1 Health Management Center, The Second hospital of Dalian Medical University, No.467, Zhongshan Road, Shahekou District, Dalian city, Liaoning Province, China.
2 Department of Gastroenterology, The Second hospital of Dalian Medical University, Dalian, Liaoning, China.
3 School of Public Health, Dalian Medical University, Dalian, Liaoning, China.
4 Health Management Center, The Second hospital of Dalian Medical University, No.467, Zhongshan Road, Shahekou District, Dalian city, Liaoning Province, China; School of Public Health, Dalian Medical University, Dalian, Liaoning, China. Electronic address: dllengsong@163.com.