Telomere Length and Magnetic Resonance Imaging Findings of Vascular Brain Injury and Central Brain Atrophy: The Strong Heart Study

Telomere length and cognitive function among middle-aged and older participants from communities underrepresented in aging research: A preliminary study

Objective

Accelerated biological aging is a plausible and modifiable determinant of dementia burden facing minoritized communities, but is not well-studied in these historically underrepresented populations. Our objective was to preliminarily characterize relationships between telomere length and cognitive health among American Indian/Alaska Native (AI/AN) and Black/African American (B/AA) middle-aged and older adults.

Methods

This study included data on telomere length and cognitive test performance from 187 participants, enrolled in one of two community-based cognitive aging cohorts and who identified their primary race as AI/AN or B/AA.

Results

Nested multivariable regression models revealed preliminary evidence for associations between telomere length and cognitive performance, and these associations were partially independent of chronological age.

Discussion

Small sample size limited estimate precision, however, findings suggest future work on telomere length and cognitive health in underrepresented populations at high risk for dementia is feasible and valuable as a foundation for social and behavioral intervention research.

Epidemiology and prevalence of dementia and Alzheimer's disease in American Indians: Data from the Strong Heart Study

INTRODUCTION

Accurate epidemiologic estimates for dementia are lacking for American Indians, despite substantive social and health disparities.

METHODS

The Strong Heart Study, a population-based cohort of 11 American Indian tribes, conducted detailed cognitive testing and examinations over two visits approximately 7 years apart. An expert panel reviewed case materials for consensus adjudication of cognitive status (intact; mild cognitive impairment [MCI]; dementia; other impaired/not MCI) and probable etiology (Alzheimer's disease [AD], vascular bain injury [VBI], traumatic brain injury [TBI], other).

RESULTS

American Indians aged 70-95 years had 54% cognitive impairment including 10% dementia. VBI and AD were primary etiology approximately equal proportions (>40%). Apolipoprotein (APO) Eε4 carriers were more common among those with dementia (p = 0.040). Plasma pTau, glial fibrillary acidic protein (GFAP), and neurofilament light chain (NfL) were higher among those with cognitive impairment, but not amyloid beta (Aβ). Cognitive intact had mean 3MSE 92.2 (SD 6.4) and mean Montreal Cognitive Assessment (MoCA) score of 21.3 (SD 3.2).

DISCUSSION

This is the first population-based study to estimate the prevalence of vascular and Alzheimer's dementias in a population-based study of American Indians.

HIGHLIGHTS

The Strong Heart Study is a population-based cohort of American Indian tribes, conducted over 30+ years and three US geographic regions (Northern Plains, Southern Plains, Southwest). Our teams conducted detailed cognitive testing, neurological examination, and brain imaging over two visits approximately 7 years apart. An expert panel reviewed collected materials for consensus-based adjudication of cognitive status (intact; MCI; dementia; other impaired/not MCI) and probable underlying etiology (AD; VBI; TBI; other). In this cohort of American Indians aged 70-95, 54% were adjudicated with cognitive impairment, including approximately 35% MCI and 10% dementia. These data expand on prior reports from studies using electronic health records, which had suggested prevalence, and incidence of dementia in American Indians to be more comparable to the majority population or non-Hispanic White individuals, perhaps due to latent case undercounts in clinical settings. Vascular and neurodegenerative injuries were approximately equally responsible for cognitive impairment, suggesting that reduction of cardiovascular disease is needed for primary prevention. Traumatic injury was more prevalent than in other populations, and common among those in the "other/not MCI" cognitive impairment category. Mean scores for common dementia screening instruments-even among those adjudicated as unimpaired-were relatively low compared to other populations (mean unimpaired 3MSE 92.2, SD 6.4; mean unimpaired MoCA 21.3, SD 3.2), suggesting the need for cultural and environmental adaptation of common screening and evaluation instruments.

