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Longitudinal

Trajectories

of

Physical

Intimate

Partner

Violence

Among

Adolescent

Girls

in

Rural

South

Africa:

Findings

From

HPTN

068

Stephanie

M.

DeLong,

M.P.H.

a,*

,

Kimberly

A.

Powers,

Ph.D.

a

,

Brian

W.

Pence,

Ph.D.

a

,

Suzanne Maman,

Ph.D.

b

, Kristin

L.

Dunkle, Ph.D.

c

, Amanda Selin, M.H.S.

d

,

Rhian Twine,

M.P.H.

e

,

Ryan

G.

Wagner,

Ph.D.

e

,

Francesc

Xavier

Gómez-Olivé,

Ph.D.

e

,

Catherine

MacPhail,

Ph.D.

f,g

,

Kathleen

Kahn,

Ph.D.

e

,

and

Audrey

Pettifor,

Ph.D.

a,e

aDepartmentofEpidemiology,GillingsSchoolofGlobalPublicHealth,UniversityofNorthCarolinaatChapelHill,ChapelHill,NorthCarolina bDepartmentofHealthBehavior,GillingsSchoolofGlobalPublicHealth,UniversityofNorthCarolinaatChapelHill,ChapelHill,NorthCarolina cGenderandHealthResearchUnit,SouthAfricanMedicalResearchCouncil,CapeTown,SouthAfrica

dCarolinaPopulationCenter,UniversityofNorthCarolinaatChapelHill,ChapelHill,NorthCarolina

eMedicalResearchCouncil/WitsRuralPublicHealthandHealthTransitionsResearchUnit(Agincourt),FacultyofHealthSciences,SchoolofPublicHealth,Universityofthe Witwatersrand,Johannesburg,SouthAfrica

fSchoolofHealthandSociety,UniversityofWollongong,Wollongong,NewSouthWales,Australia gWitsReproductiveHealthandHIVInstitute,UniversityoftheWitwatersrand,Johannesburg,SouthAfrica

Articlehistory: Received May 15, 2019; Accepted December 16, 2019

Keywords:Intimatepartnerviolence;Adolescent;Longitudinal;Trajectory;HPTN068

A B S T R A C T

Purpose: Little is known about temporal patterns of physical intimate partner violence (PIPV) among South African adolescent girls. We sought to identify and describe PIPV risk trajectories and related correlates in this population.

Methods: Our analytical cohort came from the HPTN 068 Cash Transfer Trial in Mpumalanga

Province, South Africa. Cohort members were eighth and ninth graders (median age 14 years) who enrolled in 2011 and had three to four annual, self-reported PIPV measurements. We used group-based trajectory models to identify groups of girls with similar longitudinal patterns of PIPV risk over 4 years and potential correlates of group membership.

Results:We identified two trajectory groups (n¼907): a higher-risk group (~52.8% of the cohort) with predicted PIPV probabilities of 13.5%e41.1% over time and a lower-risk group (~47.2% of the cohort) with predicted probabilities of 2.3%e10.3%. Baseline correlates of higher-risk group membership were ever having had sex (adjusted odds ratio [aOR]: 4.42, 95% confidence interval [CI]: 1.56e12.57), borrowing money (aOR: 1.95, 95% CI: 1.01e3.79), and older age (aOR per 1-year increase: 1.39, 95% CI: 1.11e1.73), while being in the 068 intervention arm (aOR: .29, 95% CI: .17e.51) and supporting more gender-equitable norms (aOR per 1-unit score increase: .89, 95% CI: .81e.97) were inversely associated.

IMPLICATIONS AND CONTRIBUTION

This study identified two longitudinal trajectories of physical intimate partner violence risk among adolescent girls in rural South Africa over four years, with annual pre-dicted probabilities of physical intimate partner violence between 13.5% and 41.1% in the higher-risk group and between 2.3% and 10.3% in the lower-risk group.

Data from a clinical trialdregistry site and number: ClinicalTrials.gov, NCT01233531.

*Address correspondence to: Stephanie M. DeLong, M.P.H, Center on Gender Equity and Health, University of California San Diego, 9500 Gilman Drive, La Jolla, CA 92093.

The poster of this work was presented at AIDS 2018, Amsterdam, the Netherlands. This article is also part of Stephanie DeLong's dissertation work.

E-mail address:sdelong@ucsd.edu(S.M. DeLong). Conflictsofinterest:Therearenorealorperceivedconflictsforanyofthe

namedauthors.Nostudysponsorsdirectedthestudydesign,datacollectionor analysis,interpretationofdata,orwritingorplanforsubmissionofthearticle. Thefirstauthorwasthepersonwholedthewritingofthemanuscriptandnota sponsor.

Disclaimer:Thecontentissolelytheresponsibilityoftheauthorsanddoesnot necessarilyrepresenttheofficialviewsoftheNationalInstitutesofHealth.

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Conclusions:A high proportion of adolescent girls experience sustained PIPV risk in rural South Africa, suggesting a need for interventions in late primary school that encourage gender-equitable norms, healthy relationships, and safe ways to earn income during adolescence.

Adolescence is a period of growth between the ages of 10 and 19 years involving physical, emotional, and social change [1]. Many adolescents enter romantic relationships [2,3] and expe-rience sexual debut [4e6] during this time. It is within the

context of these romantic interactions, whether involving sex or not, that intimate partner violence (IPV) can begin [7,8]. IPV is any form of physical, emotional, or sexual violence that occurs between two individuals who are or who have been in a romantic relationship or routine sexual partnership [9].

Little is known about longitudinal patterns of IPV risk among adolescent girls in South Africa, although IPV is prevalent. The most recent national data (2008) among female high school students (8the11th grade) suggest a period prevalence of phys-ical IPV (PIPV) in the last 6 months of 14% [10], with higher es-timates reported from school-based studies among eighth-grade urban girls in Pretoria (24%) [11] and Cape Town (39%) [12]. For comparison, 24%, 17%, 26%, and 9% of ever-partnered, urban 15-to 19-year-old girls from Baltimore, Maryland; Delhi, India; Iba-dan, Nigeria; and Shanghai, China, respectively, reported PIPV in the past year [13]. In cross-sectional analyses, factors associated with the experience of PIPV among adolescent girls in South Africa include the use of alcohol [12], showing support for less gender-equitable norms [12], and use of negative confl ict-resolution methods with a partner (such as an angry text mes-sage) [12]. They also include feeling less safe at school [14] and perpetration of PIPV against a male partner (potentially recip-rocal IPV) [14].

Although thesefindings suggest some clues for intervention, their cross-sectional nature hinders understanding of PIPV pre-dictors and the patterns by which PIPV unfolds over time. In this paper, we examine 4-year, temporal trajectories of PIPV risk among adolescent girls in grades 8 and 9 in rural, northeastern South Africa. We also assess demographic, behavioral, and structural factors correlated with these trajectories.

Methods

Study data and cohort formation

We performed secondary analyses of data from HPTN 068, a randomized controlled trial (RCT) conducted within the Medical Research Council/University of the Witwatersrand Rural Public Health and Health Transitions Research Unit (Agincourt), Mpu-malanga, South Africa. HPTN 068 examined whether girls aged 13e20 years who received a monthly cash transfer conditional on school attendance had fewer incident HIV infections than those not randomized to the intervention [15,16]. Enrollment occurred in 2011e2012, and participants completed annual follow-up visits until they graduated or completed the third annual follow-up visit, whichever wasfirst (resulting in a total of up to four possible visits). At each visit, girls completed an Audio Computer-Assisted Self-Interview [17] survey, answering

questions on demographic, behavioral, and structural factors, including experience of PIPV.

To be eligible for our trajectory analysis, participants needed to have enrolled in HPTN 068 in 2011, be in eighth or ninth grade at enrollment (to ensure sufficient study visit opportunities before graduation to contribute to trajectory modeling), and have the necessary PIPV data (as defined below) at3 visits. We did not examine trajectories of sexual IPV in this analysis because of a limited number of useable data points on this measure longitudinally.

Measurement

Outcome definition. Our outcome of interest was“any PIPV” in the last 12 months, coded dichotomously (yes/no) on the basis of answers to six PIPV questions at each visit. Questions were taken from the World Health Organization's Multi-Country Study on Women's Health and Domestic Violence against Women Ques-tionnaire [18]. These questions separately assessed (1) being slapped or having something thrown which could hurt; (2) being pushed or shoved; (3) being hit with afist or with something else which could hurt; (4) being kicked, dragged, or beaten up; (5) being choked or burned; or (6) being threatened with or having had a partner who actually used a gun, knife, or other weapon. A positive (yes) response to any of the six questions was coded as having experienced“any PIPV”for that visit.

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with Paul Wesson, PhD, February 15, 2017.) Girls could answer “agree a lot,” “somewhat agree,”or“do not agree”to each of the 13 questions, with the first two options collapsed in analysis based on item response theory analyses. Thefinal score for the gender norms variable could range from 0 to 13 (with 13 rep-resenting support for the most gender-equitable norms).

We also considered factors related to a girl's partnerships and sexual activity, such as whether she had ever had vaginal or anal sex, whether she had experienced condomless sex in the prior 3 months, and whether she had experienced transactional sex (receipt of money or gifts) with any of her (up to) three most recent sexual partners. Additional factors related to her part-nerships and sexual activity included whether she had concur-rent partnerships during any of her (up to) three most recent sexual partnerships, her number of sexual partners in the last 12 months, whether any of her (up to) three most recent sexual partners or a nonsexual partner wasfive or more years older than she was, and her HIV status as of baseline in the HPTN 068 trial (girls who tested HIV positive at baseline were excluded from the main trial analyses of HIV incidence, but they were still followed over time and included in these secondary analyses).

Finally, we considered whether a girl lived in a village where a gender norms intervention (Community Mobilization) was conducted [19] and whether the girl was randomized to the intervention arm of the HPTN 068 study [15]. Intervention girls and a parent/guardian received a conditional cash transfer of ~$30 USD a month during the study, approximately $20 USD to a parent or primary guardian and approximately $10 USD to the girl [15,16]. The cash transfer was conditional on80% school attendance.

Ethics

Institutional review board approvals were obtained from the University of North Carolina at Chapel Hill, the University of the Witwatersrand in South Africa, and the Mpumalanga Research Committee. Assent and/or consent was obtained from each girl and her participating parent/guardian. Girls who reported PIPV or other abuse during the study were offered support through local public-sector social workers.

Analysis

Identification of trajectory groups. We used group-based trajec-tory modeling, a type of finite mixture modeling, to identify latent groups of girls with similar patterns of PIPV over time [20]. This approach usesflexible polynomial functions fitted to the outcome of interest over time and allows prediction of each participant's probability of membership in each identified“ tra-jectory group,”as well as estimation of the overall proportions of participants in each group [20]. To identify the most appropriate number of trajectory groups for describing the longitudinal ex-periences of girls in our study population, we compared predictor-free models specifying one, two, three, four, andfive trajectory groups, using the Bayesian Information Criterion and the maximum posterior probabilities of group membership to select the model providing the best description of PIPV patterns in our study [20]. We conducted all group-based trajectory modeling with PROC TRAJ [21,22], specifying a logit distribution and binomial link function to reflect the dichotomous nature of the outcome [23]. We tested models with flat, linear, and quadratic polynomials but did not consider cubic polynomials to

avoid overfitting. In addition, we repeated the predictor-free trajectory analysis solely within the control arm to explore tra-jectories in the absence of the cash transfer intervention, noting that the smaller size of this restricted sample could limit our ability to detect multiple groups and would preclude predictor analyses.

Correlates of group membership. To summarize baseline charac-teristics of each latent trajectory group, we assigned each girl to the group for which she had the maximum posterior probability of membership and then conducted descriptive analyses of de-mographic, behavioral, and structural variables within each group.

To identify baseline correlates of trajectory group member-ship, we first constructed logistic regression models with the assigned trajectory group as the outcome, starting with a full model containing as predictor variables the 18 potential corre-lates described under the“Measurement”section. We note that our model building process was designed to identify a set of baseline correlates that werepredictiveof subsequent PIPV tra-jectories, rather than to construct a model for drawing causal inferences around a hypothesized exposureeoutcome relation-ship. After checking for high collinearity (andfinding none), we conducted backward selection [24], with

a

¼.2 to arrive at afinal logistic regression model. To ensure that predictor coefficient estimates and corresponding confidence intervals (CIs) properly accounted for the probabilities of membership in each group and the covariance between parameter estimates [23], we then incorporated the predictor variables from the final logistic regression model into the best-fitting predictor-free trajectory model (described in the previous subsection) to estimate adjusted odds ratios (aORs) and 95% CIs for each correlate. We used SAS software v9.4 [25] in all analyses.

Results

There were 2,533 girls enrolled in HPTN 068, 984 of whom were eighth- or ninth-grade girls enrolling in 2011. Of those 984 girls, 907 (92%) had PIPV data at three or four time points and were thus eligible for analysis. Baseline frequencies and medians of our demographic PIPV correlates of interest for the 907 girls closely resembled those for the full group of 984 girls (Appendix 1).

The median age at baseline in our study population was 14 years, with an interquartile range of 14e15 years and a range of 13e20 years (Table 1). For 26.1% of girls, the primary caregiver was someone other than a mother or father, and 57.7% of girls reported a household size of6 people. Approximately 15% of the cohort had ever been sexually active (vaginal and/or anal intercourse), and 9.6% reported past experience of sexual violence by a partner, family member, or other person outside the family. The median score for gender-equitable norms was 4.0, with an interquartile range of 2e6 and a range of 0e13.

Trajectories

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19.2, 33.2) at Year 3 (Figure 1). A“lower-risk”group, representing an estimated 47.2% of the girls, had predicted past-year PIPV probabilities of 2.3% (95% CI: .0, 8.0) at baseline, 3.8% (95% CI: .0, 10.6) at Year 1, 6.3% (95% CI: .0, 13.3) at Year 2, and 10.3% (95% CI: 3.2, 17.4) at Year 3. The average posterior probabilities of mem-bership in the higher- and lower-risk groups among girls assigned to each group were .80 and .73, respectively, indicating model adequacy in reflecting PIPV trajectories [23].

In the predictor-free trajectory subanalysis with restriction to the control arm, the best-fitting model was one with a single trajectory (Appendix 2). The shape of this trajectory was broadly consistent with the“higher risk”trajectory identified in the full sample, although predicted probabilities of PIPV were approxi-mately 5e10 percentage points lower at each time point.

Baseline correlates of higher-risk group membership. Girls assigned to the higher-risk group on the basis of the maximum posterior probability of membership were more likely than those assigned to the lower-risk group to have reported at baseline that they had ever had vaginal or anal sex, borrowed money in the past 12 months from a friend or someone outside the home to get by, and experienced sexual violence in the past (Table 1). In addition, girls in the higher-risk group were more likely to have reported partner concurrency during any of their three most recent sexual partnerships, to have any of their three most recent

sexual partners or a nonsexual partner be 5 or more years older, and to have had transactional sex. Consistent with the single (relatively high-risk) trajectory observed in our sub-analysis of control-arm participants (described previously), girls in the full-sample“higher-risk” group were less likely than those in the “lower-risk” group to have been assigned to the HPTN 068 intervention arm.

In our multivariable trajectory model with baseline correlates from thefinal logistic regression model as predictors, increased odds of higher-risk (vs. lower-risk) group membership was associated with ever having had vaginal or anal sex (aOR: 4.42, 95% CI: 1.56, 12.57), borrowing money in the last 12 months (aOR: 1.95, 95% CI: 1.01e3.79), and older age (aOR per 1-year age increase: 1.39, 95% CI: 1.11e1.73; Table 2). Support for more gender-equitable norms (aOR per one-unit score increase: .89, 95% CI: .81, .97) and being in the HPTN 068 intervention arm (aOR: .29, 95% CI: .17, .51) were inversely associated with higher-risk group membership.

Discussion

In this analysis of PIPV among adolescent girls in rural, northeastern South Africa, we identified two distinct patterns across time, with one group experiencing a consistently higher risk of PIPV than the other. For the higher-risk group, Table 1

Baseline characteristics of adolescent girls in the trajectory analysis cohort

Cohort Lower-risk groupa Higher-risk groupa

n¼907 % n¼463 % n¼444 %

Age in years (median, IQR, range) 14 14 15

14, 15 14, 15 14, 16

13e20 13e18 13e20

Primary caregiver not mother or father 237 26.1 116 25.1 121 27.3

Household size6 people 523 57.7 269 58.1 254 57.2

Moved in the last 12 months 21 2.3 11 2.4 10 2.3

Family socioeconomic statusb(value of6 ln_pce) 642 71.1 330 71.6 312 70.6 Father completed high school, university, or technikon 217 30.0 112 30.1 105 29.8 Mother completed high school, university, or technikon 184 22.6 110 26.1 74 18.8 Girl repeated any grade in school 279 30.8 121 26.1 158 35.6 Gender-equitable norms (median, IQR, range) 4 4 4

2, 6 2, 6 2, 6

0e13 0e13 0e13

Experienced pastcsexual violence 86 9.6 32 7.0 54 12.4

Consumed alcohol 76 8.4 34 7.4 42 9.5

Borrowed money in past 12 months from a friend or someone outside the home

181 20.1 76 16.5 105 23.8

HPTN 068 intervention arm 469 51.7 279 60.3 190 42.8 Village received gender norms intervention 437 48.5 231 50.3 206 46.5 Ever had vaginal or anal sex 136 15.0 41 8.9 95 21.4 Number of sex partners in the last 12 months (median, IQR, range) 0 0 0

0, 0 0, 0 0, 0

0e55 0e3 0e55

Had concurrent sex partnersd 50 5.5 10 2.2 40 9.1

Had transactional sexe 16 1.8 2 .4 14 3.2

Had unprotected sex in the prior 3 months 30 3.3 9 2.0 21 4.8 Partner 5 years or older (sexual or nonsexual)f 29 3.3 8 1.8 21 4.8

HIV statusdpositive 27 3.0 11 2.4 16 3.6

IQR¼interquartile range.

aAssigned according to each girl's maximum posterior probability of group membership.

bAs measured through the natural log of total household expenditures (food and nonfood) per capita, dichotomized at the median, to represent greater wealth versus

less in the sample.

cExperienced past sexual violence by at least one of the following: a partner, family member, or other person outside the family (not including a boyfriend or partner). dDuring the time of one or more of her three most recent sexual partners

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representing an estimated 52.8% of the sample, we saw the experience of PIPV rise rapidly from baseline when girls were a median age of 15 years, peak around Year 2 of the study, when the median age would have been 17 years, and then decline slightly again by Year 3, when the median age would have been 18 years. In contrast, for a lower-risk group, representing an estimated 47.2% of the sample, PIPV risk stayed low from baseline (median age 14 years) through Year 2 and then slightly increased by Year 3 (when the median age would have been 17 years).

Prior PIPV victimization trajectory analyses from South Af-rica are not available for comparison, but trajectory studies from the southeastern U.S. provide an opportunity to consider ourfindings against results from similarly aged populations of girls elsewhere. In a study of physical dating violence among eighth- to tenth-grade girls in North Carolina, researchers identified three PIPV victimization groups using growth mixture modeling. Girls in the high- and moderate-risk groups, comprising 3.4% and 7.8% of the cohort, respectively, began somewhat elevated (high-risk) or low (moderate-risk), peaked around grade 10, with the high-risk group being higher, and declined by grade 12 [26]. Girls in the third, lowest-risk group, representing 88.9% of the sample, exhibited little risk across time. We saw a similar qualitative peak in our higher-risk group as that seen in the North Carolina study's high-risk and moderate-risk groups. The slight rise in PIPV reporting at the last time point among our lower-risk group was not observed in theflat low-risk trajectory in the North Carolina study.

Our results are also somewhat similar to a second study [27] in which latent class mixture modeling was used to explore

physical dating violence victimization over 7 years among girls in Georgia, who were in sixth grade at the start of the study. As seen in our study, two PIPV victimization groups were identified: a risk group and a lower-risk group. PIPV risk in the higher-risk group, comprising 29.3% of the study population, began at an estimated 37% and then increased monotonically across time (to 66% at 7 years), contrasting with our study, which saw a quadratic shape of victimization in our higher-risk group. The lower-risk group, comprising 70.7% of the Georgia study popu-lation, maintained low PIPV risk (7%) across the years, whereas our lower-risk group saw slightly increasing risk at thefinal time point.

Correlates

We identified several strong correlates of higher-risk group membership. Ever having had vaginal or anal sex at baseline, a variable indicating exposure to sexual partners, was the stron-gest correlate of higher-risk group membership in our study. Older age at baseline was also associated with higher-risk group membership, consistent with the general increase in PIPV reporting over time in both groups.

In addition, we saw that borrowing money from a friend or someone outside the household to get by in the last 12 months was associated with membership in the higher-risk group. Twenty-four percent of girls assigned to the higher-risk group reported at baseline that they had borrowed money in the past year, suggesting less access to personalfinancial resources than the average study participant. In contrast, the variables repre-senting family/household structure and family socioeconomic 0

0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5 0.55 0.6

0 1 2 3

Higher risk group upper 95% CI

Higher risk of physical IPV, 52.8% of the sample Higher risk group lower 95% CI

Observed, higher risk group

Lower risk group upper 95% CI

Lower risk of physical IPV, 47.2% of the sample Lower risk group lower 95% CI

Observed, lower risk group

Years since baseline visit

Probabilit

y of experiencing PIPV in the prior 12 months

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status were not retained in ourfinal logistic regression model, suggesting that an individual girl's experience of borrowing money is more strongly predictive of PIPV risk than are less proximal family-level variables. Although we do not have data indicating the uses of borrowed money or from whom girls borrowed the money, it may be that they borrowed money from abusive partners. In this rural area, compared with a larger city in South Africa where there are more job opportunities, we spec-ulate that borrowing money from partners or engaging in transactional sex may be one of the few ways girls perceive they can earn expendable income.

The HPTN 068 trial assessed whether cash transfers provided to girls who attended school 80% of the time resulted in decreased HIV incidence [15,16]. Although there was not a dif-ference in HIV incidence resulting from receipt of the cash transfer, the risk of PIPV was previously shown to be lower among girls receiving versus not receiving the cash transfer intervention [15]. Our trajectory and correlate analyses are consistent with thisfinding, suggesting that the interventiond along with the other correlates identified in our multivariable analysisdcontributed toward the identification of the lower-risk group that we observed. As noted in other analyses of HPTN 068 results [28], this apparently protective effect of the intervention on PIPV risk may be mediated by delayed sexual debut or a reduced number of sexual partners among those in the inter-vention arm. In recent years, greater attention has been placed on examining the effects of cash transfers on IPV globally, with interest in understanding the mechanisms behind this relation-ship when an effect is observed [29].

The inverse association that we observed between higher-risk group membership and more gender-equitable norms also aligns with prior studies [11,30] in which less equitable norms were associated with the experience of different forms of IPV. It may be that within South African culture, where some men embrace a hegemonic masculinity focused on demonstrating their power and control through partnerships that sometimes include abuse [31], those girls who are expressing more equitable norms may be less likely to choose or stay with an abusive partner.

Intervention implications.Ourfindings suggest that interventions initiated in late primary school that focus on healthy romantic and sexual relationships, safe ways to earn money, and gender equity could hold promise for reducing the proportion of girls following a“high-risk”PIPV trajectory. Existing, age-appropriate, effective programs, such as Safe Dates [32], should be considered for adaptation and testing in our target population for this pur-pose. Safe Dates is a school-based program that has been tested in an RCT among eighth- and ninth-grade girls and boys in North Carolina. Among other results, it has been shown effective in reducing moderate physical dating violence victimization and perpetration at four annual time points, mediated through shifting gender role norms, dating violence norms, and making students aware of community services [32]. The effective, school-based“Fourth R: Skills for Youth Relationships”[33] interven-tion, which has been shown to decrease physical dating violence perpetration among 14- to 15-year-olds in 20 schools in Ontario, Canada, especially boys, could also be considered for adaptation and testing among adolescents in South Africa. Stepping Stones [34], a program that uses same-sex groups to discuss topics such as sexual relationships and gender-based violence, could also be adapted to a younger age group and assessed among girls and boys in late childhood/late primary school. Stepping Stones was shown effective in reducing perpetration of IPV among 15- to 26-year-old men in South Africa over 2 years [34]. Finally, cash transfers during adolescence, similar to what was provided in HPTN 068 [15], may also warrant consideration as a potential way to help protect girls against PIPV risk.

Limitations.We note that with four data points in the main trial, we were limited in our ability to discern more complex longi-tudinal patterns (if such patterns existed) beyond the two tra-jectory groups we identified on the basis of a dichotomized PIPV variable. Future research examining patterns not only of PIPV presence but also of PIPV severity in larger study populations is necessary to provide more detailed insights. In addition, we had to exclude a small percentage of eighth- and ninth-grade girls who enrolled in HPTN 068 in 2011 but had fewer than three annual PIPV data points. Although baseline demographics were similar between these girls and those who were included in analyses, if loss to follow-up was associated with increased PIPV risk, then exclusion of girls with incomplete follow-up may have resulted in underestimation of the size of the higher-risk group. Our study population was also drawn from an RCT of rural girls who were attending school, and the generalizability of our results to populations outside of this school-based RCT is uncertain. Finally, IPV is a sensitive topic and may have been underreported [35], although the use of Audio Computer-Assisted Self-Interview in our study was chosen to limit the extent of this potential bias.

Conclusions

To our knowledge, this is the rst study of longitudinal physical IPV trajectories among adolescent girls in South Africa. We identified two latent clusters of PIPV experienced across time, with approximately one half of the girls at consistently higher risk than the other half. Effective interventions among late primary school children that encourage healthy relationships and sex, gender-equitable norms, and safe ways to earn money could potentially reduce the experience of PIPV in this setting. Structural changes, as well as government and community Table 2

Adjusted odds ratios and 95% confidence intervals for baseline variables corre-lated with membership in the higher-risk trajectory groupa, 2011

e2014, HPTN 068

Odds ratio

95% confidence interval

Older age in years 1.39 1.11, 1.73 More gender-equitable normsb .89 .81, .97 Experienced past sexual violencec 2.74 .88, 8.50 Borrowed money in the past 12 months

from a friend or someone outside the home

1.95 1.01, 3.79

HPTN 068 Intervention Armd .29 .17, .51 Ever had vaginal or anal sex 4.42 1.56, 12.57

Regression coefficients used to calculate odds ratios and 95% confidence intervals were generated from the multivariable trajectory model.

aVersus the lower-risk trajectory group.

bThe total score for gender-equitable norms can range from 0 through 13,

with 13 representing a girl's endorsement of more gender-equitable norms. The adjusted odds ratio corresponds to a 1-unit increase in score.

cExperienced past lifetime sexual violence before HPTN 068 by at least one of

the following: a partner, family member, or other person outside the family (not including a boyfriend or partner).

dHPTN 068 intervention arm received a cash transfer equivalent to ~$30USD a

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support, may enhance the success of such interventions in pro-tecting at-risk youth.

Acknowledgments

The authors would also like to thank the adolescent girls from the Agincourt area, South Africa, community who participated in this study.

Funding Sources

This work was supported by Award Numbers UM1AI068619 (HPTN Leadership and Operations Center), UM1AI068617 (HPTN Statistical and Data Management Center), and UM1AI068613 (HPTN Laboratory Center) from the National Institute of Allergy and Infectious Diseases, the National Institute of Mental Health, and the National Institute on Drug Abuse of the National In-stitutes of Health. This work was also supported by NIMH R01 (R01MH087118), R01MH110186, and the Carolina Population Center and its NIH Center grant (P2C HD050924). Finally, this research was supported by the National Institute of Allergy and Infectious Diseases of the National Institutes of Health under Award Number T32-AI007001 (S.M.D.)

Supplementary Data

Supplementary data related to this article can be found at https://doi.org/10.1016/j.jadohealth.2019.12.016

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Figure

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  12. Shamu S, Gevers A, Mahlangu BP, et al. Prevalence and risk factors forintimate partner violence among grade 8 learners in urban South Africa:
  13. Russell M, Cupp PK, Jewkes RK, et al. Intimate partner violence amongadolescents in Cape Town, South Africa. Prev Sci 2014;15:283
  14. Decker MR, Peitzmeier S, Olumide A, et al. Prevalence and health impact ofintimate partner violence and non-partner sexual violence among female
  15. Mason-Jones AJ, De Koker P, Eggers SM, et al. Intimate partner violence inearly adolescence: The role of gender, socioeconomic factors and the
  16. Pettifor A, MacPhail C, Hughes JP, et al. The effect of a conditional cashtransfer on HIV incidence in young women in rural South Africa (HPTN 068):
  17. Pettifor A, MacPhail C, Selin A, et al. Hptn 068: A randomized control trialof a conditional cash transfer to reduce HIV infection in young women in
  18. http://acasi.tufts.edu/
  19. https://www.who.int/reproductivehealth/publications/violence/24159358X/en/
  20. Pettifor A, Lippman SA, Selin AM, et al. A cluster randomized-controlledtrial of a community mobilization intervention to change gender norms
  21. Nagin DS, Odgers CL. Group-based trajectory modeling in clinical research2010. Annu Rev Clin Psychol 2010;6:109
  22. Jones BL, Nagin DS, Roeder K. A SAS procedure based on mixture models forestimating developmental trajectories. Sociol Methods Res 2001;29:374
  23. https://www.andrew.cmu.edu/user/bjones/
  24. Nagin DS. Group-based modeling of development. Cambridge, Massachu-setts: Harvard University Press; 2005
  25. Harrell FE. Multivariable modeling strategies. In: Harrell FE, ed. Regressionmodeling strategies with applications to linear models, logistic and ordinal
  26. Brooks-Russell A, Foshee V, Ennett S. Predictors of latent trajectory classesof dating violence victimization. J Youth Adolesc 2013;42:566
  27. Orpinas P, Hsieh HL, Song X, et al. Trajectories of physical dating violencefrom middle to high school: Association with Relationship Quality and
  28. Kilburn KN, Pettifor A, Edwards JK, et al. Conditional cash transfers and thereduction in partner violence for young women: An investigation of causal
  29. Buller AM, Peterman A, Ranganathan M, et al. A mixed-method review ofcash transfers and intimate partner violence in low and middle-income
  30. Abramsky T, Watts CH, Garcia-Moreno C, et al. What factors are associatedwith recent intimate partner violence? Findings from the WHO
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