Longitudinal associations between β-amyloid and cortical thickness in mild cognitive impairment

How beta-amyloid accumulation influences brain atrophy in Alzheimer's disease remains contentious with conflicting findings. We aimed to elucidate the correlations of regional longitudinal atrophy with cross-sectional regional and global amyloid in individuals with mild cognitive impairment and no cognitive impairment. We hypothesized that greater cortical thinning over time correlated with greater amyloid deposition, particularly within Alzheimer's disease characteristic regions in mild cognitive impairment, and weaker or no correlations in those with no cognitive impairment. 45 patients with mild cognitive impairment and 12 controls underwent a cross-sectional [¹¹C]-Pittsburgh Compound B PET and two retrospective longitudinal structural imaging (follow-up: 23.65 ± 2.04 months) to assess global/regional amyloid and regional cortical thickness, respectively. Separate linear mixed models were constructed to evaluate relationships of either global or regional amyloid with regional cortical thinning longitudinally. In patients with mild cognitive impairment, regional amyloid in the right banks of the superior temporal sulcus was associated with longitudinal cortical thinning in the right medial orbitofrontal cortex (P = 0.04 after False Discovery Rate correction). In the mild cognitive impairment group, greater right banks amyloid burden and less cortical thickness in the right medial orbitofrontal cortex showed greater visual and verbal memory decline over time, which was not observed in controls. Global amyloid was not associated with longitudinal cortical thinning in any locations in either group. Our findings indicate an increasing influence of amyloid on neurodegeneration and memory along the preclinical to prodromal spectrum. Future multimodal studies that include additional biomarkers will be well-suited to delineate the interplay between various pathological processes and amyloid and memory decline, as well as clarify their additive or independent effects along the disease deterioration.

Association of Interleukin-6 and Interleukin-8 with Cognitive Decline in an Asian Memory Clinic Population

BACKGROUND

Neuroinflammation has been postulated to play an important role in cognitive impairment, cognitive decline, and dementia. Inflammatory biomarkers such as interleukin-6 (IL-6) and IL-8 are found to be associated with the neuro-inflammatory process and worse cognitive function. However, it is unknown whether these interleukins are associated with long-term cognitive function.

OBJECTIVE

To investigate the association of baseline IL-6 and IL-8 with cognitive function at baseline as well as its association with cognitive decline over five-year follow-up.

METHODS

387 patients were recruited from an ongoing memory clinic-based study who underwent comprehensive physical, medical, neuropsychological and blood assessments together with brain MRI. IL-6 and IL-8 were measured using LUMINEX assays. The National Institute of Neurological Disorders and Stroke-Canadian Stroke Network neuropsychological battery was used to assess cognitive decline across multiple domains.

RESULTS

Among the 387 (mean age = 72.9 years and 53.7% males) participants, 322 had at least two follow-up assessments and were included in the longitudinal analysis. Negative linear trend associations were found between tertiles of IL-8 with baseline global cognition (p-trend< 0.001), attention (p-trend = 0.005), executive function (p-trend< 0.001), and visuospatial function (p-trend = 0.002) domains. No association was found between baseline IL-8 and cognitive decline. IL-6 was not associated with both baseline and follow-up cognition.

CONCLUSION

IL-8 was associated with worse cognition especially in attention, executive function, and visuospatial function, suggesting the role of neuroinflammation in cognitive impairment. Hence, blood inflammatory biomarkers may be useful indicators in identifying patients at risk of cognitive impairment and warrant consideration for inclusion in treatment trials.

Validation of the Informant Quick Dementia Rating System (QDRS) among Older Adults in Singapore

Background: The Quick Dementia Rating System (QDRS) is a brief and rapid tool that can be administered by an informant without the need for a trained assessor. Objective: Our objective was to examine the validity, reliability, and cost-effectiveness of the informant QDRS in a Singapore memory clinic sample. Methods: We assessed a total of 177 older adults, among whom, 32 had no cognitive impairment (NCI), 61 had mild cognitive impairment (MCI), and 84 had dementia. Elderly underwent 1) the informant QDRS, 2) the Clinical Dementia Rating (CDR) as the gold standard diagnosis, 3) the Mini-Mental State Examination (MMSE), and 4) the Ascertain Dementia 8 (AD8) as comparisons to the QDRS. The extent to which the QDRS may reduce the recruitment cost (time) of clinical trials was also calculated. Results: The QDRS had excellent internal consistency (Cronbach alpha = 0.939). It correlated highly with the CDR-global (R = 0.897), CDR Sum-of-Boxes (R = 0.915), MMSE (R = –0.848), and the AD8 (R = 0.747), showing good concurrent validity. With an optimal cut-off of 1.5 for MCI (sensitivity 85.2%, specificity 96.3%) and 6 for dementia (sensitivity 90.1%, specificity 89.2%), the QDRS achieved a higher overall accuracy of 85.0%, as compared to MMSE (71.2%) and AD8 (73.4%). A simulated clinical trial recruitment scenario demonstrated that pre-screening with the QDRS followed by a confirmatory CDR would reduce the time needed to identify NCI subjects by 23.3% and MCI subjects by 75.3%. Conclusion: The QDRS is a reliable cognitive impairment screening tool which is suitable for informant-administration, especially for identification of MCI.

The SINgapore GERiatric Intervention Study to Reduce Cognitive Decline and Physical Frailty (SINGER): Study Design and Protocol

Background

The SINgapore GERiatric intervention study to reduce cognitive decline and physical frailty (SINGER) randomised controlled trial (RCT) uses a multidomain lifestyle interventions approach, shown to be effective by the Finnish Geriatric Intervention Study to Prevent Cognitive Impairment and Disability (FINGER) trial, to delay cognitive decline.

Objective

To investigate the efficacy and safety of the SINGER multidomain lifestyle interventions in older adults at risk for dementia to delay cognitive decline.

Participants

1200 participants between 60–77 years old, with Cardiovascular Risk Factors, Aging, and Incidence of Dementia (CAIDE) dementia risk score ≥6, fulfilling at least one of the following LIBRA index for diet, cognitive activity, physical activity and a Montreal Cognitive Assessment (MoCA) score ≥18, ≤27 points, will be recruited across Singapore.

Methods

SINGER is a 2-year multi-site RCT consisting of multidomain interventions: dietary advice, exercise, cognitive training, and vascular risk factors management. Participants will be randomised into either the Self-Guided Intervention (SGI; general lifestyle and health information and resources) or Structured Lifestyle Intervention (SLI) group. The SLI comprises diet training (6 group and 3 individual sessions over 12 months); exercise (supervised: 1-hour twice weekly for 6 months, unsupervised: 2–3/week for the rest of the study duration); cognitive sessions (15–30 minutes/session, 3/week for 6 months, together with 10 workshops in 24 months). Vascular management takes place every 3–6 months or otherwise as specified by study physicians. The primary outcome is global cognition measured using the modified Neuropsychological Battery assessing performance in various domains, such as episodic memory, executive function and processing speed. Secondary outcome measures include: domain-specific cognition and function, imaging evidence of brain and retinal changes, incidence and progression of chronic diseases, blood biomarkers, quality of life, mental health and cost-benefit analysis.

Conclusions

SINGER is part of the Worldwide-FINGERS international network, which is at the forefront of harmonizing approaches to effective non-pharmacological interventions in delaying cognitive decline in older adults at risk of dementia. By establishing the efficacy of multidomain interventions in preventing cognitive decline, SINGER aims to implement the findings into public health and clinical practices by informing policy makers, and guiding the design of community- and individual-level health promotion initiatives.

Electronic Supplementary Material

Supplementary material is available for this article at 10.14283/jpad.2022.5 and is accessible for authorized users.

Domain-Specific Cognitive Trajectories Among Patients with Minor Stroke or Transient Ischemic Attack in a 6-Year Prospective Asian Cohort: Serial Patterns and Indicators

BACKGROUND

Long-term post-stroke cognitive impairment (PSCI) has often been overlooked, especially among patients with minor stroke or transient ischemic attack (TIA).

OBJECTIVE

To assess 6-year domain-specific cognitive trajectories among survivors of minor stroke or TIA and to identify possible indicators associated with cognitive trajectories, as well as long-term and incident PSCI.

METHODS

Eligible participants completed cognitive and clinical assessments at baseline (2 weeks after stroke) and up to 5 follow-up visits in 6 years. Mixed linear models and generalized estimating equations were adopted to analyze longitudinal data and survival analysis to explore incident PSCI, controlling for demographic, clinical, and vascular indicators.

RESULTS

The prevalence of PSCI and mortality rate ranged from 34.6% to 53.7%, and 0 to 7.7% respectively, among 244 patients. Incidence of PSCI was 21.9%. While visual memory demonstrated a significant improvement (p <  0.05), other cognitive domains showed a fluctuating yet stable pattern across visits (all ps >  0.05). Besides age, baseline IQCODE (attention: -0.218 SD/y, executive function: -0.238 SD/y, visual memory: -0.266 SD/y), and MoCA improvement within 1 year (visuoconstruction: 0.007 SD/y, verbal memory: 0.012 SD/y) were associated with longitudinal cognitive changes. Baseline MoCA (OR = 0.66, 95% CI = [0.59-0.74]), MoCA improvement within 3-6 months (OR = 0.79, 95% CI = [0.71-0.89], and within 1 year (OR = 0.86, 95% CI = [0.76-0.96]) were associated with long-term PSCI, while baseline MoCA (OR = 0.76, 95% CI = [0.61-0.96]) was also associated with incident PSCI.

CONCLUSION

While most domains remained stable across-time, visual memory demonstrated an overall improvement. Short-term cognitive improvement could be an early indicator of long-term cognitive trajectory to identify individuals who may be resilient to PSCI.

Cerebral microinfarcts affect brain structural network topology in cognitively impaired patients

Cerebral microinfarcts (CMIs), a novel cerebrovascular marker, are prevalent in Alzheimer's disease (AD) and associated with cognitive impairment. Nonetheless, the underlying mechanism of how CMIs influence cognition remains uncertain. We hypothesized that cortical-CMIs disrupted structural connectivity in the higher-order cognitive networks, leading to cognitive impairment. We analyzed diffusion-MRI data of 92 AD (26 with cortical-CMIs) and 110 cognitive impairment no dementia patients (CIND, 28 with cortical-CMIs). We compared structural network topology between groups with and without cortical-CMIs in AD/CIND, and tested whether structural connectivity mediated the association between cortical-CMIs and cognition. Cortical-CMIs correlated with impaired structural network topology (i.e. lower efficiency/degree centrality in the executive control/dorsal attention networks in CIND, and lower clustering coefficient in the default mode/dorsal attention networks in AD), which mediated the association of cortical-CMIs with visuoconstruction dysfunction. Our findings provide the first in vivo human evidence that cortical-CMIs impair cognition in elderly via disrupting structural connectivity.

Distinct BOLD variability changes in the default mode and salience networks in Alzheimer's disease spectrum and associations with cognitive decline

Optimal levels of intrinsic Blood-Oxygenation-Level-Dependent (BOLD) signal variability (variability hereafter) are important for normative brain functioning. However, it remains largely unknown how network-specific and frequency-specific variability changes along the Alzheimer's disease (AD) spectrum and relates to cognitive decline. We hypothesized that cognitive impairment was related to distinct BOLD variability alterations in two brain networks with reciprocal relationship, i.e., the AD-specific default mode network (DMN) and the salience network (SN). We examined variability of resting-state fMRI data at two characteristic slow frequency-bands of slow4 (0.027-0.073 Hz) and slow5 (0.01-0.027 Hz) in 96 AD, 98 amnestic mild cognitive impairment (aMCI), and 48 age-matched healthy controls (HC) using two commonly used pre-processing pipelines. Cognition was measured with a neuropsychological assessment battery. Using both global signal regression (GSR) and independent component analysis (ICA), results generally showed a reciprocal DMN-SN variability balance in aMCI (vs. AD and/or HC), although there were distinct frequency-specific variability patterns in association with different pre-processing approaches. Importantly, lower slow4 posterior-DMN variability correlated with poorer baseline cognition/smaller hippocampus and predicted faster cognitive decline in all patients using both GSR and ICA. Altogether, our findings suggest that reciprocal DMN-SN variability balance in aMCI might represent an early signature in neurodegeneration and cognitive decline along the AD spectrum.

Validation of the Total Cerebrovascular Disease Burden Scale in a Community Sample

BACKGROUND

A total cerebrovascular disease (CeVD) burden scale was previously constructed and an inverse association of CeVD burden and cognition was found. However, the generalizability of the CeVD scale has not been examined.

OBJECTIVE

The objective was to validate the previously constructed total CeVD burden scale by establishing its association with cognitive function and dementia diagnosis in a community sample.

METHODS

Eligible participants were assessed on an extensive neuropsychological battery and underwent MRI scans. The total CeVD scale, comprising markers of both small- and large-vessel diseases, was derived according to previously described criteria. Association of total CeVD burden with global and domain-based cognitive performance and dementia diagnostic utility of the scale was established.

RESULTS

A total of 863 participants were included in the analysis. A stepwise association of CeVD burden score with global and domain-specific cognitive function was found. Per score increase on the total CeVD burden scale was associated with 3.6 (95% CI = 2.1-6.4) times higher odds of dementia compared to dementia-free.

DISCUSSION

The total CeVD burden scale is associated with cognition and dementia in a community sample. Longitudinal studies are required to establish the predictive ability of this scale.

Association of Magnetic Resonance Imaging Markers of Cerebrovascular Disease Burden and Cognition

BACKGROUND AND PURPOSE

The present study sought to examine the association between the burden of cerebrovascular disease (CeVD) as assessed by multimodal magnetic resonance imaging and neurocognitive function.

METHODS

Cognitively impaired patients and controls were tested on an extensive neuropsychological battery and underwent multimodal brain magnetic resonance imaging. CeVD markers determined from magnetic resonance imaging included the presence of multiple lacunes, multiple cerebral microbleeds, and moderate or severe white matter hyperintensities as markers for small-vessel disease and cortical stroke and intracranial stenosis as markers for large-vessel disease. A weighted CeVD burden score was constructed, and its association with global and domain-specific cognitive performance was investigated.

RESULTS

A total of 305 cases and 94 controls were included in the analysis. A graded association of CeVD burden with neurocognitive function was found. Moreover, a clear threshold of CeVD burden was associated with severe impairment. White matter hyperintensities was associated with global neurocognitive deficits, whereas microbleeds were associated with domain-specific impairments.

CONCLUSIONS

The weighted CeVD burden score comprising markers of both small- and large-vessel diseases were associated with deficits in both global and domain-specific neurocognitive function. Additional studies are needed to validate the use of this CeVD burden score for the prediction of dementia.