Interaction of mathematical modeling and social and behavioral HIV/AIDS research

Incorporating social determinants of health into the mathematical modeling of HIV/AIDS

Currently, it is estimated that 37.6 million people are living with the HIV/AIDS virus worldwide, placing HIV/AIDS among the ten leading causes of death, mostly among low- and lower-middle-income countries. Despite the effective intervention in the prevention and treatment, this reduction did not occur equally among populations, subpopulations and geographic regions. This difference in the occurrence of the disease is associated with the social determinants of health (SDH), which could affect the transmission and maintenance of HIV. With the recognition of the importance of SDH in HIV transmission, the development of mathematical models that incorporate these determinants could increase the accuracy and robustness of the modeling. This article aims to propose a theoretical and conceptual way of including SDH in the mathematical modeling of HIV/AIDS. The theoretical mathematical model with the Social Determinants of Health has been developed in stages. For the selection of SDH that were incorporated into the model, a narrative literature review was conducted. Secondly, we proposed an extended model in which the population (N) is divided into Susceptible (S), HIV-positive (I), Individual with AIDS (A) and individual under treatment (T). Each SDH had a different approach to embedding in the model. We performed a calibration and validation of the model. A total of 31 SDH were obtained in the review, divided into four groups: Individual Factors, Socioeconomic Factors, Social Participation, and Health Services. In the end, four determinants were selected for incorporation into the model: Education, Poverty, Use of Drugs and Alcohol abuse, and Condoms Use. the section "Numerical simulation" to simulate the influence of the poverty rate on the AIDS incidence and mortality rates. We used a Brazilian dataset of new AIDS cases and deaths, which is publicly available. We calibrated the model using a multiobjective genetic algorithm for the years 2003 to 2019. To forecast from 2020 to 2035, we assumed two lines of poverty rate representing (i) a scenario of increasing and (ii) a scenario of decreasing. To avoid overfitting, we fixed some parameters and estimated the remaining. The equations presented with the chosen SDH exemplify some approaches that we can adopt when thinking about modeling social effects on the occurrence of HIV. The model was able to capture the influence of the employment/poverty on the HIV/AIDS incidence and mortality rates, evidencing the importance of SDOH in the occurrence of diseases. The recognition of the importance of including the SDH in the modeling and studies on HIV/AIDS is evident, due to its complexity and multicausality. Models that do not take into account in their structure, will probably miss a great part of the real trends, especially in periods, as the current on, of economic crisis and strong socioeconomic changes.

Partnership dynamics in mathematical models and implications for representation of sexually transmitted infections: a review

Mathematical models of sexually transmitted disease (STI) are increasingly relied on to inform policy, practice, and resource allocation. Because STI transmission requires sexual contact between two or more people, a model's ability to represent the dynamics of sexual partnerships can influence the validity of findings. This ability is to a large extent constrained by the model type, as different modeling frameworks vary in their capability to capture patterns of sexual contact at individual, partnership, and network levels. In this paper, we classify models into three groups: compartmental, individual-based, and statistical network models. For each framework, we describe the basic model structure and discuss key aspects of sexual partnership dynamics: how and with whom partnerships are formed, partnership duration and dissolution, and temporal overlap in partnerships (concurrency). We illustrate the potential implications of accurately accounting for partnership dynamics, but these effects depend on characteristics of both the population and pathogen; the combined impact of these partnership and epidemiologic dynamics can be difficult to predict. While each of the reviewed model frameworks may be appropriate to inform certain research or policy questions, modelers and consumers of models should carefully consider the implications of sexual partnership dynamics for the questions under study.

HIV, Sexually Transmitted Infection, and Substance Use Continuum of Care Interventions Among Criminal Justice-Involved Black Men Who Have Sex With Men: A Systematic Review

BACKGROUND

Because Black men who have sex with men (BMSM) experience high rates of both HIV and incarceration relative to other groups, the various stages of criminal justice involvement may serve as important intervention points for addressing HIV and related conditions in this group. Although systematic reviews of HIV interventions targeting MSM in general and BMSM in particular exist, no review has explored the range and impact of HIV, sexually transmitted infection (STI), and substance use prevention and care continuum interventions focused on criminal justice-involved (CJI) populations.

OBJECTIVES

To describe the range and impact of published HIV, STI, and related substance use interventions for US-based CJI populations and to understand their relevance for BMSM.

SEARCH METHODS

We conducted systematic searches in the following databases: PubMed, MEDLINE, Cochrane, CINAHL, and PsycINFO, covering the period preceding December 1, 2016.

SELECTION CRITERIA

We selected articles in scientific publications involving quantitative findings for studies of US-based interventions that focused on CJI individuals, with outcomes related to sexual or substance use risk behaviors, HIV, or STIs. We excluded studies if they provided no demographic information, had minimal representation of the population of interest (< 30 African American or Black male or transgender participants), had study populations limited to those aged younger than 18 years, or were limited to evaluations of preexisting programs.

DATA COLLECTION AND ANALYSIS

We abstracted data from these articles on study design; years covered; study location; participant number, demographics, and sexual orientation (if available); criminal justice setting or type; health condition; targeted outcomes; and key findings. We scored studies by using the Downs and Black quality and bias assessment. We conducted linear regression to examine changes in study quality by publication year.

MAIN RESULTS

Fifty-eight articles met inclusion criteria, including 8 (13.8%) modeling or cost-effectiveness studies and 13 (22.4%) randomized controlled trials. Just 3 studies (5.2%) focused on sexual or gender minorities, with only 1 focused on BMSM. In most studies (n = 36; 62.1%), however, more than 50% of participants were Black. The most common intervention addressed screening, including 20 empirical studies and 7 modeling studies. Education-focused interventions were also common (n = 15) and usually employed didactic rather than skill-building approaches. They were more likely to demonstrate increases in HIV testing, knowledge, and condom-use intentions than reductions in sex- and drug-risk behaviors. Screening programs consistently indicated cost-effectiveness, including with BMSM. Care continuum interventions for people living with HIV showed mixed results; just 3 involved randomized controlled trials, and these interventions did not show significant differences compared with control conditions. A minority of programs targeted non-custody-based CJI populations, despite their constituting a majority of the CJI population at any given time.

AUTHORS' CONCLUSIONS

Screening CJI populations for HIV and other STIs is effective and cost-efficient and holds promise for reducing HIV in BMSM. Education-based and care provision interventions also hold promise for addressing HIV, STIs, mental health, and substance use in CJI populations. Additional empirical and modeling studies and results specific to sexual minorities are needed; their paucity represents a disparity in how HIV is addressed. Public Health Implications. HIV and STI screening programs focused on CJI populations should be a priority for reducing HIV risk and numbers of undiagnosed infections among BMSM. Funding agencies and public health leaders should prioritize research to improve the knowledge base regarding which care continuum intervention approaches are most effective for BMSM with criminal justice involvement. Developments in modeling approaches could allow researchers to simulate the impacts and costs of criminal justice involvement-related interventions that might otherwise be cost, time, or ethically prohibitive to study empirically.

Conceptual framework and research methods for migration and HIV transmission dynamics

Migration and mobility have had a profound influence on the global HIV epidemic. We propose a network-dyadic conceptual model to interpret previous literature and inform the development of future research with respect to study design, measurement methods, and analytic approach. In this model, HIV transmission is driven by risk behaviors of migrants that emerges and is enabled by mobility, the bridging of sub-epidemics across space and time, and the displacement effects on the primary residential sending community for migrants. To investigate these causal pathways, empirical study designs must measure the relative timing of migratory events, sexual risk behaviors, and incident HIV infections. Network-based mathematical models using empirical data on partnerships help gain insight into the dynamic disease transmission systems. Although the network-dyadic conceptual model and related network methods may not address all questions related to migration and HIV, they provide a unified approach for future research on this important topic.

The physiology of sexual violence, genito-anal injury and HIV: opportunities for improving risk estimation

Increased understanding about the relative contribution of genito-anal injury to HIV transmission may improve epidemic model estimates of the distribution of risk among and across different subpopulations. Better understanding about the distribution of HIV among subpopulations that are at highest risk of sexual violence can also improve the design and prioritization of combination prevention interventions that are most likely to reduce the risk of sexual violence and its potential contribution to HIV transmission. The effective incorporation of physiological and social variables into epidemic modelling will likely require new research approaches that can help communicate the level of risk associated with different types of 'heterosexual' transmission. Reference models that reflect the potential impact of sexual violence and genital injury can help direct attention toward key variables and uncertainties. For further research that clarifies these relationships will require multidisciplinary collaboration among groups with expertise in epidemiology, social science, public health, and clinical and basic science.

A literature review of reporting standards of HIV progression models

OBJECTIVE

We conducted a systematic review of HIV progression models to identify the mathematical structures used, the main research questions and key model aspects in terms of quality and robustness.

METHODS

We searched for articles published before February 2009 that described models of HIV progression in humans. We included two strategies of search with and without MeSH terms. We classified the models by their mathematical structure and research question. We created a checklist of desirable features of the models, reviewed and classified the articles to inform our conclusions.

RESULTS

Among 3491 articles found, 93 met the inclusion criteria. Among the selected articles, 60 used transition models, 25 applied differential equations, and eight had other structures. We did not find a relation between the type of question explored and the modeling method used. None of the studies complied with the complete set of items in the checklist, but 6.5% cover at least 90% of them.

CONCLUSION

There is an enormous heterogeneity of HIV modeling exercises in terms of methods used and topics addressed, as well as in the presentation of key aspects of the articles in terms of quality and robustness.