Vascular Contributions to Brain Health: Cross-Cutting Themes

Clinical Predictors of Postmortem Amyloid and Nonamyloid Cerebral Small Vessel Disease in Middle-Aged to Older Adults

Background and Objectives

Sporadic cerebral small vessel disease (CSVD) is a class of important pathologic processes known to affect the aging brain and to contribute to cognitive impairment. We aimed to identify clinical risk factors associated with postmortem CSVD in middle-aged to older adults.

Methods

We developed and tested risk models for their predictive accuracy of a pathologic diagnosis of nonamyloid CSVD and cerebral amyloid angiopathy (CAA) in a retrospective sample of 160 autopsied cases from the Edinburgh Brain Bank. Individuals aged 40 years and older covering the spectrum of healthy aging and common forms of dementia (i.e., highly-prevalent etiologies such as Alzheimer disease (AD), vascular cognitive impairment (VCI), and mixed dementia) were included. We performed binomial logistic regression models using sample splitting and cross-validation methods. Demographics, lifestyle habits, traditional vascular risk factors, chronic medical conditions, APOE4, and cognitive status were assessed as potential predictors.

Results

Forty percent of our sample had a clinical diagnosis of dementia (AD = 33, VCI = 26 and mixed = 5) while others were cognitively healthy (n = 96). The mean age at death was 73.8 (SD 14.1) years, and 40% were female. The presence of none-to-mild vs moderate-to-severe nonamyloid CSVD was predicted by our model with good accuracy (area under the curve [AUC] = 0.84, sensitivity [SEN] = 72%, specificity [SPE] = 95%), with the most significant clinical predictors being age, history of cerebrovascular events, and cognitive impairment. The presence of CAA pathology was also predicted with high accuracy (AUC = 0.86, SEN = 93%, SPE = 79%). Significant predictors included alcohol intake, history of cerebrovascular events, and cognitive impairment. In a subset of atypical dementias (n = 24), our models provided poor predictive performance for both nonamyloid CSVD (AUC = 0.50) and CAA (AUC = 0.43).

Discussion

CSVD pathology can be predicted with high accuracy based on clinical factors in patients within the spectrum of AD, VCI, and normal aging. Whether this prediction can be enhanced by the addition of fluid and neuroimaging biomarkers warrants additional study. Improving our understanding of clinical determinants of vascular brain health may lead to novel strategies in the prevention and treatment of vascular etiologies contributing to cognitive decline.

Classification of Evidence

This study provides Class II evidence that selected clinical factors accurately distinguish between middle-aged to older adults with and without cerebrovascular small vessel disease (amyloid and nonamyloid) pathology.

Association between Life's Essential 8 and cognitive function: insights from NHANES 2011-2014

Introduction

Life's Essential 8 (LE8) is prompted by the American Heart Association (AHA) to assess cardiovascular health. The association between LE8 and cognitive function in America is unknown. Our study was to investigate the association of LE8 with cognitive function in general adults.

Materials and methods

A total of 2,301 participants were enrolled in the National Health and Nutrition Examination Surveys (NHANES). LE8 scores (range 0-100) were obtained from measurements based on American Heart Association definitions, divided into health behavior and health factor scores. Cognitive function was assessed by three tests including the Consortium to Establish a Registry for Alzheimer's Disease (CERAD), Animal fluency test (AFT), and Digit Symbol Substitution test (DSST). The multivariable linear regression analysis explored the associations between LE8 and cognitive function. Smooth curve fitting was explored using restricted cubic splines. The inflection point was determined by the two-piecewise linear regression.

Results

In the multivariable linear regression model with full adjustment for confounding variables, AFT scores were 1.2 points higher in participants with LE8 scores >80 than in those with LE8 scores <50 (high LE8 score group: β = 1.20, 95% CI 0.37, 2.03), and 3.32 points higher in DSST (high LE8 score group: β = 3.32, 95% CI 1.24, 5.39). Although high LE8 scores show a Negative association with high CERAD, we found a significant association between higher LE8 scores and higher CERAD when LE8 scores were higher than 82.5 (β = 0.21 95%CI 0.04, 0.39, p-value = 0.0179).

Conclusion

Our study highlighted a positive association between Life's Essential 8 and cognitive function in older adults.

