Chronotype influence on the effects of COVID-19 lockdown on sleep and psychological status in France.

The present study aims to assess the influence of chronotype on lockdown-induced effects on sleep and psychological outcomes. A total of 1671 participants were recruited in France and filled out online questionnaires about their sleeping hours and sleep quality, their chronotype (morning, intermediate, evening type), and their depressive, anxiety and stress symptoms both retrospectively (before lockdown) and currently (during the lockdown). Statistical analyses estimated the chronotype effect on the impact of the lockdown on sleep and psychological outcomes. Results show that during the lockdown, sleep quality decreased, sleep duration increased, and sleep midpoint was delayed and, while fatigue perception decreased, anxiety and depression increased. The decrease in sleep quality varied according to the participants' chronotype. The evening type's sleep quality decreased the most. A similar chronotype effect was also observed on sleep duration and sleep midpoint. Evening-type participants also increased their depressive symptoms. These results suggest that evening-type individuals have lower resilience to lockdown effect on psychological status and sleep pattern.

Functional connectivity correlates of attentional networks in insomnia disorder: A pilot study.

Insomnia disorder has been associated with poor executive functioning. Functional imaging studies of executive functioning in insomnia are scarce and inconclusive. Because the Attentional Network Test relies on well-defined cortical networks and sensitively distinguishes different aspects of executive function, it might reveal brain functional alterations in relatively small samples of patients. The current pilot study assessed functional connectivity during the Attentional Network Test performed using magnetic resonance imaging in 12 participants with insomnia and 13 self-defined good sleepers. ANCOVAs were used to evaluate group differences in performance and functional connectivity in the regions of interest representing the attentional networks (i.e. alerting, orienting and executive control) at p < 0.05, uncorrected. During the orienting part, participants with insomnia showed weaker connectivity of the precentral gyrus with the superior parietal lobe (false discovery rate-corrected), while they showed stronger connectivity between premotor and visual regions. Individual differences in connectivity between premotor and visual regions correlated inversely with reaction time. Reaction times suggested more efficient executive control in participants with insomnia compared with good sleepers. During the executive control part, participants with insomnia showed stronger connectivity of thalamic parts of the arousal circuit with the middle frontal and the occipital gyri. Conversely, connectivity between the inferior and superior frontal gyri was weaker. Participants with insomnia seem to recruit more cortical resources in visuo-motor regions to orient attention than good sleepers do, and seem to have enhanced executive control that relates to stronger connectivity of arousal-related thalamic areas. This latter result should be treated with caution and requires confirmation.

Kinematics or Kinetics: Optimum Measurement of the Vertical Variations of the Center of Mass during Gait Initiation.

BACKGROUND: During gait, the braking index represents postural control, and consequently, the risk of falls. Previous studies based their determination of the braking index during the first step on kinetic methods using force platforms, which are highly variable. This study aimed to investigate whether determining the braking index with a kinematic method, through 3D motion capture, provides more precise results. METHODS: Fifty participants (20 to 40 years) performed ten trials in natural and fast gait conditions. Their braking index was estimated from their first step simultaneously using a force platform and VICON motion capture system. The reliability of each braking index acquisition method was assessed by intraclass correlation coefficients, standard error measurements, and the minimal detectable change. RESULTS: Both kinetic and kinematic methods allowed good to excellent reliability and similar minimum detectable changes (10%). CONCLUSION: Estimating the braking index through a kinetic or a kinematic method was highly reliable.

Reduced gait and postural stability under challenging conditions in fallers with upper limb fracture.

