Analysis of the Survival Time and the Causes of Death in Pneumoconiosis Patients

摘要

[Objective] Many workers in China previously worked in places with high exposure to hazardous dusts such as asbestos, coal dust, and free silica. We followed a group of miners exposed to mining dust from 1963 to 2001 to determine their fatality and complications due to dust exposure. [Methods] In the yearly check up for metallurgical workers in GuiZhou Province, a total of 386 mining workers were diagnosed as having stage Ⅰ, Ⅱ, or Ⅲ pneumoconiosis from 1963 to 2001. These workers were then followed-up regularly. If fatality occurred, time and cause of death and combined medical conditions were recorded. The stage of pneumoconiosis at death was also recorded. In 2001, all surviving workers were invited to have a follow-up physical examination, including chest radiography. Survival analysis with Kaplan-Meier method was conducted using stage as predictors and duration of follow-up as outcome. Cox's regression model was done using stage and age at initial examination as X's and duration of follow-up as Y. [Results] People with fibrotic change stages Ⅰ, Ⅱ, and Ⅲ at the initial examination had median survival time of 29.3, 27.3, and 14.0 years, respectively. While adjusted for age at initial examination, risk ratio was 1.03 (95% Cl 0.77-1.36) for stage Ⅱ, and 1.57 (95% Cl 1.09-2.16) for stage Ⅲ as compared to stage Ⅰ. Among 137 deceased workers, the direct causes of deaths included 37 (27.0%) pneumoconiosis, 21 (15.3%) pulmonary tuberculosis, 7 (5.1%) non-specified lung infection, 22 (16.1%) lung cancer, 10 (7.3%) other cancers, 12 (8.8%) cerebrovascular accidents, and 28 (20.4%) other causes. Lung tuberculosis frequently complicated pneumoconiosis and was found in 14.3% of followed workers. The prevalence of tuberculosis was associated with initial staging of pneumoconiosis, i.e., in stage Ⅰ, Ⅱ, and Ⅲ, 10.0%, 20.0%, and 32.4% were later complicated with tuberculosis, respectively. [Conclusion] It was concluded that the mining workers' survival time is correlated with the stage of the elementary X-ray examination for chest. In workers with more advanced radiographic stages, early intervention may be useful to decline fatality in later years. Tuberculosis is a common complication of pneumoconiosis and a significant cause of death.