Psychological stress-induced changes in sleep patterns and their generation mechanism

The Influence of Life Stress and Sleep Disturbance on White Matter Integrity

OBJECTIVE

This study investigated whether sleep and stress mutually interact to induce changes in white matter integrity.

METHODS

Diffusion tensor imaging (DTI) was conducted on 36 participants (male=22, female=14; mean age=38.33±12.78 years). Participants were divided into three groups depending on their sleep quality and stress levels: poor sleepers with stress, poor sleepers without stress, and good sleepers. Sleep quality and stress level were evaluated using the Pittsburgh Sleep Quality Index and the Life Experiences Survey, respectively. Fractional anisotropy (FA) values were calculated employing DTI tractography.

RESULTS

After controlling for age and sex, poor sleepers with stress exhibited a lower FA of the left inferior cerebellar peduncle (ICP) than did poor sleepers without stress (t=2.81, p=0.02). Poor sleepers without stress showed a higher FA of the right middle longitudinal fasciculus (MdLF) than did good sleepers (t=3.35, p=0.006).

CONCLUSION

The current study reports the effects of sleep, stress, and their interaction on the white matter integrities of the ICP and MdLF. ICP change seems to be associated with sleep disturbances related to stress, while MdLF change would be associated with sleep disturbances unrelated to stress.

The Association Between Dry Eye and Sleep Disorders: The Evidence and Possible Mechanisms

Dry eye is a disease that severely affects patients' quality of life, increasing the global burden on public health and finance. There is growing evidence that a poor lifestyle is a significant risk factor for dry eye. Along with the development of society, sleep, as a way of life, is also constantly changing. The main manifestations of sleep disorders are reduced sleep time, circadian rhythm disturbances, and sleep breathing disturbances. Sleep disorders and their secondary systemic diseases have attracted wide attention in recent years. This review mainly explored the correlation between sleep disorders and dry eye, and found that sleep-related problems and other factors potentially leading from sleep disorders could be critical factors for dry eye. These results suggest that ophthalmologists should pay attention to the sleep health problems in patients with dry eye, and we hope that this paper can provide help for future research in this field.

The Effects of Milk and Dairy Products on Sleep: A Systematic Review

Several studies have assessed the effects of milk and dairy product intake on sleep quality and duration. Such investigations have varied in terms of their geographic locations, amounts of milk and dairy products, study participants (age, sex, race), and study designs. The present study aimed to summarize this literature and provide a unified view on whether the intake of milk and dairy products affects sleep quality. This systematic review was conducted according to the preferred reporting items for systematic reviews and meta-analyses (PRISMA) guidelines. The following keywords were chosen as electronic database search items from MeSH (medical subject headings) terms and descriptors in health sciences (DeHS) lists: milk, yogurt, dairy product, cheese, sleep, human, observational study, and interventional study. As a result, a total of 14 studies published between 1972 and 2019 were included in this review, including eight randomized controlled trials, two experimental studies with cross-over designs, one longitudinal study, and three cross-sectional studies. Four studies targeted older adults, three included toddlers, two targeted children, and six enrolled adults inclusive of university students. Overall, these studies indicated that a well-balanced diet that includes milk and dairy products is effective in improving sleep quality, despite mixed results across studies attributable to differences in study populations and methods.

Contents of Functionally Bioactive Peptides, Free Amino Acids, and Biogenic Amines in Dutch-Type Cheese Models Produced with Different Lactobacilli

Cheese ripening involves a number of biochemical processes, mainly of a proteolytic nature, which are initially triggered principally by milk-coagulating enzymes and, afterward, by microorganisms or enzymes of microbial origin. The proteolytic reactions affect, primarily, the synthesis of macro- and medium-molecular peptides from casein. In turn, the advanced proteolysis ends in the formation of short peptides and free amino acids. Further reactions may lead to the formation of nutritionally unfavorable biogenic amines. The present study aimed to determine changes in the contents of bioactive peptides (anserine and L-carnosine), free amino acids, and biogenic amines throughout the ripening of cheese models produced with the addition of Lactobacillus genus bacteria. The contents of amino acids varied considerably in the cheese models, depending on the bacterial strain added and ripening time. After five weeks of ripening, the total content of free amino acids in the cheese models ranged from 611.02 (a cheese model with Lactobacillus casei 2639) to 1596.64 mg kg⁻¹ (a cheese model with Lb. acidophilus 2499). After the same time, the contents of the total biogenic amines in the cheese models with the addition of lactobacilli were lower than in the control cheese model (except for the model with Lb. rhamnosus 489). Anserine was detected in all cheese models (79.29–119.02 mg kg⁻¹), whereas no L-carnosine was found over a five-week ripening period in the cheese models with Lb. delbrueckii 490 and Lb. casei 2639. After a five-week ripening, the highest total content of bioactive peptides was determined in the cheese models containing Lb. acidophilus 2499 (136.11 mg kg⁻¹).