Psychometric Properties of Controlled Oral Word Association (COWA) Test and Associations With Education and Bilingualism in American Indian Adults: The Strong Heart Study

The Controlled Oral Word Association (COWA) test is used to assess phonemic fluency and executive function. Formal validation of test scores is important for accurate cognitive evaluation. However, there is a dearth of psychometric validation among American Indian adults. Given high burden of dementia risk and key contextual factors associated with cognitive assessments, this represents a critical oversight. In a large, longitudinal population-based cohort study of adult American Indians, we examined several validity inferences for COWA, including scoring, generalization, and extrapolation inferences, by investigation of factor structure, internal consistency, test-retest reliability, and differential test functioning. We found adequate unidimensional model fit, with high factor loadings. Internal consistency reliability and test-retest reliability were 0.88 and 0.77, respectively, for the full group. COWA scores were lowest among the oldest, lowest education, bilingual speakers; group effects for sex and bilingual status were small; age effect was medium; and education effect was largest. However, Wide Range Achievement Test (WRAT) score effect was stronger than education effect, suggesting better contextualization may be needed. These results support interpretation of total COWA score, including across sex, age, or language use strata.

Mitigating cellular aging and enhancing cognitive functionality: visual arts-mediated Cognitive Activation Therapy in neurocognitive disorders

The growing phenomenon of population aging is redefining demographic dynamics, intensifying age-related conditions, especially dementia, projected to triple by 2050 with an enormous global economic burden. This study investigates visual arts-mediated Cognitive Activation Therapy (CAT) as a non-pharmacological CAT intervention targets both biological aging [leukocyte telomere length (LTL), DNA methylation age (DNAmAge)] and cognitive functionality. Aligning with a broader trend of integrating non-pharmacological approaches into dementia care. The longitudinal study involved 20 patients with mild to moderate neurocognitive disorders. Cognitive and functional assessments, and biological aging markers -i.e., LTL and DNAmAge- were analyzed before and after CAT intervention. Change in LTL was positively correlated with days of treatment (p =0.0518). LTL significantly elongated after intervention (p =0.0269), especially in men (p =0.0142), correlating with younger age (p =0.0357), and higher education (p =0.0008). DNAmAge remained instead stable post-treatment. Cognitive and functional improvements were observed for Copy of complex geometric figure, Progressive Silhouettes, Position Discrimination, Communication Activities of Daily Living-Second edition, Direct Functional Status (p < 0.0001) and Object decision (p =0.0594), but no correlations were found between LTL and cognitive gains. Visual arts-mediated CAT effectively mitigates cellular aging, especially in men, by elongating LTL. These findings underscore the potential of non-pharmacological interventions in enhancing cognitive and functional status and general well-being in dementia care. Further research with larger and longer-term studies is essential for validation.

Plasma biomarkers of Alzheimer's disease and related dementias in American Indians: The Strong Heart Study

INTRODUCTION

Identification of Alzheimer's disease (AD) needs inexpensive, noninvasive biomarkers, with validation in all populations.

METHODS

We collected plasma markers in older American Indian individuals: phosphorylated-tau181 (pTau181); amyloid-beta (Aβ) 40,42; glial fibrillary acidic protein (GFAP); and neurofilament light chain (NfL). Plasma markers were analyzed for discriminant properties with cognitive status and etiology using receiver operating characteristic (ROC) analysis.

RESULTS

PTau181, GFAP, NfL plasma values were significantly associated with cognition, but Aβ were not. Discriminant performance was moderate for individual markers, with pTau181, GFAP, NfL performing best, but an empirically selected panel of markers (age, sex, education, pTau181, GFAP, NfL, Aβ4240 ratio) had excellent discriminant performance (AUC > 0.8).

DISCUSSION

In American Indian individuals, pTau181 and Aβ values suggested more common pathology than in majority populations. Aβ was less informative than in other populations; however, all four markers were needed for a best-performing dementia diagnostic model. These data validate utility of AD plasma markers, while suggesting population-specific diagnostic characteristics.

Assessing the Causal Association between Biological Aging Biomarkers and the Development of Cerebral Small Vessel Disease: A Mendelian Randomization Study

Biological aging biomarkers, such as leukocyte telomere length (LTL) and epigenetic clocks, have been associated with the risk of cerebral small vessel disease (CSVD) in several observational studies. However, it is unclear whether LTL or epigenetic clocks play causal roles as prognostic biomarkers in the development of CSVD. We performed a Mendelian randomization (MR) study of LTL and four epigenetic clocks on ten subclinical and clinical CSVD measures. We obtained genome-wide association (GWAS) data for LTL from the UK Biobank (N = 472,174). Data on epigenetic clocks were derived from a meta-analysis (N = 34,710), and CSVD data (N cases =1293-18,381; N controls = 25,806-105,974) were extracted from the Cerebrovascular Disease Knowledge Portal. We found that genetically determined LTL and epigenetic clocks were not individually associated with ten measures of CSVD (IVW p > 0.05), and this result was consistent across sensitivity analyses. Our findings imply that LTL and epigenetic clocks may not help in predicting CSVD development as causal prognostic biomarkers. Further studies are needed to illustrate the potential of reverse biological aging in serving as an effective form of preventive therapy for CSVD.

