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The Gut Microbiome in Early Life Stress: A Systematic Review.
Agusti, A, Lamers, F, Tamayo, M, Benito-Amat, C, Molina-Mendoza, GV, Penninx, BWJH, Sanz, Y
Nutrients. 2023;15(11)
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Children exposed to early life stress (ELS) show alterations in brain development and are at increased risk of developing mental illness. This study aims to clarify whether ELS influences the gut microbiome and whether this can be a predictor for the development of mental disorders. 13 articles were included in this systemic review. 4 looked at pre-natal stress and 9 at post-natal stress. Prenatal stress (via maternal stress) may be associated with an increase in Proteobacteria phylum and with a lower abundance of Bifidobacterium and lactic acid bacteria. In the postnatal group, greater microbiome diversity was related to lower depression and anxiety. In boys scores for adaptive skills were higher in those with good levels of Bifidobacterium. A positive association was found between EA (early adversity) experiences and gastrointestinal symptoms and anxiety. This review demonstrates links between ELS and gut microbiome changes. Further research will be necessary to draw more robust conclusions.
Expert Review
Conflicts of interest:
None
Take Home Message:
- This systematic review consolidated and discussed existing evidence on the link between early life stress (ELS) and changes to the human microbiome
- Exposure to ELS, prenatal or postnatal during childhood and adolescence, may impact mental and physical health.
Evidence Category:
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A: Meta-analyses, position-stands, randomized-controlled trials (RCTs)
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B: Systematic reviews including RCTs of limited number
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C: Non-randomized trials, observational studies, narrative reviews
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D: Case-reports, evidence-based clinical findings
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E: Opinion piece, other
Summary Review:
Introduction
A systematic review was conducted to consolidate clinical evidence examining the impact of early life stress (ELS) on the human intestinal microbiome.
Method
Thirteen observational studies were included in the review, sourced from Pubmed, Scopus, Web of Science, and EMBASE. Methodological quality was assessed using the Newcastle-Ottawa Assessment Scale (NOS), with most studies scoring seven or eight out of nine stars.
Study designs varied, including prospective prenatal studies, postnatal longitudinal studies, case-control studies, and cross-sectional studies. Four prenatal studies were prospective in design. The other nine postnatal studies included one longitudinal study, five case-control studies, and three cross-sectional studies. All 13 studies were published between 2015 and 2022. Because study designs and outcome assessments varied, the results were presented in a narrative form. Data was extracted by 2 independent authors.
Results
The primary findings from the review were as follows:
- Four longitudinal stress studies indicated that pregnant mothers experiencing psychological stress, increased cortisol levels, HIV, and lack of social support exhibited a lower abundance of beneficial Bifidobacterium and an increased abundance of Enterobacter genus.
- One postnatal stress longitudinal study (n=260) demonstrated lower depression and anxiety and improved internalising behaviour in patients with high microbiome diversity.
- . One postnatal stress case-control study (n=344) showed changes in the microbiome and an abundance of several bacterial taxa in stressed groups, including genera Prevotella, Bacteroides (Bacteroidetes), Coprococcus, Streptococcus, and Escherichia.
- One cross-sectional study of 128 adults without psychiatric conditions revealed that higher stress correlated with increased levels of Bacteroides, Parabacteroides, Rhodococcus, Methanobrevibacter, and Roseburia at the genus level, as well as lower Phascolarcto bacterium and Firmicutes at the phylum level.
- One large prospective study (n=446) found infants exposed to higher cumulative stress exhibited an increased relative abundance of Proteobacteria groups and lower Bifidobacterium.
Conclusion:
Due to the inconsistency of study designs and their results this review failed to find consensus microbiome signatures associated with pre- or postnatal stress, or both.
Clinical practice applications:
- Early life stress, and alterations in the gut microbiome, have been linked to mental health conditions
- Maternal prenatal stress may be linked to emotional, behavioural, and cognitive outcomes in infants.
Considerations for future research:
- Future research should standardise questionnaires, to ensure consistency and comparability across studies
- Additionally, future studies should consider using standard procedures and specific species and strain resolution shotgun metagenomics sequencing
- Consideration should be given to the influence of environmental variables (diet, physical activity, etc.) and sex in gut microbiome analysis.
Abstract
Exposure to early life stress (ELS), prenatal or postnatal during childhood and adolescence, can significantly impact mental and physical health. The role of the intestinal microbiome in human health, and particularly mental health, is becoming increasingly evident. This systematic review aims to summarize the clinical data evaluating the effect of ELS on the human intestinal microbiome. The systematic review (CRD42022351092) was performed following PRISMA guidelines, with ELS considered as exposure to psychological stressors prenatally and during early life (childhood and adolescence). Thirteen articles met all inclusion criteria, and all studies reviewed found a link between ELS and the gut microbiome in both prenatal and postnatal periods. However, we failed to find consensus microbiome signatures associated with pre- or postnatal stress, or both. The inconsistency of results is likely attributed to various factors such as different experimental designs, ages examined, questionnaires, timing of sample collection and analysis methods, small population sizes, and the type of stressors. Additional studies using similar stressors and validated stress measures, as well as higher-resolution microbiome analytical approaches, are needed to draw definitive conclusions about the links between stress and the human gut microbiome.
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Paroxysmal slow wave events are associated with cognitive impairment in patients with obstructive sleep apnea.
Li, M, Sun, Z, Sun, H, Zhao, G, Leng, B, Shen, T, Xue, S, Hou, H, Li, Z, Zhang, J
Alzheimer's research & therapy. 2022;14(1):200
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Obstructive sleep apnoea (OSA) is a disorder which results in an individual’s breathing being cut off momentarily whilst asleep. OSA has been associated with the development of cognitive impairment, which is characterised by declining memory. The reason for the link is thought to involve a dysfunction in the blood brain barrier, which can be measured by paroxysmal slow wave events (PSWEs). This study of 339 individuals with complaints of snoring aimed to determine the correlation between PSWEs and cognitive impairment. The results showed that cognitive impairment in individuals with OSA due to a lack of oxygen could be due to a dysfunction in the blood brain barrier and that PSWEs are a reliable measure of this. It was concluded that PSWEs can be used as a measure of cognitive impairment in patients with OSA and that brain barrier dysfunction may be involved in its development in this subset of individuals. This study could be used by healthcare professionals to understand that sleep apnoea is more than just snoring, it can be involved in the development of certain chronic diseases.
Abstract
BACKGROUND Increasing evidence has supported a link between obstructive sleep apnea (OSA) and cognition, and blood-brain barrier (BBB) dysfunction which can be reflected by paroxysmal slow wave events (PSWEs) may be a potential mechanism. The purpose of our study was to investigate the correlation between the PSWEs and cognitive impairment in patients with OSA, with a focus on the possible mechanism. METHODS In total, 339 subjects with subjective snoring complaints from the Sleep Medicine Center underwent magnetic resonance imaging and whole-night polysomnography. OSA was defined as apnea-hypopnea index (AHI) ≥ 5 events/h. MCI was defined as the MoCA < 26 and met the criteria: (1) subjective cognitive impairment; (2) objective impairment in one or more cognitive domains; (3) slightly impaired complex instrumental daily abilities, but independent daily living abilities; and (4) no dementia. The PSWEs calculated by self-developed Python scripts were defined for EEG recordings as a median power frequency of < 6 Hz for more than five consecutive seconds. Serum cyclophilin A (CyPA) and matrix metalloproteinase-9 (MMP-9) levels and amyloid-β 42 levels in neuron-derived exosomes were determined. The participants who received continuous positive airway pressure (CPAP) were followed up and their PSWEs were recalculated after 1 year of treatment. RESULTS A total of 339 participants were divided into the OSA+MCI group (n = 157), OSA-MCI group (n = 118), and controls (normal cognitive state without OSA) (n = 64). The total PSWEs and the occurrence per minute of PSWEs at stage REM in the OSA+MCI group were higher than those in the OSA-MCI and control groups. The duration ratio of PSWEs at stage REM in the OSA+MCI group significantly increased. The total PSWEs and PSWEs at the F4-M1, O1-M2, and O2-M1 channels in stage REM were independently associated with cognitive impairment in OSA patients. There were positive correlations between the PSWEs and serum CyPA and MMP-9 levels in patients with OSA. The mediation analysis showed that the relationship between mean SaO2 and percentage of sleep time spent with oxygen saturation <90% with MoCA scores was mediated by the total PSWEs (proportion of mediation 77.89% and 82.89%). The PSWEs were negatively correlated with global cognitive performance and cognitive subdomains. After 1 year of CPAP treatment, the total PSWEs, PSWEs in stage REM, and serum CyPA and MMP-9 levels decreased significantly, and MoCA scores were improved compared with baseline. CONCLUSIONS The PSWEs were implicated in cognitive impairment in patients with OSA, and the mechanisms of cognitive impairment due to hypoxia in OSA patients could be BBB dysfunction. The PSWEs can be used as a marker of cognitive impairment in patients with OSA. TRIAL REGISTRATION This trial is registered on the Chinese Clinical Trial Registry, number ChiCTR1900021544. The trial was registered on February 27, 2019.
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Immediate and long-term consequences of COVID-19 infections for the development of neurological disease.
Heneka, MT, Golenbock, D, Latz, E, Morgan, D, Brown, R
Alzheimer's research & therapy. 2020;12(1):69
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Covid-19 may cause brain dysfunction evidenced by symptoms individuals experience once they have contracted the disease. Loss of smell, taste and confusion have all been reported by patients and a number of severe cases have reported incidences of stroke. These are all of concern, as Covid-19 can severely affect the elderly who ordinarily are the most likely to suffer from brain disorders. This small review paper of 27 studies stated that there are four possible ways in which Covid-19 may affect the brain, which put Covid-19 sufferers at an increased risk of long-term brain disorders. This was supported by findings, which showed one third of Covid-19 patients leave hospital with evidence of brain dysfunction. Inflammation was heavily reviewed by the authors as a possible causal factor. It was concluded that patients who survive Covid-19 infection are at an increased risk for developing brain disorders such as Alzheimer's disease, however it was acknowledged that further studies are required. Clinicians could use this study to understand the possible need for both short-term and long-term monitoring of brain function in individuals who have survived Covid-19, especially if they are elderly.
Abstract
Increasing evidence suggests that infection with Sars-CoV-2 causes neurological deficits in a substantial proportion of affected patients. While these symptoms arise acutely during the course of infection, less is known about the possible long-term consequences for the brain. Severely affected COVID-19 cases experience high levels of proinflammatory cytokines and acute respiratory dysfunction and often require assisted ventilation. All these factors have been suggested to cause cognitive decline. Pathogenetically, this may result from direct negative effects of the immune reaction, acceleration or aggravation of pre-existing cognitive deficits, or de novo induction of a neurodegenerative disease. This article summarizes the current understanding of neurological symptoms of COVID-19 and hypothesizes that affected patients may be at higher risk of developing cognitive decline after overcoming the primary COVID-19 infection. A structured prospective evaluation should analyze the likelihood, time course, and severity of cognitive impairment following the COVID-19 pandemic.
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Health anxiety and illness-related fears across diverse chronic illnesses: A systematic review on conceptualization, measurement, prevalence, course, and correlates.
Lebel, S, Mutsaers, B, Tomei, C, Leclair, CS, Jones, G, Petricone-Westwood, D, Rutkowski, N, Ta, V, Trudel, G, Laflamme, SZ, et al
PloS one. 2020;15(7):e0234124
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Living with a chronic disease is often accompanied by feelings of worry and has been termed health anxiety (HA). HA is complex, with aspects of psychological and environmental factors that affect its development. This systematic review aimed to determine the prevalence, course and who is most likely to be affected by HA. The results showed that most research studies consider this to be a symptom of the disease and not a psychological illness. The development of HA should be considered on a continuum going from mild and transient to severe. There is no agreement on when the disease should be considered excessive. It was concluded that fears of the illness or symptoms worsening or returning are often experienced by those with a chronic disease.
Abstract
BACKGROUND Patients with chronic diseases commonly report fears of illness or symptoms recurring or worsening. These fears have been addressed from an illness-specific perspective (e.g., fear of cancer recurrence), a generic illness perspective (e.g., fear of progression), and a psychiatric perspective (DSM-5 illness anxiety disorder and somatic symptom disorder). The broader concept of health anxiety (HA) can also be applied to patients with a chronic disease. This review was conducted to investigate the conceptual, theoretical, measurement-overlap, and differences between these distinct perspectives. We also aimed to summarize prevalence, course, and correlates of these fears in different chronic illnesses. METHODS We used PsycINFO, PubMED, CINAHL, Web of Science, SCOPUS, and PSYNDEX to conduct a systematic review of studies pertaining to these fears in chronic illness published from January 1996 to October 2017. A total of 401 articles were retained. RESULTS There were commonalities across different conceptualizations and diseases: a high prevalence of clinical levels of fears (>20%), a stable course over time, and a deleterious impact on quality of life. Reviewed studies used definitions, models, and measures that were illness-specific, with only a minority employing a psychiatric perspective, limiting cross-disease generalizability. There appears to be some applicability of DSM-5 disorders to the experience of fear of illness/symptoms in patients with a chronic illness. While conceptualizing HA on a continuum ranging from mild and transient to severe may be appropriate, there is a lack of agreement about when the level of fear becomes 'excessive.' The definitions, models, and measures of HA across chronic illnesses involve affective, cognitive, behavioral, and perceptual features. CONCLUSIONS The concept of HA may offer a unifying conceptual perspective on the fears of illness/symptoms worsening or returning commonly experienced by those with chronic disease.
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How Does the Brain Implement Adaptive Decision Making to Eat?
Compan, V, Walsh, BT, Kaye, W, Geliebter, A
The Journal of neuroscience : the official journal of the Society for Neuroscience. 2015;35(41):13868-78
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While food intake is critical for survival, adaptive decision-making can be altered through various mechanisms and eventually lead to disordered eating patterns. Feeding behaviour is dependent on homeostatic rules, motivational drives, biological predispositions and external stressors. This complex web elucidates how humans can decide to satisfy or abstain from hunger cues, and the underlying mechanisms of this behaviour have been increasingly explored. This review summarises the overall neural circuitry in restrictive food choice and binge eating. Serotonergic systems play a key role in eating disorders because they are involved in responses to stress, emotions and feeding behaviour. The decision to overeat or abstain from eating is a reward, and this goal-directed and persistent behaviour mirror some aspects of drug dependence. This review found that voluntary processes in the nervous system could be modified to predominate over homeostatic control of hunger. Eating disorders may emerge when serotonin neurons reach their limit of adaptive capacities, potentially to the extent of compromised survival. This study provides a basis for developing more effective interventions for this population.
Abstract
Adaptive decision making to eat is crucial for survival, but in anorexia nervosa, the brain persistently supports reduced food intake despite a growing need for energy. How the brain persists in reducing food intake, sometimes even to the point of death and despite the evolution of multiple mechanisms to ensure survival by governing adaptive eating behaviors, remains mysterious. Neural substrates belong to the reward-habit system, which could differ among the eating disorders. The present review provides an overview of neural circuitry of restrictive food choice, binge eating, and the contribution of specific serotonin receptors. One possibility is that restrictive food intake critically engages goal-directed (decision making) systems and "habit," supporting the view that persistent caloric restriction mimics some aspects of addiction to drugs of abuse. SIGNIFICANCE STATEMENT An improved understanding of the neural basis of eating disorders is a timely challenge because these disorders can be deadly. Up to 70 million of people in the world suffer from eating disorders. Anorexia nervosa affects 1-4% of women in United States and is the first cause of death among adolescents in Europe. Studies relying on animal models suggest that decision making to eat (or not) can prevail over actual energy requirements due to emotional disturbances resulting in abnormal habitual behavior, mimicking dependence. These recent studies provide a foundation for developing more specific and effective interventions for these disorders.
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Simultaneous comparison of helium and nitrogen expiratory "closing volumes".
Travis, DM, Green, M, Don, H
Journal of applied physiology. 1973;34(3):304-8
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Restricted sleep has been linked to obesity but the underlying mechanisms are not clear. This study aimed to assess whether restricted sleep (4.5hrs for 4 consecutive nights) alters the appetite-regulating hormones ghrelin, leptin and pancreatic polypeptide in the following 24hrs in 19 healthy, lean men (BMI 19-24.9). This randomised crossover study assessed whether those hormonal changes predicted the food intake during ad libitum feeding. The study found that Ghrelin levels were increased after sleep restriction but did not alter leptin or pancreatic polypeptide profiles. Sleep restriction was associated with an increase in calorie consumption from snacks, primarily from carbohydrates. They concluded that restricted sleep significantly increases ghrelin levels. Elevated ghrelin is associated with an increased calorie consumption which may lead to the development of obesity.