The rhythm of mental health: the relationship of chronotype with psychiatric trait dimensions and diurnal variation in psychiatric symptoms.

To advance the emergence of circadian-based therapies, this study characterized how psychiatric symptoms fluctuate across the day and vary between individuals. Using a dimensional approach, we determined how chronotype relates to 13 psychiatric traits, and modeled the temporal development of symptoms throughout the day using generalized additive mixed effects models. In this preregistered study, a subclinical sample completed 13 psychiatric trait scales and a chronotype scale at baseline (N = 515, n = 404 women, 109 men, n = 2 non-binary, M age = 32.4 years, range 18-77), followed by 22 psychiatric symptoms and behaviors rated repeatedly between ~08:00-00:00 (n = 410). Key findings are that 11 out of 13 psychiatric traits were associated with being an evening-type, ranging from depression to obsessive comulsive disorder, social anxiety, and delusional ideation, while only mania was associated with being a morning-type. Four distinct psychiatric trait factors were identified, each predicting worse symptom levels throughout the day. Fatigue-related symptoms exhibited strong time-of-day changes with evening-types experiencing worse fatigue in the morning and morning-types in the evening. Evening-types had considerably lower drive and motivation than morning-types from morning to early evening. Evening-types also had more pronounced negative emotional symptoms and ADHD-type symptoms in the evening, particularly among those high in psychiatric trait factors. These findings identified important research targets that hold promise for improving mental health outcomes, such as strategies to boost morning motivation. Furthermore, the results emphasize the relevance of incorporating circadian factors, including chronotype, into translational psychiatric research and interventions.

Diurnal variation in anxiety and activity is influenced by chronotype and probable anxiety-related disorder status.

Anxiety symptoms vary moment-to-moment within a day. One factor that may influence these variations is chronotype. Evening chronotypes prefer to engage in activities (e.g., sleep, physical and social activity) later in the day, and evening chronotype is implicated in psychopathology, including anxiety-related disorders. However, it is unknown whether chronotype influences diurnal variation in anxiety symptoms and whether these effects are amplified in individuals with a probable anxiety-related disorder. We examined the diurnal variation in anxiety symptoms and daily activities in morning and evening chronotypes with and without probable generalized anxiety disorder (GAD) or obsessive-compulsive disorder (OCD) in a community sample of adults (N = 410). Evening chronotypes reported higher anxiety symptoms, particularly in the evening hours, and lower engagement in daily activities, predominantly in the morning hours. Evening chronotypes with probable GAD or OCD reported worse anxiety symptoms in the evening. Our findings indicate that anxiety symptoms and engagement in daily activities fluctuate considerably across the day, and these patterns differ depending on chronotype. Evening chronotypes have more anxiety symptoms in the evening, despite preferring this time of day. Personalized treatment approaches that consider chronotype and target certain times of day may be efficient in alleviating peaks in anxiety symptoms.

Sleep and subjective age: protect your sleep if you want to feel young.

The current studies examined the impact of insufficient sleep and sleepiness on the subjective experience of age. Study 1, a cross-sectional study of 429 participants (282 females (66%), 144 males, 3 other gender; age range 18-70), showed that for each additional day of insufficient sleep in the last 30 days, subjective age increased by 0.23 years. Study 2, an experimental crossover sleep restriction study (n = 186; 102 females (55%), 84 males; age range 18-46), showed that two nights of sleep restriction (4 h in bed per night) made people feel 4.44 years older compared to sleep saturation (9 h in bed per night). Additionally, moving from feeling extremely alert (Karolinska Sleepiness Scale (KSS) score of 1) to feeling extremely sleepy (KSS score of 9) was associated with feeling 10 years older in both studies. These findings provide compelling support for insufficient sleep and sleepiness to exert a substantial influence on how old we feel, and that safeguarding sleep is probably a key factor in feeling young.

Discriminating between sick and healthy faces based on early sickness cues: an exploratory analysis of sex differences.

