Measures of sexual partnerships: Lengths, gaps, overlaps, and sexually transmitted infection

Goal: The length of time between partnerships (gap) is an important determinant of the overall transmission system of sexually transmitted infections. We describe the distributions of gaps, lengths, and overlaps among participants in a random-digit dialing survey conducted among 1194 Seattle residents during 2003-2004. Methods: Survey participants were restricted to those 18 to 39 years of age with fluency in the English language. We limited our analysis to the 1051 (88%) participants who reported ever engaging in vaginal, oral, or anal intercourse and reported information on gaps, lengths, and overlaps. Results: Most (59%) observed gaps between partnerships were of length <= 56 months; therefore, the majority of 18- to 39-year-olds seeking new partners find a new partner well within the infectious period of chlamydia infection, gonorrhea, and syphilis (if no treatment is received) and herpes simplex virus, human papilloma virus, and human immunodeficiency virus infections. This was generally true independent of gender, race, income, or education. Gap length, however, correlated with age. Conclusions: The observed shorter gap lengths among younger individuals reinforce the need to focus interventions on adolescents and young adults, particularly those with the potential to mix with infected individuals.