BACKGROUND: While most fractures are caused by falls, not all falls result in fractures. Risk factors for falls are well established, but only weak associations have been demonstrated for risk factors for fractures. Conflicting results on the implication of bone mineral density (BMD) suggest that other risk factors should be studied, such as gait and balance disorders. AIMS: Gait and postural stability in challenging conditions were, therefore, compared between fallers with and without fracture. METHODS: We enrolled 80 adults aged 55 and older who fell in the previous year. We compared gait and posture after obstacle crossing between fallers with an upper-limb fracture (n = 38), and fallers without fracture (n = 42). Data on BMD, body mass index, handgrip strength, fear of falling, number of comorbidities, number of falls, global cognition, executive functioning and education level were collected. RESULTS: Compared to fallers without fracture, fallers with fracture had significant lower gait velocity (Likelihood-Ratio = 4.93; P = 0.03) and lower postural stability during stabilization after obstacle crossing (Likelihood-Ratio = 10.99; P < 0.001). In addition, fallers with fracture had lower handgrip strength (Likelihood-Ratio = 9.92; P = 0.002), lower education level (Likelihood-Ratio = 8.32; P = 0.004), poorer executive functions (Likelihood-Ratio = 5.81; P = 0.02, higher fear of falling (Likelihood-Ratio = 5.55; P = 0.02) and were more likely women (Likelihood-Ratio = 17.55; P < 0.001), compared to fallers without fracture. DISCUSSION: This study demonstrated that the main difference between fallers with upper-limb fracture and fallers without fracture is mobility in dynamic condition. Poor executive function and low muscular strength could also be involved. CONCLUSIONS: These factors should be taken into account when assessing risk factors for fracture and implementing preventive programs. CLINICAL TRIAL REGISTRATION: clinicaltrials.gov. NCT02292316.

The manual orienting response habituation to repeated tactile stimuli in preterm neonates: Discrimination of stimulus locations and interstimulus intervals.

Preterm infants frequently develop atypical sensory profiles, the tactile modality being particularly affected. However, there is a lack of recent investigation of neonatal tactile perception in a passive context, especially in preterms who are particularly exposed to this tactile stimuli. Our aims were to provide evidence of orienting responses (behavioral modifications directing subject's attention towards stimuli) and habituation to passive tactile stimuli in preterm neonates, to explore their ability to perceive spatial and temporal aspects of the stimulus, and to evaluate the effect of clinical factors on these abilities. We included 61 preterm neonates, born between 32 and 34 weeks of gestational age. At 35 weeks of corrected gestational age, we measured orienting responses (forearm, hand, and fingers movements) during vibrotactile stimulation of their hand and forearm; during a habituation and dishabituation paradigm, the dishabituation being either a location change or a pause in the stimulation sequence. Preterm newborns displayed a manual orienting response to vibrotactile stimuli which significantly decreased when the stimulus was repeated, regardless of the stimulated location on the limb. Habituation was delayed in subjects born at a younger gestational age, smaller birth weight, and having experienced more painful care procedures. Preterm neonates perceived changes in stimulus location and interstimulus time interval. Our findings provide insights on several aspects of the perception of repeated tactile stimuli by preterm neonates, and the first evidence of the early development of temporal processing abilities in the tactile modality. Future work will investigate the links between this ability and neurodevelopmental disorders.

Development and validation of a French version of the morningness-eveningness questionnaire.

The aim of this study was to validate a French version (FMEQ) of the morningness-eveningness questionnaire (MEQ). Study 1 consisted of a translation by experts and an evaluation. The FMEQ and MEQ were proposed to 19 bilingual participants (age = 38.7 ± 13.7 years). Strong correlations between MEQ and FMEQ were obtained for most items. Study 2 tested the factorial structure and reliability of the FMEQ on a sample of 187 participants (20.46 ± 1.31 years). The confirmatory factor analysis indicated that the model had a good fit (χ2/df = 1.8; SRMR = 0.057) and a good reliability (Cronbach's alphas = 0.8). Concerning the temporal stability (20 participants: 20.48 ± 1.04 years), the Pearson r correlation coefficient for test-retest reliability was 0.87 (p < 0.001). Study 3 examined the predictive validity with 42 participants (19.52 ± 2.08 years). The global score of the FMEQ was significantly correlated with the time of peak temperature, wake-up time and bedtime. We did not observe superiority of a three-factors solution of the FMEQ. From now on, French subjects chronotype could be rigorously scored, and results from MEQ and FMEQ could be compared.

Effectiveness of multi-modal home-based videoconference interventions on sleep in older adults: study protocol for a randomized controlled trial.

Aging is characterized by substantial changes in sleep architecture that negatively impact fitness, quality of life, mood, and cognitive functioning. Older adults often fail to reach the recommended level of physical activity to prevent the age-related decline in sleep function, partly because of geographical barriers. Implementing home-based interventions could surmount these obstacles, thereby encouraging older adults to stay active, with videoconference administration emerging as a promising solution. Increasing the availability of biological rhythms synchronizers, such as physical activity, light exposure, or vestibular stimulation, represents a viable non-pharmacological strategy for entraining circadian rhythms and potentially fortifying the sleep-wake cycle, thereby enhancing sleep in aging. This study aims to (1) assess the impact of remote physical exercise training and its combination with bright light exposure, and (2) investigate the specific contribution of galvanic vestibular stimulation, to sleep quality among healthy older adults with sleep complaints. One hundred healthy older adults aged 60-70 years with sleep complaints will be randomly allocated to one of four groups: a physical exercise training group (n = 25), a physical exercise training combined with bright light exposure group (n = 25), a galvanic vestibular stimulation group (n = 25) or a control group (i.e., health education) (n = 25). While physical exercise training and health education will be supervised via videoconference at home, bright light exposure (for the physical exercise training combined with bright light exposure group) and vestibular stimulation will be self-administered at home. Pre-and post-tests will be conducted to evaluate various parameters, including sleep (polysomnography, subjective questionnaires), circadian rhythms (actigraphy, temperature), fitness (physical: VO2 peak, muscular function; and motor: balance, and functional mobility), cognition (executive function, long-term memory), quality of life and mood (anxiety and depression). The findings will be anticipated to inform the development of recommendations and non-pharmaceutical preventive strategies for enhancing sleep quality in older adults, potentially leading to improvements in fitness, cognition, quality of life, and mood throughout aging.

Effects of acute bouts of evening resistance or endurance exercises on sleep EEG and salivary cortisol.

Introduction: Deleterious effects of exercise close to bedtime could be due to increased physiological arousal that can be detected during sleep using sleep spectral analysis. Resistance and endurance exercises have different effects on cortisol release that may lead them to impact sleep spectral signatures differently. The present study aimed to investigate the effects of two types of evening exercise on sleep architecture, sleep spectral parameters and salivary cortisol. Methods: Young healthy participants came to our laboratory to undergo 3 counterbalanced pre-sleep conditions that started 1 h before bedtime (a resistance and an endurance exercise conditions of 30 min duration, identical in terms of workload; and a control condition) followed by polysomnographic recordings. Results were compared between the three conditions for 16 participants. Results: Sleep efficiency was lower after both endurance and resistance exercise than after the control condition. Total sleep time was lower after endurance exercise compared to the control condition. Sleep spectral analyses showed that both endurance and resistance exercises led to greater alpha power during N1 sleep stage and greater theta power during N2 sleep stage compared to the control condition. The endurance exercise led to greater beta power during N2 sleep stage, greater alpha power during REM sleep, and higher cortisol levels compared to the control condition (trend), and compared to the resistance exercise condition (significant). The resistance exercise led to lower beta power during N2 sleep stage than the control condition and lower cortisol levels than the endurance exercise condition. Discussion: This study underlines significant modifications of sleep quality and quantity after both moderate evening endurance and resistance exercises. Still, these effects cannot be considered as deleterious. In contrast to the resistance exercise, endurance exercise led to an increase in sleep EEG activity associated with hyperarousal during sleep and higher cortisol levels, suggesting an hyperarousal effect of endurance exercise performed in the evening. These results align with previous warning about the arousal effects of evening exercise but do not support the notion of deleterious effects on sleep. While these results provide support for the physiological effects of evening exercises on sleep, replication with larger sample size is needed.

A Survey Exploring How Watch Officers Manage Effects of Sleep Restrictions during Maritime Navigation.

Merchant marine officers work shifted hours with a sometimes very tiring work/rest rhythm that can lead to sleep restrictions and increased sleepiness during navigation. The aim of this study is to assess the risk of sleep deprivation-related sleepiness during navigation and the factors contributing to this risk. A second objective is to evaluate the use and effectiveness of sleepiness countermeasures. An online quantitative survey of 43 questions was conducted on 183 French maritime officers. A total of 39.9% of the participants experienced at least occasionally severe sleepiness and 29% had fallen asleep during navigation. A total of 42.6% reported not being able to experience enough sleep on board. Sleep requirements were affected by time spent on board, area of activity, and watch system. Sleepiness was more common during monotonous than demanding sailing. Officers frequently use caffeine, as well as vigilance-enhancing activities that they consider effective, which are not yet validated, (i.e., social interactions). However, they are not inclined to seek replacements in case of severe sleepiness. Sleep deprivation is common among maritime officers and leads to the risk of severe sleepiness while operating the vessel, with few effective countermeasures available. Strategies used for sleep management and sleepiness prevention should focus more on sleep duration, safety culture, and improving countermeasures to sleepiness.