Telomere length and brain imaging phenotypes in UK Biobank

Telomeres form protective caps at the ends of chromosomes, and their attrition is a marker of biological aging. Short telomeres are associated with an increased risk of neurological and psychiatric disorders including dementia. The mechanism underlying this risk is unclear, and may involve brain structure and function. However, the relationship between telomere length and neuroimaging markers is poorly characterized. Here we show that leucocyte telomere length (LTL) is associated with multi-modal MRI phenotypes in 31,661 UK Biobank participants. Longer LTL is associated with: i) larger global and subcortical grey matter volumes including the hippocampus, ii) lower T1-weighted grey-white tissue contrast in sensory cortices, iii) white-matter microstructure measures in corpus callosum and association fibres, iv) lower volume of white matter hyperintensities, and v) lower basal ganglia iron. Longer LTL was protective against certain related clinical manifestations, namely all-cause dementia (HR 0.93, 95% CI: 0.91-0.96), but not stroke or Parkinson's disease. LTL is associated with multiple MRI endophenotypes of neurodegenerative disease, suggesting a pathway by which longer LTL may confer protective against dementia.

Telomere length and brain aging: A systematic review and meta-analysis

The current evidence on the association of leukocyte telomere length (LTL) with age-related structural and cognitive changes in the brain is mixed. Herein conforming to PRISMA 2020 guidelines, we performed a systematic review and meta-analysis using data from 27 observational studies in non-demented individuals. We used effect size and p-value based meta-analysis methods considering marked heterogeneity among studies. We found that the longer LTL was associated with higher brain volume (β = 0.43, 95%CI: 0.36-0.50%, p = 0.008, N = 1102) and with higher global cognition (β = 0.01; 95%CI: 0.00-0.02, p = 0.03, N = 19609) by effect size based meta-analysis and with brain volume, hippocampal volume, global cognition, cognitive domains of attention/speed as well as executive functions by p-value based meta-analysis. No significant association of LTL with brain white matter hyperintensities was detected. Furthermore, the evidence strongly suggests a subgroup-specific canonical effect of telomeres, notably in older individuals and females. In conclusion, we provide meta-analytic evidence on the beneficial effect of telomeres on brain structure as well as cognition and advocate for a beneficial subgroup-specific effect that warrants further attention.

Comparing Vascular Brain Injury and Stroke by Cranial Magnetic Resonance Imaging, Physician-Adjudication, and Self-Report: Data from the Strong Heart Study

BACKGROUND

Epidemiologic studies often use self-report as proxy for clinical history. However, whether self-report correctly identifies prevalence in minority populations with health disparities and poor health-care access is unknown. Furthermore, overlap of clinical vascular events with covert vascular brain injury (VBI), detected by imaging, is largely unexamined.

METHODS

The Strong Heart Study recruited American Indians from 3 regions, with surveillance and adjudication of stroke events from 1989 to 2013. In 2010-2013, all 817 survivors, aged 65-95 years, underwent brain imaging, neurological history interview, and cognitive testing. VBI was defined as imaged infarct or hemorrhage.

RESULTS

Adjudicated stroke was prevalent in 4% of participants and separately collected, self-reported stroke in 8%. Imaging-defined VBI was detected in 51% and not associated with any stroke event in 47%. Compared with adjudication, self-report had 76% sensitivity and 95% specificity. Participants with adjudicated or self-reported stroke had the poorest performance on cognitive testing; those with imaging-only (covert) VBI had intermediate performance.

CONCLUSION

In this community-based cohort, self-report for prior stroke had good performance metrics. A majority of participants with VBI did not have overt, clinically recognized events but did have neurological or cognitive symptoms. Data collection methodology for studies in a resource-limited setting must balance practical limitations in costs, accuracy, feasibility, and research goals.

