Decreased salivary alpha-amylase levels are associated with performance deficits during sleep loss

Salivary α-amylase as a marker of sleep disorders: A theoretical review

Sleep disorders are commonplace in our modern societies. Specialized hospital departments are generally overloaded, and sleep assessment is an expensive process in terms of equipment, human resources, and time. Biomarkers would usefully complement current measures in the screening and follow-up of sleep disorders and their daytime repercussions. Among salivary markers, a growing body of literature suggests that salivary α-amylase (sAA) may be a cross-species marker of sleep debt. However, there is no consensus as to the direction of variation in sAA with sleep disorders. Herein, after describing the mechanisms of sAA secretion and its relationship with stress, studies assessing the relationship between sAA and sleep parameters are reviewed. Finally, the influence of confounding factors is discussed, along with methodological considerations, to better understand the fluctuations in sAA and facilitate future studies in the field.

Accurate detection of acute sleep deprivation using a metabolomic biomarker-A machine learning approach

Sleep deprivation enhances risk for serious injury and fatality on the roads and in workplaces. To facilitate future management of these risks through advanced detection, we developed and validated a metabolomic biomarker of sleep deprivation in healthy, young participants, across three experiments. Bi-hourly plasma samples from 2 × 40-hour extended wake protocols (for train/test models) and 1 × 40-hour protocol with an 8-hour overnight sleep interval were analyzed by untargeted liquid chromatography-mass spectrometry. Using a knowledge-based machine learning approach, five consistently important variables were used to build predictive models. Sleep deprivation (24 to 38 hours awake) was predicted accurately in classification models [versus well-rested (0 to 16 hours)] (accuracy = 94.7%/AUC 99.2%, 79.3%/AUC 89.1%) and to a lesser extent in regression (R2 = 86.1 and 47.8%) models for within- and between-participant models, respectively. Metabolites were identified for replicability/future deployment. This approach for detecting acute sleep deprivation offers potential to reduce accidents through "fitness for duty" or "post-accident analysis" assessments.

Sleepiness in adults: An umbrella review of a complex construct

Sleepiness involves many dimensions that require investigation. Since sleepiness is often defined operationally, we exhaustively inventoried all the assessment tools designed to measure it in an umbrella review, without any preconceptions, i.e. a review of reviews. We included all reviews and systematic reviews related to sleepiness assessment tools published up to March 2021. Three investigators independently assessed the eligibility of studies for inclusion and identified 36 relevant reviews. In total, 99 tools were identified and classified into 8 categories. We classified them depending on their category, their publication year and the number of mentions in the 36 included reviews. The 6 most frequently cited were the Epworth sleepiness scale, the multiple sleep latency test, the maintenance of wakefulness test, the Stanford sleepiness scale, the Karolinska sleepiness scale, and the psychomotor vigilance task. Despite the limitation that we may have missed some recently developed tools, this historical perspective on sleepiness measurement is a first step toward a better delineation of the different dimensions underlying the constructs of sleepiness, and will serve as a basis for further discussion in the clinical and research sleep community.

Interest of the BLAST paradigm and salivary markers for the evaluation of sleepiness in drivers

Objectives

Sleepiness is associated with decreased cognitive abilities and remains one of the main causes of fatal road accidents. The tools currently available to assess sleepiness, such as questionnaires, are subject to intra- and inter-individual variability, while multiple sleep latency tests are only feasible in few sleep laboratories. The main objective of this study was to explore new potential markers (neurocognitive, biological) to objectively assess sleepiness in drivers.

Methods

A total of 186 drivers (median age 44 years, range 20–74 years, 73% men, 14% obese) were included during a break at a highway service area, in the morning, while on the road for vacation. Questionnaires on sleepiness and sleep characteristics (habitual and on the night before travel), the Bron-Lyon Attention Stability Test (BLAST), and two salivary samples (α-amylase and oxalate) were collected. Associations between measures of sleepiness [Epworth Sleepiness Scale (ESS), and Stanford Sleepiness Scale (SSS)], sleep characteristics, neurocognitive, and biological markers were tested using regression models adjusted for confounding factors.

Results

The night before travel, 83% of the drivers reduced their sleep time and 30% slept 5 h or less. The higher the number of miles to be traveled, the higher the decrease, and the shorter the sleep time. The night before travel, 18 and 24% of the drivers complained of poor sleep quality and difficulty falling asleep. The sleep characteristics on the night before travel were associated with the habitual sleep characteristics. At the time of the test, 47% of the drivers scored pathologically on the SSS. Poor sleep quality and difficulty falling asleep the night before travel were associated with increased sleepiness as assessed by the SSS and decreased attentional ability as assessed by the BLAST. No association between salivary markers and acute sleepiness was observed.

Conclusions

The sleep characteristics of the night before travel were associated with sleepiness and attentional performance. The SSS and the BLAST could be used by individual drivers in a self-evaluation context. Biological markers showed a high variability and limited association with sleep parameters across subjects, emphasizing the need for within-subject designs to assess their usefulness.

Effects of Nature-Based Intervention in Occupational Health Care on Stress – A Finnish Pilot Study Comparing Stress Evaluation Methods

Purpose

To assess methodology and its limitations for measuring effects of nature-based intervention (NBI).

Patients and Methods

Participants were 11 middle-aged female health care workers with lowered capacity to work. NBI included six group appointments in six months study period. Heart rate variability (HRV) and self-reported pain and work exhaustion were measured pre-post study period. Salivary α-amylase samples were collected immediately before and after three individual interventions. Salivary cortisol samples were collected on the same three interventions, on three consecutive days starting from the day of intervention, to assess (a) month effect (pre-post study period) and (b) day effect (intervention day vs non-intervention day).

Results

Individual interventions resulted in increase in α-amylase activity. However, the average fold increase decreased from the 3.05 ± 1.20 of the first intervention to 1.91 ± 1.00 and 1.46 ± 0.77 in the second and third intervention, respectively (p < 0.001). Cortisol concentrations were lower on intervention days vs non-intervention days, the difference being indicative (p = 0.050). Pain and work exhaustion decreased during the study period, as well as HRV, although any of these changes was not statistically significant.

Conclusion

For a large-scale study, it would be ideal to select assays for both major pathways: hypothalamic-pituitary-adrenal axis can be measured by cortisol, whereas response via autonomic nervous system can be measured by HRV, when roles of sympathetic and parasympathetic nervous systems can be pinpointed separately. Salivary α-amylase can be used when continuous monitoring is not possible. Psychological well-being of participants should be surveyed, as well as their activities and moods on sampling days recorded.

Strategies to Limit Cognitive Impairments under Sleep Restriction: Relationship to Stress Biomarkers

Adding relaxation techniques during nap or auditory stimulation of EEG slow oscillation (SO) during nighttime sleep may limit cognitive impairments in sleep-deprived subjects, potentially through alleviating stress-releasing effects. We compared daytime sleepiness, cognitive performances, and salivary stress biomarker responses in 11 volunteers (aged 18–36) who underwent 5 days of sleep restriction (SR, 3 h per night, with 30 min of daily nap) under three successive conditions: control (SR-CT), relaxation techniques added to daily nap (SR-RT), and auditory stimulation of sleep slow oscillations (SO) during nighttime sleep (SR-NS). Test evaluation was performed at baseline (BASE), the fifth day of chronic SR (SR5), and the third and fifth days after sleep recovery (REC3, REC5, respectively). At SR5, less degradation was observed for percentage of commission errors in the executive Go–noGo inhibition task in SR-RT condition compared to SR-CT, and for sleepiness score in SR-NS condition compared both to SR-CT and SR-RT. Beneficial effects of SR-RT and SR-NS were additionally observed on these two parameters and on salivary α-amylase (sAA) at REC3 and REC5. Adding relaxation techniques to naps may help performance in inhibition response, and adding nocturnal auditory stimulation of SO sleep may benefit daytime sleepiness during sleep restriction with persistent effects during recovery. The two strategies activated the autonomic nervous system, as shown by the sAA response.

Caffeine may disrupt the impact of real-time drowsiness on cognitive performance: a double-blind, placebo-controlled small-sample study

Caffeine is widely used to promote alertness and cognitive performance under challenging conditions, such as sleep loss. Non-digestive modes of delivery typically reduce variability of its effect. In a placebo-controlled, 50-h total sleep deprivation (TSD) protocol we administered four 200 mg doses of caffeine-infused chewing-gum during night-time circadian trough and monitored participants' drowsiness during task performance with infra-red oculography. In addition to the expected reduction of sleepiness, caffeine was found to disrupt its degrading impact on performance errors in tasks ranging from standard cognitive tests to simulated driving. Real-time drowsiness data showed that caffeine produced only a modest reduction in sleepiness (compared to our placebo group) but substantial performance gains in vigilance and procedural decisions, that were largely independent of the actual alertness dynamics achieved. The magnitude of this disrupting effect was greater for more complex cognitive tasks.

Motorcycling performance and sleepiness during an extended ride on a dynamic simulator: relationship with stress biomarkers

OBJECTIVE

Powered two-wheelers (PTW) make up a large proportion of fatal accidents. The aim of this study was to investigate the effects of time-of-day and total sleep deprivation (SD) on simulated motorcycling performance during extended riding sessions (60 min), while evaluating stress mechanisms.

APPROACH

A total of 16 healthy males participated in four simulated motorcycling sessions at 07:00, 11:00, 15:00 and 19:00, including city (8 min), country (2 min) and highway pathways (40 min), after a normal night of sleep and after total SD (30 h), in a randomized counterbalanced order. The recorded motorcycle parameters included: variation of lateral position, number of inappropriate line crossings (ILC), falls, riding errors, speed and speed limit violations. Subject parameters included the number of microsleeps in each pathway, the number of lapses during the 3-min psychomotor vigilance task (PVT-Brief version), and the Karolinska sleepiness scale (KSS) score. Saliva samples were used to assess cortisol (sC), α-amylase (sAA), and chromogranin-A (sCgA). ANOVAs and Pearson's correlation analysis were performed between these variables.

MAIN RESULTS

Most parameters were influenced by an interaction effect between 'Motorcycling pathways' × 'SD' (speed (p < 0.05), legal speed violations (p < 0.01), variation of lateral position (p < 0.001), falls (p < 0.001), EEG-microsleeps (p < 005)). An interaction effect between 'SD' × 'Time-of-day' influenced the number of ILCs (p < 0.01), sC (p < 0.05) and sCgA (p < 0.05) levels. SD affected KSS scores (p < 0.001) and PVT lapses (p < 0.05). The highest disturbances were associated with highway motorcycling simulation.

SIGNIFICANCE

Sleepiness due to circadian or SD and fatigue effects significantly affect riding and increase the risks involved with PTWs. The activation of both stress systems seems not sufficient to alleviate these deleterious effects.

The role of sleep disturbances in depressive-like behavior with emphasis on α-ketoglutarate dehydrogenase activity in rats

Sleep disorders may induce anxiety- and depressive-like behaviors. Furthermore, sleep disorders can alter the function of α-KGDH (α-ketoglutarate dehydrogenase), which is involved in the citric acid cycle. In this study, we evaluated the effect of two models of sleep deprivation (SD) including total SD (TSD) and partial SD (PSD), and two models of napping combined with each models of SD on rats' performance in Forced Swim Test (FST) and α-KGDH activity in both hemispheres of the amygdala. 64 male Wistar rats were used in this study. A modified water box was also used to induce SD. The results showed that, immobility was increased in 48-hour PSD group, indicating a possible depressive-like behavior. Swimming time was also increased following 48-hour TSD. However, climbing time was decreased in 48-hour PSD/TSD groups. Additionally, α-KGDH activity was increased in the left amygdala in 48-hour TSD and PSD groups. In conclusion, PSD may increase depressive-like behavior. TSD and PSD can decrease swimming time but increase climbing time, and these effects may be related to serotonergic and noradrenergic transmissions, respectively. Increase in α-KGDH activity in the left amygdala may be related to the brain's need for more energy during prolonged wakefulness. α-KGDH activity in the right amygdala was unaffected probably due to a decrease in alertness following SD.

Effects of strategic early-morning caffeine gum administration on association between salivary alpha-amylase and neurobehavioural performance during 50 h of sleep deprivation

Self-assessment is the most common method for monitoring performance and safety in the workplace. However, discrepancies between subjective and objective measures have increased interest in physiological assessment of performance. In a double-blind placebo-controlled study, 23 healthy adults were randomly assigned to either a placebo (n = 11; 5 F, 6 M) or caffeine condition (n = 12; 4 F, 8 M) while undergoing 50 h (i.e. two days) of total sleep deprivation. In previous work, higher salivary alpha-amylase (sAA) levels were associated with improved psychomotor vigilance and simulated driving performance in the placebo condition. In this follow-up article, the effects of strategic caffeine administration on the previously reported diurnal profiles of sAA and performance, and the association between sAA and neurobehavioural performance were investigated. Participants were given a 10 h baseline sleep opportunity (monitored via standard polysomnography techniques) prior to undergoing sleep deprivation (total sleep time: placebo = 8.83 ± 0.48 h; caffeine = 9.01 ± 0.48 h). During sleep deprivation, caffeine gum (200 mg) was administered at 01:00 h, 03:00 h, 05:00 h, and 07:00 h to participants in the caffeine condition (n = 12). This strategic administration of caffeine gum (200 mg) has been shown to be effective at maintaining cognitive performance during extended wakefulness. Saliva samples were collected, and psychomotor vigilance and simulated driving performance assessed at three-hour intervals throughout wakefulness. Caffeine effects on diurnal variability were compared with previously reported findings in the placebo condition (n = 11). The impact of caffeine on the circadian profile of sAA coincided with changes in neurobehavioural performance. Higher sAA levels were associated with improved performance on the psychomotor vigilance test during the first 24 h of wakefulness in the caffeine condition. However, only the association between sAA and response speed (i.e. reciprocal-transform of mean reaction time) was consistent across both days of sleep deprivation. The association between sAA and driving performance was not consistent across both days of sleep deprivation. Results show that the relationship between sAA and reciprocal-transform of mean reaction time on the psychomotor vigilance test persisted in the presence of caffeine, however the association was relatively weaker as compared with the placebo condition.

Poor night's sleep predicts following day's salivary alpha-amylase under high but not low stress

Although sleep is linked to physiological stress systems like the autonomic nervous system (ANS), research is still limited regarding night-and-day interactions between nocturnal sleep characteristics, stress, and diurnal parameters of salivary alpha-amylase (sAA) as a surrogate marker of ANS activity. Fifty healthy university students rated their chronic stress burden and completed two five-day periods of ecological momentary assessment - under everyday conditions of both low stress (beginning of semester) and high stress (final examination preparation). Participants collected saliva six times daily and reported on the previous night's sleep (quality, latency, duration, disturbances) immediately after awakening. Additionally, a sub-sample wore actigraphs recording 'time in bed'. In contrast to previous assumptions, poor sleep predicted lower sAA awakening values, more decreased awakening responses, and steeper diurnal slopes the following day only under high stress, but not under low stress. Diurnal sAA parameters did not predict the following night's sleep characteristics. The sAA profile does not seem to be sensitive to everyday occurring sleep variations, but rather seems to be an indicator of more prolonged stress induced ANS dysregulation.

Does sleep deprivation increase the vulnerability to acute psychosocial stress in young and older adults?

Sleep loss and psychosocial stress often co-occur in today's society, but there is limited knowledge on the combined effects. Therefore, this experimental study investigated whether one night of sleep deprivation affects the response to a psychosocial challenge. A second aim was to examine if older adults, who may be less affected by both sleep deprivation and stress, react differently than young adults. 124 young (18-30 years) and 94 older (60-72 years) healthy adults participated in one of four conditions: i. normal night sleep & Placebo-Trier Social Stress Test (TSST), ii. normal night sleep & Trier Social Stress Test, iii. sleep deprivation & Placebo-TSST, iv. sleep deprivation & TSST. Subjective stress ratings, heart rate variability (HRV), salivary alpha amylase (sAA) and cortisol were measured throughout the protocol. At the baseline pre-stress measurement, salivary cortisol and subjective stress values were higher in sleep deprived than in rested participants. However, the reactivity to and recovery from the TSST was not significantly different after sleep deprivation for any of the outcome measures. Older adults showed higher subjective stress, higher sAA and lower HRV at baseline, indicating increased basal autonomic activity. Cortisol trajectories and HRV slightly differed in older adults compared with younger adults (regardless of the TSST). Moreover, age did not moderate the effect of sleep deprivation. Taken together, the results show increased stress levels after sleep deprivation, but do not confirm the assumption that one night of sleep deprivation increases the responsivity to an acute psychosocial challenge.