title: Case-crossover study of partner and situational factors for unprotected sex.
abstract: OBJECTIVE
  To identify situational and partner characteristics associated with unprotected sex among women at risk for HIV infection.
  
  
  METHODS
  The most recent unprotected and protected sexual encounters were compared using a case-crossover design among 1,647 women enrolled in a prospective cohort study conducted in six U.S. cities. Information collected via audio computer-assisted self-interview included detailed situational and partner characteristics for participants' most recent sexual encounters, with and without condom use. Paired odds ratios (ORs) and 95% confidence intervals were calculated for situational or partner characteristics that may differ between unprotected and protected sexual encounters, using conditional logistic regression.
  
  
  RESULTS
  In the adjusted analysis, partner age of older than 40 years (OR = 2.42), partner type (OR = 2.45 for a "steady" partner), partner use of alcohol (OR = 1.67) and drugs within 2 hours (OR = 1.42) of the sexual encounter, time since the encounters (OR = 0.41, 0.33, and 0.19), and exchange of sex for money or drugs (OR = 0.68) remained significantly associated with women's most recent unprotected sexual encounter.
  
  
  CONCLUSIONS
  Considerations related to partner and relationship characteristics should provide information for the development of interventions for women.
authors.affiliation: Department of Epidemiology, Harvard School of Public Health, Boston, Massachusetts 02115, USA. gseage@hsph.harvard.edu
authors.forename: George R
authors.initials: GR
authors.lastname: Seage
authors.forename: Sarah
authors.initials: S
authors.lastname: Holte
authors.forename: Michael
authors.initials: M
authors.lastname: Gross
authors.forename: Beryl
authors.initials: B
authors.lastname: Koblin
authors.forename: Michael
authors.initials: M
authors.lastname: Marmor
authors.forename: Kenneth H
authors.initials: KH
authors.lastname: Mayer
authors.forename: William R
authors.initials: WR
authors.lastname: Lenderking
mesh_terms: D000328:Adult; D000367:Age Factors; D000428:Alcohol Drinking; D017280:Condoms; D016001:Confidence Intervals; D018592:Cross-Over Studies; D005260:Female; D018023:HIV Seronegativity; D006679:HIV Seropositivity / Q000453:epidemiology; D006801:Humans; D007182:Income; D007407:Interviews as Topic; D008297:Male; D016017:Odds Ratio; D012309:Risk-Taking; D021841:Safe Sex; D012725:Sexual Behavior; D019966:Substance-Related Disorders / Q000453:epidemiology; D014481:United States