysema, inflammatory changes and thickening of the walls of the large
      and small airways)detected by computer tomography as well as the symptoms of COPD. The study
      has three study groups: smokers of conventional cigarettes; those who had quit smoking 1 - 5
      years ago, and those who haven't smoked cigarettes.
    

Detailed description: 
      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.
    

Observational model: Case-Control
Time perspective: Cross-Sectional
Sampling method: Non-Probability Sample
Study population: 
        The study population is three groups of male and female residents of City of Almaty, the
        largest city in Kazakhstan, with a population of 1,7 million people, containing 9% of the
        country's total population aged 33-59. The first group is current smokers with more than 10
        pack-year history of smoking. The second group is individuals who quitted smoking from one
        to five years ago and have more than 10 pack-year history of smoking. The third group is
        persons who has never smoked regularly, i.e. smoked less than 100 cigarettes in his or her
        lifetime.
      
Biospecimen description: 
      Serum
    
Keywords: chronic obstructive pulmonary disease; smoking; prevalence; cross-sectional study; Kazakhstan