Our study shows that one-third of the aging Ugandan HIV population had kidney function impairment that was significantly higher than the prevalence in community-matched HIV-uninfected controls. Data documenting the burden of kidney function impairment in aging HIV populations come mostly from high-income countries [8, 19, 29]. Overall, we found a high prevalence of kidney function impairment among people aged ≥ 60 years living with and without HIV in Uganda. Our data agree with studies that have shown that PLWH experience a high burden of kidney disease [19, 29, 30]. HIV infection significantly increases the odds of kidney function impairment [8, 9, 31, 32] and various forms of HIV-associated nephropathy have been documented in previous research[9, 33]. However, our study demonstrated an excess burden of kidney function impairment among older PLWH compared to previous prevalences reported in the general population of PLWH in Uganda[34, 35] and other LICs[18, 30, 36, 37]. These findings imply that there is a need for research and clinical care programs to evolve and prioritize kidney disease detection in the population of older PLWH.
The prevalence of proteinuria in our study was at least two times higher in PLWH than in people without HIV. Other studies such as the AGEhIV cohort study [38] have shown that the burden of albuminuria is higher among people living with HIV than in people without HIV. However, our study reported higher estimates of proteinuria than what has been reported in non-African settings [38, 39]. Previous studies have pointed to genetic risks for kidney injury such as the presence of the APOL1 gene which is unique to African populations and may account for racial disparities in the burden of CKD [40–43]. Proteinuria is a biomarker for kidney injury[28]; thus further research into context-specific risk factors for kidney disease is needed to understand the cause of kidney injury in older PLWH.
Kidney disease is progressive; thus these findings of the excess prevalence of kidney function impairment and proteinuria may have implications for the health and survival of old PLWH in a country where there is limited access to life-saving therapies such as dialysis and renal transplants for kidney failure [15, 16].
Increasing age and female sex were significantly associated with kidney function impairment in both PLWH and people without HIV. These findings are consistent with previous studies from Uganda and Africa where increasing age and female sex were associated with kidney disease in both PLWH and people without HIV [18, 31, 44, 45].
Among older PLWH, a prior diagnosis of hypertension significantly increased the odds of kidney function impairment. Hypertension is a known traditional risk factor for CKD [46] and hypertensive nephrosclerosis is a well-recognized pathological process that eventually leads to kidney failure [47]. A high prevalence of hypertension has been reported among aging PLWH [2, 48] and the association of such traditional risk factors with CKD is documented in previous studies [46, 49]. The implementation of blood pressure control programs in older PLWH and hypertension can benefit kidney health as the same approach has been shown to improve outcomes in other populations at risk of hypertension-related kidney injury such as people with cardiovascular diseases and diabetes mellitus[50].
In our study, HIV was the strongest significantly associated factor with kidney function impairment. Unlike other studies, we did not find an association between diabetes mellitus[29, 51] and kidney function impairment, smoking [9, 52, 53], body mass index (BMI), socioeconomic status (monthly household income) [44, 54] or prior diagnosis of tuberculosis [55] [56] as other studies did. Unlike these previous studies, in our study, fewer participants reported a history of smoking, and there were fewer diabetic patients. The monthly household income was not different between PLWH and people without HIV or between people with and without kidney function impairment. Likewise, the BMI was not different between people with and without kidney function impairment and all the people who had a previous diagnosis of tuberculosis were among PLWH.
Among the PLWH in our study, only a small proportion, 2.2%, had CD4 less than 200 cells per ml and only 5.8% had detectable viral loads (> 50copies/ml). Almost all (95.7%) of our PLWH had ever used TDF. These proportions may explain the lack of association between these variables and kidney function impairment in our study although previous studies have shown a significant association[8, 18, 57, 58]. In our study, we observed higher prevalence of kidney function impairment in participants on abacavir-based regimens; most of the participants on abacavir-based regimens had previously been on TDF, but were switched over due to low eGFR.
Previous studies on kidney function impairment among old people with HIV in Uganda and sub-Saharan Africa have not included uninfected controls. A strength of our study was a comparator group of older people without HIV from similar communities which allowed us to compare the characteristics between the two populations as well as the outcome and ascertain the excess prevalence of kidney function impairment attributable to HIV. A limitation of our study was that it was cross-sectional so we were unable to observe changes in kidney function over three months. In addition, we did not perform ultrasound scanning so we could not differentiate between acute and chronic kidney function impairment. We also used dipsticks to detect proteinuria which is a less specific method than the urine albumin to creatinine ratio (UACR).