Comprehensive assessment of sleep duration, insomnia, and brain structure within the UK Biobank cohort

The association between insomnia and cognitive decline: A scoping review

OBJECTIVE

This study aimed to investigate the association between insomnia and cognitive decline to provide insights for clinical interventions and future research.

METHODS

The PubMed, Embase, Web of Science, Scopus, Cochrane Library, and ProQuest databases were systematically searched to identify studies on the association between insomnia and cognitive decline published within the last decade. The quality of the included studies was evaluated, followed by data extraction and summary analysis.

RESULTS

A total of 36 studies were included in the review. Both subjective and objective measures were utilized across 12 indices to assess sleep status, while cognitive function was evaluated using 5 scales and 34 tests. The results revealed a significantly increased risk of cognitive decline or Alzheimer's disease among patients with insomnia, alongside notable impairments in attention, memory, visuospatial abilities, executive function, and verbal memory. Comprehensive assessments of cognitive domains were more sensitive in detecting group differences compared to assessments of specific cognitive sub-functions. Furthermore, MRI analyses showed reduced gray matter volumes in regions such as the prefrontal cortex, cingulate gyrus, temporal lobe, and hippocampus, together with reduced integrity of the white matter in patients with insomnia.

CONCLUSIONS

The findings indicate a potentially bidirectional relationship between insomnia and cognitive decline, suggesting that each may influence and exacerbate the other. Insomnia may increase the risk of cognitive decline and appears to be associated with reduced gray matter volume and compromised white matter integrity in the brain, which could potentially lead to declines in attention, memory, visuospatial abilities, executive function, and verbal memory. Conversely, cognitive decline may contribute to the onset of insomnia, further deteriorating sleep quality. However, further research is necessary to fully comprehend this intricate relationship.

Healthy Lifestyle, Metabolic Signature, and Risk of Cardiovascular Diseases: A Population-Based Study

BACKGROUND

Although healthy lifestyle has been linked with a reduced risk of cardiovascular diseases (CVDs), the potential metabolic mechanism underlying this association remains unknown.

METHODS

We included 161,018 CVD-free participants from the UK Biobank. Elastic net regression was utilized to generate a healthy lifestyle-related metabolic signature. The Cox proportional hazards model was applied to investigate associations of lifestyle-related metabolic signature with incident CVDs, and mediation analysis was conducted to evaluate the potential mediating role of metabolic profile on the healthy lifestyle-CVD association. Mendelian randomization (MR) analysis was conducted to detect the causality.

RESULTS

During 13 years of follow-up, 17,030 participants developed incident CVDs. A healthy lifestyle-related metabolic signature comprising 123 metabolites was established, and it was inversely associated with CVDs. The hazard ratio (HR) was 0.83 (95% confidence interval [CI]: 0.81, 0.84) for CVD, 0.83 (95% CI: 0.81, 0.84) for ischemic heart disease (IHD), 0.86 (95% CI: 0.83, 0.90) for stroke, 0.86 (95% CI: 0.82, 0.89) for myocardial infarction (MI), and 0.75 (95% CI: 0.72, 0.77) for heart failure (HF) per standard deviation increase in the metabolic signature. The metabolic signature accounted for 20% of the association between healthy lifestyle score and CVD. Moreover, MR showed a potential causal association between the metabolic signature and stroke.

CONCLUSIONS

Our study revealed a potential link between a healthy lifestyle, metabolic signatures, and CVD. This connection suggests that identifying an individual's metabolic status and implementing lifestyle modifications may provide novel insights into the prevention of CVD.

The therapeutic potential of Ziziphi Spinosae Semen and Polygalae Radix in insomnia management: Insights from gut microbiota and serum metabolomics techniques

ETHNOPHARMACOLOGICAL RELEVANCE

Ziziphi Spinosae Semen and Polygalae Radix (ZSS-PR) constitute a traditional Chinese herbal combination with notable applications in clinical and experimental settings due to their evident sedative and calming effects. Aligned with traditional Chinese medicine principles, Ziziphi Spinosae Semen supports cardiovascular health, nourishes the liver, and induces mental tranquillity. Simultaneously, Polygalae Radix elicits calming effects, fosters clear thinking, and reinstates proper coordination between the heart and kidneys. ZSS-PR is commonly employed as a therapeutic intervention for various insomnia types, demonstrating distinct clinical efficacy. Our previous study findings provide evidence that ZSS-PR administration significantly reduces sleep onset latency, increases overall sleep duration, and improves abnormal neurotransmitter levels in a murine insomnia model.

AIM OF STUDY

This investigation aimed to scrutinize the intrinsic regulatory mechanism of ZSS-PR in managing insomnia using gut microbiota and serum metabolomics techniques.

MATERIALS AND METHODS

Mice were given DL-4-Chlorophenylalanine to induce insomnia and then treated with ZSS-PR. The open-field test assessed the animals' spontaneous activity. Concentrations of neurotransmitters, endocrine hormones, and cytokines in the duodenum were measured using enzyme linked immunosorbent assay, and brain histopathology was evaluated with H&E staining. The impact of ZSS-PR on the metabolic profile was examined by liquid chromatography couped to high resolution mass spectrometry, and 16S rDNA sequencing was used to study the influence of ZSS-PR on the gut microbiota. Additionally, the content of short-chain fatty acids (SCFAs) was analyzed by GC-MS. Finally, correlation analysis investigated relationships between biochemical markers, metabolites, SCFAs, and gut microbiota.

RESULTS

ZSS-PR treatment significantly increased movement time and distance in mice with insomnia and improved pathological impairments in the cerebral cortex and hippocampus. It also restored abnormal levels of biochemical markers in the gut of insomnia-afflicted mice, including 5-hydroxytryptamine, dopamine, gastrin, melatonin, tumour necrosis factor-α, and interleukin-1β. Metabolomics findings showed that ZSS-PR had a significant restorative effect on 15 endogenous metabolites in mice with insomnia. Furthermore, ZSS-PR primarily influenced five metabolic pathways, such as phenylalanine, tyrosine, and tryptophan biosynthesis, glutamine, and glutamate metabolism. Additionally, gut microbiota analysis revealed notable alterations in both diversity and microbial composition after ZSS-PR treatment. These changes were primarily attributed to the relative abundances of microbiota, including Firmicutes, Bacteroidota, Fusobacteriota, Muribaculaceae_unclassified, and Ligilactobacillus. The results of SCFAs analysis demonstrated that ZSS-PR effectively restored abnormal levels of acetic acid, propionic acid, isobutyric acid, butyric acid, isovaleric acid, and valeric acid in insomniac mice. Subsequent correlation analysis revealed that microbiota show obvious correlations with both biochemical markers and metabolites.

CONCLUSIONS

The results provide compelling evidence that ZSS-PR effectively mitigates abnormal activity, reduces cerebral pathological changes, and restores abnormal levels of neurotransmitters, endocrine hormones, and cytokines in mice with insomnia. The underlying mechanism is intricately linked to the modulation of gut microbiota and endogenous metabolic pathways.

Poor sleep and decreased cortical thickness in veterans with mild traumatic brain injury and post-traumatic stress disorder

BACKGROUND

Poor sleep quality has been associated with changes in brain volume among veterans, particularly those who have experienced mild traumatic brain injury (mTBI) and post-traumatic stress disorder (PTSD). This study sought to investigate (1) whether poor sleep quality is associated with decreased cortical thickness in Iraq and Afghanistan war veterans, and (2) whether these associations differ topographically depending on the presence or absence of mTBI and PTSD.

METHODS

A sample of 440 post-9/11 era U.S. veterans enrolled in the Translational Research Center for Traumatic Brain Injury and Stress Disorders study at VA Boston, MA from 2010 to 2022 was included in the study. We examined the relationship between sleep quality, as measured by the Pittsburgh Sleep Quality Index (PSQI), and cortical thickness in veterans with mTBI (n = 57), PTSD (n = 110), comorbid mTBI and PTSD (n = 129), and neither PTSD nor mTBI (n = 144). To determine the topographical relationship between subjective sleep quality and cortical thickness in each diagnostic group, we employed a General Linear Model (GLM) at each vertex on the cortical mantle. The extent of topographical overlap between the resulting statistical maps was assessed using Dice coefficients.

RESULTS

There were no significant associations between PSQI and cortical thickness in the group without PTSD or mTBI (n = 144) or in the PTSD-only group (n = 110). In the mTBI-only group (n = 57), lower sleep quality was significantly associated with reduced thickness bilaterally in frontal, cingulate, and precuneus regions, as well as in the right parietal and temporal regions (β = -0.0137, P < 0.0005). In the comorbid mTBI and PTSD group (n = 129), significant associations were observed bilaterally in frontal, precentral, and precuneus regions, in the left cingulate and the right parietal regions (β = -0.0094, P < 0.0005). Interaction analysis revealed that there was a stronger relationship between poor sleep quality and decreased cortical thickness in individuals with mTBI (n = 186) compared to those without mTBI (n = 254) specifically in the frontal and cingulate regions (β = -0.0077, P < 0.0005).

CONCLUSIONS

This study demonstrates a significant relationship between poor sleep quality and lower cortical thickness primarily within frontal regions among individuals with both isolated mTBI or comorbid diagnoses of mTBI and PTSD. Thus, if directionality is established in longitudinal and interventional studies, it may be crucial to consider addressing sleep in the treatment of veterans who have sustained mTBI.

