Funding for this research was provided by:
National Basic Research Program of China (973 Program) (2017YDF0500304)
National Natural Science Foundation of China (U1803236)
Received: 30 December 2019
Accepted: 9 June 2020
First Online: 16 June 2020
Compliance with ethical standards
: The authors declare that they have no conflict of interest.
: We have complied with the World Medical Association Declaration of the 1964 Helsinki regarding ethical conduct of research involving human subjects. The hospital based case–control study was approved by the Review Board of Kashgar Pulmonary Hospital (Xinjiang, China).
: A written informed consent was obtained from all subjects who were recruited and interviewed for the study.