Background and objectives: It has been argued that sex and disease-related traits should influence how observers respond to sensory sickness cues. In fact, there is evidence that humans can detect sensory cues related to infection in others, but lack of power from earlier studies prevents any firm conclusion regarding whether perception of sickness cues is associated with sex and disease-related personality traits. Here, we tested whether women (relative to men), individuals with poorer self-reported health, and who are more sensitive to disgust, vulnerable to disease, and concerned about their health, overestimate the presence of, and/or are better at detecting sickness cues. Methodology: In a large online study, 343 women and 340 men were instructed to identify the sick faces from a series of sick and healthy photographs of volunteers with an induced acute experimental inflammation. Participants also completed several disease-related questionnaires. Results: While both men and women could discriminate between sick and healthy individuals above chance level, exploratory analyses revealed that women outperformed men in accuracy and speed of discrimination. Furthermore, we demonstrated that higher disgust sensitivity to body odors is associated with a more liberal decision criterion for categorizing faces as sick. Conclusion: Our findings give strong support for the human ability to discriminate between sick and healthy individuals based on early facial cues of sickness and suggest that women are significantly, although only slightly, better at this task. If this finding is replicated, future studies should determine whether women's better performance is related to increased avoidance of sick individuals.

Human scent as a first-line defense against disease.

Individuals may have a different body odor, when they are sick compared to healthy. In the non-human animal literature, olfactory cues have been shown to predict avoidance of sick individuals. We tested whether the mere experimental activation of the innate immune system in healthy human individuals can make an individuals' body odor be perceived as more aversive (intense, unpleasant, and disgusting). Following an endotoxin injection (lipopolysaccharide; 0.6 ng/kg) that creates a transient systemic inflammation, individuals smelled more unpleasant compared to a placebo group (saline injection). Behavioral and chemical analyses of the body odor samples suggest that the volatile components of samples from "sick" individuals changed qualitatively rather than quantitatively. Our findings support the hypothesis that odor cues of inflammation in axillary sweat are detectable just a few hours after experimental activation of the innate immune system. As such, they may trigger behavioral avoidance, hence constituting a first line of defense against pathogens of infected conspecifics.

Is snoozing losing? Why intermittent morning alarms are used and how they affect sleep, cognition, cortisol, and mood.

Pressing the snooze button is a common way to start the day, but little is known about this behaviour. Through two studies we determined predictors and effects of snoozing. In Study 1 (n = 1732) respondents described their waking habits, confirming that snoozing is widespread, especially in younger individuals and later chronotypes. Morning drowsiness and shorter sleep were also more common for those who snooze. Study 2 was a within-subjects laboratory study (with polysomnography) on habitual snoozers (n = 31), showing that 30 min of snoozing improved or did not affect performance on cognitive tests directly upon rising compared to an abrupt awakening. Bayes factors indicate varying strengths of this evidence. Snoozing resulted in about 6 min of lost sleep, while preventing awakenings from slow-wave sleep (N3). There were no clear effects of snoozing on the cortisol awakening response, morning sleepiness, mood, or overnight sleep architecture. A brief snooze period may thus help alleviate sleep inertia, without substantially disturbing sleep, for late chronotypes and those with morning drowsiness.

Humans can detect axillary odor cues of an acute respiratory infection in others.

Background and objectives: Body odor conveys information about health status to conspecifics and influences approach-avoidance behaviors in animals. Experiments that induce sickness in otherwise healthy individuals suggest that humans too can detect sensory cues to infection in others. Here, we investigated whether individuals could detect through smell a naturally occurring acute respiratory infection in others and whether sickness severity, measured via body temperature and sickness symptoms, was associated with the accuracy of detection. Methodology: Body odor samples were collected from 20 donors, once while healthy and once while sick with an acute respiratory infection. Using a double-blind, two-alternative forced-choice method, 80 raters were instructed to identify the sick body odor from paired sick and healthy samples (i.e. 20 pairs). Results: Sickness detection was significantly above chance, although the magnitude of the effect was low (56.7%). Raters' sex and disgust sensitivity were not associated with the accuracy of sickness detection. However, we find some indication that greater change in donor body temperature, but not sickness symptoms, between sick and healthy conditions improved sickness detection accuracy. Conclusion and implications: Our findings suggest that humans can detect individuals with an acute respiratory infection through smell, albeit only slightly better than chance. Humans, similar to other animals, are likely able to use sickness odor cues to guide adaptive behaviors that decrease the risk of contagion, such as social avoidance. Further studies should determine how well humans can detect specific infections through body odor, such as Covid-19, and how multisensory cues to infection are used simultaneously.