Associations of Binge Drinking With Vascular Brain Injury and Atrophy in Older American Indians: The Strong Heart Study

Objectives: American Indians (AIs) generally consume less alcohol than the US general population; however, the prevalence of alcohol use disorder is higher. This is the first large cohort study to examine binge drinking as a risk factor for vascular brain injury (VBI). Methods: We used linear and Poisson regression to examine the association of self-reported binge drinking with VBI, measured via magnetic resonance imaging (MRI), in 817 older AIs who participated in the Strong Heart and Cerebrovascular Disease and Its Consequences in American Indians studies. Results: Any binge drinking at multiple time-points was associated with increased sulcal (β = 0.360, 95% CI [0.079, 0.641]) and ventricle dilatation (β = 0.512, 95% CI [0.174, 0.850]) compared to no binge drinking. Discussion: These observed associations are consistent with previous findings. Identifying how binge drinking may contribute to VBI in older AIs may suggest modifiable health behaviors for neurological risk reduction and disease prevention.

Urinary Arsenic and Cadmium Associations with Findings from Cranial MRI in American Indians: Data from the Strong Heart Study

BACKGROUND

Arsenic and cadmium are known cardiovascular toxicants that pose disproportionate risk to rural communities where environmental exposures are high. American Indians have high vascular risk, which may be attributable in part to these exposures.

OBJECTIVE

We examined urine metal concentrations in association with magnetic resonance imaging findings of vascular brain injury or cerebral atrophy in adult American Indians.

METHODS

We measured arsenic and cadmium in American Indian participants from the Strong Heart Study (1989-1991) and evaluated these associations with later (2010-2013) measures of infarct, hemorrhage, white matter hyperintensity (WMH) grade, brain and hippocampal volume, and sulcal and ventricle atrophy using nested multivariate regression analyses.

RESULTS

Among participants with available data (N=687), the median urine arsenic:creatinine ratio was 7.54μg/g [interquartile range (IQR): 4.90-11.93] and the cadmium:creatinine ratio was 0.96μg/g (IQR: 0.61-1.51). Median time between metal measurement and brain imaging was 21 y (range: 18-25 y). Statistical models detected significant associations between arsenic and higher burden of WMH [grade increase=0.014 (95% CI: 0.000, 0.028) per 10% increase in arsenic]; and between cadmium and presence of lacunar infarcts [relative risk (RR)=1.024 (95% CI: 1.004, 1.045) per 10% increase in cadmium].

DISCUSSION

This population-based cohort of American Indian elders had measured values of urine arsenic and cadmium several times higher than previous population- and clinic-based studies in the United States and Mexico, and comparable values with European industrial workers. Our findings of associations for arsenic and cadmium exposures with vascular brain injury are consistent with established literature. Environmental toxicant accumulation is modifiable; public health policy may benefit from focusing on reductions in environmental metals. https://doi.org/10.1289/EHP6930.

Leukocyte Telomere Length Shortening and Alzheimer's Disease Etiology

BACKGROUND

Several observational studies have found leukocyte telomere length (TL) to be associated with Alzheimer's diseases (AD) or dementia. However, these findings were based on small sample sizes and cannot clarify whether this relationship was causal. Genome-wide association studies (GWAS) have identified common variants associated with TL, providing a valuable resource for examining the causal effect of TL on AD using Mendelian Randomization (MR) methods.

OBJECTIVE

To examine if TL was causally associated with AD using GWAS summary statistics.

METHODS

Using a genetic risk score comprised of seven variants associated with leukocyte TL as an instrumental variable, we tested whether shorter TL was associated with a higher risk of AD by applying an MR approach to the summarized genome-wide association study data.

RESULTS

The genetic risk score for TL was associated with higher risk of AD [log-odds ratio (OR) = 0.003 for per TL-decreasing allele; 95% confidence interval (CI): 0.001, 0.005, p = 0.005]. Moreover, the MR analysis provided support for shorter TL to be causally associated with a higher risk of AD (log-OR = 0.04 per SD-decrease of TL; 95% CI: 0.01, 0.08, p = 0.01).

CONCLUSION

We suggest that TL has a causal effect on the risk of AD.

Cognitive Correlates of MRI-defined Cerebral Vascular Injury and Atrophy in Elderly American Indians: The Strong Heart Study

OBJECTIVE

American Indians experience substantial health disparities relative to the US population, including vascular brain aging. Poorer cognitive test performance has been associated with cranial magnetic resonance imaging findings in aging community populations, but no study has investigated these associations in elderly American Indians.

