Sleep markers in psychiatry: do insomnia and disturbed sleep play as markers of disrupted neuroplasticity in mood disorders? A proposed model

Epidemiology of insomnia disorder in older persons according to the Diagnostic and Statistical Manual of Mental Disorders: a systematic review and meta-analysis

PURPOSE

There is a scarcity of summarizing data on the epidemiology of insomnia in older persons, especially when diagnosed with international criteria. This study aimed to estimate the prevalence and correlates of insomnia disorder in older persons, according to the Diagnostic and Statistical Manual of Mental Disorders (DSM).

METHODS

Through PubMed/MEDLINE, EMBASE, and Web of Science (WoS), we searched for relevant articles published before June 28, 2023. The risk of bias was weighed using the Joanna Briggs Institute's (JBI's) critical appraisal checklist for studies reporting prevalence data. For our analyses, we used a random-effect model, with subgroup analyses, meta-regression, and sensitivity analyses to explore potential sources of heterogeneity. We followed the Preferred Reporting Items for Systematic reviews and Meta-Analyses statement.

RESULTS

We included 18,270 participants across 16 studies. The male/female ratio was 0.89 (12 studies), and the mean age varied from 65.9 to 83.1 years (8 studies). The pooled prevalence of insomnia was 19.6% (95% CI = [12.3%; 28.3%]), with substantial heterogeneity. This prevalence fluctuated according to the sample size, the minimal age for inclusion, and the study quality, considering that the risk of bias was moderate for most of studies. There was a publication bias, with a very low level of certainty. Insomnia disorder was associated with the female gender, depression, anxiety, and somatic illnesses notably cardiovascular, respiratory, and painful ones.

CONCLUSION

Nearly one in every five old individuals was considered to have insomnia disorder, which was associated with the gender and the existence of mental health and/or somatic conditions.

REGISTRATION

We registered the protocol in the International Prospective Register of Systematic Reviews (PROSPERO) with registration number: CRD42022344675.

Repeated sleep deprivation decreases the flux into hexosamine biosynthetic pathway/O-GlcNAc cycling and aggravates Alzheimer's disease neuropathology in adult zebrafish

This study investigated chronic and repeated sleep deprivation (RSD)-induced neuronal changes in hexosamine biosynthetic pathway/O-linked N-acetylglucosamine (HBP/O-GlcNAc) cycling of glucose metabolism and further explored the role of altered O-GlcNAc cycling in promoting neurodegeneration using an adult zebrafish model. RSD-triggered degenerative changes in the brain led to impairment of memory, neuroinflammation and amyloid beta (Aβ) accumulation. Metabolite profiling of RSD zebrafish brain revealed a significant decrease in glucose, indicating a potential association between RSD-induced neurodegeneration and dysregulated glucose metabolism. While RSD had no impact on overall O-GlcNAcylation levels in the hippocampus region, changes were observed in two O-GlcNAcylation-regulating enzymes, specifically, a decrease in O-GlcNAc transferase (OGT) and an increase in O-GlcNAcase (OGA). Glucosamine (GlcN) treatment induced an increase in O-GlcNAcylation and recovery of the OGT level that was decreased in the RSD group. In addition, GlcN reversed cognitive impairment by RSD. GlcN reduced neuroinflammation and attenuated Aβ accumulation induced by RSD. Repeated treatment of zebrafish with diazo-5-oxo-l-norleucine (DON), an inhibitor of HBP metabolism, resulted in cognitive dysfunction, neuroinflammation and Aβ accumulation, similar to the effects of RSD. The pathological changes induced by DON were restored to normal upon treatment with GlcN. Both the SD and DON-treated groups exhibited a common decrease in glutamate and γ-aminobutyric acid compared to the control group. Overexpression of OGT in zebrafish brain rescued RSD-induced neuronal dysfunction and neurodegeneration. RSD induced a decrease in O-GlcNAcylation of amyloid precursor protein and increase in β-secretase activity, which were reversed by GlcN treatment. Based on the collective findings, we propose that dysregulation of HBP and O-GlcNAc cycling in brain plays a crucial role in RSD-mediated progression of neurodegeneration and Alzheimer's disease pathogenesis. Targeting of this pathway may, therefore, offer an effective regulatory approach for treatment of sleep-associated neurodegenerative disorders.

Sleep-associated insulin resistance promotes neurodegeneration

Lifestyle modification can lead to numerous health issues closely associated with sleep. Sleep deprivation and disturbances significantly affect inflammation, immunity, neurodegeneration, cognitive depletion, memory impairment, neuroplasticity, and insulin resistance. Sleep significantly impacts brain and memory formation, toxin excretion, hormonal function, metabolism, and motor and cognitive functions. Sleep restriction associated with insulin resistance affects these functions by interfering with the insulin signalling pathway, neurotransmission, inflammatory pathways, and plasticity of neurons. So, in this review, We discuss the evidence that suggests that neurodegeneration occurs via sleep and is associated with insulin resistance, along with the insulin signalling pathways involved in neurodegeneration and neuroplasticity, while exploring the role of hormones in these conditions.

