[Risk factors of lung cancer and relevant comprehensive preventive strategy--a cohort study in Xuanwei, Yunnan Province, China].

OBJECTIVE

To systematically analyze the risk factors of lung cancer in Xuanwei, Yunnan Province, an area with a high prevalence of lung cancer, and in view of the above to propose a comprehensive preventive strategy.

METHODS

A cohort study of 42,434 Xuanwei farmers who were born 1917-195, and still alive on 1st January 1976 was carried out from 1992 to 1996 with a follow-up time of 21 years. The data collection was done in two steps. A retrospective cohort study was conducted in the form of questionnaire survey in 1992 to understand the health situation of the interviewees from 1st January 1976 to 31st December 1991. In the second stage, a prospective cohort study was conducted to review the death records of the interviewees from 1st January 1992 to 31st December 1996. The data thus collected were analyzed by the Mantel-Haenszel analysis method, COX model and risk state analysis method.

RESULTS

Indoor air pollution caused by biturminous coal burning is the major risk factor of lung cancer in Xuanwei. Stove improvement decreased the lung cancer mortality rate in both male and female subjects, but its beneficial can be recognized at least 10 years after. Smoking is another important risk factor of lung cancer in males in Xuanwei. In course of a long time since stove improvement smoking will become the major risk factor of lung cancer. The risky factors can be arranged in sequence of riskiness from high to low as bituminous coal burning, family history of lung cancer, personal history of chronic bronchitis, and smoking in males; and bituminous coal burning, family history of lung cancer, and personal history of chronic bronchitis in females. The risk state classification model established upon the basis of risk state analysis can be used in identifying effectively high risk population quantitatively for local administrators of health as well as for local residents.

CONCLUSION

According to the comprehensive strategy for lung cancer control in Xuanwei, priority should be given to primary prevention with three steps: firstly to further reduce indoor air pollution by means of stove improvement and ventilation improvement, secondly strengthen smoking cessation, and thirdly to carry out chemoprevention and susceptibility study of lung cancer among high risk populations.