Employment status and the association of sociocultural stress with sleep in the Hispanic Community Health Study/Study of Latinos (HCHS/SOL)

STUDY OBJECTIVES

We examined the association of sociocultural stress severity (i.e. acculturation stress, ethnic discrimination) and chronic stress burden with multiple dimensions of sleep in a population-based sample of US Hispanics/Latinos. We also explored whether employment status modified stress-sleep associations.

METHODS

We conducted survey linear regressions to test the cross-sectional association of sociocultural stress severity and stress burden with sleep dimensions using data collected between 2010 and 2013 from individuals who participated in both the Hispanic Community Health Study/Study of Latinos Sueño and Sociocultural Ancillary studies (N = 1192).

RESULTS

Greater acculturation stress (B = 0.75, standard error [SE] = 0.26, p < .01) and chronic psychosocial stress burden (B = 1.04, SE = 0.18, p < .001) were associated with greater insomnia symptoms but were not associated with actigraphic measures of sleep. Ethnic discrimination was not associated with any of the sleep dimensions. The association of acculturation stress with insomnia severity was greater in unemployed (B = 2.06, SE = 0.34) compared to employed (B = 1.01, SE = 0.31) participants (p-interaction = .08).

CONCLUSIONS

Acculturation stress severity and chronic stress burden are important and consistent correlates of insomnia, but not actigraphically measured sleep dimensions. If replicated, future research should test whether interventions targeting the resolution of sociocultural stress improve sleep quality in Hispanics/Latinos.

Sleep macrostructure is modulated by positive and negative social experience in adult pet dogs

The effects of emotionally valenced events on sleep physiology are well studied in humans and laboratory rodents. However, little is known about these effects in other species, despite the fact that several sleep characteristics differ across species and thus limit the generalizability of such findings. Here we studied the effect of positive and negative social experiences on sleep macrostructure in dogs, a species proven to be a good model of human social cognition. A non-invasive polysomnography method was used to collect data from pet dogs (n = 16) participating in 3-hour-long sleep occasions. Before sleep, dogs were exposed to emotionally positive or negative social interactions (PSI or NSI) in a within-subject design. PSI consisted of petting and ball play, while NSI was a mixture of separation, threatening approach and still face test. Sleep macrostructure was markedly different between pre-treatment conditions, with a shorter sleep latency after NSI and a redistribution of the time spent in the different sleep stages. Dogs' behaviour during pre-treatments was related to the macrostructural difference between the two occasions, and was further modulated by individual variability in personality. This result provides the first direct evidence that emotional stimuli affect subsequent sleep physiology in dogs.

Simultaneous Changes in Sleep, qEEG, Physiology, Behaviour and Neurochemistry in Rats Exposed to Repeated Social Defeat Stress

Depression is a heterogeneous disorder characterized by alterations at psychological, behavioural, physiological, neurophysiological, and neurochemical levels. Social stress is a prevalent stress in man, and the repeated social defeat stress model in rats has been proposed as being the rodent equivalent to loss of control, which in subordinate animals produces alterations that resemble several of the cardinal symptoms found in depressed patients. Here, rats followed a resident-intruder protocol for 4 consecutive days during which behavioural, physiological, and electroencephalographic (EEG) parameters were simultaneously monitored in subordinate rats. On day 5, prefrontal dopamine (DA) and hippocampal serotonin (5-HT) as well as corticosterone were measured in submissive rats that had visual, acoustic, and olfactory (but no physical) contact with a dominant, resident conspecific rat. Socially defeated rats demonstrated increases in ultrasonic vocalizations (20-25 KHz), freezing, submissive defensive behaviour, inactivity, and haemodynamic response, while decreases were found in repetitive grooming behaviour and body weight. Additionally, alterations in the sleep-wake architecture were associated with reduced active waking, enhanced light sleep, and increased frequency of transitions from light sleep to quiet wakefulness, indicating sleep instability. Moreover, the attenuation of EEG power over the frequency range of 4.2-30 Hz, associated with a sharp transient increase in delta oscillations, appeared to reflect increased brain activity and metabolism in subordinate animals. These EEG changes were synchronous with a marked increase in body temperature and a decrease in locomotor activity. Furthermore, psychosocial stress consistently increased 5-HT, DA, and corticosterone levels. The increased levels of cortical DA and hippocampal 5-HT during social threat may reflect a coping mechanism to promote alertness and psychological adaptation to provocative and threatening stimuli. These neurophysiological changes are hypothesized to be the consequence of dynamics in monoamine systems, which could be useful markers for disease progression in the aetiology of depression.

Sociodemographic and cultural determinants of sleep deficiency: implications for cardiometabolic disease risk

Sleep is a biological imperative associated with cardiometabolic disease risk. As such, a thorough discussion of the sociocultural and demographic determinants of sleep is warranted, if not overdue. This paper begins with a brief review of the laboratory and epidemiologic evidence linking sleep deficiency, which includes insufficient sleep and poor sleep quality, with increased risk of chronic cardiometabolic diseases such as obesity, diabetes and hypertension. Identification of the determinants of sleep deficiency is the critical next step to understanding the role sleep plays in human variation in health and disease. Therefore, the majority of this paper describes the different biopsychosocial determinants of sleep, including age, gender, psychosocial factors (depression, stress and loneliness), socioeconomic position and race/ethnicity. In addition, because sleep duration is partly determined by behavior, it will be shaped by cultural values, beliefs and practices. Therefore, possible cultural differences that may impact sleep are discussed. If certain cultural, ethnic or social groups are more likely to experience sleep deficiency, then these differences in sleep could increase their risk of cardiometabolic diseases. Furthermore, if the mechanisms underlying the increased risk of sleep deficiency in certain populations can be identified, interventions could be developed to target these mechanisms, reduce sleep differences and potentially reduce cardiometabolic disease risk.

Relationships between polysomnographic variables, parameters of glucose metabolism, and serum androgens in obese adolescents with polycystic ovarian syndrome

The aim of this study was to compare polysomnographic variables of obese adolescents with polycystic ovarian syndrome (PCOS) to those of healthy controls and to analyse whether polysomnographic variables correlate to parameters of body weight/body composition, to serum androgens and to parameters of glucose metabolism. Thirty-one obese adolescents with PCOS (15.0 years ± 1.0, body mass index 32.7 kg per m(2) ± 6.2) and 19 healthy obese adolescents without PCOS (15.2 years ± 1.1, body mass index 32.4 kg per m(2) ± 4.0) underwent polysomnography to compare apnoea index, hypopnoea index, apnoea-hypopnoea index, the absolute number of obstructive apnoeas, percentage sleep Stages 1, 2, 3 and 4 of non-rapid eye movement (NREM) sleep, percentage of REM sleep, TIB, total sleep time (TST), sleep-onset latency, total wake time (TWT), wakefulness after sleep onset (WASO) and sleep efficiency. Furthermore, we correlated polysomnographic variables to parameters of body weight/body composition, to serum androgens and to parameters of glucose metabolism. We found no differences between the two groups concerning the respiratory indices, percentage sleep Stages 2, 3 and 4 of NREM sleep, TIB and sleep-onset latency. The girls with PCOS differed significantly from the controls regarding TST, WASO, TWT, sleep efficiency, percentage Stage 1 of NREM sleep and percentage of REM sleep. We found a weak significant correlation between insulin resistance and apnoea index and between insulin resistance and apnoea-hypopnoea index. Concerning the respiratory variables, adolescents with PCOS do not seem to differ from healthy controls; however, there seem to be differences concerning sleep architecture.

The effect of baclofen on alterations in the sleep patterns induced by different stressors in rats

We have previously reported that sleep patterns are significantly affected by both physical and psychological stress induced by a communication box; however, the mechanism by which stress alters sleep patterns was not established. In the present study, we investigated the role of gamma-aminobutyric acid (GABA), acting through the GABA(B) receptor, on stress-induced changes in sleep patterns. Our results show that physical stress increased the total wakefulness time by increasing sleep latency and inhibiting both rapid eye movement (REM) and non rapid eye movement (NREM) sleep during a 6 h sleep-recording period. The GABA(B) agonist baclofen (20 pmol/2 microl) attenuated the effects of physical stress on sleep latency, total wakefulness, and NREM sleep, but not total REM sleep. In contrast, psychological stress enhanced total REM sleep and shortened REM sleep latency without altering other sleep patterns. The effect of psychological stress on total REM sleep was also reversed by baclofen. These results suggest that GABA via GABA(B) receptors may play a role in the regulation of specific sleep patterns by both physical and psychological stress.