UC Berkeley

The widespread availability of antiretroviral therapy (ART) for HIV infection in Sub-Saharan Africa (SSA) has resulted in decreased morbidity, mortality, and transmission of HIV. This region, however, still represents the majority of the global burden of HIV. Furthermore, levels of retention in care and medication adherence, critical determinants of ART effectiveness, are currently suboptimal, and, thus, continue to be the target of many interventions. This dissertation is comprised of three chapters related to understanding ART adherence and interventions to improve it.

Chapter 1 quantitatively describes and examines the distribution of poor adherence to antiretroviral therapy in a study of HIV-positive patients in Zambia. In a novel application of the Lorenz curve, a tool used commonly in economics, this analysis characterized the concentration of medication non-possession in a network of clinics in order to identify “hotspots” and predictors of poor adherence. Results extend previous studies by revealing that even though average adherence is high, lapses in adherence are common and concentrated among a minority of patients, and also in certain clinics. This concentration and variability varies with time on ART. Furthermore, a small fraction of patients accounts for the majority of days of medication non-possession, with the size of this group increasing with time on ART. This suggests that targeted interventions may represent a preferable overall strategy as compared to those targeting all patients to improve adherence. Furthermore, there was high variability across clinics suggesting that interventions targeting clinic “hotspots” may also represent an efficient use of resources to improve ART adherence.

Chapter 2 presents the results of the first qualitative study to examine conditional incentives for ART adherence and their potential pathways of action among people living with HIV. This study was conducted within a study of conditional food and cash transfers to increase retention in care and adherence to ART among HIV-positive food insecure recent adults in Shinyanga, Tanzania. Although financial and in-kind incentives have been shown to improve outcomes along the HIV care cascade, results are mixed, and there is little evidence about the pathways through which incentives work. Results of this qualitative study and analysis revealed that incentives acted through three primary pathways to potentially increase retention in care and adherence to ART: 1) addressing competing needs and offsetting opportunity costs associated with clinic attendance, 2) increasing motivation and 3) alleviating stress associated with attending clinic, worry about providing for oneself and one’s family, and providing hope for a better future. The first pathway was the strongest, which was consistent with field observations and discussions with local clinic staff, research staff, and Ministry of Health officials. Participants did not report any harmful events associated with the incentives, and reported a variety of beneficial spillover effects on household welfare. Understanding these pathways can help improve design and targeting of future food or cash incentive interventions.

Chapter 3 focused on intrinsic motivation within the aforementioned study of food and cash transfers for ART adherence in Tanzania. Some critical of incentives argue that incentives can ‘crowd out’ intrinsic motivation, making the individual less likely to engage in the desired behavior after the incentive is removed, potentially leading to limited durability of effect and causing harm in the long term. This hypothesis was examined among recent antiretroviral treatment initiates in Tanzania by comparing participants’ level of intrinsic motivation before receiving transfers to the level once the transfer period ended. The analysis revealed that, not only did intrinsic motivation not decrease after the transfer period ended, but that the level of intrinsic motivation increased overall and within study arms. Furthermore, the change in motivation did not differ by study arms. As the first study to empirically examine the crowding out hypothesis regarding incentives in a real-world, resource-limited setting, these results suggest that incentive interventions in such settings should not be impeded by concerns of crowding out intrinsic motivation.

Together these chapters contribute to improving our understanding of antiretroviral adherence and intervention response. The Lorenz curve and medication possession analysis provides a more comprehensive and detailed measurement and illustration of adherence and its variability across individuals and clinics in Zambia. Such information is critical to targeting and designing future interventions. Next, by examining an ongoing intervention to improve adherence in Tanzania, we were able to elucidate and examine the potential pathways of action of food and cash transfers. Furthermore, we found no evidence that these incentives decreased intrinsic motivation. Knowledge gleaned from this deep exploration of the incentives’ mechanism of action in a real-world setting not only informs refinement of the intervention, but also helps to fill the gap in understanding how and when these interventions may work.