Cognitive Intra-individual Variability in HIV: an Integrative Review

Within-Person Test Score Distributions: How Typical Is "Normal"?

We evaluated within-person variability across a cognitive test battery by analyzing the shape of the distribution of each individual's scores within a battery of tests. We hypothesized that most healthy adults would produce test scores that are normally distributed around their own personal battery-wide, within-person (wp) mean. Using cross-sectional data from 327 neurologically healthy adults, we computed each person's mean, standard deviation, skew, and kurtosis for 30 neuropsychological measures. Raw scores were converted to T-scores using three degrees of calibration: (a) none, (b) age, and (c) age, sex, race, education, and estimated premorbid IQ. Regardless of calibration, no participant showed abnormal within-person skew (wpskew) and only 10 (3.1%) to 16 (4.9%) showed wpkurtosis greater than 2. If replicated in other samples and measures, these findings could illuminate how healthy individuals are endowed with different cognitive abilities and provide the foundation for a new method of inference in clinical neuropsychology.

Self-perceived cognitive fluctuations and their relationship to everyday functioning in older adults with and without HIV disease

Objective: HIV is associated with elevated performance-based cognitive intra-individual variability (IIV) in the laboratory that can reflect difficulty regulating cognitive resources over time (i.e., cognitive fluctuations) and disrupt everyday functioning. Whether persons living with HIV (PLWH) experience appreciable cognitive fluctuations in their daily lives is unclear. This study examined the presence of cognitive fluctuations and their relationship to everyday functioning in PLWH. Methods: Participants were 145 PLWH and 61 seronegative individuals age ≥ 50 years who completed a self-report version of the Mayo Fluctuations Scale (MFS), structured psychiatric interview, medical evaluation, and well-validated measures of mood, cognitive symptoms, and activities of daily living (ADLs). A confirmatory factor analysis of the MFS yielded three factors, including a 7-item cognitive fluctuations scale. Results: Univariable analyses showed that HIV was associated with moderately higher MFS Cognitive Fluctuation subscale scores (d = 0.46), but this effect was no longer significant a multiple regression model that included medical comorbidities and affective disorders, which emerged as unique predictors. Of clinical relevance, higher MFS Cognitive Fluctuation subscale scores were independently associated with more frequent cognitive symptoms and dependence in ADLs in the full sample. Conclusions: Higher frequency of self-perceived cognitive fluctuations disrupts management of ADLs among middle-aged and older adults independent of HIV status and general cognitive symptoms. Future studies are needed to understand the full clinical significance of self-perceived cognitive fluctuations among PLWH and their impact on daily life.

A Systematic Review and Meta-Analysis of Social Cognition Among People Living with HIV: Implications for Non-Social Cognition and Social Everyday Functioning

Social cognition-the complex mental ability to perceive social stimuli and negotiate the social environment-has emerged as an important cognitive ability needed for social functioning, everyday functioning, and quality of life. Deficits in social cognition have been well documented in those with severe mental illness including schizophrenia and depression, those along the autism spectrum, and those with other brain disorders where such deficits profoundly impact everyday life. Moreover, subtle deficits in social cognition have been observed in other clinical populations, especially those that may have compromised non-social cognition (i.e., fluid intelligence such as memory). Among people living with HIV (PLHIV), 44% experience cognitive impairment; likewise, social cognitive deficits in theory of mind, prosody, empathy, and emotional face recognition/perception are gradually being recognized. This systematic review and meta-analysis aim to summarize the current knowledge of social cognitive ability among PLHIV, identified by 14 studies focused on social cognition among PLHIV, and provides an objective consensus of the findings. In general, the literature suggests that PLHIV may be at-risk of developing subtle social cognitive deficits that may impact their everyday social functioning and quality of life. The causes of such social cognitive deficits remain unclear, but perhaps develop due to (1) HIV-related sequelae that are damaging the same neurological systems in which social cognition and non-social cognition are processed; (2) stress related to coping with HIV disease itself that overwhelms one's social cognitive resources; or (3) may have been present pre-morbidly, possibly contributing to an HIV infection. From this, a theoretical framework is proposed highlighting the relationships between social cognition, non-social cognition, and social everyday functioning.

Microglial- neuronal crosstalk in chronic viral infection through mTOR, SPP1/OPN and inflammasome pathway signaling

HIV-infection of microglia and macrophages (MMs) induces neuronal injury and chronic release of inflammatory stimuli through direct and indirect molecular pathways. A large percentage of people with HIV-associated neurologic and psychiatric co-morbidities have high levels of circulating inflammatory molecules. Microglia, given their susceptibility to HIV infection and long-lived nature, are reservoirs for persistent infection. MMs and neurons possess the molecular machinery to detect pathogen nucleic acids and proteins to activate innate immune signals. Full activation of inflammasome assembly and expression of IL-1β requires a priming event and a second signal. Many studies have demonstrated that HIV infection alone can activate inflammasome activity. Interestingly, secreted phosphoprotein-1 (SPP1/OPN) expression is highly upregulated in the CNS of people infected with HIV and neurologic dysfunction. Interestingly, all evidence thus far suggests a protective function of SPP1 signaling through mammalian target of rapamycin (mTORC1/2) pathway function to counter HIV-neuronal injury. Moreover, HIV-infected mice knocked down for SPP1 show by neuroimaging, increased neuroinflammation compared to controls. This suggests that SPP1 uses unique regulatory mechanisms to control the level of inflammatory signaling. In this mini review, we discuss the known and yet-to-be discovered biological links between SPP1-mediated stimulation of mTOR and inflammasome activity. Additional new mechanistic insights from studies in relevant experimental models will provide a greater understanding of crosstalk between microglia and neurons in the regulation of CNS homeostasis.

Differential sensitivity of intraindividual variability dispersion and global cognition in the prediction of functional outcomes and mortality in precariously housed and homeless adults

OBJECTIVE

To examine cognitive intraindividual variability (IIV) dispersion as a predictor of everyday functioning and mortality in persons who are homeless or precariously housed.

METHOD

Participants were 407 community-dwelling adults, followed for up to 13 years. Neurocognition was assessed at baseline and IIV dispersion was derived using a battery of standardized tests. Functional outcomes (social, physical) were obtained at baseline and last follow-up. Mortality was confirmed with Coroner's reports and hospital records (N  = 103 deaths). Linear regressions were used to predict current social and physical functioning from IIV dispersion. Repeated measures Analysis of Covariance were used to predict long-term change in functioning. Cox regression models examined the relation between IIV dispersion and mortality. Covariates included global cognition (i.e. mean-level performance), age, education, and physical comorbidities.

RESULTS

Higher IIV dispersion predicted poorer current physical functioning (B = -0.46 p = .010), while higher global cognition predicted better current (B  = 0.21, p = .015) and change in social functioning over a period of up to 13 years (F  = 4.23, p = .040). Global cognition, but not IIV dispersion, predicted mortality in individuals under 55 years old (HR = 0.50, p = .013).

CONCLUSIONS

Our findings suggest that indices of neurocognitive functioning (i.e. IIV dispersion and global cognition) may be differentially related to discrete dimensions of functional outcomes in an at-risk population. IIV dispersion may be a complimentary marker of emergent physical health dysfunction in precariously housed adults and may be best used in conjunction with traditional neuropsychological indices.

Recent advances in HIV-associated neurocognitive disorders: a focus on older adults and sub-Saharan Africa

PURPOSE OF REVIEW

We reviewed recent literature on prevalence and interventional approaches for cognitive impairment in the context of HIV infection alongside current controversies and challenges around its nomenclature, screening, and diagnosis.

RECENT FINDINGS

Prevalence estimates for HIV-associated neurocognitive disorder (HAND) indicate that HAND remains highly prevalent despite combination antiretroviral treatment (cART) widely used. The available data are heterogeneous, particularly in sub-Saharan Africa (SSA) where recent reviews indicate substantial heterogeneity, wide prevalence estimates and lack of data from the majority SSA countries, despite them currently experiencing the greatest burden worldwide of both HIV and HAND.Several alternative approaches to diagnosis and classification of cognitive impairment in HIV have been published, taking into account changing clinical phenotypes.

SUMMARY

Cognitive impairment remains a significant challenge in the care of people living with HIV despite advances in treatment. Ongoing controversies exist around nomenclature and classification, screening measures, and the phenotype and aetiology of observed impairments. Two current areas of research priority and focus include understanding current phenotypes of individuals living and ageing with treated HIV and differing levels of risk for HAND in these phenotypes, alongside the effects of commonly occurring comorbidities.The current evidence base for interventional approaches is limited, but growing. The most promising avenues appear to be multidisciplinary. These are currently focussed on high income settings rather than SSA where the majority of people living with HIV, and affected by cognitive impairment in the context of HIV, currently reside.

Cognitive Intra-individual Variability in the Laboratory Is Associated With Greater Executive Dysfunction in the Daily Lives of Older Adults With HIV

BACKGROUND

Executive dysfunction, which is common among persons with HIV (PWH), can have an adverse impact on health behaviors and quality of life. Intra-individual variability (IIV) is a measure of within-person variability across cognitive tests that is higher in PWH and is thought to reflect cognitive dyscontrol.

OBJECTIVE

To assess whether cognitive IIV in the laboratory is associated with self-reported executive dysfunction in daily life among older PWH.

METHOD

Participants included 71 PWH aged ≥50 years who completed six subtests from the Cogstate battery and two subscales from the Frontal Systems Behavior Scale (FrSBe; self-report version). Cognitive IIV was calculated from the Cogstate as the coefficient of variation derived from age-adjusted normative T scores.

RESULTS

Cognitive IIV as measured by the Cogstate showed a significant, positive, medium-sized association with current FrSBe ratings of executive dysfunction but not disinhibition.

CONCLUSION

Higher cognitive IIV in the laboratory as measured by the Cogstate may be related to the expression of HIV-associated symptoms of executive dysfunction in daily life for older PWH.

A 2-year longitudinal randomized controlled trial examining the transfer of speed of processing training to secondary cognitive domains in middle-aged and older adults with HIV-associated neurocognitive disorder: Results of the think fast study

OBJECTIVE

As people with HIV (PWH) age, they are at-risk of developing cognitive impairments compared to their seronegative counterparts. Although speed of processing (SOP) training may help improve this cognitive ability, less work has examined transfer to other cognitive domains. This study examined the effect of SOP training has on secondary cognitive domains in PWH aged 40+ years.

METHOD

In this 3-group 2-year longitudinal study, 216 PWH with HIV-associated neurocognitive disorder (HAND) or borderline HAND were randomized to either: (1) 10 h of SOP training (n = 70); (2) 20 h of SOP training (n = 73); or (3) 10 h of an active control training (n = 73). Participants completed a comprehensive cognitive battery at baseline, immediately after training, and at 1 and 2 years. This battery yielded global and domain specific T-scores as well as a cognitive impairment variable. Generalized linear mixed-effect models were fitted to estimate between-group mean differences at the follow-up time-points adjusted for baseline.

RESULTS

No clinically or statistically significant improvements in any of the cognitive outcomes were observed. A sensitivity analysis was conducted; conclusions replicated those of the main analysis, with two exceptions: Global Function T and Psychomotor Speed T showed relevant training improvements among the intervention groups over the control group at the immediate post time point.

CONCLUSIONS

Although SOP training has been shown to improve cognitive abilities that correspond to driving and mobility, such training has limited therapeutic utility in improving cognition in other domains in PWH with HAND.

Cognitive intraindividual variability, cognitive impairment and psychosocial functioning in first-episode psychosis patients

Cognitive intraindividual variability (IIV) refers to fluctuations in performance across tasks (i.e. dispersion) or in a single task on multiple occasions (i.e. inconsistency). Little is known about IIV in patients with first-episode psychosis (FEP). We aimed to explore the association between IIV and both global cognitive performance and psychosocial functioning in a sample of 103 FEP patients. Patients were recruited at discharge from the PEPsNa program, a FEP follow-up intervention program lasting 24 months. The Social and Occupational Functioning Scale (SOFAS) and the Cognitive Assessment Interview (CAI-Sp) were employed for assessing psychosocial functioning. Cognitive assessments were performed using the MATRICS Cognitive Assessment Battery (MCCB), and the variability in the cognitive functions assessed with the MCCB was used to calculate the IIV. Significant correlations were obtained between IIV and global MCCB scores, the CAI-Sp and the SOFAS. We found significant differences in psychosocial functioning and cognitive performance between patients with high and low IIV. A higher IIV in FEP patients was related both to worse psychosocial functioning and worse global cognitive performance. Unlike global cognitive performance, IIV was not related to clinical characteristics, suggesting that it could be an indicator of cognitive impairment even in the absence of global impairment.

Predictors of within-individual variability in cognitive performance in schizophrenia in a South African case-control study

INTRODUCTION

Cognitive dysfunction in schizophrenia may be assessed by measuring within-individual variability (WIV) in performance across a range of cognitive tests. Previous studies have found increased WIV in people with schizophrenia, but no studies have been conducted in low- to middle-income countries where the different sociocultural context may affect WIV. We sought to address this gap by exploring the relationship between WIV and a range of clinical and demographic variables in a large study of people with schizophrenia and matched controls in South Africa.

METHODS

544 people with schizophrenia and 861 matched controls completed an adapted version of The University of Pennsylvania Computerized Neurocognitive Battery (PennCNB). Demographic and clinical information was collected using the Structured Clinical Interview for DSM-IV Diagnoses. Across-task WIV for performance speed and accuracy on the PennCNB was calculated. Multivariate linear regression was used to assess the relationship between WIV and a diagnosis of schizophrenia in the whole sample, and WIV and selected demographic and clinical variables in people with schizophrenia.

RESULTS

Increased WIV of performance speed across cognitive tests was significantly associated with a diagnosis of schizophrenia. In people with schizophrenia, increased speed WIV was associated with older age, a lower level of education and a lower score on the Global Assessment of Functioning scale. Increased accuracy WIV was significantly associated with a younger age in people with schizophrenia.

CONCLUSIONS

Measurements of WIV of performance speed can add to the knowledge gained from studies of cognitive dysfunction in schizophrenia in resource-limited settings.

Cognitive dispersion is elevated in amyloid-positive older adults and associated with regional hypoperfusion

OBJECTIVE

Cognitive dispersion across neuropsychological measures within a single testing session is a promising marker predictive of cognitive decline and development of Alzheimer's disease (AD). However, little is known regarding brain changes underlying cognitive dispersion, and the association of cognitive dispersion with in vivo AD biomarkers and regional cerebral blood flow (CBF) has received limited study. We therefore examined associations among cognitive dispersion, amyloid-beta (Aβ) positivity, and regional CBF among older adults free of dementia.

METHOD

One hundred and forty-eight Alzheimer's Disease Neuroimaging Initiative (ADNI) participants underwent neuropsychological testing and neuroimaging. Pulsed arterial spin labeling (ASL) magnetic resonance imaging (MRI) was acquired to quantify CBF. Florbetapir positron emission tomography (PET) imaging determined Aβ positivity.

RESULTS

Adjusting for age, gender, education, and mean cognitive performance, older adults who were Aβ+ showed higher cognitive dispersion relative to those who were Aβ-. Across the entire sample, higher cognitive dispersion was associated with reduced CBF in inferior parietal and temporal regions. Secondary analyses stratified by Aβ status demonstrated that higher cognitive dispersion was associated with reduced CBF among Aβ+ individuals but not among those who were Aβ-.

CONCLUSIONS

Cognitive dispersion may be sensitive to early Aβ accumulation and cerebrovascular changes adjusting for demographics and mean neuropsychological performance. Associations between cognitive dispersion and CBF were observed among Aβ+ individuals, suggesting that cognitive dispersion may be a marker of brain changes among individuals on the AD continuum. Future studies should examine whether cognitive dispersion predicts brain changes in diverse samples and among those with greater vascular risk burden.