title: Concurrent sexual partnerships among young heterosexual adults at increased HIV risk: types and characteristics.
abstract: BACKGROUND
  The impact of concurrency on sexually transmitted infection transmission depends on coital frequency, condom use, duration of relationship overlap, and number of partners. Previous research has identified distinct concurrency types; however, little is known about their risk characteristics.
  
  
  METHODS
  Men (n = 261) and women (n = 275) aged 18 to 30 years at increased risk for acquiring HIV were recruited from community locations in Los Angeles. Participants completed 4 in-person interviews for 12 months. Partnership data were used to characterize the prevalence of 4 types of concurrency: transitional (2 overlapping relationships in which the first relationship ended before the second), single day (a second relationship of 1 day's duration during the course of another relationship), contained (a second relationship >1 day began and ended during the course of another), and multiple (≥3 overlapping relationships). Multilevel random intercept models were used to estimate mean coital frequency, proportion of condom-protected acts, total duration of overlap, and lifetime sex partners.
  
  
  RESULTS
  At baseline, 47% of male and 32% of female participants reported any type of concurrency in the previous 4 months, and 26% of men and 10% of women reported multiple concurrencies. Condom use ranged from 56% to 64%, with the highest use in transitional concurrency (61% for men, 68% for women) and the lowest in contained (52% for men, 54% for women). Coital frequency, total overlap, and lifetime sex partners also varied by concurrency type.
  
  
  CONCLUSIONS
  Inconsistent condom use and repeated opportunities for exposure characterize common types of concurrency among high-risk young adults.
authors.affiliation: From the *Lane County Health and Human Services, Eugene; †Oregon State University, Corvallis, OR; ‡Oklahoma State University, Stillwater, OK; §UNC Gillings School of Global Public Health, Chapel Hill, NC; and ¶Purdue University, West Lafayette, IN.
authors.forename: Jocelyn T
authors.initials: JT
authors.lastname: Warren
authors.forename: S Marie
authors.initials: SM
authors.lastname: Harvey
authors.forename: Isaac Joel
authors.initials: IJ
authors.lastname: Washburn
authors.forename: Diana Maria
authors.initials: DM
authors.lastname: Sanchez
authors.forename: Victor J
authors.initials: VJ
authors.lastname: Schoenbach
authors.forename: Christopher R
authors.initials: CR
authors.lastname: Agnew
mesh_terms: D000328:Adult; D003075:Coitus; D017280:Condoms / Q000706:statistics & numerical data*; D005260:Female; D007722:Health Knowledge, Attitudes, Practice; D006801:Humans; D008137:Longitudinal Studies; D015141:Los Angeles / Q000453:epidemiology; D008297:Male; D015995:Prevalence; D012307:Risk Factors; D012725:Sexual Behavior / Q000523:psychology / Q000706:statistics & numerical data; D012747:Sexual Partners; D012749:Sexually Transmitted Diseases / Q000517:prevention & control* / Q000523:psychology / Q000635:transmission; D013997:Time Factors