METHODS

We examined 786 American Indians aged 64 years and older from the Cerebrovascular Disease and its Consequences in American Indians study (2010-2013). Cranial magnetic resonance images were scored for cortical and subcortical infarcts, hemorrhages, severity of white matter disease, sulcal widening, ventricle enlargement, and volumetric estimates for white matter hyperintensities (WMHs), hippocampus, and brain. Participants completed demographic, medical history, and neuropsychological assessments including testing for general cognitive functioning, verbal learning and memory, processing speed, phonemic fluency, and executive function.

RESULTS

Processing speed was independently associated with the presence of any infarcts, white matter disease, and hippocampal and brain volumes, independent of socioeconomic, language, education, and clinical factors. Other significant associations included general cognitive functioning with hippocampal volume. Nonsignificant, marginal associations included general cognition with WMH and brain volume; verbal memory with hippocampal volume; verbal fluency and executive function with brain volume; and processing speed with ventricle enlargement.

CONCLUSIONS

Brain-cognition associations found in this study of elderly American Indians are similar to those found in other racial/ethnic populations, with processing speed comprising an especially strong correlate of cerebrovascular disease. These findings may assist future efforts to define opportunities for disease prevention, to conduct research on diagnostic and normative standards, and to guide clinical evaluation of this underserved and overburdened population.

Leukocyte Telomere Length Is Related to Brain Parenchymal Fraction and Attention/Speed in the Elderly: Results of the Austrian Stroke Prevention Study

There are controversial results if leukocyte telomere length (LTL) is related to structural brain changes and cognitive decline in aging. Here, we investigated the association between LTL and 1) global MRI correlates of brain aging such as brain parenchymal fraction (BPF) and white matter hyperintensities (WMH) load and Fazekas score as well as 2) global (g-factor) and domain-specific cognition such as attention/speed, conceptualization, memory, and visuopractical skills. In total, 909 participants of the Austrian Stroke Prevention Study with LTL, MRI, and cognitive tests were included. There were 388 (42.7%) men, and the mean age was 65.9 years. Longer LTL was significantly associated with larger BPF (β = 0.43, p < 0.001), larger WMH load (β = 0.03, p = 0.04), and score (β = 0.05, p = 0.04) after adjusting for age, sex, vascular risk factors, and ApoE4 carrier status. The effect on BPF was more significant in the subgroups of women (β = 0.51, p = 0.001), age >65 years (β = 0.58, p = 0.002), BMI ≥ 25 (β = 0.40, p = 0.004), education ≤10 years (β = 0.42, p = 0.002), hypertensives (β = 0.51, p = 0.001), cardiovascular disease (CVD) (β = 0.58, p = 0.005), non-diabetics (β = 0.42, p < 0.001), and Apoe4 non-carriers (β = 0.49, p < 0.001). The effect on WMH was significant within the hypertensives (load: β = 0.04, p = 0.02), non-diabetics (load:β = 0.03, p = 0.01; score: β = 0.06, p = 0.02), in those with education ≤10 years (load: β = 0.03, p = 0.04; score: β = 0.07, p = 0.02), in ApoE4 non-carriers (load: β = 0.03, p = 0.02; score: β = 0.07, p = 0.01) and in subjects without CVD (score: β = 0.06, p = 0.05). We only observed a significant association between LTL and the cognitive domain of attention/speed, which was confined to the subgroups of BMI ≥ 25 (β = 0.04, p = 0.05) and education ≤10 years (β = 0.04, p = 0.05). The effect of LTL on attention/speed was partly mediated in both subgroups by BPF (β = 0.02, 95% CI = 0.01:0.03) when tested by bootstrapping. Our results support a strong protective role of longer LTL on global brain volume which in turn may contribute to better cognitive functions, especially in the attention/speed domain in the elderly.

Neurocognitive Impairment and Associated Genetic Aspects in HIV Infection

HIV enters the central nervous system (CNS) early after infection. HIV-associated neurocognitive disorders (HAND) remain a serious complication of HIV infection despite available antiretroviral therapy (ART). Neurocognitive deficits observed in HAND are heterogeneous, suggesting a variability in individuals' susceptibility or resiliency to the detrimental CNS effects of HIV infection. This chapter reviews primary host genomic changes (immune-related genes, genes implicated in cognitive changes in primary neurodegenerative diseases), epigenetic mechanisms, and genetic interactions with ART implicated in HIV progression or HAND/neurocognitive complications of HIV. Limitations of the current findings include diversity of the HAND phenotype and limited replication of findings across cohorts. Strategies to improve the precision of future (epi)genetic studies of neurocognitive consequences of HIV infection are offered.