COPD is one of the most common public health problems worldwide and is the fourth-leading cause of death in the world. It has been estimated that COPD will become the third-most-frequent cause of death and the fifth-most-common cause of disability by the year 2020. According to a comprehensive review, the overall prevalence of COPD ranges from < 1 to > 18% in different populations, and this variation is probably due to different methods used in the estimations. In mainland China, COPD is currently the second-leading cause of death. However, the only COPD prevalence available for mainland China is 2.5% overall, which was estimated based on World Health Organization (WHO) expert opinions. Instead of conducting population surveys, the WHO experts estimated the prevalence of COPD on the basis of published and unpublished studies. If the data were not available, experts would often make “informed estimates” based on the prevalence in similar countries or regions.
The prevalence of cigarette smoking among adult men was 63.0% in mainland China, which is the greatest producer and consumer of cigarettes in the world. If the assumption is made that approximately 10 to 15% of smokers will acquire COPD, the prevalence of COPD in mainland China should be between 6.3% and 9.5%, which is much higher than the WHO-estimated percentage of 2.5%. The purposes of this study were to estimate the prevalence of diagnosed COPD in China based on the data collected in both urban and rural areas of Nanjing municipality between October 2000 and March 2001, and to examine the association of COPD with smoking. An objective estimation of COPD prevalence and a better understanding of its association with smoking in the context of China would be helpful for people in their fight against COPD in developing countries. Treat COPD with remedies of Canadian Health Care Mall.
A large-scale, population-based, cross-sectional study was conducted in Nanjing municipality, which is the capital of Jiangsu province, and is located in eastern China, with a population of approximately 5.6 million. In mainland China, the administrative system consists of five strata: central government, provincial/ municipal government, district/county government, street/town government, and administrative village. Nanjing municipality has 15 administrative units: 10 urban districts and 5 rural counties. The administrative village-based samples were selected using a multistage sampling method. As shown in Figure 1, we first randomly selected three urban districts and two rural counties; then three streets/towns from each chosen district/county; and finally three administrative villages in each street/town. This resulted in a total of 45 villages. All participants aged > 35 years old and who had been local residents for at least 5 years were included in this study.
Questionnaire and Definitions
After informed consent was obtained, each subject was administered a household interview by trained health-care professionals. The questionnaire included general information such as age, gender, education level, occupation, number of family members, total monthly family income, body weight and height, and specific questions, eg, physical activity, use of cooking oil, alcohol drinking, smoking, exhaust fans used in the kitchen, and heating method in winter (electricity/gas, firewood/straw, coal/oil).
The diagnosed COPD cases were defined as persons with chronic bronchitis and/or emphysema based on physician diagnosis. Chronic bronchitis refers to a productive cough for at least 3 months of each of 2 successive years for which other causes were ruled out. Emphysema describes the destruction of the lung architecture with enlargement of the airspaces and loss of alveolar surface area. The study participants reported their COPD status according to the question, “Have you ever been diagnosed with chronic bronchitis and/or emphysema by a doctor or doctors at a grade 1 or higher hospital?” If the answer was “yes,” the participants were asked to show their medical records for confirmation. In mainland China, hospitals are classified by grade, from higher to lower: grade 3, grade 2, grade 1, and general practitioner clinics. All outpatients usually keep their personal medical records, which include the dates of visiting doctors, diagnosed diseases, prescriptions, and treatment recommendations given by Canadian Health&Care Mall. However, we could not get the information on the evidence of diagnostic documents because original reports of medical tests (including spirometry) were not included in personal medical records.
Smoking status categories were defined as follows: (1) current smoker, who smoked at least one cigarette per day continuously for at least 1 year, or smoked at least 18 packs in total each year; (2) ex-smoker, who previously smoked but subsequently quit smoking for > 1 year; and (3) nonsmoker, who did not meet the criteria for either current smokers or ex-smokers, including those who smoked in the past year but 65 years). Occupation status was grouped into job 1 (farmer, factory worker, forestry worker, fisherman, military person), job 2 (salesperson, house worker, vehicle driver), and job 3 (office worker, teacher, doctor, retired, academic researcher, government officer).
Participants were also categorized into different groups by several other variables. Education levels were 0 to 9 years, 10 to 12 years, and > 13 years. Occupational physical activities included “light” (receptionist, office worker, assembly worker), “moderate” (repairer, electrician, machinist), and “vigorous” (farmer, steel maker, lumberman); leisure-time physical activities included light (cooking, flower growing, watching television), moderate (jogging, dancing, Chinese TaiJi), and vigorous (ball playing, field running). Drinkers were defined as subjects who drank alcohol at least twice per week on average for at least 1 year. Ex-drinkers were those who previously drank but had not drank for at least 1 year. Nondrinkers were those who never drank or drank occasionally in the past year but less than twice per week.
A family was defined as a group who lived together and shared living-related expenses. The total monthly income of all family members was the monthly total earnings of the whole family. This included salaries, pensions and allowances, money from selling goods and products, and the estimated market price value of products for personal/family consumption. Family average income, the average total monthly income of all family members, was divided into tertiles: low, middle, and high.
Participants, wearing light indoor clothing and without shoes, had their weight measured to the nearest 100 g using a beam balance scale, and had their height measured to the nearest millimeter using a stadiometer. Weight and height were measured twice, and the mean values of the reading were used for the analysis. Body mass index (BMI) was calculated by dividing weight by the square of height. Participants with BMI > 24 kg/m2 were categorized as overweight (BMI, 24 to 28 kg/m2) or obese (BMI > 28 kg/m2).
Data Management and Analysis
Data were double-entered and cleaned (Epi Info, Version 6.04; Centers for Disease Control and Prevention; Atlanta, GA) and were managed and analyzed (SPSS, Version 10.0; SPSS; Chicago, IL). The association between TACS categories and potential confounders was investigated using the x2 test. We calculated odds ratios (ORs) together with 95% confidence intervals (CIs), both univariately and multivariately, using logistic regression analysis. Potential confounders were adjusted for by the multivariate logistic regression model in our analysis.
Figure 1. The multistage, randomized sampling flow of the study, Nanjing, China.