Sex differences in plasma p-tau181 associations with Alzheimer's disease biomarkers, cognitive decline, and clinical progression

Studies have shown that women on the Alzheimer's disease (AD) continuum have more pathological tau in the brain and cerebrospinal fluid (CSF), than men. Some studies have found that higher levels of tau biomarkers are more strongly associated with clinical AD, cognitive decline and neurodegeneration in women than in men. Despite major developments in the use of plasma tau phosphorylated at threonine 181 (p-tau181) as an AD biomarker, it is unknown whether these sex differences apply to plasma p-tau181. In 1060 Alzheimer's Disease Neuroimaging Initiative (ADNI) participants (47% women, 73.8 ± 7.6 years old), we examined sex differences in plasma p-tau181 levels and their association with other biomarkers, cognitive decline and incident AD. Linear regressions tested for an effect of sex on plasma p-tau181 levels and for plasma p-tau181 × sex interactions on CSF p-tau181, as well as entorhinal cortex tau, cortical amyloid-β (Aβ) deposition, and brain glucose metabolism, quantified using PET imaging. Linear mixed effects models tested for a sex × baseline plasma p-tau181 interaction on change in cognition over time. Finally, Cox models tested for a sex × plasma p-tau181 interaction on the risk of AD dementia in participants who were free of dementia at baseline. Despite similar plasma p-tau181 levels between sexes, women had lower brain glucose metabolism, greater brain Aβ and entorhinal cortex tau deposition, higher CSF p-tau181 and faster cognitive decline in relation to higher baseline plasma p-tau181 levels compared with men. Among Aβ positive, dementia-free participants, women had higher rates of incident AD dementia associated with increasing baseline plasma p-tau181 levels, relative to men. Our results suggest that sex may impact the clinical interpretation of plasma p-tau181 concentrations. If replicated, these findings could have important implications for the use of plasma p-tau181 as an accessible AD biomarker and screening tool for preventive and therapeutic clinical trials.

The relationship between vascular endothelial growth factor (VEGF) and amnestic mild cognitive impairment among older adults living with HIV

Older people with HIV (PWH) experience increased risk of age-related neurodegenerative disorders and cognitive decline, such as amnestic mild cognitive impairment (aMCI). The objective of this study was to examine the relationship between aMCI and plasma VEGF biomarkers among older PWH. Data were collected at a university-based research center from 2011 to 2013. Participants were 67 antiretroviral therapy-treated, virally suppressed PWH. Participants completed comprehensive neurobehavioral and neuromedical evaluations. aMCI status was determined using adapted Jak/Bondi criteria, classifying participants as aMCI + if their performance was > 1 SD below the normative mean on at least two of four memory assessments. VEGF family plasma biomarkers (i.e., VEGF, VEGF-C, VEGF-D, and PIGF) were measured by immunoassay. Logistic regression models were conducted to determine whether VEGF biomarkers were associated with aMCI status. Participants were mostly non-Hispanic white (79%) men (85%) with a mean age of 57.7 years. Eighteen (26.9%) participants met criteria for aMCI. Among potential covariates, only antidepressant drug use differed by aMCI status, and was included as a covariate. VEGF-D was significantly lower in the aMCI + group compared to the aMCI - group. No other VEGF levels (VEGF, VEGF-C, PIGF) differed by aMCI classification (ps > .05). In a sample of antiretroviral therapy-treated, virally suppressed PWH, lower levels of VEGF-D were associated with aMCI status. Longitudinal analyses in a larger and more diverse sample are needed to support VEGF-D as a putative biological marker of aMCI in HIV.

Improving Detection of Amnestic Mild Cognitive Impairment with Sex-Specific Cognitive Norms

BackgroundDespite a female advantage in verbal memory, normative data for verbal memory tests used to diagnose Alzheimer's disease (AD) dementia and amnestic mild cognitive impairment (aMCI) often are not sex-adjusted.ObjectiveTo determine whether sex-adjusted norms improve aMCI diagnostic accuracy when accuracy was evaluated by progression to AD dementia over time.MethodsNon-sex-specific and sex-specific verbal memory test norms were incorporated into Jak/Bondi aMCI criteria and applied to older (age 65-90) non-demented women (N = 1,036) and men (N = 355) from the Rush Memory and Aging Project. Using sex-specific aMCI diagnosis as the "true" condition versus non-sex-specific aMCI diagnosis as the "predicted" condition, we identified True Positives, False Positives, True Negatives, and False Negatives and compared AD dementia risk over 10 years among groups.ResultsRates of aMCI were higher in men versus women (χ2 = 15.39, p < 0.001) when determined based on typical diagnostic criteria, but this difference reversed when using sex-specific diagnostic criteria (χ2 = 8.38, p = 0.004). We identified 8%of women as False Negatives and 12%of men as False Positives. Risk of incident AD dementia in False Positive men was significantly lower than in True Positive men (HR = 0.26, 95%CI = 0.12-0.58, p = 0.001). Risk of incident AD dementia in False Negative women was substantially higher than in True Negative women (HR = 3.11, 95%CI = 2.09-4.63, p < 0.001).ConclusionResults suggest that previous reports of higher aMCI rates in men versus women may be an artifact of non-sex-adjusted norms/cut-scores. Incorporation of sex-specific norms/cut-scores for verbal memory impairment into aMCI diagnostic criteria may improve diagnostic accuracy and avoid diagnostic errors in approximately 20%.

Arterial Stiffening Moderates the Relationship Between Type-2 Diabetes Mellitus and White Matter Hyperintensity Burden in Older Adults With Mild Cognitive Impairment

Background: Cerebrovascular dysfunction has been proposed as a possible mechanism underlying cognitive impairment in the context of type 2 diabetes mellitus (DM). Although magnetic resonance imaging (MRI) evidence of cerebrovascular disease, such as white matter hyperintensities (WMH), is often observed in DM, the vascular dynamics underlying this pathology remain unclear. Thus, we assessed the independent and combined effects of DM status and different vascular hemodynamic measures (i.e., systolic, diastolic, and mean arterial blood pressure and pulse pressure index [PPi]) on WMH burden in cognitively unimpaired (CU) older adults and those with mild cognitive impairment (MCI). Methods: 559 older adults (mean age: 72.4 years) from the Alzheimer's Disease Neuroimaging Initiative were categorized into those with diabetes (DM+; CU = 43, MCI = 34) or without diabetes (DM-; CU = 279; MCI = 203). Participants underwent BP assessment, from which all vascular hemodynamic measures were derived. T2-FLAIR MRI was used to quantify WMH burden. Hierarchical linear regression, adjusting for age, sex, BMI, intracranial volume, CSF amyloid, and APOE ε4 status, examined the independent and interactive effects of DM status and each vascular hemodynamic measure on total WMH burden. Results: The presence of DM (p = 0.046), but not PPi values (p = 0.299), was independently associated with greater WMH burden overall after adjusting for covariates. Analyses stratified by cognitive status revealed a significant DM status x PPi interaction within the MCI group (p = 0.001) such that higher PPi values predicted greater WMH burden in the DM + but not DM- group. No significant interactions were observed in the CU group (all ps > 0.05). Discussion: Results indicate that higher PPi values are positively associated with WMH burden in diabetic older adults with MCI, but not their non-diabetic or CU counterparts. Our findings suggest that arterial stiffening and reduced vascular compliance may have a role in development of cerebrovascular pathology within the context of DM in individuals at risk for future cognitive decline. Given the specificity of these findings to MCI, future exploration of the sensitivity of earlier brain markers of vascular insufficiency (i.e., prior to macrostructural white matter changes) to the effects of DM and arterial stiffness/reduced vascular compliance in CU individuals is warranted.

Alterations in Brain Cannabinoid Receptor Levels Are Associated with HIV-Associated Neurocognitive Disorders in the ART Era: Implications for Therapeutic Strategies Targeting the Endocannabinoid System

HIV-associated neurocognitive disorders (HAND) persist despite the advent of antiretroviral therapy (ART), suggesting underlying systemic and central nervous system (CNS) inflammatory mechanisms. The endogenous cannabinoid receptors 1 and 2 (CB₁ and CB₂) modulate inflammatory gene expression and play an important role in maintaining neuronal homeostasis. Cannabis use is disproportionately high among people with HIV (PWH) and may provide a neuroprotective effect for those on ART due to its anti-inflammatory properties. However, expression profiles of CB₁ and CB₂ in the brains of PWH on ART with HAND have not been reported. In this study, biochemical and immunohistochemical analyses were performed to determine CB₁ and CB₂ expression in the brain specimens of HAND donors. Immunoblot revealed that CB₁ and CB₂ were differentially expressed in the frontal cortices of HAND brains compared to neurocognitively unimpaired (NUI) brains of PWH. CB₁ expression levels negatively correlated with memory and information processing speed. CB₁ was primarily localized to neuronal soma in HAND brains versus a more punctate distribution of neuronal processes in NUI brains. CB₁ expression was increased in cells with glial morphology and showed increased colocalization with an astroglial marker. These results suggest that targeting the endocannabinoid system may be a potential therapeutic strategy for HAND.

Elevated Inflammatory Markers and Arterial Stiffening Exacerbate Tau but Not Amyloid Pathology in Older Adults with Mild Cognitive Impairment

BACKGROUND

Age-related cerebrovascular and neuroinflammatory processes have been independently identified as key mechanisms of Alzheimer's disease (AD), although their interactive effects have yet to be fully examined.

OBJECTIVE

The current study examined 1) the influence of pulse pressure (PP) and inflammatory markers on AD protein levels and 2) links between protein biomarkers and cognitive function in older adults with and without mild cognitive impairment (MCI).

METHODS

This study included 218 ADNI (81 cognitively normal [CN], 137 MCI) participants who underwent lumbar punctures, apolipoprotein E (APOE) genotyping, and cognitive testing. Cerebrospinal (CSF) levels of eight pro-inflammatory markers were used to create an inflammation composite, and amyloid-beta 1-42 (Aβ42), phosphorylated tau (p-tau), and total tau (t-tau) were quantified.

RESULTS

Multiple regression analyses controlling for age, education, and APOE ɛ4 genotype revealed significant PP x inflammation interactions for t-tau (B = 0.88, p = 0.01) and p-tau (B = 0.84, p = 0.02); higher inflammation was associated with higher levels of tau within the MCI group. However, within the CN group, analyses revealed a significant PP x inflammation interaction for Aβ42 (B = -1.01, p = 0.02); greater inflammation was associated with higher levels of Aβ42 (indicative of lower cerebral amyloid burden) in those with lower PP. Finally, higher levels of tau were associated with poorer memory performance within the MCI group only (p s < 0.05).

CONCLUSION

PP and inflammation exert differential effects on AD CSF proteins and provide evidence that vascular risk is associated with greater AD pathology across our sample of CN and MCI older adults.

Validation of the mobile verbal learning test: Illustration of its use for age and disease-related cognitive deficits

OBJECTIVE

We developed a mobile cognitive test of verbal learning and memory, the mobile verbal learning test (mVLT), to allow for brief, repeated and portable delivery of a 12-item list learning test through a smartphone. This study examined the psychometric properties of the mVLT among older persons with and without human immunodeficiency virus (HIV).

METHODS

Sixty-eight persons with HIV and 36 HIV-negative individuals (aged 50-74) completed three trials of the mVLT on a smartphone once daily for 14 days. A different word list was administered each day.

RESULTS

Participants completed 80% of the 14 mVLT administrations, equating to 1166 valid and complete mVLTs. Neither adherence nor mean mVLT total score (number correct in 3 recall trials) differed by HIV status. No practice effects from repeated mVLT administration were observed, and there were moderately strong correlations of mVLT performance with performance on the in-lab version of the task and with traditional cognitive assessments of cognitive processes contributing to memory. We found evidence of within-person learning across mVLT trials, with persons with HIV demonstrating less learning from trials 1 to 3 compared to HIV-negative participants.

CONCLUSIONS

The mVLT is a valid method to assess learning in the real world in older adults with and without HIV.

The utility of olfactory function in distinguishing early-stage Alzheimer's disease from HIV-associated neurocognitive disorders

OBJECTIVES

Given the rising number of older people with HIV (PWH) and the overlap in cognitive dysfunction profiles in HIV-associated neurocognitive disorders (HAND) and Alzheimer's disease and its precursor, amnestic mild cognitive impairment (aMCI), methods are needed to distinguish aMCI/Alzheimer's disease from HAND. As an early indicator of Alzheimer's disease, we examined whether olfactory dysfunction could help to distinguish between aMCI/Alzheimer's disease and HAND among PWH.

DESIGN

An observational cohort study.

METHODS

Eighty-one older (≥50 years) PWH (83% men, 65% white) from the California NeuroAIDS Tissue Consortium completed the University of Pennsylvania Smell Identification Test (UPSIT; higher scores = better smell identification) and a comprehensive seven-domain neuropsychological test battery and neuromedical evaluation. HAND was classified via Frascati criteria. High aMCI risk was defined as impairment (>1.0 SD below normative mean) on two of four delayed recall or recognition outcomes (at least one recognition impairment required) from the Hopkins Verbal Learning Test-Revised and the Brief Visuospatial Memory Test-Revised. We examined UPSIT scores in relation to aMCI risk and HAND status, and continuous memory scores considering adjustments for demographics and relevant clinical or HIV disease characteristics.

RESULTS

Fifty-seven participants were classified with HAND (70%) and 35 participants were classified as high aMCI risk (43%). UPSIT scores were lower (worse) in the high versus low aMCI risk group [F (1,76) = 10.04, P = 0.002], but did not differ by HAND status [F (1,76) = 0.62, P = 0.43]. UPSIT scores positively correlated with all memory outcomes (Ps < 0.05).

CONCLUSION

Olfactory assessments may help in detecting early aMCI/Alzheimer's disease among PWH and allow for appropriate and early disease intervention.

Prediabetes Is Associated With Brain Hypometabolism and Cognitive Decline in a Sex-Dependent Manner: A Longitudinal Study of Nondemented Older Adults

Although type 2 diabetes is a well-known risk factor for Alzheimer's disease (AD), little is known about how its precursor-prediabetes-impacts neuropsychological function and brain health. Thus, we examined the relationship between prediabetes and AD-related biological and cognitive/clinical markers in a well-characterized sample drawn from the Alzheimer's Disease Neuroimaging Initiative. Additionally, because women show higher rates of AD and generally more atherogenic lipid profiles than men, particularly in the context of diabetes, we examined whether sex moderates any observed associations. The total sample of 911 nondemented and non-diabetic participants [normal control = 540; mild cognitive impairment (MCI) = 371] included 391 prediabetic (fasting blood glucose: 100-125 mg/dL) and 520 normoglycemic individuals (age range: 55-91). Linear mixed effects models, adjusted for demographics and vascular and AD risk factors, examined the independent and interactive effects of prediabetes and sex on 2-6 year trajectories of FDG-PET measured cerebral metabolic glucose rate (CMRglu), hippocampal/intracranial volume ratio (HV/IV), cerebrospinal fluid phosphorylated tau-₁₈₁/amyloid-β_1-42 ratio (p-tau₁₈₁/Aβ_1-42), cognitive function (executive function, language, and episodic memory) and the development of dementia. Analyses were repeated in the MCI subsample. In the total sample, prediabetic status had an adverse effect on CMRglu across time regardless of sex, whereas prediabetes had an adverse effect on executive function across time in women only. Within the MCI subsample, prediabetic status was associated with lower CMRglu and poorer executive function and language performance across time within women, whereas these associations were not seen within men. In the total sample and MCI subsample, prediabetes did not relate to HV/IV, p-tau₁₈₁/Aβ_1-42, memory function or dementia risk regardless of sex; however, among incident dementia cases, prediabetic status related to earlier age of dementia onset in women but not in men. Results suggest that prediabetes may affect cognition through altered brain metabolism, and that women may be more vulnerable to the negative effects of glucose intolerance.

Sex Differences in the Patterns and Predictors of Cognitive Function in HIV

Despite advancements in antiretroviral therapy, mild cognitive deficits persist in nearly half of people with HIV (PWH). The profile of impairment in HIV is highly variable with deficits observed in a range of cognitive domains. Despite evidence of greater cognitive impairment among women with HIV (WWH) vs. men with HIV (MWH), it is unclear how MWH and WWH differ in the type of cognitive impairment and in risk factors associated with cognitive impairment profiles. In a large and well-characterized sample of PWH, we used machine learning to identify profiles of cognitive functioning and their associated factors overall and within sex. Participants included 1,666 PWH (201 WWH; 1,465 MMH) from the HIV Neurobehavioral Research Program who completed a neuropsychological test battery at their baseline visits. Using demographically-adjusted T-scores from 13 test outcomes assessing motor skills, executive functioning, attention/working memory, episodic learning and memory, verbal fluency, and processing speed, we used Kohonen self-organizing maps to identify patterns of high-dimensional data by mapping participants to similar nodes based on T-scores (MCLUST R package). Random forest models were used to determine how sociodemographic (e.g., age, education), clinical (e.g., depressive symptoms, substance use disorder), and biological (e.g., HIV disease characteristics) factors differentially related to membership within a cognitive profile. All analyses were repeated within sex. Three cognitive profiles were identified overall and within each sex. Overall and within MWH, there were unimpaired and global weakness profiles. The third profile in the total sample demonstrated relatively weak auditory attention whereas in MWH showed relative strengths in attention and processing speed. Conversely, there was no unimpaired profile among WWH. Rather, WWH demonstrated separate profiles reflecting weakness in motor skills, a relative weakness in learning and delayed recall, and global weaknesses with spared recognition memory. Despite different cognitive profiles by sex, the most discriminative factors were similar between men and women and included reading level (cognitive reserve), current and nadir CD4 count, plasma HIV viral load, duration of HIV disease, age, depressive symptoms, and race/ethnicity. Findings fill a knowledge gap concerning sex differences in cognitive impairment in PWH and inform personalized risk reduction and therapeutic strategies.

Distinguishing Amnestic Mild Cognitive Impairment From HIV-Associated Neurocognitive Disorders

BACKGROUND

Memory impairment occurs in human immunodeficiency virus (HIV)-associated neurocognitive disorders (HAND) and amnestic mild cognitive impairment (aMCI), the precursor to Alzheimer disease (AD). Methods are needed to distinguish aMCI-associated from HAND-associated impairment in people with HIV (PWH). We developed a neuropsychological method of identifying aMCI in PWH and tested this by relating AD neuropathology (β-amyloid, phospho-Tau) to aMCI versus HAND classification.

METHODS

Seventy-four HIV-positive cases (aged 50-68 years) from the National NeuroAIDS Tissue Consortium had neurocognitive data within 1 year of death and data on β-amyloid and phospho-Tau pathology in frontal brain tissue. High aMCI risk was defined as impairment (<1.0 SD below normative mean) on 2 of 4 delayed recall or recognition outcomes from a verbal and nonverbal memory test (at least 1 recognition impairment required). Differences in β-amyloid and phospho-Tau by aMCI and HAND classification were examined.

RESULTS

High aMCI risk was more common in HAND (69.0%) versus no HAND (37.5%) group. β-amyloid pathology was 4.75 times more likely in high versus low aMCI risk group. Phospho-Tau pathology did not differ between aMCI groups. Neither neuropathological feature differed by HAND status.

CONCLUSIONS

Amnestic mild cognitive impairment criteria that include recognition impairment may help to detect AD-like cognitive/biomarker profiles among PWH.

Women's higher brain metabolic rate compensates for early Alzheimer's pathology

INTRODUCTION

The female advantage in brain metabolic function may confer cognitive resilience against Alzheimer's disease (AD).

METHODS

A total of 1259 participants (44% women; 52% mild cognitive impairment; 18% AD) aged 55 to 90 from the Alzheimer's Disease Neuroimaging Initiative (ANDI) completed tests of global cognition, verbal memory, and executive function, and neuroimaging assessments of regional glucose metabolism, hippocampal volume (HV), and amyloid beta (Aβ). We examined sex differences in brain metabolism and cognition by AD biomarker quartiles (Aβ, HV). We then examined if metabolism mediates sex differences in cognition.

RESULTS

Metabolism was higher in women versus men when pathology was mild-to-moderate (quartiles 2 to 3). Women outperformed men on all cognitive outcomes at ≥1 biomarker quartile, reflecting minimal-to-moderate pathology; however, these differences were eliminated/attenuated after adjusting for metabolism. The female advantage in verbal memory was also observed at minimal pathology quartiles but was unchanged after metabolism adjustment.

DISCUSSION

Women's greater brain metabolism may confer cognitive resilience against early AD.

Nucleic acid oxidation is associated with biomarkers of neurodegeneration in CSF in people with HIV

OBJECTIVE

To determine whether oxidative stress in virologically suppressed people with HIV (PWH) may contribute to or result from neurodegeneration, we measured 7,8-dihydro-8-oxoguanine (8-oxo-dG), a marker of DNA damage due to oxidative stress, and markers of age-related neurodegeneration, specifically, reduced levels of CSF Aβ-42, and elevated CSF total tau and neurofilament light (NFL).

METHODS

This cross-sectional study prospectively enrolled participants at 6 US centers in the CNS HIV Antiretroviral Effects Research study. Inclusion criteria included HIV+ with a plasma level of HIV RNA ≤50 copies/mL. Exclusions included significant CNS confounding conditions. Measurements of total tau and Aβ-42 were performed by bead suspension array. NFL and 8-oxo-dG were measured using ELISA.

RESULTS

Participants were 53 PWH, mean age 55 (±9.3) years, 19% women, and 48% non-Hispanic White. Higher 8-oxo-dG correlated with markers of AD-related neurodegeneration including lower CSF Aβ-42 (r = -0.34; p = 0.012) and higher CSF NFL (r = 0.39; p = 0.0091) and total tau (r = 0.6696; p < 0.0001). Relationships remained after adjusting for demographic variables. Levels of protein carbonyls, a marker of protein oxidation, were not related to neurodegeneration markers.

CONCLUSIONS

Among virologically suppressed PWH, nucleic acid oxidation was associated with standard CSF biomarkers of neurodegeneration. Potential sources of oxidative stress in PWH include low-level HIV replication, inflammation, mitochondrial dysfunction, and specific antiretroviral drugs. Results suggest that the higher levels of oxidative stress among PWH may play a role in neurodegeneration.

CLASSIFICATION OF EVIDENCE

This study provides Class II evidence that among virologically suppressed PWH, nucleic acid oxidation is associated with standard CSF biomarkers of neurodegeneration.

Smartphone-Based Measurement of Executive Function in Older Adults with and without HIV

OBJECTIVE

To examine feasibility, convergent validity and biases associated with a mobile color-word interference test (mCWIT) among older persons living with HIV (PLHIV).

METHOD

Over a 14-day period, 58 PLHIV and 32 HIV-uninfected individuals (aged 50-74) completed the mCWIT on smartphones once per day in real-world settings. Participants also completed a comprehensive laboratory-based neuropsychological evaluation.

RESULTS

A high rate of compliance was observed (86%) in the repeated administration of the mCWIT. A practice effect was observed in the overall sample concerning mCWIT subscores, and these learning effects were greater for PLHIV. Stabilization of performance was observed after 6 (HIV+) and 7 days (HIV-) for completion time and after 2 (HIV-) and 3 days (HIV+) for mCWIT errors. A minor fatigue effect was observed in the overall sample which was unassociated with group status. Moderate to strong correlations were found between mCWIT completion time and mCWIT errors with global neurocognition and with all of the individual neurocognitive domains. The strongest associations were with mCWIT completion time and laboratory-based global neurocognition, executive function, and working memory scores.

CONCLUSIONS

Cognitive testing administered within the context of a person's daily life provides qualitatively different data than neuropsychological testing completed in clinical settings, and it may constitute a more ecologically valid indicator of cognitive performance than traditional methods. Mobile cognitive testing has potential to help characterize real-time cognitive performance and serve as a complementary assessment tool to traditional methods.

COMT val158met genotype alters the effects of methamphetamine dependence on dopamine and dopamine-related executive function: preliminary findings

The Met-allele of the COMT Val158Met polymorphism slows metabolism and increases bioavailability of dopamine (DA) in the prefrontal cortex compared to the Val-allele. Healthy Met-carriers outperform Val-carriers on executive function (EF) tests, yet this 'advantage' disappears in methamphetamine (METH) dependence. Met-carriers may be disproportionately vulnerable to METH-related perturbations of DA, yet it is unknown whether COMT modulates METH effects on CSF DA biomarkers. Participants were 75 METH+ and 47 METH- men who underwent neurocognitive testing, COMT genotyping, and lumbar puncture. CSF was assayed for DA and its metabolite, homovanillic acid (HVA). Separate linear models regressed DA, HVA, and HVA/DA ratios on COMT, METH and their interaction. Pearson correlations examined associations between DA and EF. Significant interactions indicated that METH+ had lower DA and higher HVA/DA ratios among Met/Met, but not Val/Met-or Val/Val. Met/Met-exhibited the highest DA levels among METH-, whereas DA levels were comparable between Met/Met-and Val-carriers among METH+. Higher DA correlated with better EF in METH- Met/Met, but did not predict EF in the entire sample. DA was expectedly higher in METH- Met/Met, yet a discordant genotype-phenotype profile emerged in METH+ Met/Met, consistent with the notion that slow DA clearance exacerbates METH-associated DA dysregulation.

Sex differences in Alzheimer's-related Tau biomarkers and a mediating effect of testosterone

Women show greater pathological Tau biomarkers than men along the Alzheimer's disease (AD) continuum, particularly among apolipoprotein ε-E4 (APOE4) carriers; however, the reason for this sex difference in unknown. Sex differences often indicate an underlying role of sex hormones. We examined whether testosterone levels might influence this sex difference and the modifying role of APOE4 status. Analyses included 172 participants (25 cognitively normal, 97 mild cognitive impairment, 50 AD participants) from the Alzheimer's Disease Neuroimaging Initiative (34% female, 54% APOE4 carriers, aged 55-90). We examined the separate and interactive effects of plasma testosterone levels and APOE4 on cerebrospinal fluid phosphorylated-tau181 (p-Tau) levels in the overall sample and the sex difference in p-Tau levels before and after adjusting for testosterone. A significant APOE4-by-testosterone interaction revealed that lower testosterone levels related to higher p-Tau levels among APOE4 carriers regardless of sex. As expected, women had higher p-Tau levels than men among APOE4 carriers only, yet this difference was eliminated upon adjustment for testosterone. Results suggest that testosterone is protective against p-Tau particularly among APOE4 carriers. The lower testosterone levels that typically characterize women may predispose them to pathological Tau, particularly among female APOE4 carriers.

Risk of developing cerebral β-amyloid plaques with posttranslational modification among HIV-infected adults

OBJECTIVES

Evidence of accelerated brain aging among HIV-infected adults argues for the increased risk of developing cerebral β-amyloid (Aβ) plaques. We compared the frequency of Aβ plaque-bearing cases in our HIV cohort with that in a general cohort reported by Braak et al. We explored posttranslationally modified Aβ forms (N3pE, E22P, phospho-Ser8) in plaques and E22P-Aβ in the postmortem cerebrospinal fluid (CSF) in the HIV cohort.

DESIGN

Clinicopathological study of HIV-infected adults.

METHODS

To assess frontal Aβ plaque deposition, we conducted immunohistochemistry for generic Aβ (4G8) and three modified Aβ forms. We determined CSF E22P-Aβ levels by ELISA.

RESULTS

We found 4G8-Aβ plaques in 29% of 279 HIV-infected cases. Within the age range of 31-70 years, the frequency of 4G8-Aβ plaque-bearing cases was higher in our HIV cohort (n = 273) compared with the general cohort (n = 1110) overall (29.3 vs. 25.8%) and across four age groups by decade (odds ratio 2.35, P < 0.0001). In HIV-infected cases with (n = 37) and without (n = 12) 4G8-Aβ plaques, modified Aβ forms occurred in order: N3pE, E22P, and phospho-Ser8. In CSF assays of HIV-infected cases with (n = 27; 17 focal, 10 widespread) and without (n = 11) 4G8-Aβ plaques, the median E22P-Aβ/Aβ40 ratio was higher among cases with widespread plaques than in cases with focal or absent plaques (P = 0.047).

CONCLUSION

Our findings suggest HIV-infected adults are at increased risk of developing cerebral Aβ plaques. The occurrence of modified Aβ forms in order suggests the progression stages of Aβ plaque deposition. The potential for E22P-Aβ as a CSF biomarker of cerebral Aβ plaques should be investigated.

Sex-specific norms for verbal memory tests may improve diagnostic accuracy of amnestic MCI

OBJECTIVE

To examine whether the use of sex-specific norms and cut scores to identify memory impairment improves diagnostic accuracy of amnestic mild cognitive impairment (aMCI) compared to non-sex-specific (typical) norms/cut scores given the female advantage in verbal memory.

METHODS

We calculated sex-specific and typical norms/cut scores (age and education specific) for impairment on the Rey Auditory Verbal Learning Test in the Mayo Clinic Study of Aging. Norms/cut scores were applied to 453 women and 532 men from the Alzheimer's Disease Neuroimaging Initiative. We compared sex differences in rates of aMCI (Jak/Bondi criteria) for sex-specific vs typical norms/cut scores. Using sex-specific cut scores as the true condition and typical cut scores as the predicted condition, we categorized participants as true positives (TPs), false positives (FPs), true negative (TNs), or false negative (FNs). In cross-sectional analyses within sex, we compared positivity rates of CSF hyperphosphorylated tau/β-amyloid (Aβ) and cortical Aβ deposition ([¹⁸F]AV45 PET) and APOE ε4 frequency among diagnostic comparison groups.

RESULTS

The frequency of aMCI was higher in men when using typical norms/cut scores. Using sex-adjusted norms/cut scores led to the identification of 10% FNs (missed aMCI cases) among women and 10% FPs among men. Biomarker analyses supported the hypothesis that sex-specific diagnostic criteria improves diagnostic accuracy. Biomarkers rates were higher in FNs vs TNs and similar in FNs and TPs. Biomarker rates were lower in FPs vs TPs and similar between FPs and TNs.

CONCLUSION

Results suggest that non-sex-specific aMCI diagnostic criteria led to a 20% diagnostic error rate. Accounting for sex differences in verbal memory performance may improve aMCI classification.