Pilot-Scale Antioxidant Dipping of Herring (Clupea harengus) Co-products to Allow Their Upgrading to a High-Quality Mince for Food Production.

To enable production of high-quality mince from herring backbones, a scalable antioxidant strategy is needed due to the high susceptibility of herring muscle to lipid oxidation. We here measured the stabilizing effect of lab-/pilot-scale predipping of herring backbones (30-500 kg) in antioxidant solutions prior to production of mechanically separated mince (MSM). The antioxidants were (i) Duralox MANC, a mixture of rosemary extract, ascorbic acid, α-tocopherol, and citric acid, and (ii) rosemary extract with or without isoascorbic acid. Delivery of the key rosemary-derived antioxidant components carnosol and carnosic acid was monitored during the dipping process and ice/frozen storage. Predipping in 2% Duralox MANC gave MSM with 26.7-31.7 mg/kg carnosol + carnosic acid and extended the oxidation lag phase from <1 to 12 days during ice storage and from <1 to 6 months during frozen storage compared to control. Dipping in 0.2% rosemary extract with or without 0.5% isoascorbic acid solution gave MSM with 20.6-28.2 mg/kg carnosol + carnosic acid and extended the lag phase to 6 days and 9 months during ice and frozen storage, respectively. Our results confirmed, in pilot scale, that predipping herring coproducts in antioxidant solutions is a promising strategy to utilize these raw materials for, e.g., mince and burger production rather than for low value products as fish meal.

Lipopolysaccharide-induced changes in the kynurenine pathway and symptoms of sickness behavior in humans.

Metabolites of the kynurenine pathway are hypothesized to be implicated in inflammation-associated depression, but there is a lack of experimental studies in humans assessing the kinetics of kynurenine metabolites in relation to experimentally-induced sickness. The aim of the present study was to assess changes in the kynurenine pathway and to explore its relation to symptoms of sickness behavior during an acute experimental immune challenge. This double-blind placebo-controlled randomized cross-over study included 22 healthy human participants (n = 21 both sessions, Mage = 23.4, SD = 3.6, nine women) who received an intravenous injection of 2.0 ng/kg lipopolysaccharide (LPS) and saline (placebo) on two different occasions in a randomized order. Blood samples (0 h, 1 h, 1.5 h, 2 h, 3 h, 4 h, 5 h, 7 h post-injection) were analyzed for kynurenine metabolites and inflammatory cytokines. The intensity of symptoms of sickness behavior was assessed using the 10-item Sickness Questionnaire at 0 h, 1.5 h, 3 h, 5 h, and 7 h post-injection. LPS induced significantly lower concentrations of plasma tryptophan (at 2 h, 4 h, 5 h, and 7 h post-injection), kynurenine (at 2 h, 3 h, 4 h, and 5 h post-injection), nicotinamide (at 4 h, 5 h, and 7 h post-injection), and higher levels for quinolinic acid at 5 h post-injection as compared to placebo. LPS did not affect kynurenic acid, 3-hydroxykynurenine, and picolinic acid. The development of the sickness symptoms was largely similar across items, with the highest levels around 1.5-3 h post-injection. Changes in plasma levels of kynurenine metabolites seem to coincide rather than precede or follow changes in subjective sickness. Exploratory analyses indicate that higher Sickness Questionnaire total scores at 1.5-5 h post-injection were correlated with lower kynurenic acid and nicotinamide levels. These results lend further support for LPS-induced changes in the kynurenine pathway, but may not, as interpreted from blood levels, causally link to LPS-induced acute symptoms of sickness behavior. Future research may consider a larger sample to further scrutinize the role of the kynurenine pathway in the sickness response.

Intelligence predicts better cognitive performance after normal sleep but larger vulnerability to sleep deprivation.

