Cardiovascular Risk Factors and Brain Health: Impact on Long-Range Cortical Connections and Cognitive Performance

Non-linear relationship between serum cholesterol levels and cognitive change among older people in the preclinical and prodromal stages of dementia: a retrospective longitudinal study in Taiwan

BACKGROUND

Adverse effects of rigorously lowering low-density lipoprotein cholesterol on cognition have been reported; therefore, we aimed to study the contribution of serum cholesterol in cognitive decline in older people with or without dementia.

METHODS

Cognitive function was assessed by the Cognitive Abilities Screening Instrument (CASI). We investigated associations between serum cholesterol with cognitive decline using multiple regressions controlling for the effects of demographics, vascular risk factors, and treatments.

RESULTS

Most associations between cholesterol and CASI scores could be explained by non-linear and inverted U-shaped relationships (R2 = 0.003-0.006, p < 0.016, Šidákcorrection). The relationships were most evident between changes in cholesterol and CASI scores in older people at the preclinical or prodromal stages of dementia (R2 = 0.02-0.064, p values < 0.016). There were no differences in level of changes in CASI scores between individuals in 1st decile and 10th decile groups of changes in cholesterol (p = 0.266-0.972). However, individuals in the 1st decile of triglyceride changes and with stable and normal cognitive functions showed significant improvement in CASI scores compared to those in the 10th decile (t(202) = 2.275, p values < 0.05).

CONCLUSION

These findings could implicate that rigorously lowering cholesterol may not be suitable for the prevention of cognitive decline among older people, especially among individuals in preclinical or prodromal stages of dementia.

Association between Large Neutral Amino Acids and Brain Integrity in Middle-Aged Adults at Metabolic Risk

This investigation delves into the interplay between large neutral amino acids (LNAA) and metabolic syndrome (MetS) in midlife adults, examining their collective influence on brain structure and cognitive function. While LNAA, such as tryptophan and phenylalanine, are known to bolster cognition in youth, our study hypothesizes a reversal of these benefits in older adults with MetS, potentially signaling premature cognitive aging. Eighty participants between 40-61 years underwent MetS component quantification, LNAA measurement via high-performance liquid chromatography, and brain imaging to evaluate white matter hyperintensity (WMH) volume and medial temporal lobe (MTL) cortical thickness. Our linear regression analysis, adjusting for sex, age, and education, revealed that phenylalanine levels moderated the relationship between MetS and WMH volume (F(6, 69) = 3.134, p < 0.05, R2 = 0.214), suggesting that MetS's cognitive impact may be partly due to phenylalanine catabolism byproducts. However, LNAA metabolites did not significantly modulate the MetS-MTL cortical thickness relationship. The findings suggest that LNAA metabolic dysregulation, marked by elevated levels in the presence of MetS, could correlate with brain structural compromises, particularly in the form of MTL cortical thinning and increased WMH load, detectable in midlife. This nuanced understanding of LNAA's role in cognitive health amid cardiovascular risk factors is pivotal, proposing a potential biomarker for early intervention. Further research is crucial to elucidate the longitudinal influence of LNAA and MetS on brain health, thereby informing strategies to mitigate cognitive decline.

Microvascular Dysfunction as a Possible Link Between Heart Failure and Cognitive Dysfunction

BACKGROUND

Microvascular function in the brain and heart may play an important role in the course of patients with heart failure (HF), but its relationship with ventricular and cognitive function is not well understood. We hypothesized that microvascular function in HF is closely related to both, cardiac and cognitive function.

METHODS

In healthy controls and symptomatic patients with HF (New York Heart Association functional class II or III), we used oxygenation-sensitive magnetic resonance imaging during a standardized breathing maneuver to determine the cerebral oxygenation reserve and the myocardial oxygenation reserve (MORE) as markers for microvascular function. A stepwise multivariable linear regression was performed to determine the variables that best predict changes in cerebral oxygenation reserve and MORE. We also measured cognitive function using the Montreal Cognitive Assessment test.

RESULTS

Twenty patients with HF (age 64.4±8.3 years; 50% female sex), and 21 healthy controls (age 55.0±5.1 years; 62% female sex) were included in the analysis. In patients with HF, cerebral oxygenation reserve and MORE were lower than in healthy controls (MORE, -0.1±3.3 versus 5.0±4.2, cerebral oxygenation reserve: 0.43±0.47 versus 1.21±0.60, respectively) as were Montreal Cognitive Assessment score results (HF, 23.9±3.7; healthy, 27.8±1.5; P=0.002). The Montreal Cognitive Assessment score in patients was correlated with cardiac output (r=0.55, P=0.011) and MORE (r=0.46, P=0.040). In addition to the presence of HF, significant predictors of cerebral and myocardial oxygenation reserve were cardiac output and end-diastolic volume, respectively.

