Relationship between smoking and the risk of morbidity of chronic obstructive pulmonary diseases among residents aged 30 years and above in Sichuan Province: a prospective study

Abstract

Objective: To investigate the morbidity of chronic obstructive pulmonary diseases (COPD) in residents aged 30 years and above in Sichuan Province, and analyze the effect of smoking on the risk of morbidity on COPD. Methods: From 2004 to 2008, people were randomly selected from Pengzhou, Sichuan Province. All the local people aged 30-79 years were asked to receive questionnaire survey, physical examination and pulmonary function testing, and long-term follow-up to determine the morbidity of COPD. Cox proportional hazard regression model was used to analyze the relationship between smoking and COPD. Results: In 46 540 participants, the current smoking rates were 67.31% in males and 8.67% in females, there were 3 101 new cases of COPD, with a cumulative incidence of 6.66%. Adjusted for age, gender, occupation, marriage, income level, educational level, BMI, daily total physical activity, current cooking frequency, whether there was smoke exhaust device at present and frequency of passive smoking exposure, multivariate Cox proportional hazard regression analysis showed that compared with the non-smoking population, current smoking and quitting smoking increased the risk of COPD, with HR of 1.42 (95%CI:1.29-1.57) and 1.34 (95%CI:1.16-1.53). Compared with people who never or occasionally smoke, the risk of morbidity on COPD increased with the increase of average daily smoking volume, mixed smoking at present, mixed smoking at the beginning increased the risk of COPD, with HR of 1.79 (95%CI: 1.42-2.25) and 2.12 (95%CI: 1.53-2.92), started smoking at the age of <18 years old and ≥18 years old increased the risk of COPD, with HR of 1.61 (95%CI:1.43-1.82) and 1.34 (95%CI: 1.22-1.48), inhaling into the mouth, throat and lung during smoking increased the risk of COPD, with HR of 1.30 (95%CI: 1.16-1.45), 1.63 (95%CI: 1.45-1.83) and 1.37 (95%CI: 1.21-1.55). Adjusted for multiple confounding factors and adjusted for regression dilution bias, the average daily smoking volume, the age of starting smoking and the depth of smoking inhalation had an impact on the incidence of COPD, and the gender difference was particularly prominent. Conclusions: Smoking increased the risk of morbidity on COPD, which was related to the average daily smoking volume, the type of smoking, the age of starting smoking and the depth of smoking inhalation. Tobacco control should comprehensively consider the specific characteristics of smoking, so as to prevent COPD.