Fluid intelligence is seen as a beneficial attribute, protecting against stress and ill-health. Whether intelligence provides resilience to the cognitive effects of insufficient sleep was tested in the current pre-registered experimental study. Participants (N = 182) completed the Raven's test (measuring fluid intelligence) and a normal night of sleep or a night of total sleep deprivation. Sleepiness and four cognitive tests were completed at 22:30 hours (baseline), and the following day after sleep manipulation. At baseline, higher fluid intelligence was associated with faster and more accurate arithmetic calculations, and better episodic memory, but not with spatial working memory, simple attention or sleepiness. Those with higher fluid intelligence were more, not less, impacted by sleep deprivation, evident for arithmetic ability, episodic memory and spatial working memory. We need to establish a more nuanced picture of the benefits of intelligence, where intelligence is not related to cognitive advantages in all situations.

Development and performance of a sleep estimation algorithm using a single accelerometer placed on the thigh: an evaluation against polysomnography.

Accelerometers placed on the thigh provide accurate measures of daily physical activity types, postures and sedentary behaviours, over 24 h and across consecutive days. However, the ability to estimate sleep duration or quality from thigh-worn accelerometers is uncertain and has not been evaluated in comparison with the 'gold-standard' measurement of sleep polysomnography. This study aimed to develop an algorithm for sleep estimation using the raw data from a thigh-worn accelerometer and to evaluate it in comparison with polysomnography. The algorithm was developed and optimised on a dataset consisting of 23 single-night polysomnography recordings, collected in a laboratory, from 15 asymptomatic adults. This optimised algorithm was then applied to a separate evaluation dataset, in which, 71 adult males (mean [SD] age 57 [11] years, height 181 [6] cm, weight 82 [13] kg) wore ambulatory polysomnography equipment and a thigh-worn accelerometer, simultaneously, whilst sleeping at home. Compared with polysomnography, the algorithm had a sensitivity of 0.84 and a specificity of 0.55 when estimating sleep periods. Sleep intervals were underestimated by 21 min (130 min, Limits of Agreement Range [LoAR]). Total sleep time was underestimated by 32 min (233 min LoAR). Our results evaluate the performance of a new algorithm for estimating sleep and outline the limitations. Based on these results, we conclude that a single device can provide estimates of the sleep interval and total sleep time with sufficient accuracy for the measurement of daily physical activity, sedentary behaviour, and sleep, on a group level in free-living settings.

Experimental Sleep Deprivation Results in Diminished Perceptual Stability Independently of Psychosis Proneness.

Psychotic disorders as well as psychosis proneness in the general population have been associated with perceptual instability, suggesting weakened predictive processing. Sleep disturbances play a prominent role in psychosis and schizophrenia, but it is unclear whether perceptual stability diminishes with sleep deprivation, and whether the effects of sleep deprivation differ as a function of psychosis proneness. In the current study, we aimed to clarify this matter. In this preregistered study, 146 participants successfully completed an intermittent version of the random dot kinematogram (RDK) task and the 21-item Peters Delusion Inventory (PDI-21) to assess perceptual stability and psychosis proneness, respectively. Participants were randomized to sleep either as normal (8 to 9 h in bed) (n = 72; Mage = 24.7, SD = 6.2, 41 women) or to stay awake through the night (n = 74; Mage = 24.8, SD = 5.1, 44 women). Sleep deprivation resulted in diminished perceptual stability, as well as in decreases in perceptual stability over the course of the task. However, we did not observe any association between perceptual stability and PDI-21 scores, nor a tendency for individuals with higher PDI-21 scores to be more vulnerable to sleep-deprivation-induced decreases in perceptual stability. The present study suggests a compromised predictive processing system in the brain after sleep deprivation, but variation in psychosis trait is not related to greater vulnerability to sleep deprivation in our dataset. Further studies in risk groups and patients with psychosis are needed to evaluate whether sleep loss plays a role in the occurrence of objectively measured perceptual-related clinical symptoms.

Anterior insula morphology and vulnerability to psychopathology-related symptoms in response to acute inflammation.