Cardiorespiratory changes associated with micro-arousals during naps.

The autonomic nervous system (ANS) and the central nervous system (CNS) interplay during sleep, particularly during phasic events such as micro-arousals, has been the subject of several studies. The underlying mechanisms of such relationship which remain unclear, specifically during daytime sleep, were partly investigated in this study. Napping polysomnography was performed on two occasions at least one week apart in 15 healthy subjects. The following cardiorespiratory variables were extracted from the recordings: tachogram, pulse transit time (PTT), pulse wave amplitude, respiratory cycle amplitude, and frequency. Two experts first detected micro-arousal events, then, cardiorespiratory variables were averaged by 30-s epochs over 2 min centered on the onset of the micro-arousals. We found that in the 30 s preceding the arousal events as detected on the electroencephalogram (EEG) recordings, there was a decrease in tachogram, pulse wave amplitude, and PTT values while the respiratory amplitude increased. These changes were more prominent in stage N2 and N3 sleep than in stage N1. The present findings provide new insights into the autonomic changes during the pre-arousal period in daytime naps, as all the variables investigated suggest a sympathetic physiological origin for the changes.

Rest activity rhythms characteristics of breast cancer women following endocrine therapy.

Rest-activity rhythm (RAR) disruptions are frequently associated with chemotherapy in breast cancer (BC), but they are less known in BC with endocrine therapy (ET). The aim of this ancillary study was to characterize the RAR and estimated sleep characteristics from actigraphy in BC patients either treated (ET+) or untreated with ET (ET-), compared to healthy controls (HC) and using a cross-sectional design. Eighteen ET+, 18 ET-, and 16 HC completed questionnaires and wore wrist actigraphs at home for 2 weeks. Parametric and nonparametric RAR, sleep parameters, and quality of life were compared between groups (p < .05). BC groups presented lower daytime activity than HC according to RAR analysis (mesor and M10 parameters). Compared to HC, ET- had lower inter-daily stability and ET+ had greater sleep complaints. Compared to ET-, ET+ had lower sleep efficiency, more time awake, and higher activity levels at night, as assessed with actigraphy. Our results suggest an effect of cancer independent of treatment on RAR in BC, highlighting the need for further investigation of this topic. In contrast, sleep as assessed with actigraphy seems modified only during ET which matches with patients' sleep complaints. Further longitudinal studies would aid in confirming the latter hypothesis.

Effect of vestibular stimulation using a rotatory chair in human rest/activity rhythm.

The vestibular system is responsible for sensing every angular and linear head acceleration, mainly during periods of motor activity. Previous animal and human experiments have shown biological rhythm disruptions in small rodents exposed to a hypergravity environment, but also in patients with bilateral vestibular loss compared to a control population. This raised the hypothesis of the vestibular afferent influence on circadian rhythm synchronization. The present study aimed to test the impact of vestibular stimulation induced by a rotatory chair on the rest/activity rhythm in human subjects. Thirty-four healthy adults underwent both sham (SHAM) and vestibular stimulation (STIM) sessions scheduled at 18:00 h. An off-vertical axis rotation on a rotatory chair was used to ecologically stimulate the vestibular system by head accelerations. The rest/activity rhythm was continuously registered by actigraphy. The recording started one week before the first session (BASELINE), continued in the week between the two sessions and one week after the second session. Vestibular stimulation caused a significant decrease in the average activity level in the evening following the vestibular stimulation. A significant phase advance in the rest/activity rhythm occurred two days after the 18:00 h vestibular stimulation session. Moreover, the level of motion sickness symptoms increased significantly after vestibular stimulation. The present study confirms previous results on the effect of vestibular stimulation and the role of vestibular afferents on circadian biological rhythmicity. Our results support the hypothesis of the implication of vestibular afferents as non-photic stimuli acting on circadian rhythms.

Author Correction: Dual orexin receptor antagonist induces changes in core body temperature in rats after exercise.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Corrigendum: Impact of Galvanic Vestibular Stimulation on Anxiety Level in Young Adults.

[This corrects the article DOI: 10.3389/fnsys.2019.00014.].

Impact of Galvanic Vestibular Stimulation on Anxiety Level in Young Adults.

Galvanic vestibular stimulation (GVS) is a non-invasive method used to stimulate the vestibular system. The vestibular system includes the sensors, neural pathways, vestibular nuclei and the cortical areas receiving integrated vestibular inputs. In addition to its role in postural control or gaze stabilization, the vestibular system is involved in some cognitive functions and in emotion processing. Several studies have revealed a modulating effect of vestibular stimulation on mood state, emotional control, and anxiety level. Nevertheless, GVS is known to induce motion sickness symptoms such as nausea. The aim of the present study was to evaluate the tolerability and efficacy of a GVS protocol to be used potentially as a treatment for anxiety, and also to test the impact of stimulation parameters (duration) on anxiety. Twenty-two students underwent three stimulation conditions: (1) a sham session (no stimulation); (2) a single-duration session (38 min of GVS); and (3) a double-duration session (76 min of GVS). Before and after each stimulation, participants completed a Graybiel Scale form for motion sickness symptoms evaluation and a visual analog scale form for anxiety. We observed a significant diminution of anxiety level after a 38-min session of GVS, while a low level of motion sickness was only found following a 76-min session of GVS. Our preliminary study confirms the feasibility of using GVS to modulate anxiety and corroborates the involvement of the vestibular system in the emotional process.

Dual orexin receptor antagonist induces changes in core body temperature in rats after exercise.

Hypothalamic orexin neurons are involved in various physiological functions, including thermoregulation. The orexinergic system has been considered as a potent mediator of the exercise response. The present study describes how the antagonization of the orexinergic system by a dual orexin receptor antagonist (DORA) modifies the thermoregulatory process during exercise. Core Body Temperature (CBT) and Spontaneous Locomotor Activity (SLA) of 12 male Wistar rats were recorded after either oral administration of DORA (30 mg/kg or 60 mg/kg) or placebo solution, both at rest and in exercise conditions with treadmill running. DORA ingestion decreased SLA for 8 hours (p < 0.001) and CBT for 4 hours (p < 0.01). CBT (°C) response was independent of SLA. The CBT level decreased from the beginning to the end of exercise when orexin receptors were antagonized, with a dose-dependent response (39.09 ± 0.36 and 38.88 ± 0.28 for 30 and 60 mg/kg; p < 0.001) compared to placebo (39.29 ± 0.31; p < 0.001). CBT increased during exercise was also blunted after DORA administration, but without dose effects of DORA. In conclusion, our results favor the role of orexin in the thermoregulation under stress related to exercise conditions.

Effect of time of day on aerobic contribution to the 30-s Wingate test performance.

The purpose of this study was to evaluate the effects of time of day on aerobic contribution during high-intensity exercise. A group of 11 male physical education students performed a Wingate test against a resistance of 0.087 kg . kg(-1) body mass. Two different times of day were chosen, corresponding to the minimum (06:00 h) and the maximum (18:00 h) levels of power. Oxygen uptake (.VO(2)) was recorded breath by breath during the test (30 sec). Blood lactate concentrations were measured at rest, just after the Wingate test, and again 5 min later. Oral temperature was measured before each test and on six separate occasions at 02:00, 06:00, 10:00, 14:00, 18:00, and 22:00 h. A significant circadian rhythm was found in body temperature with a circadian acrophase at 18:16+/-00:25 h as determined by cosinor analysis. Peak power (P(peak)), mean power (P(mean)), total work done, and .VO(2) increased significantly from morning to afternoon during the Wingate Test. As a consequence, aerobic contribution recorded during the test increased from morning to afternoon. However, no difference in blood lactate concentrations was observed from morning to afternoon. Furthermore, power decrease was greater in the morning than afternoon. Altogether, these results indicate that the time-of-day effect on performances during the Wingate test is mainly due to better aerobic participation in energy production during the test in the afternoon than in the morning.

Circadian Characteristics of Older Adults and Aerobic Capacity.

BACKGROUND: Alteration of circadian rhythmicity with aging might depend on physical aerobic capacity. METHODS: Three groups of participants were established based on their peak oxygen consumption (Group 1 < 20mL/min/kg; Group 2 > 20mL/min/kg and <30mL/min/kg; Group 3 > 30mL/min/kg). Each participant had an individual evaluation of their circadian rhythmicity characteristics through two well-known circadian rhythms: core temperature and rest/activity cycles. Nocturnal sleep was also recorded using actimetry and diurnal vigilance tested in a car driving simulator. RESULTS: The amplitude of the oral temperature fluctuations for Group 1 is significantly lower (p < .05) than that of Group 3. Group 2 (p < .01) and Group 3 (p < .05) were significantly more active during the day than Group 1. The index of inactivity during the night for Groups 2 (p < .05) and 3 (p < .01) was higher than Group 1. Results of the car driving simulation showed that for Group 1, the number of lane crossings was significantly higher than Groups 2 (p < .01) and 3 (p < .01). In addition, diurnal vigilance was lower in Group 1. CONCLUSIONS: The biological clock seems to be enhanced in older participants with a higher level of physical capacity.

Diurnal variation in gait characteristics and transition speed.

The aim of this study was to investigate the effect of time-of-day on Preferred Transition Speed (PTS) and spatiotemporal organization of walking and running movements. Twelve active male subjects participated in the study (age: 27.2 ± 4.9 years; height: 177.9 ± 5.4 cm; body mass: 75.9 ± 5.86 kg). First, PTS was determined at 08:00 h and 18:00 h. The mean of the two PTS recorded at the two times-of-day tested was used as a reference (PTSm). Then, subjects were asked to walk and run on a treadmill at three imposed speeds (PTSm, PTSm + 0.3 m.s(-1), and PTSm - 0.3 m.s(-1)) at 08:00 h and 18:00 h. Mean stride length, temporal stride, spatial stride variability, and temporal stride variability were used for gait analysis. The PTS observed at 08:00 h (2.10 ± 0.17 m.s(-1)) tends to be lower (p = 0.077) than that recorded at 18:00 h (2.14 ± 0.19 m.s(-1)). Stride lengths recorded while walking (p = 0.038) and running (p = 0.041) were shorter at 08:00 h than 18:00 h. No time-of-day effect was observed for stride frequency during walking and running trials. When walking, spatial stride variability (p = 0.020) and temporal stride variability (p = 0.028) were lower at 08:00 h than at 18:00 h. When running, no diurnal variation of spatial stride variability or temporal stride variability was detected.

Morning anaerobic performance is not altered by vigilance impairment.

The aim of this study was to determine the role played by vigilance on the anaerobic performance recorded during a Wingate test performed at the bathyphase (nadir) of the circadian rhythmicity. Twenty active male participants performed a 60-s Wingate test at 6 a.m. during 3 test sessions in counter-balanced order the day after either (i) a normal reference night, (ii) a total sleep deprivation night, or (iii) a total sleep deprivation night associated with an extended simulated driving task from 9 p.m. to 5 a.m. During this task, the number of inappropriate line crossings (ILCs) was used to control and quantify the effective decrease in the level of vigilance. The main findings show that (i) vigilance of each participant was significantly altered (i.e., a drastic and progressive increase in ILCs is shown during the 7.5 hours of driving) by the sleep deprivation night associated with an extended driving task; (ii) the subjective evaluation of vigilance performed by self-rated scale revealed an increased impairment of the vigilance level between the normal reference night, the total sleep deprivation night and the total sleep deprivation night associated with an extended driving task; and (iii) the morning following this last condition, during the Wingate test, the recorded cycling biomechanical parameters (peak power, mean power and fatigue index values, power decrease, and cycling kinetic and kinematic patterns) were not significantly different from the two other conditions. Consequently, these results show that anaerobic performances recorded during a Wingate test performed at the bathyphase of the circadian rhythmicity are not altered by a drastic impairment in vigilance. These findings seem to indicate that vigilance is probably not a factor that contributes to circadian variations in anaerobic performance.