title: Syphilis among middle-aged female sex workers in China: a three-site cross-sectional study.
abstract: This study addresses the lack of empirical studies about the epidemic of syphilis among middle-aged female sex workers (FSWs). The objectives of this study were to investigate prevalence of syphilis, and its potential risk factors among middle-aged FSWs in China.
  
  
  
  A cross-sectional study with respondent-driven sampling (RDS).
  
  
  
  A multisite study conducted at three Chinese cites (Nanning, Hefei, and Qingdao) with different levels of sexually transmitted diseases in 2014.
  
  
  
  1245 middle-aged female sex workers who were over 35 years old (about 400 per study site).
  
  
  
  Unprotected commercial sex, and syphilis and HIV infection were biologically tested and measured.
  
  
  
  The RDS-adjusted prevalence of active syphilis was 17.3% in Hefei, 9.9% in Qingdao, and 5.4% in Nanning. The RDS-adjusted prevalence of prevalent syphilis was between 6.8% and 33.6% in the three cities. The proportion of unprotected sex in the past 48 h verified by the prostate-specific antigen test (PSA) was between 27.8% and 42.4%. Multiple log-binomial regression analyses indicate that middle-aged FSWs who had 5 or more clients in the past week prior to interviews and engaged in unprotected sex were more likely to be active syphilitic cases. Middle-aged FSWs who had rural residency were less likely to be active syphilitic cases.
  
  
  
  In contrast with previous studies that reported low prevalence of syphilis and high prevalence of protected sex among FSWs in China, both the prevalence of syphilis and unprotected sex were high among middle-aged FSWs. Evidence-based intervention programmes should be developed and evaluated among this vulnerable population in China and other countries with similar settings.
authors.affiliation: Department of Epidemiology and Biostatistics, School of Public Health, University of Maryland, College Park, Maryland, USA.
authors.forename: Hongjie
authors.initials: H
authors.lastname: Liu
authors.affiliation: Department of Epidemiology and Biostatistics, College of Public Health, Temple University, Philadelphia, Pennsylvania, USA.
authors.forename: Levent
authors.initials: L
authors.lastname: Dumenci
authors.affiliation: Department of Community Health Sciences, UCLA Fielding School of Public Health, Los Angeles, California, USA.
authors.forename: Donald E
authors.initials: DE
authors.lastname: Morisky
authors.affiliation: Department of AIDS/STD Prevention, Nanning Center for Disease Control and Prevention, Nanning, Guangxi, China.
authors.forename: Yongfang
authors.initials: Y
authors.lastname: Xu
authors.affiliation: Department of AIDS/STD Prevention, Hefei Center for Disease Control and Prevention, Hefei, Anhui, China.
authors.forename: Xiaojing
authors.initials: X
authors.lastname: Li
authors.affiliation: Department of Epidemiology, School of Public Health, Shandong University, Jinan, Shandon, China.
authors.forename: Baofa
authors.initials: B
authors.lastname: Jiang
mesh_terms: D000328:Adult; D000367:Age Factors; D002681:China / Q000453:epidemiology; D003430:Cross-Sectional Studies; D005260:Female; D015658:HIV Infections / Q000453:epidemiology; D006801:Humans; D008875:Middle Aged; D015995:Prevalence; D012044:Regression Analysis; D012111:Residence Characteristics; D012307:Risk Factors; D060386:Sex Workers / Q000706:statistics & numerical data*; D013587:Syphilis / Q000453:epidemiology*; D047568:Unsafe Sex / Q000706:statistics & numerical data
keywords: China; middle-aged female sex workers; respondent-driving sampling; risk factors; syphilis