We found that half of urban poor HIV-infected individuals in a particularly well-resourced North American setting were food insecure, and that food insecurity independently increases the risk of incomplete viral suppression. The prevalence of food insecurity in this study is consistent with Normén’s estimate that 48% of individuals on antiretrovirals in a drug-treatment program in Vancouver are food insecure.8
The consistency in two well-resourced settings with well-established public health delivery systems suggests that food insecurity may be a significant problem in other North American settings as well. We also found that severe food insecurity was associated with nearly 80% lower odds of viral suppression when controlling for other covariates. This suggests that ensuring consistent access to food may be an important and neglected intervention to improve antiretroviral treatment effectiveness. These findings support recommendations by the World Health Organization, UNAIDS, the World Food Program, and other international organizations that interventions addressing food insecurity should be integrated with HIV/AIDS programming activities where possible.11–13
While there is a growing international concern that food insecurity may compromise treatment effectiveness in emerging antiretroviral treatment programs in developing countries, our findings suggest that food insecurity may compromise treatment efficacy even in well-resourced settings. The finding that food insecurity is independently associated with viral suppression adds to the body of literature suggesting that non-medical services, such as access to food, adequate housing49
and case management,50
impact upon HIV clinical outcomes and should be considered as part of comprehensive HIV care packages.
Adherence modified the association between food insecurity and HIV RNA suppression; for individuals who were less adherent, severe food insecurity was associated with an 85% reduction in the odds of viral suppression. For individuals with >80% adherence, there was still a 66% reduction in the odds of viral suppression for individuals who were severely food insecure, but this association was no longer significant. Given the small sample, we can not exclude an association for more adherent individuals. These findings, however, suggest that food security interventions may exert the largest impacts in terms of treatment efficacy on food insecure individuals with low levels of adherence.
Food insecurity was associated with non-adherence in a non-linear fashion. People with severe food insecurity were more likely to have 20–80% adherence than those who were not severely food insecure. The finding that food insecurity is associated with lower levels of adherence is especially important given that these lower ranges of adherence (<80%) are more likely to be associated with incomplete viral suppression with currently used regimens.39,40
Our data suggest that the association between food insecurity and viral suppression is not explained by difference in average monthly adherence. Unannounced pill count adherence is one of the best available adherence measurement strategies, yet it does not pick up patterns of adherence including treatment interruptions, which are associated with viral rebound within defined strata of average adherence.51
Food insecurity may also impact viral suppression through biologic mechanisms. While not explicitly examined in this study, once such mechanism is that food may impact the pharmacokinetics of antiretroviral medications. The association between food insecurity and viral suppression was strong for individuals using PI-based regimens. Several protease inhibitors such as nelfinavir and ritonavir require food for maximal absorption, and the absence of food may negatively affect the pharmacokinetics of these drugs.31,32,52
Given that only a minority of participants in this study were receiving NNRTIs, larger studies with more patients on NNRTIs will help determine whether regimen type modifies the association between food insecurity and HIV RNA suppression. Nutritional status is another putative mechanism for how food insecurity may be associated with incomplete viral suppression and poor clinical outcomes. Malnutrition is a potential consequence of food insecurity,53
and studies have shown that low body mass index (BMI) and weight loss are associated with both higher HIV RNA levels and mortality for individuals on HAART.26,54,55
As we did not assess BMI or other nutritional parameters in this population, we cannot infer the extent to which poor nutritional status or HIV wasting may have contributed to the association between food insecurity and viral suppression.
There were several important limitations to this study. The cross-sectional design does not demonstrate causality. One possible interpretation of our findings is that individuals who were sicker as a result of poor virologic response subsequently had difficulties procuring food. Yet, we found that the impact of food insecurity on VL suppression was similar among people with higher CD4 counts making this possibility less likely. We could not determine the role of malnutrition on mediating relationships between food insecurity and VL suppression. In addition, socioeconomic status is a complex and multidimensional construct and may not be completely represented by income, education, employment and housing status. Finally, because of the small sample, cross-sectional design and the fact that we measured average adherence rather than patterns of adherence, including treatment interruptions, we were unable to determine whether adherence was on the causal pathway between food insecurity and viral load suppression. Longitudinal or intervention studies using larger sample sizes with detailed measures of patterns of adherence are, therefore, needed to better understand the relationships between food insecurity, antiretroviral adherence and HIV RNA suppression.
In summary, food insecurity was associated with incomplete viral suppression in the urban poor of San Francisco, one of the best-resourced settings for HIV-positive individuals in the world. The impact of food insecurity on viral suppression may be due to the combined effect of behavioral (adherence) and biologic (pharmacokinetics) mechanisms that lead to suboptimal drug levels required for viral suppression. These findings suggest that addressing fundamental human needs, such as access to food, should be an integral component of HIV programs serving impoverished populations in the United States.