Fall Risk, Sleep Behavior, and Sleep-Related Movement Disorders in Young Urbanites Exposed to Air Pollution

BACKGROUND

Quadruple aberrant hyperphosphorylated tau, amyloid-β, α-synuclein, and TDP-43 pathology had been documented in 202/203 forensic autopsies in Metropolitan Mexico City ≤40-year-olds with high exposures to ultrafine particulate matter and engineered nanoparticles. Cognition deficits, gait, equilibrium abnormalities, and MRI frontal, temporal, caudate, and cerebellar atrophy are documented in young adults.

OBJECTIVE

This study aimed to identify an association between falls, probable Rapid Eye Movement Sleep Behavior Disorder (pRBD), restless leg syndrome (RLS), and insomnia in 2,466 Mexican, college-educated volunteers (32.5±12.4 years).

METHODS

The anonymous, online study applied the pRBD and RLS Single-Questions and self-reported night-time sleep duration, excessive daytime sleepiness, insomnia, and falls.

RESULTS

Fall risk was strongly associated with pRBD and RLS. Subjects who fell at least once in the last year have an OR = 1.8137 [1.5352, 2.1426] of answering yes to pRBD and/or RLS questions, documented in 29% and 24% of volunteers, respectively. Subjects fell mostly outdoors (12:01 pm to 6:00 pm), 43% complained of early wake up hours, and 35% complained of sleep onset insomnia (EOI). EOI individuals have an OR of 2.5971 [2.1408, 3.1506] of answering yes to the RLS question.

CONCLUSION

There is a robust association between falls, pRBD, and RLS, strongly suggesting misfolded proteinopathies involving critical brainstem arousal and motor hubs might play a crucial role. Nanoparticles are likely a significant risk for falls, sleep disorders, insomnia, and neurodegenerative lethal diseases, thus characterizing air particulate pollutants' chemical composition, emission sources, and cumulative exposure concentrations are strongly recommended.

Sleep matters: Neurodegeneration spectrum heterogeneity, combustion and friction ultrafine particles, industrial nanoparticle pollution, and sleep disorders-Denial is not an option

Sustained exposures to ubiquitous outdoor/indoor fine particulate matter (PM_2.5), including combustion and friction ultrafine PM (UFPM) and industrial nanoparticles (NPs) starting in utero, are linked to early pediatric and young adulthood aberrant neural protein accumulation, including hyperphosphorylated tau (p-tau), beta-amyloid (Aβ_{1 - 42}), α-synuclein (α syn) and TAR DNA-binding protein 43 (TDP-43), hallmarks of Alzheimer's (AD), Parkinson's disease (PD), frontotemporal lobar degeneration (FTLD), and amyotrophic lateral sclerosis (ALS). UFPM from anthropogenic and natural sources and NPs enter the brain through the nasal/olfactory pathway, lung, gastrointestinal (GI) tract, skin, and placental barriers. On a global scale, the most important sources of outdoor UFPM are motor traffic emissions. This study focuses on the neuropathology heterogeneity and overlap of AD, PD, FTLD, and ALS in older adults, their similarities with the neuropathology of young, highly exposed urbanites, and their strong link with sleep disorders. Critical information includes how this UFPM and NPs cross all biological barriers, interact with brain soluble proteins and key organelles, and result in the oxidative, endoplasmic reticulum, and mitochondrial stress, neuroinflammation, DNA damage, protein aggregation and misfolding, and faulty complex protein quality control. The brain toxicity of UFPM and NPs makes them powerful candidates for early development and progression of fatal common neurodegenerative diseases, all having sleep disturbances. A detailed residential history, proximity to high-traffic roads, occupational histories, exposures to high-emission sources (i.e., factories, burning pits, forest fires, and airports), indoor PM sources (tobacco, wood burning in winter, cooking fumes, and microplastics in house dust), and consumption of industrial NPs, along with neurocognitive and neuropsychiatric histories, are critical. Environmental pollution is a ubiquitous, early, and cumulative risk factor for neurodegeneration and sleep disorders. Prevention of deadly neurological diseases associated with air pollution should be a public health priority.

Sleep, insomnia and mental health

While sleep serves important regulatory functions for mental health, sleep disturbances, in particular insomnia, may favour a state of allostatic overload impairing brain neuroplasticity and stress immune pathways, hence contributing to mental disorders. In this framework, the aim of this work was to link current understanding about insomnia mechanisms with current knowledge about mental health dysregulatory mechanisms. The focus of the present work was on mood, anxiety, and psychotic disorders, which represent important challenges in clinical practice. Literature searches were conducted on clinical, neurobiological, and therapeutic implications for insomnia comorbid with these mental disorders. Given the complexity and heterogeneity of the existing literature, we ended up with a narrative review. Insomnia may play an important role as a risk factor, a comorbid condition and transdiagnostic symptom for many mental disorders including mood/anxiety disorders and schizophrenia. Insomnia may also play a role as a marker of disrupted neuroplasticity contributing to dysregulation of different neurobiological mechanisms involved in these different mental conditions. In this framework, insomnia treatment may not only foster normal sleep processes but also the stress system, neuroinflammation and brain plasticity. Insomnia treatment may play an important preventive and neuroprotective role with cognitive behavioural therapy for insomnia being the treatment with important new evidence of efficacy for insomnia, psychopathology, and indices of disrupted neuroplasticity. On the other hand, pharmacological pathways for insomnia treatment in these mental conditions are still not well defined. Therapeutic options acting on melatonergic systems and new therapeutic options acting on orexinergic systems may represents interesting pathways of interventions that may open new windows on insomnia treatment in mental disorders.