CONCLUSIONS

Our results indicate that heart failure is an independent predictor of coronary and cerebral microvascular dysfunction as defined by a reduced response to a vasodilatory breathing maneuver. This impaired response was associated with reduced cognitive function.

Dynamic network properties of the superior temporal gyrus mediate the impact of brain age gap on chronic aphasia severity

Brain structure deteriorates with aging and predisposes an individual to more severe language impairments (aphasia) after a stroke. However, the underlying mechanisms of this relation are not well understood. Here we use an approach to model brain network properties outside the stroke lesion, network controllability, to investigate relations among individualized structural brain connections, brain age, and aphasia severity in 93 participants with chronic post-stroke aphasia. Controlling for the stroke lesion size, we observe that lower average controllability of the posterior superior temporal gyrus (STG) mediates the relation between advanced brain aging and aphasia severity. Lower controllability of the left posterior STG signifies that activity in the left posterior STG is less likely to yield a response in other brain regions due to the topological properties of the structural brain networks. These results indicate that advanced brain aging among individuals with post-stroke aphasia is associated with disruption of dynamic properties of a critical language-related area, the STG, which contributes to worse aphasic symptoms. Because brain aging is variable among individuals with aphasia, our results provide further insight into the mechanisms underlying the variance in clinical trajectories in post-stroke aphasia.

Mania-related effects on structural brain changes in bipolar disorder - a narrative review of the evidence

Cross-sectional neuroimaging studies show that bipolar disorder is associated with structural brain abnormalities, predominantly observed in prefrontal and temporal cortex, cingulate gyrus, and subcortical regions. However, longitudinal studies are needed to elucidate whether these abnormalities presage disease onset or are consequences of disease processes, and to identify potential contributing factors. Here, we narratively review and summarize longitudinal structural magnetic resonance imaging studies that relate imaging outcomes to manic episodes. First, we conclude that longitudinal brain imaging studies suggest an association of bipolar disorder with aberrant brain changes, including both deviant decreases and increases in morphometric measures. Second, we conclude that manic episodes have been related to accelerated cortical volume and thickness decreases, with the most consistent findings occurring in prefrontal brain areas. Importantly, evidence also suggests that in contrast to healthy controls, who in general show age-related cortical decline, brain metrics remain stable or increase during euthymic periods in bipolar disorder patients, potentially reflecting structural recovering mechanisms. The findings stress the importance of preventing manic episodes. We further propose a model of prefrontal cortical trajectories in relation to the occurrence of manic episodes. Finally, we discuss potential mechanisms at play, remaining limitations, and future directions.

Diabetes, brain health, and treatment gains in post-stroke aphasia

In post-stroke aphasia, language improvements following speech therapy are variable and can only be partially explained by the lesion. Brain tissue integrity beyond the lesion (brain health) may influence language recovery and can be impacted by cardiovascular risk factors, notably diabetes. We examined the impact of diabetes on structural network integrity and language recovery. Seventy-eight participants with chronic post-stroke aphasia underwent six weeks of semantic and phonological language therapy. To quantify structural network integrity, we evaluated the ratio of long-to-short-range white matter fibers within each participant's whole brain connectome, as long-range fibers are more susceptible to vascular injury and have been linked to high level cognitive processing. We found that diabetes moderated the relationship between structural network integrity and naming improvement at 1 month post treatment. For participants without diabetes (n = 59), there was a positive relationship between structural network integrity and naming improvement (t = 2.19, p = 0.032). Among individuals with diabetes (n = 19), there were fewer treatment gains and virtually no association between structural network integrity and naming improvement. Our results indicate that structural network integrity is associated with treatment gains in aphasia for those without diabetes. These results highlight the importance of post-stroke structural white matter architectural integrity in aphasia recovery.

The role of population-level preventive care for brain health in ageing

Over the past several decades, a worldwide demographic transition has led to an increasing number of older adults with chronic neurological conditions. These conditions, which have a profound effect on the cognitive function and physical ability of older adults, also have a long preclinical phase. This feature provides a unique opportunity to implement preventive measures for high-risk groups and the population as a whole, and therefore to reduce the burden of neurological diseases. The concept of brain health has emerged as the overarching theme to define overall brain function independently of underlying pathophysiological processes. We review the concept of brain health from the ageing and preventive care perspectives, discuss the mechanisms underpinning ageing and brain ageing, highlight the interplay of various forces resulting in deviation from brain health towards brain disease, and provide an overview of strategies to promote brain health with a life-course approach.

Small Vessel Disease, a Marker of Brain Health: What the Radiologist Needs to Know

Small vessel disease, a disorder of cerebral microvessels, is an expanding epidemic and a common cause of stroke and dementia. Despite being almost ubiquitous in brain imaging, the clinicoradiologic association of small vessel disease is weak, and the underlying pathogenesis is poorly understood. The STandards for ReportIng Vascular changes on nEuroimaging (STRIVE) criteria have standardized the nomenclature. These include white matter hyperintensities of presumed vascular origin, recent small subcortical infarcts, lacunes of presumed vascular origin, prominent perivascular spaces, cerebral microbleeds, superficial siderosis, cortical microinfarcts, and brain atrophy. Recently, the rigid categories among cognitive impairment, vascular dementia, stroke, and small vessel disease have become outdated, with a greater emphasis on brain health. Conventional and advanced small vessel disease imaging markers allow a comprehensive assessment of global brain heath. In this review, we discuss the pathophysiology of small vessel disease neuroimaging nomenclature by means of the STRIVE criteria, clinical implications, the role of advanced imaging, and future directions.

Impact of polygenic risk for coronary artery disease and cardiovascular medication burden on cognitive impairment in psychotic disorders

BACKGROUND

Cognitive impairment is a core deficit across psychotic disorders, the causes and therapeutics of which remain unclear. Epidemiological observations have suggested associations between cognitive dysfunction in psychotic disorders and cardiovascular risk factors, but an underlying etiology has not been established.

METHODS

Neuropsychological performance using the Brief Assessment of Cognition in Schizophrenia (BACS) was assessed in 616 individuals of European ancestry (403 psychosis, 213 controls). Polygenic risk scores for coronary artery disease (PRSCAD) were quantified for each participant across 13 p-value thresholds (PT 0.5-5e-8). Cardiovascular and psychotropic medications were categorized for association analyses. Each PRSCAD was examined in relation to the BACS and the optimized PT was confirmed with five-fold cross-validation and independent validation. Functional enrichment analyses were used to identify biological mechanisms linked to PRSCAD-cognition associations. Multiple regression analyses examined PRSCAD under the optimal PT and medication burden in relation to the BACS composite and subtest scores.

RESULTS

Higher PRSCAD was associated with lower BACS composite scores (p = 0.001) in the psychosis group, primarily driven by the Verbal Memory subtest (p < 0.001). Genes linked to multiple nervous system related processes and pathways were significantly enriched in PRSCAD. After controlling for PRSCAD, a greater number of cardiovascular medications was also correlated with worse BACS performance in patients with psychotic disorders (p = 0.029).

CONCLUSIONS

Higher PRSCAD and taking more cardiovascular medications were both significantly associated with cognitive impairment in psychosis. These findings indicate that cardiovascular factors may increase the risk for cognitive dysfunction and related functional outcomes among individuals with psychotic disorders.

Language Recovery after Brain Injury: A Structural Network Control Theory Study

Aphasia recovery after stroke depends on the condition of the remaining, extralesional brain network. Network control theory (NCT) provides a unique, quantitative approach to assess the interaction between brain networks. In this longitudinal, large-scale, whole-brain connectome study, we evaluated whether controllability measures of language-related regions are associated with treated aphasia recovery. Using probabilistic tractography and controlling for the effects of structural lesions, we reconstructed whole-brain diffusion tensor imaging (DTI) connectomes from 68 individuals (20 female, 48 male) with chronic poststroke aphasia who completed a three-week language therapy. Applying principles of NCT, we computed regional (1) average and (2) modal controllability, which decode the ability of a region to (1) spread control input through the brain network and (2) to facilitate brain state transitions. We tested the relationship between pretreatment controllability measures of 20 language-related left hemisphere regions and improvements in naming six months after language therapy using multiple linear regressions and a parsimonious elastic net regression model with cross-validation. Regional controllability of the inferior frontal gyrus (IFG) pars opercularis, pars orbitalis, and the anterior insula were associated with treatment outcomes independently of baseline aphasia severity, lesion volume, age, education, and network size. Modal controllability of the IFG pars opercularis was the strongest predictor of treated aphasia recovery with cross-validation and outperformed traditional graph theory, lesion load, and demographic measures. Regional NCT measures can reflect the status of the residual language network and its interaction with the remaining brain network, being able to predict language recovery after aphasia treatment.SIGNIFICANCE STATEMENT Predicting and understanding language recovery after brain injury remains a challenging, albeit a fundamental aspect of human neurology and neuroscience. In this study, we applied network control theory (NCT) to fully harness the concept of brain networks as dynamic systems and to evaluate their interaction. We studied 68 stroke survivors with aphasia who underwent imaging and longitudinal behavioral assessments coupled with language therapy. We found that the controllability of the inferior frontal regional network significantly predicted recovery in language production six months after treatment. Importantly, controllability outperformed traditional demographic, lesion, and graph-theoretical measures. Our findings shed light on the neurobiological basis of human language and can be translated into personalized rehabilitation approaches.

Integrating multiple brain imaging modalities does not boost prediction of subclinical atherosclerosis in midlife adults

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Brain measures from MRI do not improve Framingham Risk Score prediction of CA-IMT.

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Prediction stacking is a flexible approach to determine added predictive utility.

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Multimodal stacking can be applied to individual difference factors.

Background

Human neuroimaging evidence suggests that cardiovascular disease (CVD) risk may relate to functional and structural features of the brain. The present study tested whether combining functional and structural (multimodal) brain measures, derived from magnetic resonance imaging (MRI), would yield a multivariate brain biomarker that reliably predicts a subclinical marker of CVD risk, carotid-artery intima-media thickness (CA-IMT).

Methods

Neuroimaging, cardiovascular, and demographic data were assessed in 324 midlife and otherwise healthy adults who were free of (a) clinical CVD and (b) use of medications for chronic illnesses (aged 30–51 years, 49% female). We implemented a prediction stacking algorithm that combined multimodal brain imaging measures and Framingham Risk Scores (FRS) to predict CA-IMT. We included imaging measures that could be easily obtained in clinical settings: resting state functional connectivity and structural morphology measures from T1-weighted images.

Results

Our models reliably predicted CA-IMT using FRS, as well as for several individual MRI measures; however, none of the individual MRI measures outperformed FRS. Moreover, stacking functional and structural brain measures with FRS did not boost prediction accuracy above that of FRS alone.

Conclusions

Combining multimodal functional and structural brain measures through a stacking algorithm does not appear to yield a reliable brain biomarker of subclinical CVD, as reflected by CA-IMT.

High b-value diffusion tractography: Abnormal axonal network organization associated with medication-refractory epilepsy

Diffusion magnetic resonance imaging (dMRI) tractography has played a critical role in characterizing patterns of aberrant brain network reorganization among patients with epilepsy. However, the accuracy of dMRI tractography is hampered by the complex biophysical properties of white matter tissue. High b-value diffusion imaging overcomes this limitation by better isolating axonal pathways. In this study, we introduce tractography derived from fiber ball imaging (FBI), a high b-value approach which excludes non-axonal signals, to identify atypical neuronal networks in patients with epilepsy. Specifically, we compared network properties obtained from multiple diffusion tractography approaches (diffusion tensor imaging, diffusion kurtosis imaging, FBI) in order to assess the pathophysiological relevance of network rearrangement in medication-responsive vs. medication-refractory adults with focal epilepsy. We show that drug-resistant epilepsy is associated with increased global network segregation detected by FBI-based tractography. We propose exploring FBI as a clinically feasible alternative to quantify topological changes that could be used to track disease progression and inform on clinical outcomes.

Association between metabolic syndrome and resting-state functional brain connectivity

The objective of this study is to examine whether metabolic syndrome (MetS), the clustering of 3 or more cardiovascular risk factors, disrupts the resting-state functional connectivity (FC) of the large-scale cortical brain networks. Resting-state functional magnetic resonance imaging data were collected from seventy-eight middle-aged and older adults living with and without MetS (27 MetS; 51 non-MetS). FC maps were derived from the time series of intrinsic activity in the large-scale brain networks by correlating the spatially averaged time series with all brain voxels using a whole-brain seed-based FC approach. Participants with MetS showed hyperconnectivity across the core brain regions with evidence of loss of modularity when compared with non-MetS individuals. Furthermore, patterns of higher between-network MetS-related effects were observed across most of the seed regions in both right and left hemispheres. These findings indicate that MetS is associated with altered intrinsic communication across core neural networks and disrupted between-network connections across the brain due to the co-occurring vascular risk factors in MetS.

The association between cardiovascular risk burden and cognitive function amongst the old: a 9-year longitudinal cohort study

BACKGROUND AND PURPOSE

Cardiovascular risk burden in midlife has been linked to cognitive decline in later life, but whether this association still exists in older cohorts is unclear.

METHODS

The association between the cardiovascular risk score and cognitive function was investigated using 9-year follow-up data. The risk score algorithms were from the Chinese guidelines on the prevention and treatment of dyslipidemia in adults (2016 revised), which were assessed at baseline and categorized into tertiles (low, middle and high). Full intelligence quotient (FIQ), verbal intelligence quotient (VIQ) and performance intelligence quotient (PIQ) were assessed at follow-ups with the Wechsler Adult Intelligence Scale-Chinese, revised (WAIS-RC). Data were analyzed using the linear mixed-effects model.

RESULTS

A total of 924 participants (mean age 78.06 ± 7.58 years) were included in our study. In all participants, the risk score ranged from 0.02 to 0.55 (mean score 0.16 ± 0.08). Compared with the low tertile, a higher risk score was associated with lower FIQ (β -0.094, 95% confidence interval [CI] -0.181, -0.007) and VIQ (β -0.100; 95% CI -0.192, -0.007) at the follow-up. There is a more significant association between higher risk score and lower FIQ amongst females (β -0.263; 95% CI -0.462, -0.065) and VIQ (β -0.268; 95% CI -0.478, -0.057).

CONCLUSIONS

A higher cardiovascular risk score was associated with lower FIQ and VIQ. Higher cardiovascular risk burden increased the risk of cognition impairment and accelerated its progression over time. This study has implications for early detection of cognition impairment.

Ten things to know about ten imaging studies: A preventive cardiology perspective ("ASPC top ten imaging")

Knowing the patient's current cardiovascular disease (CVD) status, as well as the patient's current and future CVD risk, helps the clinician make more informed patient-centered management recommendations towards the goal of preventing future CVD events. Imaging tests that can assist the clinician with the diagnosis and prognosis of CVD include imaging studies of the heart and vascular system, as well as imaging studies of other body organs applicable to CVD risk. The American Society for Preventive Cardiology (ASPC) has published "Ten Things to Know About Ten Cardiovascular Disease Risk Factors." Similarly, this "ASPC Top Ten Imaging" summarizes ten things to know about ten imaging studies related to assessing CVD and CVD risk, listed in tabular form. The ten imaging studies herein include: (1) coronary artery calcium imaging (CAC), (2) coronary computed tomography angiography (CCTA), (3) cardiac ultrasound (echocardiography), (4) nuclear myocardial perfusion imaging (MPI), (5) cardiac magnetic resonance (CMR), (6) cardiac catheterization [with or without intravascular ultrasound (IVUS) or coronary optical coherence tomography (OCT)], (7) dual x-ray absorptiometry (DXA) body composition, (8) hepatic imaging [ultrasound of liver, vibration-controlled transient elastography (VCTE), CT, MRI proton density fat fraction (PDFF), magnetic resonance spectroscopy (MRS)], (9) peripheral artery / endothelial function imaging (e.g., carotid ultrasound, peripheral doppler imaging, ultrasound flow-mediated dilation, other tests of endothelial function and peripheral vascular imaging) and (10) images of other body organs applicable to preventive cardiology (brain, kidney, ovary). Many cardiologists perform cardiovascular-related imaging. Many non-cardiologists perform applicable non-cardiovascular imaging. Cardiologists and non-cardiologists alike may benefit from a working knowledge of imaging studies applicable to the diagnosis and prognosis of CVD and CVD risk - both important in preventive cardiology.

Cardiovascular Risk Factors and Brain Health: Impact on Long-Range Cortical Connections and Cognitive Performance

Background Cardiovascular risk factor burden in the absence of clinical or radiological "events" is associated with mild cognitive impairment. Magnetic resonance imaging techniques exploring the integrity of neuronal fiber connectivity within white matter networks supporting cognitive processing could be used to measure the impact of cardiovascular disease on brain health and be used beyond bedside neuropsychological tests to detect subclinical changes and select or stratify participants for entry into clinical trials. Methods and Results We assessed the relationship between verbal IQ and brain network integrity and the effect of cardiovascular risk factors on network integrity by constructing whole-brain structural connectomes from magnetic resonance imaging diffusion images (N=60) from people with various degrees of cardiovascular risk factor burden. We measured axonal integrity by calculating network density and determined the effect of fiber loss on network topology and efficiency, using graph theory. Multivariate analyses were used to evaluate the relationship between cardiovascular risk factor burden, physical activity, age, education, white matter integrity, and verbal IQ . Reduced network density, resulting from a disproportionate loss of long-range white matter fibers, was associated with white matter network fragmentation ( r=-0.52, P<10^-4), lower global efficiency ( r=0.91, P<10^-20), and decreased verbal IQ (adjusted R²=0.23, P<10^-4). Conclusions Cardiovascular risk factors may mediate negative effects on brain health via loss of energy-dependent long-range white matter fibers, which in turn leads to disruption of the topological organization of the white matter networks, lowered efficiency, and reduced cognitive function.