The focus of this study was to estimate COPD prevalence and to examine its associations with smoking in a Chinese population. To the best of our knowledge, this is the first systematic population survey (n = 29,319) on COPD prevalence based on patients reported in mainland China. This study presents a diagnosed COPD prevalence (5.9%) among urban and rural populations > 35 years old, which is higher than that (2.5%) estimated by WHO experts and what was reported (3.5%) in Hong Kong, China. Inhabitants of China may also make orders via My Canadian Pharmacy with the help of http://my-medstore-canada.net/. We are waiting for your orders.
After adjusting for possible confounding variables, smoking was positively associated with COPD prevalence in both men and women in this Chinese population. Men had higher COPD prevalence than women. The relationship between prevalence of COPD and TACS was dose dependent by gradient in women, while men with only upper TACS were more likely to have COPD. These findings indicate that cigarette smoking is more harmful to women than men regarding COPD. However, there was no statistical association of COPD with fuels, heating in winter, kitchen ventilation, cooking oil, and passive smoking in this study population. This is inconsistent with other reports that indoor air pollution from combustion of biomass/traditional fuels and coal is a risk factor of COPD. In China, biomass/traditional fuels (coal, oil, firewood, and straw) are widely used in rural areas. In this study, 92.0% (8,717 of 9,470 participants) from rural areas used biomass/traditional fuels. In fact, the kitchens were usually larger in the rural areas than the urban areas, and the kitchen doors and windows were usually opened at the time of cooking. In urban areas, 79.9% (15,868 of 19849 participants) used exhaust fans in kitchens when cooking. Thus, the kitchen air of participants in this study might not be severely polluted, and this may be an explanation for the inconsistency.
The smoking rate was 58.6% for men and 2.2% for women. The prevalence of COPD in women (4.7%) was higher than the overall estimate (2.5%) by WHO experts but was significantly lower than that in men (7.2%), which was consistent with other reports.- Similar to a report from Canada, the COPD prevalence in female smokers was higher than that in male smokers (15.74% vs 6.98%; OR, 2.50; 95% CI, 1.83 to 3.40), indicating that female smokers are more susceptible to COPD compared to male smokers in this Chinese population. Generally, women do more housework (such as housekeeping and cooking) in China but, after adjustment for potential confounding factors, fuels and cooking oil were not associated with COPD in this population. There was no convincing evidence from this study to explain why female smokers are more likely to acquire COPD compared to male smokers. Further studies are warranted to explore whether gender is an independent risk factor of COPD.
This study has two primary limitations. First, the diagnostic methods, especially spirometry, were not examined, thus leading to potential misclassification of COPD. Second, it is possible that bias could have resulted from different patients receiving a diagnosis of COPD by different physicians in different hospitals at different times.
The overall prevalence of diagnosed COPD (5.9%) among Chinese adults was higher than that (2.5%) estimated by WHO experts, and COPD was positively associated with smoking in this Chinese population. There was a significant gradient increase in COPD prevalence from the stratum of nonsmokers to the stratum of upper TACS in this study, and female smokers were more likely to acquire COPD compared to male smokers. Fuels, heating in winter, ventilation in kitchens, and use of cooking oil were not significantly associated with COPD.