Our results show that the age at HIV diagnosis and the duration since HIV diagnosis are associated with differences in the pace of biological aging. HIV diagnosis at older age showed a marked reduction in the pace of biological aging, and conversely, those living with HIV for a longer duration since HIV diagnosis displayed increased pace of biological aging. Additionally, we found that the average daily intake of fruits and vegetables was associated with decrease in the pace of biological aging and modified the relationship between HIV-related variables, PhenoAge EAA, and DunedinPACE. Taken together, these results suggest that HIV-related variables may differentially affect the rate of epigenetic or biological aging in OPLHIV in Eswatini, and lifestyle behaviors may have a protective effect on these trajectories in aging.
Prior to DNAm-based measures of biological aging, several studies have reported increased incidence of age-related phenotypes and biological processes associated with aging in PLHIV, which occurred at a significantly younger age compared to non-infected counterparts (17, 53, 54). This has been further established with the recent improvement in epigenetic clocks, with results showing that epigenetic age is accelerated in PLHIV compared to HIV-uninfected individuals, although most of these studies were conducted in higher-income countries (38, 55). In our study, we also found epigenetic age is accelerated in OPLHIV in Eswatini, which is consistent with previous evidence on biological aging in PLHIV (38, 55). Additionally, our results showed that those who were diagnosed with HIV at an older age—and potentially living with HIV for a shorter duration prior to enrollment in this study—exhibited decreases in the pace of biological aging. HIV infection has extensive effects on immune cellular activity and function, including, most notably, CD4+ cell depletion (56), and such changes in immune cell activity are characteristic of biological aging (57). Even with early ART administration, immune cell functions are incompletely restored, and chronic adverse immune-related phenotypes persist (58, 59). Low-grade, chronic inflammation is a significant feature of biological aging, termed by some as ‘inflammaging’, and it can have detrimental effects on physiology and cellular functions, and has been linked to age-related disease pathogenesis (60, 61). Likewise, diagnosis of HIV at an older age may have occurred at a time when there was widespread access to ART in Eswatini enabling rapid initiation of such treatment, compared to those that were diagnosed at a younger age and potentially had lived longer with untreated HIV during years with limited access to ART in the country (62). Notably, biological aging was accelerated in PLHIV that have untreated HIV infection (63) and initiation of ART may decelerate biological aging (64). Taken together, it is possible that the longer duration of living with untreated HIV may elicit long-term effects on biological aging trajectories through inducing chronic proinflammatory phenotypes, while timely initiation of ART may benefit aging trajectories by attenuating the effects of untreated HIV.
Despite the use of ART, the risk of developing comorbidities in OPLHIV remains relatively high, which is likely due to one or more factors (e.g., effects of HIV, ART, lifestyle behaviors, etc.) that influence the aging process. To address this, several interventions have been implemented to reduce HIV-associated comorbidities. For example, the PRECluDE Consortium, funded by the National Institute of Health, has modeled several interventions and clinical trials for PLHIV for CVD prevention (40) and the REPRIEVE phase 3 trial has shown marked reductions in CVD risk using pitavastatin calcium in PLHIV (65), although these efforts have yet these have yet to be implemented in sub-Saharan Africa. Mounting evidence suggests that health-promoting behaviors are linked to slower aging (66, 67). Thus, developing practical strategies to mitigate comorbidities in OPLHIV will be valuable in lower-income countries where resources are constrained. Indeed, practical interventions have been developed for prevention and management of chronic diseases in OPLHIV, including physical activity and nutritional interventions (68, 69). While we found no association nor modification by physical activity and quality of life (SF-36) with biological aging, we did observe that dietary intake of fruits and vegetables was associated with the pace of biological aging and may have a modifying role in the association between HIV-related factors and biological aging trajectories. The lack of effect of physical activity may be due to the fact that most participants accumulated their physical activity from work-related activities, whereas previous evidence suggested that leisure/recreational may have beneficial effects on biological aging and overall health as opposed to the opposite effect with work-related activity (70, 71).
In our study, we found that dietary intake of fruits and vegetables modified the relationships between age at HIV diagnosis, years living with HIV since diagnosis, and CD4+ cell count. To our knowledge, there is no data on the association of dietary interventions and biological aging trajectories in PLHIV. However, previous evidence in HIV-uninfected individuals suggests that dietary interventions can have beneficial effects on biological aging, decelerating, and potentially reversing, biological aging, including interventions focused on higher quality foods and specific types of diets (e.g., Mediterranean Diet, DASH Diet, etc.) (72–76). For associations between age at HIV diagnosis and years since HIV diagnosis, we found contradictory results when including dietary intake in our models, although both reduced the relative change in biological aging. This may suggest that the higher intake of fruits and vegetables can have a beneficial effect on aging in PLHIV, particularly those with longer time since HIV diagnosis, by counteracting the adverse long-term effects of HIV and subsequent toxicity caused by long-term adherence to ARTs on the epigenome with the beneficial effects of healthy dietary behaviors (77–80). Conversely, when someone becomes HIV infected later in life, dietary patterns may be less effective in affecting aging trajectories, which may be due to elderly individuals having different nutritional needs, metabolic changes, and physiological changes that effect digestion (81). The significant negative association between CD4+ cell counts and lower PhenoAge EAA when adjusting for dietary patterns, which was not observed in any other model, suggests a protective role for diet on immune function, which could precede aging and age-related disease risk. Evidence suggests nutrient quality both predicts CD4+ cell counts and is associated with a lower risk of mortality in PLHIV (82), and diet quality is associated with lower CD4+ cell count (83). This suggests that diet may not only improve immune cell function, but that this rebound of CD4 + cell count may be reflected in improved biological aging trajectories. Altogether, our findings suggest a beneficial role for diet on the relationship between HIV-related variables and biological aging trajectories and supports the utilization of practical dietary interventions that would be beneficial for modifying aging trajectories and NCD risk for PLHIV in resource-constrained regions of the world.
While this study is, to our knowledge, the first to investigate biological aging in OPLHIV in Eswatini, it has several limitations. First, this is an exploratory study and thus the findings are constrained by the limited sample of participants (45). As our study used a cross-sectional design, we could not ascertain whether biological aging trajectories changed over time, especially from early stages of infection (untreated) to ART initiation and viral load suppression. Likewise, these data were limited to the HIV-related factors included in the study. For example, time since HIV diagnosis is not reflective of time since HIV infection. Accumulating evidence suggests that HIV-related factors prior to ART initiation may be important to biological aging trajectories and long-term health outcomes (63, 84). Future research should examine changes in biological aging trajectories longitudinally, prior to ART initiation. Finally, our study was performed exclusively in OPLHIV in Eswatini, thus, the findings may not be generalizable to other populations or regions in sub-Saharan Africa. Although our study had these limitations, this exploratory study showed compelling evidence that may underlie aging trajectories in OPLHIV in a lower-income country which may provide a foundation for future studies to further explore the molecular mechanisms of aging in PLHIV in sub-Saharan Africa and other resource limited settings.