Deven T. Hamilton

Concurrent Partnerships and HIV Prevalence Disparities by Race: Linking Science and Public Health Practice

Concurrent sexual partnerships may help to explain the disproportionately high prevalence of HIV and other sexually transmitted infections among African Americans. The persistence of such disparities would also require strong assortative mixing by race. We examined descriptive evidence from 4 nationally representative US surveys and found consistent support for both elements of this hypothesis. Using a data-driven network simulation model, we found that the levels of concurrency and assortative mixing observed produced a 2.6-fold racial disparity in the epidemic potential among young African American adults.

Degree distributions in sexual networks: a framework for evaluating evidence.

Objective: We present a likelihood based statistical framework to test the fit of power-law and alternative social process models for the degree distribution, and derive the sexually transmitted infection epidemic predictions from each model. Study Design: Five surveys from the United States are analyzed. Model fit is formally compared via Akaike Information Criterion and Bayesian Information Criterion, and substantively assessed via the prediction of a generalized epidemic. Results: Formal goodness-of-fit tests do not consistently identify any model as the best all around fit to the US data. Power-law models predict a generalized sexually transmitted infection epidemic in the United States, while most alternative models do not. Conclusions: Power-law models do not fit the data better than alternative models, and they consistently make inaccurate epidemic predictions. Better models are needed to represent the behavioral basis of sexual networks and the structures that result, if these data are to be used for disease transmission modeling.

Unloader Knee Braces for Osteoarthritis: Do Patients Actually Wear Them?

BackgroundUnloader braces are a nonsurgical approach for predominantly unicompartmental knee arthritis. Although noninvasive, braces are expensive and it is unclear whether clinical factors, if any, will predict regular brace use.Questions/purposesWe asked: (1) Do patients continue to use the unloader brace more than 1 year after it is prescribed? (2) Do any clinical or radiographic factors predict continued use of the unloader brace after the first year? (3) What are the most common subjective reasons that patients give for discontinuing the brace?MethodsWe administered 110 surveys to all patients who were fitted for unloader knee braces for predominantly unicompartmental osteoarthritis 12 to 40 months before administration of the survey. Standardized indications and fitting protocols were used. The following parameters were tested for association with ongoing brace use: alignment, arthritis severity, compartment involved, BMI, weight, age, gender, pain and function, number of refittings, and problems with the brace. The survey response rate was 81% (89 of 110).ResultsOf the 89 responders, 28% reported regular brace use (twice per week, an hour at a time, or more); at 2 years, 25% used the brace regularly. No clinical or radiographic factors considered were associated with ongoing brace use. Patients reported lack of symptomatic relief, brace discomfort, poor fit, and skin irritation as reasons for discontinuing the brace.ConclusionsSurgeons and patients need to balance the benefits and absence of complications of bracing against cost and the low likelihood of ongoing use 1 year or more after the prescription of the brace.Level of EvidenceLevel III, prognostic study. See Instructions for Authors for a complete description of levels of evidence.

Consistency of Self-Reported Sexual Behavior in Surveys

Accurate data on sexual behavior have become increasingly important for demographers and epidemiologists, but self-reported data are widely regarded as unreliable. We examined the consistency in the number of sexual partners reported by participants in seven population-based surveys of adults in the U.S. Differences between studies were quite modest and much smaller than those associated with demographic attributes. Surprisingly, the mode of survey administration did not appear to influence disclosure when the questions were similar. We conclude that there is more consistency in sexual partnership reporting than is commonly believed.

The racial disparities in STI in the U.S.: Concurrency, STI prevalence, and heterogeneity in partner selection.

Background There is a large and persistent racial disparity in STI in the U.S. which has placed non-Hispanic-Blacks at disproportionately high risk. We tested a hypothesis that both individual-level risk factors (partner number, anal sex, condom use) and local-network features (concurrency and assortative mixing by race) combine to account for the association between race and chlamydia status. Methods Data from the Longitudinal Survey of Adolescent Health Wave III were used. Chlamydia status was determined using biomarkers. Individual-level risk behaviors were self-reported. Network location variables for concurrency and assortative mixing were imputed using egocentrically sample data on sexual partnerships. Results After controlling for demographic attributes including age, sex, marital status, education and health care access there remained a strong association between race and chlamydia status (OR = 5.23, 95% CI] 3.83–7.15], p < .001 for Non-Hispanic Blacks with Non-Hispanic Whites as the reference category). The inclusion of individual-level risk factors did not alter the association between race and chlamydia(OR = 5.23 for Non-Hispanic Blacks). The inclusion of concurrency and assortative mixing by race substantially reduced the association between race and chlamydia status (OR = 1.87, 95% CI [0.89–3.91] p > .05 for Non-Hispanic Blacks).