Associations between vascular health, brain stiffness and global cognitive function

Vascular brain injury results in loss of structural and functional connectivity and leads to cognitive impairment. Its various manifestations, including microinfarcts, microhaemorrhages and white matter hyperintensities, result in microstructural tissue integrity loss and secondary neurodegeneration. Among these, tissue microstructural alteration is a relatively early event compared with atrophy along the aging and neurodegeneration continuum. Understanding its association with cognition may provide the opportunity to further elucidate the relationship between vascular health and clinical outcomes. Magnetic resonance elastography offers a non-invasive approach to evaluate tissue mechanical properties, providing a window into the microstructural integrity of the brain. This retrospective study evaluated brain stiffness as a potential biomarker for vascular brain injury and its role in mediating the impact of vascular dysfunction on cognitive impairment. Seventy-five participants from the Mayo Clinic Study of Aging underwent brain imaging using a 3T MR imager with a spin-echo echo-planar imaging sequence for magnetic resonance elastography and T1- and T2-weighted pulse sequences. This study evaluated the effects of vascular biomarkers (white matter hyperintensities and cardiometabolic condition score) on brain stiffness using voxelwise analysis. Partial correlation analysis explored associations between brain stiffness, white matter hyperintensities, cardiometabolic condition and global cognition. Mediation analysis determined the role of stiffness in mediating the relationship between vascular biomarkers and cognitive performance. Statistical significance was set at P-values < 0.05. Diagnostic accuracy of magnetic resonance elastography stiffness for white matter hyperintensities and cardiometabolic condition was evaluated using receiver operator characteristic curves. Voxelwise linear regression analysis indicated white matter hyperintensities negatively correlate with brain stiffness, specifically in periventricular regions with high white matter hyperintensity levels. A negative association between cardiovascular risk factors and stiffness was also observed across the brain. No significant patterns of stiffness changes were associated with amyloid load. Global stiffness (µ) negatively correlated with both white matter hyperintensities and cardiometabolic condition when all other covariables including amyloid load were controlled. The positive correlation between white matter hyperintensities and cardiometabolic condition weakened and became statistically insignificant when controlling for other covariables. Brain stiffness and global cognition were positively correlated, maintaining statistical significance after adjusting for all covariables. These findings suggest mechanical alterations are associated with cognitive dysfunction and vascular brain injury. Brain stiffness significantly mediated the indirect effects of white matter hyperintensities and cardiometabolic condition on global cognition. Local cerebrovascular diseases (assessed by white matter hyperintensities) and systemic vascular risk factors (assessed by cardiometabolic condition) impact brain stiffness with spatially and statistically distinct effects. Global brain stiffness is a significant mediator between vascular disease measures and cognitive function, highlighting the value of magnetic resonance elastography-based mechanical assessments in understanding this relationship.

Scheltens ratings, clinical white matter hyperintensities and executive: Functioning in the Cache County Memory Study

OBJECTIVE

Examine the association between neuropsychologically assessed executive function and clinically identifiable white matter burden from magnetic resonance imaging, using a visual rating system (Scheltens Rating System) applied to the Cache County Memory Study (CCMS) archival database.

METHOD

We used the Scheltens Ratings Scale to quantify white matter lesion burden in the CCMS sample and used this metric as a predictor of executive function. The sample included 60 individuals with dementia and 13 healthy controls.

RESULTS

Higher Scheltens ratings were associated with poorer task performance on an Executive Function composite score of common neuropsychological tests. This association held true for both controls and dementing cases.

CONCLUSIONS

The current findings support extensive prior literature demonstrating the association between brain vascular health determined by white matter burden and clinical outcomes based on neuropsychological assessment of cognitive performance.

[Cerebral Small Vessel Disease: Advances in Understanding its Pathophysiology]

