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Case-crossover study of partner and situational factors for unprotected sex
George R Seage1, Sarah Holte, Michael Gross
1Department of Epidemiology, Harvard School of Public Health, Boston, Massachusetts 02115, USA. gseage@hsph.harvard.edu
Objectives:
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.