Development of an Agent-Based Model to Investigate the Impact of HIV Self-Testing Programs on Men Who Have Sex With Men in Atlanta and Seattle.

Background In the United States HIV epidemic, men who have sex with men (MSM) remain the most profoundly affected group. Prevention science is increasingly being organized around HIV testing as a launch point into an HIV prevention continuum for MSM who are not living with HIV and into an HIV care continuum for MSM who are living with HIV. An increasing HIV testing frequency among MSM might decrease future HIV infections by linking men who are living with HIV to antiretroviral care, resulting in viral suppression. Distributing HIV self-test (HIVST) kits is a strategy aimed at increasing HIV testing. Our previous modeling work suggests that the impact of HIV self-tests on transmission dynamics will depend not only on the frequency of tests and testers’ behaviors but also on the epidemiological and testing characteristics of the population. Objective The objective of our study was to develop an agent-based model to inform public health strategies for promoting safe and effective HIV self-tests to decrease the HIV incidence among MSM in Atlanta, GA, and Seattle, WA, cities representing profoundly different epidemiological settings. Methods We adapted and extended a network- and agent-based stochastic simulation model of HIV transmission dynamics that was developed and parameterized to investigate racial disparities in HIV prevalence among MSM in Atlanta. The extension comprised several activities: adding a new set of model parameters for Seattle MSM; adding new parameters for tester types (ie, regular, risk-based, opportunistic-only, or never testers); adding parameters for simplified pre-exposure prophylaxis uptake following negative results for HIV tests; and developing a conceptual framework for the ways in which the provision of HIV self-tests might change testing behaviors. We derived city-specific parameters from previous cohort and cross-sectional studies on MSM in Atlanta and Seattle. Each simulated population comprised 10,000 MSM and targeted HIV prevalences are equivalent to 28% and 11% in Atlanta and Seattle, respectively. Results Previous studies provided sufficient data to estimate the model parameters representing nuanced HIV testing patterns and HIV self-test distribution. We calibrated the models to simulate the epidemics representing Atlanta and Seattle, including matching the expected stable HIV prevalence. The revised model facilitated the estimation of changes in 10-year HIV incidence based on counterfactual scenarios of HIV self-test distribution strategies and their impact on testing behaviors. Conclusions We demonstrated that the extension of an existing agent-based HIV transmission model was sufficient to simulate the HIV epidemics among MSM in Atlanta and Seattle, to accommodate a more nuanced depiction of HIV testing behaviors than previous models, and to serve as a platform to investigate how HIV self-tests might impact testing and HIV transmission patterns among MSM in Atlanta and Seattle. In our future studies, we will use the model to test how different HIV self-test distribution strategies might affect HIV incidence among MSM.

Psychosocial Results from a Phase I Trial of a Nonsurgical Circumcision Device for Adult Men in Zimbabwe

Male circumcision (MC), an effective HIV prevention tool, has been added to Zimbabwes Ministry of Health and Child Care HIV/AIDS Prevention Program. A Phase I safety trial of a nonsurgical male circumcision device was conducted and extensive psychosocial variables were assessed. Fifty-three men (18 and older) were recruited for the device procedure; 13 follow-up clinical visits were completed. Interviews conducted three times (before the procedure, at 2 weeks and 90 days post-procedure) assessed: Satisfaction; expectations; actual experience; activities of daily living; sexual behavior; and HIV risk perception. Using the Integrated Behavioral Model, attitudes towards MC, sex, and condoms, and sources of social influence and support were also assessed. Men (mean age 32.5, range 18-50; mean years of education = 13.6; 55% employed) were satisfied with device circumcision results. Men understand that MC is only partially protective against HIV acquisition. Most (94.7%) agreed that they will continue to use condoms to protect themselves from HIV. Pain ratings were surprisingly negative for a procedure billed as painless. Men talked to many social networks members about their MC experience; post-procedure (mean of 14 individuals). Minimal impact on activities of daily living and absenteeism indicate possible cost savings of device circumcisions. Spontaneous erections occurred frequently post-procedure. The results had important implications for changes in the pre-procedure clinical counseling protocol. Clear-cut counseling to manage pain and erection expectations should result in improved psychosocial outcomes in future roll-out of device circumcisions. Mens expectations must be managed through evidence-based counseling, as they share their experiences broadly among their social networks.

Sexual role and HIV-1 set point viral load among men who have sex with men

Background: HIV-1 set point viral load (SPVL) is a highly variable trait that influences disease progression and transmission risk. Men who are exclusively insertive (EI) during anal intercourse require more sexual contacts to become infected than exclusively receptive (ER) men. Thus, we hypothesize that EIs are more likely to acquire their viruses from highly infectious partners (i.e., with high SPVLs) and to have higher SPVLs than infected ERs. Methods: We used a one-generation Bernoulli model, a dynamic network model, and data from the Multicenter AIDS Cohort Study (MACS) to examine whether and under what circumstances MSM differ in SPVL by sexual role. Results: Both models predicted higher SPVLs in EIs than role versatile (RV) or ER men, but only in scenarios where longer-term relationships predominated. ER and RV men displayed similar SPVLs. EI men remained far less likely than ER men to become infected, however. When the MACS data were limited by some estimates of lower sex partner counts (a proxy for longer relationships), EI men had higher SPVLs; these differences were clinically relevant (> 0.3 log10 copies/mL) and statistically significant (p < 0.05). Conclusions: Mode of acquisition may be an important aspect of SPVL evolution in MSM, with clinical implications.

Evidence-Based Identification of Key Beliefs Explaining Infant Male Circumcision Motivation Among Expectant Parents in Zimbabwe: Targets for Behavior Change Messaging

Slow adult male circumcision uptake is one factor leading some to recommend increased priority for infant male circumcision (IMC) in sub-Saharan African countries. This research, guided by the integrated behavioral model (IBM), was carried out to identify key beliefs that best explain Zimbabwean parents’ motivation to have their infant sons circumcised. A quantitative survey, designed from qualitative elicitation study results, was administered to independent representative samples of 800 expectant mothers and 795 expectant fathers in two urban and two rural areas in Zimbabwe. Multiple regression analyses found IMC motivation among fathers was explained by instrumental attitude, descriptive norm and self-efficacy; while motivation among mothers was explained by instrumental attitude, injunctive norm, descriptive norm, self-efficacy, and perceived control. Regression analyses of beliefs underlying IBM constructs found some overlap but many differences in key beliefs explaining IMC motivation among mothers and fathers. We found differences in key beliefs among urban and rural parents. Urban fathers’ IMC motivation was explained best by behavioral beliefs, while rural fathers’ motivation was explained by both behavioral and efficacy beliefs. Urban mothers’ IMC motivation was explained primarily by behavioral and normative beliefs, while rural mothers’ motivation was explained mostly by behavioral beliefs. The key beliefs we identified should serve as targets for developing messages to improve demand and maximize parent uptake as IMC programs are rolled out. These targets need to be different among urban and rural expectant mothers and fathers.

Targeting Human Immunodeficiency Virus Pre-Exposure Prophylaxis to Adolescent Sexual Minority Males in Higher Prevalence Areas of the United States: A Modeling Study

PURPOSE Pre-exposure prophylaxis (PrEP) is an effective and safe intervention to prevent human immunodeficiency virus (HIV) transmission in men who have sex with men; current Centers for Disease Control and Prevention guidelines indicate its use among high-risk adults. Adolescent sexual minority males (ASMM) also have significant HIV risk, but implementation strategies are likely to differ for this population. We aimed to estimate impact and efficiency of PrEP for ASMM in higher prevalence US settings, using a variety of implementation strategies and assumptions about coverage, adherence, and background prevalence. METHODS We develop a stochastic, dynamic, network-based model, parametrized using numerous ASMM behavioral and clinical data sources. We simulate 10 years with and without PrEP, comparing percent of incident infections averted (impact) and number of person-years on PrEP per infection averted (efficiency). RESULTS Our main scenario (PrEP for 16- to 18-year-old ASMM, initiating PrEP 6 months after first anal intercourse, 40% coverage, adherence profiles from the ATN 113 trial; 2.9% background HIV prevalence among ASMM) prevents 27.8% of infections, with 38 person-years on PrEP per infection averted. Expanding implementation to cover younger ages or earlier initiation has small effects on impact and efficiency. Targeting highest risk ASMM increases efficiency, but requires querying sexual histories. Across levels examined, coverage and adherence do not have major impacts on efficiency, whereas background prevalence does. CONCLUSIONS PrEP can have a large impact on HIV incidence among ASMM in the United States, especially in settings with high prevalence. However, willingness of, and support for, providers will be central to achieving the coverage needed to make this a success.