Background: Assortative sexual mixing, the tendency for individuals to choose partners with similar characteristics to themselves, may be an important contributor to the unequal distribution of sexually transmitted infections in populations. We analyzed the tendency for assortative mixing on demographic and sexual behaviors characteristics in newly formed young adults dating partnerships.
Methods: Women aged 18 to 24 years and their male sexual partners of no more than 6 months were recruited during 2005 to 2010 at universities in Montreal, Canada. New dating partners were also prospectively recruited during the 2-year follow-up. We used Spearman and Newman coefficients to examine correlations between partners' demographic characteristics and sexual behaviors, and multivariable logistic modeling to determine which characteristics were assortative.
Results: Participants in 502 recruited partnerships were assortative on age (Spearman P = 0.60), smoking behavior (P = 0.43), ethnicity (Newman coefficient=0.39), lifetime number of sexual partners (P = 0.36), sex partner acquisition rates (P = 0.22), gap length between partnerships (P = 0.20), and on whether they had concurrent partners (P = 0.33). Partners were assortative on number of lifetime partners, sexual partner acquisition rates, concurrency, and gap length between partnerships even after adjustment for demographic characteristics. Reported condom use was correlated between initial and subsequently recruited partners (P = 0.35). There was little correlation between the frequencies of vaginal/oral/digital/anal sex between subsequent partnerships.
Conclusions: Dating partnerships were substantially assortative on various sexual behaviors as well as demographic characteristics. Though not a representative population sample, our recruitment of relatively new partnerships reduces survivor bias inherent to cross-sectional surveys where stable long-term partnerships are more likely to be sampled.
A study of newly formed young adult heterosexual couples found that partners were assortative on sexual behaviors (number of lifetime partners, concurrency, gap lengths) even after adjustment for demographic characteristics.
From the *Division of Cancer Epidemiology, Department of Oncology, McGill University, Montréal; †Department of Family and Community Medicine and Centre for Urban Health Solutions, Li Ka Shing Knowledge Institute, St. Michael's Hospital; ‡ Department of Family and Community Medicine and Dalla Lana School of Public Health, University of Toronto, Toronto; § Department of Family Medicine, McGill University; ¶ Département de Microbiologie et Infectiologie, Centre Hospitalier de l'Université de Montréal; ∥ Département de Microbiologie et Immunologie, Université de Montréal; and **Department of Epidemiology, Biostatistics and Occupational Health, McGill University, Montréal, Canada
Source of Funding: This work was supported by operating grant 68893, team grant 83320, and a Fellowship Award (support to TM) from the Canadian Institutes for Health Research (CIHR), grant AI073889 from the US National Institutes of Health, and by supplementary and unconditional funding support from Merck-Frosst Canada Ltd and Merck & Co. Ltd. The funders played no role in the writing of the manuscript or the decision to submit it for publication.
Conflicts of Interest: E.L.F. has served as advisory board member for companies involved with HPV vaccines (Merck and GSK) and as an occasional consultant to companies involved with HPV diagnostics (Roche, BD, Abbott). P.P.T. has received payment for lectures by Merck-Frosst Canada and Bayers. F.C. has participated in an expert group by Merck Sharp and Dohme. All other authors declare no potential conflicts of interest.
Additional collaborators in the HITCH study group: McGill Student Health Services: Gail Kelsall, Suzanne Dumais; Concordia University Student Health Services: Melanie Drew; Research nurses: Gail Kelsall, Suzanne Dumais, Natalia Morykon, Amela Rocamora, Nathalie Slavtcheva. Study management: Allita Rodriges. Study promotion: Vicky D’Anjou-Pomerleau, Jennifer Selinger, Elizabeth Montpetit-Dubrule, Jessica Sammut, Emilie Lapointe, Johanna Bleecker, Shady Rahayel; HPV DNA testing laboratories: Hélène Voyer, Véronique Legault, Julie Guénoun, Emilie Comète.
Correspondence: Talía Malagón, PhD, Division of Cancer Epidemiology, Department of Oncology, McGill University, 5100 Boulevard de Maisonneuve W Suite 720, Montreal, QC, Canada H4A 3T2. E-mail: firstname.lastname@example.org.
Received for publication January 9, 2017, and accepted February 10, 2017.
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