The role of cognitive reserve in mediating cognitive impairment in cART-treated HIV positive older adults in Mbeya, Tanzania

AbstractIntroduction: HIV-associated neurocognitive disorders (HAND) are a spectrum of cognitive impairments occurring in chronic HIV infection. HAND are highly prevalent in sub-Saharan Africa (SSA), despite combination antiretroviral therapy (cART). Older people appear to be at increased risk. Cognitive reserve (CR), shown to be protective in neurodegenerative dementias, may also protect against HAND.Aim: To evaluate the association of CR and risk of HAND in an older cART-treated population in SSA.Methods: This was a cross-sectional observational study undertaken at hospital outpatient clinics in Mbeya, Southwest Tanzania. HIV-positive participants aged ≥ 50 years and established on cART underwent diagnostic assessment by operationalised AAN criteria. Assessment included neuropsychological test battery, functional assessment, informant history and depression screen. HIV-negative control participants were attendees of other chronic disease clinics who completed neuropsychological assessments to provide normative scores for HAND diagnosis. CR was measured using the Cognitive Reserve Index (CRI) and other proxy measures including years of formal education.Results: Lower total Cognitive Reserve Index (CRI) score, lack of formal education, unemployment and low-skilled manual work were associated with increased risk of HAND. Lower CRI score and lack of formal education were independent risk factors for HAND but HIV disease severity measures were not.Conclusion: Higher total CRI score and formal education appeared to be protective for HAND, in this cohort. These are potentially modifiable factors, though education may be difficult to modify in later life. Cognitive reserve may be more important than HIV-disease control in risk of HAND in older people with treated HIV.