High Risk Sharing Behaviors: The Effect of Sex within Injecting Partnerships Meghan D. Morris, PhD, MPH Postdoctoral Research Fellow Department of Epidemiology & Biostatistics University of California, San Francisco

Acknowledgements Co-Authors Jennifer Evans, Michelle Yu, Alya Briceno, Martha Montgomery, Kimberly Page, Judith Hahn Collaborators Paula Lum, Michael Busch, Eric Delwart, Leslie Tobler Funding (NIH-NIDA) R01-DA016017, R01-DA031056, K01-DA The research participants and staff!

Background Research has supported the notion that relationships between IDU, rather than individual risk behaviors alone, contribute significantly to the disease transmission patterns in IDU populations.  Few studies have considered both the individual and their injecting partner when identifying factors associated with drug using behaviors. For most young injection drug users (IDU), injecting drugs is a highly social activity.

Study Objectives To characterize injecting partnerships within a cohort of young (<30 years) IDU To measure the prevalence and estimate partnership characteristics associated with two high risk sharing behaviors: (1)receptive syringe sharing (2)receptive cooker use

Study Hypothesis 1.Female-Male injecting partnerships are at greater odds of high risk sharing behaviors than Male-Male injecting partnerships. 1.Partnerships engaging in both injection and sexual behaviors are at even greater odds of high risk sharing behaviors compared to partnerships engaged in only injecting.

The UFO “Partnership Study” Study Design: Prospective study of hepatitis C (HCV) transmission and acquisition within injecting dyads Injecting partnerships were interviewed monthly for up to 6 months; with possibility of reenrollment San Francisco, CA USA Injecting Partnership Definition: 1.Injected together ≥ 5x in past month AND 2.HCV RNA discordant upon enrollment  Eligibility did not require that drugs or injection equipment were shared HCV+ Index HCV- Partner

Analytic Methods Statistical Analysis: Multilevel Generalized Estimating Equations were used: – To examine the effect of partnership type on high risk sharing behaviors. Egocentric analysis focused on the “at risk” HCV- negative partner Outcomes: 1.Recent Receptive Syringe Sharing “Within the past 30 days, did you inject with a needle that your partner had already used, even if by accident or mistake?” 2.Recent Receptive Cooker Sharing “Within the past 30 days, was there any time that your partner’s previously used needle had been used with a cooker before you used that cooker?” Receptive Risk HCV+ Index HCV- Partner

28% receptive cooker sharing 17% receptive syringe sharing Study Sample Baseline Sample Baseline + Followup Sample 58 “at risk” partners 58 Injecting Partnerships 251 interviews among “at risk” partners Median of 4 interviews per partnership 9 new HCV infections  85% agreement in reporting of high risk sharing behaviors within partnerships

Median age 24 (IQR: ) Median duration of injection drug use was 6 years (IQR:3-9) Baseline characteristics of “at risk” partners (n=58)

Baseline Partnership-level Characteristics (n=58) 34% of injecting partnerships were engaged in sexual behaviors 56% always pooled money to buy drugs 80% lived together Median duration of injecting partnership was 4 months (IQR:2-12) Median time known partner was 10 months (IQR: 4-18)

Bivariate associations with high risk sharing behaviors Receptive Syringe Sharing (n=251) Receptive Cooker Sharing (n=251) OR (95% CI) Male-Female injecting partnership vs. Male-Male injecting partnership 1.8 ( ) 1.1 ( ) Sex with injection partner in past month 2.8 ( ) 2.5 ( ) Age at first injection drug use (per year increase) 0.9 ( ) 0.9 ( ) Biological Sex is Female vs. Male 1.1 ( ) 0.8 ( ) Known partner for ≥ 1 year vs. <1 year 1.1 ( ) 0.6 ( ) *GEE models with link logit, controlling for multiple partnerships

Recent sex with injecting partner independently associated with high risk sharing behaviors Receptive Syringe Sharing (n=251) Receptive Cooker Sharing (n=251) OR (95% CI)AOR (95% CI)OR (95% CI)AOR (95% CI) Sex with injection partner in past month 2.84 ( ) 4.01 ( ) 2.50 ( ) 4.29 ( ) Age at first injection drug use (per year increase) 0.96( ) ns 0.88 ( ) ns Biological Sex is Female vs. Male 1.06 ( ) ns 0.77 ( ) ns Known partner for ≥ 1 year vs. <1 year 1.10 ( ) ns 0.60 ( ) ns *GEE models with link logit, controlling for multiple partnerships AOR=Adjusted Odds Ratio ns= not significant

A higher proportion of recent high risk sharing behaviors occur within female-male sex + injecting partnerships Overall p<0.01

Summary Sex-composition alone was not significantly associated with an increased odds of high risk sharing behaviors. Injecting partnerships engaged in sexual behaviors were at significantly greater odds of both receptive syringe sharing and receptive cooker use. For female-male injection partnerships, it appears to be the combination of a sexual and injecting partnership that drives high risk injection behaviors.

Future Directions Future studies are needed to examine: Decision making processes within these injecting partnerships resulting in [or protecting from] high risk sharing behaviors. Why some partnerships remain HCV- even though they engage in high risk sharing behaviors with their HCV+ partners. Underlying factors influencing high risk sharing behaviors within sexual+injecting partnerships.

Acknowledgements to community collaborators and contributors Food Runners HIV Prevention Project, SF AIDS Foundation Homeless Youth Alliance San Francisco Needle Exchange SFDPH AIDS Office SFDPH Adult Immunization Clinic SFDPH Community Health Epidemiology & Disease Control SFDPH Housing and Urban Health Street Outreach Services, SFCCC Tenderloin Clinical Research Center (TCRC)

THANK YOU! For more information: UFO study: InC3 Study: InC3.epi-ucsf.org