Sporadic cerebral small vessel disease determines age- and vascular-risk-factor-related processes of the small brain vasculature. The underlying pathology develops in a stage-dependent manner - probably over decades - often already starting in midlife. Endothelial and pericyte activation precedes blood-brain barrier leaks, extracellular matrix remodeling and neuroinflammation, which ultimately result in bleeds, synaptic and neural dysfunction. Hemodynamic compromise of the small vessel walls promotes perivascular drainage failure and accumulation of neurotoxic waste products in the brain. Clinical diagnosis is mainly based on magnetic resonance imaging according to the Standards for Reporting Vascular Changes on Neuroimaging 2. Cerebral amyloid angiopathy is particularly stratified according to the Boston v2.0 criteria. Small vessel disease of the brain could be clinically silent, or manifested through a heterogeneous spectrum of diseases, where cognitive decline and stroke-related symptoms are the most common ones. Prevention and therapy are centered around vascular risk factor control, physically and cognitively enriched life style and, presumably, maintenance of a good sleep quality, which promotes sufficient perivascular drainage. Prevention of ischemic stroke through anticoagulation that carries at the same time an increased risk for large brain hemorrhages - particularly in the presence of disseminated cortical superficial siderosis - remains one of the main challenges. The cerebral small vessel disease field is rapidly evolving, focusing on the establishment of early disease stage imaging and biofluid biomarkers of neurovascular unit remodeling and the compromise of perivascular drainage. New prevention and therapy strategies will correspondingly center around the dedicated targeting of, e. g., cellular small vessel wall and perivascular tissue structures. Growing knowledge about brain microvasculature bridging neuroimmunological, neurovascular and neurodegenerative fields might lead to a rethink about apparently separate disease entities and the development of overarching concepts for a common line of prevention and treatment for several diseases.

Brain Vascular Health in ALS Is Mediated through Motor Cortex Microvascular Integrity

Brain vascular health appears to be critical for preventing the development of amyotrophic lateral sclerosis (ALS) and slowing its progression. ALS patients often demonstrate cardiovascular risk factors and commonly suffer from cerebrovascular disease, with evidence of pathological alterations in their small cerebral blood vessels. Impaired vascular brain health has detrimental effects on motor neurons: vascular endothelial growth factor levels are lowered in ALS, which can compromise endothelial cell formation and the integrity of the blood-brain barrier. Increased turnover of neurovascular unit cells precedes their senescence, which, together with pericyte alterations, further fosters the failure of toxic metabolite removal. We here provide a comprehensive overview of the pathogenesis of impaired brain vascular health in ALS and how novel magnetic resonance imaging techniques can aid its detection. In particular, we discuss vascular patterns of blood supply to the motor cortex with the number of branches from the anterior and middle cerebral arteries acting as a novel marker of resistance and resilience against downstream effects of vascular risk and events in ALS. We outline how certain interventions adapted to patient needs and capabilities have the potential to mechanistically target the brain microvasculature towards favorable motor cortex blood supply patterns. Through this strategy, we aim to guide novel approaches to ALS management and a better understanding of ALS pathophysiology.

Brain microvascular disease and functional network connectivity-a call for a stage-based approach

This scientific commentary refers to 'Functional connectivity in older adults-the effect of cerebral small vessel disease' by Drenth et al. (https://doi.org/10.1093/braincomms/fcad126).

Systemic Immune-Inflammation Index is Associated with Cerebral Small Vessel Disease Burden and Cognitive Impairment

OBJECTIVE

This study sought to explore the associations of the systemic immune-inflammation index (SII) with total cerebral small vessel disease (CSVD) burden and cognitive impairment.

METHODS

We enrolled 201 patients in the retrospective study with complete clinical and laboratory data. The SII was calculated as platelet count × neutrophil count/lymphocyte count. Cognitive function was evaluated by the Mini-Mental State Examination (MMSE). Total CSVD burden was assessed based on magnetic resonance imaging. We performed logistic regression models, Spearman correlation, and mediation analysis to evaluate the associations of SII with CSVD burden and cognitive impairment.

RESULTS

After adjustment for confounding factors in the multivariate binary logistic regression model, elevated SII (odds ratio [OR], 3.263; 95% confidence interval [CI], 1.577-6.752; P = 0.001) or severe CSVD burden (OR, 2.794; 95% CI, 1.342-5.817; P = 0.006) was significantly associated with the risk of cognitive impairment. Correlation analyses revealed that SII levels were negatively associated with MMSE scores (rs = -0.391, P < 0.001), and positively associated with the total CSVD burden score (rs = 0.361, P < 0.001). Moreover, SII was significantly related to the severity of the CSVD burden (OR, 2.674; 95% CI, 1.359-5.263; P = 0.004). The multivariable-adjusted odds ratios (95% CI) in highest tertile versus lowest tertile of SII were 8.947 (3.315-24.145) for cognitive impairment and 4.945 (2.063-11.854) for severe CSVD burden, respectively. The effect of higher SII on cognitive impairment development was partly mediated by severe CSVD burden.

CONCLUSION

Elevated SII is associated with severe CSVD burden and cognitive impairment. The mediating role of severe CSVD burden suggests that higher SII may contribute to cognitive impairment through aggravating CSVD burden.