INTRODUCTION: The role of inflammation in common psychiatric diseases is now well acknowledged. However, the factors and mechanisms underlying inter-individual variability in the vulnerability to develop psychopathology-related symptoms in response to inflammation are not well characterized. Herein, we aimed at investigating morphological brain regions central for interoception and emotion regulation, and if these are associated with acute inflammation-induced sickness and anxiety responses. METHODS: Systemic inflammation was induced using an intravenous injection of lipopolysaccharide (LPS) at a dose of 0.6 ng/kg body weight in 28 healthy individuals, while 21 individuals received an injection of saline (placebo). Individuals' gray matter volume was investigated by automated voxel-based morphometry technique on T1-weighted anatomical images derived from magnetic resonance imaging (MRI). Plasma concentrations of TNF-α and IL-6, sickness symptoms (SicknessQ), and state anxiety (STAI-S) were measured before and after the injection. RESULTS: A stronger sickness response to LPS was significantly associated with a larger anterior insula gray matter volume, independently from increases in cytokine concentrations, age, sex and body mass index (R2 = 65.6%). Similarly, a greater LPS-induced state anxiety response was related to a larger anterior insula gray matter volume, and also by a stronger increase in plasma TNF-α concentrations (R2 = 40.4%). DISCUSSION: Anterior insula morphology appears central in the sensitivity to develop symptoms of sickness and anxiety in response to inflammation, and could thus be one risk factor in inflammation-related psychopathologies. Because of the limited sample size, the current results need to be replicated.

Do Mothers Have Worse Sleep Than Fathers? Sleep Imbalance, Parental Stress, and Relationship Satisfaction in Working Parents.

PURPOSE: Previous research indicates that mothers take a larger responsibility for child care during the night and that they have more disturbed sleep than fathers. The purpose of this study was to determine whether such a sleep imbalance exists in working parents of young children, and the extent to which it depends on the way sleep is measured. The study also examined whether imbalanced sleep between parents predicts parental stress and relationship satisfaction. METHODS: Sleep was measured for seven consecutive days in 60 parenting couples (average age of the youngest child: 3.3 years ± SD 2.5 years). Actigraphs were worn across the week, and ratings of sleep, parental stress, and relationship satisfaction were made daily. RESULTS: Mothers perceived their sleep quality as worse (b= -0.38 scale units, p<0.001), with more wake periods (b= +0.96 awakenings, p<0.001) but with longer sleep duration (b= +32.4 min, p<0.01) than fathers. Actigraphy data confirmed that mothers slept longer than fathers (b= +28.03 min, p<0.001), but no significant differences were found for wake time, number of awakenings or who woke up first during shared awakenings. Furthermore, there was no difference in whether mothers and fathers slept sufficiently. The level of sleep imbalance between parents did not predict parental stress. A larger imbalance in subjective sleep sufficiency predicted decreased relationship satisfaction for fathers (b= -0.13 scale units, p<0.01) but increased relationship satisfaction for mothers (b= 0.14 scale units, p<0.05). No other sleep imbalance measures predicted relationship satisfaction. CONCLUSION: Our findings are in line with previous research on sleep in men and women in general, with longer sleep and subjective reports of sleep disturbances in women, rather than previous research on sleep in parents of young children. Thus, we found no evidence of a sleep imbalance when both parents have similar working responsibilities.

Poor sleep quality is associated with worse self-rated health in long sleep duration but not short sleep duration.

Unhealthy sleep duration, either short or long, is associated with worse health and central subjective dimensions of sleep and health such as fatigue. It has been argued that the link between sleep duration and health may depend on the quality of the slept hours, and on its functional impact (ie, fatigue). The present study therefore assessed whether the relationship between last night's sleep duration and general self-rated health (SRH) differs as a function of sleep quality, and secondly, whether current fatigue and sleep quality are factors linking sleep duration and SRH. The present cross-sectional dataset involved 1304 individuals (57% female, Mage = 28.8, range 18-79). Participants completed surveys for general SRH, previous night's sleep duration and sleep quality, and current fatigue. Results showed the expected inverted U-shaped (ie, quadratic) relation between last night's sleep duration and SRH and a linear relation between last night's sleep quality and SRH. However, long sleep duration was only associated with poorer SRH in individuals who also reported poor sleep quality. Further, the quadratic relationship between sleep duration and SRH was partially mediated by fatigue and sleep quality. The results of this multi-study analysis suggest that SRH is particularly poor in those who slept both long and with poor quality the night before, while good sleep quality may protect those with a long sleep duration from poor SRH. Thus, last night's long sleep does not seem to be associated with poor subjective health unless it is coupled with poor sleep quality. