SOCIAL NETWORKS AND HEALTH 2017 workshop

1. Using Social Network Analysis to
Inform HIV Prevention and
Treatment Efforts in Tanzania
Marta Mulawa, M.H.S., Ph.D.
Postdoctoral Scholar
Duke Global Health Institute
May 22, 2017

2. Two on-going projects
1. Structural network position and performance of popular opinion
health leaders within an HIV prevention trial
2. Peer selection and influence effects on intimate partner violence
perpetration over time

3. 1. Structural network position
and performance of popular
opinion health leaders within an
HIV prevention trial

4. Network Position of Popular Opinion Leaders
(POLs)
• POLs are people who influence the attitudes, beliefs, and behaviors of
others (Valente & Pumpuang, 2007)
• Engaging POLs has been fruitful HIV prevention approach (Medley et al., 2009)
• Significantly increase HIV knowledge and condom use
• Decrease risk behaviors like equipment sharing among IDUs
• Effectiveness of popular opinion leaders may depend on the position
they occupy within their networks (Schneider et al., 2015)
• Individuals who bridge sub-groups that are otherwise minimally connected
• Individuals who are centrally located within a network

5. Vijana Vijiweni II
• NIMH-funded trial (R01MH098690)(Kajula et al., 2016)
• PI: Suzanne Maman, PhD (UNC), site PI: Lusajo Kajula
(MUHAS)
• Cluster-randomized control trial
• Clusters are peer groups locally referred to as “camps”
(Yamanis et al., 2010)
• Intervention
• Health leadership intervention combined with
microfinance(Maman et al., 2015)
• Outcomes
• STI incidence, perpetration of physical or sexual
violence against female sexual partners

6. Camp-based Peer Networks

7. Study procedures
• N= 1,249 men at baseline; n=978 men (78%) at 12-month assessment
• Study assessments: behavioral & sociocentric network enumerations
• Shown camp roster: Do you know this person?
• If known: What relationship do you have with this person?
• Friend
• Acquaintance
• Something I don’t get along with
• Who are your 3 closest friends?
• Timing of assessments
• Conducted as baseline, 12-months and 30-months post-intervention launch
• In intervention clusters, popular opinion health leaders (called camp health
leaders, CHLs) identified through a peer nomination process

8. Aims of Present Analysis
• Describe the structural network position (i.e., degree and
betweenness centrality) of the CHLs at baseline
• Examine the associations between structural network positions and
• Total number of conversations about HIV and GBV at 12-months
• Response options for both topics were:
• 0= “none”
• 1= “1-4”
• 2= “5-9”
• 3= “10-15”
• 4 = “More than 15”
• Self-reported confidence in educating network members about HIV and GBV
• Confidence in both topics was assessed using a 4-point Likert scale

9. Methods
• igraph package in R used to compute
measures of in-degree centrality and
betweenness centrality for “closest
friend” networks
• Models were fit using generalized
estimating equations with standardized
predictors in SAS
• Controlling for:
• Camp: friendship density, reciprocity
• Participant: age, gender, SES, marital status,
and education

10. Camp Network Characteristics (n = 59)
Variables Mean SD Range
Networks size 32.6 12.4 20 – 77
Number of responders 25.3 10.8 7 – 66
Number male responders 21.2 8.9 7 – 40
Avg. age of network members 26.0 4.4 17.5 - 38.7
Number of ties (known relationships) 459.9 376.3 71.0 – 1722.0
Density 0.43 0.20 0.09 - 0.89
Reciprocity 0.43 0.19 0.08 - 0.88
Transitivity 0.70 0.19 0.20 - 0.99
Degree centralization 0.34 0.10 0.06 - 0.50
% friendship ties 74.4 21.8 26.5 - 100
% acquaintance ties 24.6 21.1 0 - 73.5
% negative ties 0.8 1.4 0 - 5.3

11. Predictors of # of Conversations
Model 1
Coeff. P
Intercept 4.7576 <0.001
Individual-Level Controls
Age 0.0170 0.96
Gender -1.1938 0.05
SES 0.1122 0.62
Marital Status 0.1158 0.69
Education 0.2597 0.18
Individual-Level Structural Position
In-Degree -0.1152 0.40
Betweenness Centrality
Network Level Structural Controls
Friendship Density -2.6219 0.58
Friendship Reciprocity 1.9558 0.74

12. Predictors of # of Conversations
Model 1 Model 2
Coeff. P Coeff. P
Intercept 4.7576 <0.001 4.0702 <0.001
Individual-Level Controls
Age 0.0170 0.96 0.0547 0.86
Gender -1.1938 0.05 0.0280 0.91
SES 0.1122 0.62 0.0949 0.74
Marital Status 0.1158 0.69 -0.8570 0.13
Education 0.2597 0.18 0.2171 0.24
Individual-Level Structural Position
In-Degree -0.1152 0.40
Betweenness Centrality 0.2093 0.009
Network Level Structural Controls
Friendship Density -2.6219 0.58 -2.3557 0.6090
Friendship Reciprocity 1.9558 0.74 2.1941 0.7022

13. Predictors of CHL Confidence
Model 1
Coeff. P
Intercept 9.1426 <.0001
Individual-Level Controls
Age 0.0529 0.77
Gender -1.1540 0.004
SES 0.1008 0.62
Marital Status 0.1065 0.47
Education 0.3314 0.04
Individual-Level Structural Position
In-Degree 0.1578 0.12
Betweenness Centrality
Network Level Structural Controls
Friendship Density 4.8772 0.16
Friendship Reciprocity -7.9411 0.05

14. Predictors of CHL Confidence
Model 1 Model 2
Coeff. P Coeff. P
Intercept 9.1426 <.0001 9.2256 <.0001
Individual-Level Controls
Age 0.0529 0.77 0.0524 0.78
Gender -1.1540 0.004 -1.2542 0.002
SES 0.1008 0.62 0.0861 0.68
Marital Status 0.1065 0.47 0.1299 0.35
Education 0.3314 0.04 0.3526 0.02
Individual-Level Structural Position
In-Degree 0.1578 0.12
Betweenness Centrality 0.0756 0.37
Network Level Structural Controls
Friendship Density 4.8772 0.16 4.7359 0.19
Friendship Reciprocity -7.9411 0.05 -7.4921 0.09

15. Results
• Neither degree or betweenness centrality were significantly
associated with CHL’s confidence
• Increasing betweenness centrality was associated with greater
number of conversations reported
• Opinion leaders who occupy spaces between sub-groups of network
members may be more effective in engaging their peer in
conversations about HIV and gender-based violence

16. 2. Peer selection and influence
effects on intimate partner
violence perpetration over time

17. Intimate Partner Violence (IPV), HIV, and SNA
• Men’s perpetration of IPV is widespread (Devries, 2013; WHO 2013a)
• Consequences of IPV are severe (Coker, 2002; Maxwell, 2015; Reid, 2008)
• Theoretical perspectives highlight the role of peer networks (Bandura, 1977,
Kelman, 1958)
• Previous research found that men’s peer networks (camps) were
more internally homogeneous and externally heterogeneous with
regard to IPV perpetration (Mulawa, 2016)
• Differentiating between selection and influence effects not possible using
cross-sectional data

18. Aims of Present Analysis
• Examine the longitudinal interplay between friendship formation and
the perpetration of intimate partner violence
• Modeling both how behavior influences the formation of friendship
ties and how friendship ties influence behavior

19. Examining changes in friendship ties and IPV
perpetration
Baseline 12-Month 36-Month

20. Thank you

21. References
• Bandura, A. (1977). Social learning theory. Englewood Cliff, NJ: Prentice Hall.
• Coker, A. L., Davis, K. E., Arias, I., Desai, S., Sanderson, M., Brandt, H. M., & Smith, P. H. (2002). Physical and mental
health effects of intimate partner violence for men and women. Am J Prev Med, 23(4), 260-268.
• Devries, K. M., Mak, J. Y., Garcia-Moreno, C., Petzold, M., Child, J. C., Falder, G., . . . Watts, C. H. (2013). Global
health. The global prevalence of intimate partner violence against women. Science, 340(6140), 1527-1528.
doi:10.1126/science.1240937
• Kajula, L., P. Balvanz, M. N. Kilonzo, G. Mwikoko, T. Yamanis, M. Mulawa, D. Kajuna, L. Hill, D. Conserve, H. L. Reyes,
S. Leatherman, B. Singh, and S. Maman. 2016. "Vijana Vijiweni II: a cluster-randomized trial to evaluate the efficacy
of a microfinance and peer health leadership intervention for HIV and intimate partner violence prevention among
social networks of young men in Dar es Salaam." BMC Public Health 16:113. doi: 10.1186/s12889-016-2774-x.
• Kelman, H. C. (1958). Compliance, Identification, and Internalization: Three Processes of Attitude Change. The
Journal of Conflict Resolution, 2(1), 51-60. Retrieved from http://www.jstor.org/stable/172844
• Maman, S., L. Kajula, P. Balvanz, M. Kilonzo, M. Mulawa, and T. Yamanis. 2015. "Leveraging strong social ties among
young men in Dar es Salaam: a pilot intervention of microfinance and peer leadership for HIV and gender-based
violence prevention." Glob Public Health:1-14. doi: 10.1080/17441692.2015.1094105.
• Maxwell, L., Devries, K., Zionts, D., Alhusen, J. L., & Campbell, J. (2015). Estimating the effect of intimate partner
violence on women's use of contraception: a systematic review and meta-analysis. PLoS One, 10(2), e0118234.

22. References
• Medley, A., C. Kennedy, K. O'Reilly, and M. Sweat. 2009. "Effectiveness of peer education interventions for
HIV prevention in developing countries: a systematic review and meta-analysis." AIDS Educ Prev 21 (3):181-
206. doi: 10.1521/aeap.2009.21.3.181.
• Mulawa, M., T. J. Yamanis, L. M. Hill, P. Balvanz, L. J. Kajula, and S. Maman. 2016. "Evidence of social network
influence on multiple HIV risk behaviors and normative beliefs among young Tanzanian men." Social Science
& Medicine 153:35-43. doi: http://dx.doi.org/10.1016/j.socscimed.2016.02.002.
• Reid, R. J., Bonomi, A. E., Rivara, F. P., Anderson, M. L., Fishman, P. A., Carrell, D. S., & Thompson, R. S. (2008).
Intimate partner violence among men prevalence, chronicity, and health effects. Am J Prev Med, 34(6), 478-
485.
• Schneider, J. A., A. N. Zhou, and E. O. Laumann. 2015. "A new HIV prevention network approach: sociometric
peer change agent selection." Soc Sci Med 125:192-202. doi: 10.1016/j.socscimed.2013.12.034.
• Valente, T. W., and P. Pumpuang. 2007. "Identifying opinion leaders to promote behavior change." Health
Educ Behav 34 (6):881-96. doi: 10.1177/1090198106297855.
• Yamanis, T. J., S. Maman, J. K. Mbwambo, J. A. Earp, and L. J. Kajula. 2010. "Social venues that protect against
and promote HIV risk for young men in Dar es Salaam, Tanzania." Soc Sci Med 71 (9):1601-9. doi:
10.1016/j.socscimed.2010.07.039.
• World Health Organization. (2013a). Global and regional estimates of violence against women: prevalence
and health effects of intimate partner violence and non-partner sexual violence Retrieved from Geneva,
Switzerland: