Identifying brain functional alterations in postmenopausal women with cognitive impairment

Convergent and distinct neural structural and functional patterns of mild cognitive impairment: a multimodal meta-analysis

Mild cognitive impairment (MCI) is regarded as a transitional stage between normal aging and Alzheimer's disease. Numerous voxel-based morphometry (VBM) and resting-state fMRI (rs-fMRI) studies have provided strong evidence of abnormalities in the structure and intrinsic function of brain regions in MCI. Studies have recently begun to explore their association but have not employed systematic information in this pursuit. Herein, a multimodal meta-analysis was performed, which included 43 VBM datasets (1,247 patients and 1,352 controls) of gray matter volume (GMV) and 42 rs-fMRI datasets (1,468 patients and 1,605 controls) that combined 3 metrics: amplitude of low-frequency fluctuation, the fractional amplitude of low-frequency fluctuation, and regional homogeneity. Compared to controls, patients with MCI displayed convergent reduced regional GMV and altered intrinsic activity, mainly in the default mode network and salience network. Decreased GMV alone in ventral medial prefrontal cortex and altered intrinsic function alone in bilateral dorsal anterior cingulate/paracingulate gyri, right lingual gyrus, and cerebellum were identified, respectively. This meta-analysis investigated complex patterns of convergent and distinct brain alterations impacting different neural networks in MCI patients, which contributes to a further understanding of the pathophysiology of MCI.

The effect of hormone replacement therapy on cognition and mood

OBJECTIVES

To summarise the available data regarding the effect of hormone replacement therapy (HRT) on cognition and mood in women.

BACKGROUND

Complaints of impaired cognition and mood are common in the peri-menopausal and menopausal period. There is debate as to whether HRT can ameliorate this phenomenon.

DESIGN

A literature search of studies using electronic databases was conducted. Both randomised control trials and observational studies were included.

PATIENTS

Perimenopausal and menopausal women.

RESULTS

Due to the heterogenicity of results it is challenging to draw firm conclusions. The preparations used in many of the studies are older regimes no longer routinely used clinically. The notion of a 'critical window' for HRT is compelling, suggesting HRT has a positive impact on cognition when administered in the peri-menopausal or early postmenopausal period but may have negative effects on cognition in the older, postmenopausal woman. The evidence would seem to suggest importance of hormonal replacement in woman undergoing a surgical menopause, especially when young. It remains unclear for how long they ought to continue HRT though until at least the natural age of the menopause seems reasonable. Evidence for a positive effect of HRT on mood is more convincing, though possibly more efficacious in the younger age group. The effect of HRT on anxiety is less clear.

CONCLUSIONS

Further study, particularly focusing on the more contemporaneous HRT preparations, is warranted before evidence-based conclusions can be drawn.

Altered Frequency-Dependent Brain Activation and White Matter Integrity Associated With Cognition in Characterizing Preclinical Alzheimer's Disease Stages

Background

Subjective cognitive decline (SCD), non-amnestic mild cognitive impairment (naMCI), and amnestic mild cognitive impairment (aMCI) are regarded to be at high risk of converting to Alzheimer's disease (AD). Amplitude of low-frequency fluctuations (ALFF) can reflect functional deterioration while diffusion tensor imaging (DTI) is capable of detecting white matter integrity. Our study aimed to investigate the structural and functional alterations to further reveal convergence and divergence among SCD, naMCI, and aMCI and how these contribute to cognitive deterioration.

Methods

We analyzed ALFF under slow-4 (0.027-0.073 Hz) and slow-5 (0.01-0.027 Hz) bands and white matter fiber integrity among normal controls (CN), SCD, naMCI, and aMCI groups. Correlation analyses were further utilized among paired DTI alteration, ALFF deterioration, and cognitive decline.

Results

For ALFF calculation, ascended ALFF values were detected in the lingual gyrus (LING) and superior frontal gyrus (SFG) within SCD and naMCI patients, respectively. Descended ALFF values were presented mainly in the LING, SFG, middle frontal gyrus, and precuneus in aMCI patients compared to CN, SCD, and naMCI groups. For DTI analyses, white matter alterations were detected within the uncinate fasciculus (UF) in aMCI patients and within the superior longitudinal fasciculus (SLF) in naMCI patients. SCD patients presented alterations in both fasciculi. Correlation analyses revealed that the majority of these structural and functional alterations were associated with complicated cognitive decline. Besides, UF alterations were correlated with ALFF deterioration in the SFG within aMCI patients.

Conclusions

SCD shares structurally and functionally deteriorative characteristics with aMCI and naMCI, and tends to convert to either of them. Furthermore, abnormalities in white matter fibers may be the structural basis of abnormal brain activation in preclinical AD stages. Combined together, it suggests that structural and functional integration may characterize the preclinical AD progression.

Menopause, cognition and dementia - A review

There is increasing evidence that menopausal changes can have an impact on women’s cognition and potentially, the future development of dementia. In particular, the role of reduced levels of estrogen in postmenopausal changes has been linked to an increased risk of developing dementia in observational studies. Not surprisingly, this has led to several clinical trials investigating whether postmenopausal hormone replacement therapy can potentially delay/avoid cognitive changes and subsequently, the onset of dementia. However, the evidence of these trials has been mixed, with some showing positive effects while others show no or even negative effects. In the current review, we investigate this controversy further by reviewing the existing studies and trials in cognition and dementia. Based on the current evidence, we conclude that previous approaches may have used a mixture of women with different genetic risk factors for dementia which might explain these contradicting findings. Therefore, it is recommended that future interventional studies take a more personalised approach towards hormone replacement therapy use in postmenopausal women, by taking into account the women’s genetic status for dementia risk.

Gradual Disturbances of the Amplitude of Low-Frequency Fluctuations (ALFF) and Fractional ALFF in Alzheimer Spectrum

Background: Alzheimer’s disease (AD) is a common neurodegenerative disease in which the brain undergoes alterations for decades before symptoms become obvious. Subjective cognitive decline (SCD) have self-complain of persistent decline in cognitive function especially in memory but perform normally on standard neuropsychological tests. SCD with the presence of AD pathology is the transitional stage 2 of Alzheimer’s continuum, earlier than the prodromal stage, mild cognitive impairment (MCI), which seems to be the best target to research AD. In this study, we aimed to detect the transformational patterns of the intrinsic brain activity as the disease burden got heavy.

Method: In this study, we enrolled 44 SCD, 55 amnestic MCI (aMCI), 47 AD dementia (d-AD) patients and 57 normal controls (NC) in total. A machine learning classification was utilized to detect identification accuracies between groups by using ALFF, fALFF, and fusing ALFF with fALFF features. Then, we measured the amplitude of the low-frequency fluctuation (ALFF) and fractional ALFF (fALFF) levels in three frequency bands (classic: 0.01–0.1 Hz; slow-5: 0.01–0.027 Hz; and slow-4: 0.027–0.073 Hz) and compared alterations in patients with NC.

Results: In the machine learning verification, the identification accuracy of SCD, aMCI, d-AD from NC was higher when fused ALFF and fALFF features (76.44, 81.94, and 91.83%, respectively) than only using ALFF or fALFF features. Several brain regions showed significant differences in ALFF/fALFF within these bands among four groups: brain regions presented decreasing trend of values, including the Cingulum_Mid_R (aal), bilateral inferior cerebellum lobe, bilateral precuneus, and the Cingulum_Ant_R (aal); increasing trend of values were detected in the Hippocampus_L (aal), Frontal_Mid_Orb_R (aal), Frontal_Sup_R (aal) and Paracentral_Lobule_R (aal) as disease progressed. The normalized ALFF/fALFF values of these features were significantly correlated with the neuropsychological test scores.

Conclusion: This study revealed gradual disturbances in intrinsic brain activity as the disease progressed: the normal objective performance in SCD may be dependent on compensation; as disease advanced, the cognitive function gradually impaired and decompensated in aMCI, severer in d-AD. Our results indicated that the ALFF and fALFF may help detect the underlying pathological mechanism in AD continuum.

Clinical Trial Registration:ClinicalTrials.gov, identifier NCT02353884 and NCT02225964.

Impact of sex and reproductive status on memory circuitry structure and function in early midlife using structural covariance analysis

Research on age-related memory alterations traditionally targets individuals aged ≥65 years. However, recent studies emphasize the importance of early aging processes. We therefore aimed to characterize variation in brain gray matter structure in early midlife as a function of sex and menopausal status. Subjects included 94 women (33 premenopausal, 29 perimenopausal, and 32 postmenopausal) and 99 demographically comparable men from the New England Family Study. Subjects were scanned with a high-resolution T1 sequence on a 3 T whole body scanner. Sex and reproductive-dependent structural differences were evaluated using Box's M test and analysis of covariances (ANCOVAs) for gray matter volumes. Brain regions of interest included dorsolateral prefrontal cortex (DLPFC), inferior parietal lobule (iPAR), anterior cingulate cortex (ACC), hippocampus (HIPP), and parahippocampus. While we observed expected significant sex differences in volume of hippocampus with women of all groups having higher volumes than men relative to cerebrum size, we also found significant differences in the covariance matrices of perimenopausal women compared with postmenopausal women. Associations between ACC and HIPP/iPAR/DLPFC were higher in postmenopausal women and correlated with better memory performance. Findings in this study underscore the importance of sex and reproductive status in early midlife for understanding memory function with aging.

Aberrant Cerebral Activity in Early Postmenopausal Women: A Resting-State Functional Magnetic Resonance Imaging Study

Background: Early postmenopausal women frequently suffer from cognitive impairments and emotional disorders, such as lack of attention, poor memory, deficits in executive function and depression. However, the underlying mechanisms of these impairments remain unclear. Method: Forty-three early postmenopausal women and forty-four age-matched premenopausal controls underwent serum sex hormone analysis, neuropsychological testing and resting-state functional magnetic resonance imaging (rs-fMRI). Degree centrality (DC) analysis was performed to confirm the peak points of the functionally abnormal brain areas as the centers of the seeds. Subsequently, the functional connectivity (FC) between these abnormal seeds and other voxels across the whole brain was calculated. Finally, the sex hormone levels, neuroimaging indices and neuropsychological data were combined to detect potential correlations. Results: Compared with the premenopausal controls, the early postmenopausal women exhibited significantly higher serum follicle-stimulating hormone (FSH) levels, more severe climacteric and depressive symptoms, worse sleep quality and more extensive cognitive impairments. Concurrently, the neuroimaging results showed elevated DC values in the left amygdala (AMYG.L), reduced DC values in the left middle occipital gyrus (MOG.L) and right middle occipital gyrus (MOG.R). When we used the AMYG.L as the seed point, FC with the left insula (INS.L), bilateral prefrontal cortex (PFC) and right superior frontal gyrus (SFG.R) was increased; these regions are related to depressive states, poor sleep quality and decreased executive function. When bilateral MOG were used as the seed points, FC with left inferior parietal gyrus (IPG.L), this area closely associated with impaired memory, was decreased. Conclusion: These results illuminated the regional and network-level brain dysfunction in early postmenopausal women, which might provide information on the underlying mechanisms of the different cognitive impairments and emotional alterations observed in this group.

Aberrant spontaneous low-frequency brain activity in amnestic mild cognitive impairment: A meta-analysis of resting-state fMRI studies

Recent resting-state functional magnetic resonance imaging (rs-fMRI) studies have provided strong evidence of abnormal spontaneous brain activity in amnestic mild cognitive impairment (aMCI). However, the conclusions have been inconsistent. A meta-analysis of whole-brain rs-fMRI studies that measured differences in the amplitude of low-frequency fluctuations (ALFF) between aMCI patients and healthy controls was conducted using the Seed-based d Mapping software package. Twelve studies reporting 14 datasets were included in the meta-analysis. Compared to healthy controls, patients with aMCI showed decreased ALFFs in the bilateral precuneus/posterior cingulate cortices, bilateral frontoinsular cortices, left occipitotemporal cortex, and right supramarginal gyrus and increased ALFFs in the right lingual gyrus, left middle occipital gyrus, left hippocampus, and left inferior temporal gyrus. A meta-regression analysis demonstrated that the increased severity of cognitive impairment in aMCI patients was associated with greater decreases in ALFFs in the cuneus/precuneus cortices. Our comprehensive meta-analysis suggests that aMCI is associated with widespread aberrant regional spontaneous brain activity, predominantly involving the default mode, salience, and visual networks, which contributes to understanding its pathophysiology.

Alteration of spontaneous brain activity in COPD patients

Background and objective

Airflow limitation in chronic obstructive pulmonary disease (COPD) results in a decrease in oxygen transport to the brain. The aim of the present study was to explore the alteration of spontaneous brain activity induced by hypoxia in patients with COPD.

Patients and methods

Twenty-five stable patients with COPD and 25 matching healthy volunteers were investigated. Amplitude of low-frequency fluctuation (ALFF) of blood oxygenation level-dependent signal at resting state in the brain was analyzed using functional magnetic resonance imaging.

Results

Whole-brain analysis using functional magnetic resonance imaging revealed significant decreases in ALFF in the bilateral posterior cingulate gyri and right lingual gyrus and an increase in ALFF in the left postcentral gyrus of patients with COPD. After controlling for SaO₂, patients with COPD only showed an increase in ALFF in the left postcentral gyrus. Region of interest analysis showed a decrease in ALFF in the left precentral gyrus and an increase in ALFF in the left caudate nucleus of patients with COPD. In all subjects, ALFF in the bilateral posterior cingulate gyri and right lingual gyrus showed positive correlations with visual reproduction.

Conclusion

We demonstrated abnormal spontaneous brain activity of patients with COPD, which may have a pathophysiologic meaning.