Association of past and current sleep duration with structural brain differences: A large population-based study from the UK Biobank

OBJECTIVE

This study aimed to examine the association between past/current sleep duration and macro-/micro-structural brain outcomes and explore whether hypertension or social activity plays a role in such association.

METHODS

Within the UK Biobank, 40 436 dementia-free participants (age 40-70 years) underwent a baseline assessment followed by a brain magnetic resonance imaging (MRI) scan 9 years later. Past (baseline) and current (MRI scans) sleep duration (hours/day) were recorded and classified as short (≤5), intermediate (6-8), and long (≥9). Brain structural volumes and diffusion markers were assessed by MRI scans.

RESULTS

Compared with past intermediate sleep, past short sleep was related to smaller cortex volumes (standardized β [95 % CI]: -0.04 [-0.07, -0.02]) and lower regional fractional anisotropy (FA) (-0.08 [-0.13, -0.03]), while past long sleep was related to smaller regional subcortical volumes (standardized β: -0.04 to -0.07 for thalamus, accumbens, and hippocampus). Compared to current intermediate sleep, current short sleep was associated with smaller cortex volumes (-0.03 [-0.05, -0.01]), greater white matter hyperintensities (WMH) volumes (0.04 [0.01, 0.08]), and lower regional FA (-0.07 [-0.11, -0.02]). However, current long sleep was related to smaller total brain (-0.03 [-0.05, -0.02]), grey matter (-0.05 [-0.07, -0.03]), cortex (-0.05 [-0.07, -0.03]), regional subcortical volumes [standardized β: -0.05 to -0.09 for putamen, thalamus, hippocampus, and accumbens]), greater WMH volumes (0.06 [0.03, 0.09]), as well as lower regional FA (-0.05 [-0.09, -0.02]). The association between current long sleep duration and poor brain health was stronger among people with hypertension or low frequency of social activity (all Pinteraction <0.05).

CONCLUSIONS

Both past and current short/long sleep are associated with smaller brain volume and poorer white matter health in the brain, especially in individuals with hypertension and low frequency of social activity. Our findings highlight the need to maintain 6-8 h' sleep duration for healthy brain aging.

The subcortical basis of subjective sleep quality

Study objectives

To assess the association between self-reported sleep quality and cortical and subcortical local morphometry.

Methods

Sleep and neuroanatomical data from the full release of the young adult Human Connectome Project dataset were analyzed. Sleep quality was operationalized with the Pittsburgh Sleep Quality Index (PSQI). Local cortical and subcortical morphometry was measured with subject-specific segmentations resulting in voxelwise thickness measurements for cortex and relative (i.e., cross-sectional) local atrophy measurements for subcortical regions.

Results

Relative atrophy across several subcortical regions, including bilateral pallidum, striatum, and thalamus, was negatively associated with both global PSQI score and sub-components of the index related to sleep duration, efficiency, and quality. Conversely, we found no association between cortical morphometric measurements and self-reported sleep quality.

Conclusions

This work shows that subcortical regions such as the bilateral pallidum, thalamus, and striatum, might be interventional targets to ameliorate self-reported sleep quality.

Chronotype and subjective sleep quality predict white matter integrity in young people with emerging mental disorders

Protecting brain health is a goal of early intervention. We explored whether sleep quality or chronotype could predict white matter (WM) integrity in emerging mental disorders. Young people (N = 364) accessing early-intervention clinics underwent assessments for chronotype, subjective sleep quality, and diffusion tensor imaging. Using machine learning, we examined whether chronotype or sleep quality (alongside diagnostic and demographic factors) could predict four measures of WM integrity: fractional anisotropy (FA), and radial, axial, and mean diffusivities (RD, AD and MD). We prioritised tracts that showed a univariate association with sleep quality or chronotype and considered predictors identified by ≥80% of machine learning (ML) models as 'important'. The most important predictors of WM integrity were demographics (age, sex and education) and diagnosis (depressive and bipolar disorders). Subjective sleep quality only predicted FA in the perihippocampal cingulum tract, whereas chronotype had limited predictive importance for WM integrity. To further examine links with mood disorders, we conducted a subgroup analysis. In youth with depressive and bipolar disorders, chronotype emerged as an important (often top-ranking) feature, predicting FA in the cingulum (cingulate gyrus), AD in the anterior corona radiata and genu of the corpus callosum, and RD in the corona radiata, anterior corona radiata, and genu of corpus callosum. Subjective quality was not important in this subgroup analysis. In summary, chronotype predicted altered WM integrity in the corona radiata and corpus callosum, whereas subjective sleep quality had a less significant role, suggesting that circadian factors may play a more prominent role in WM integrity in emerging mood disorders.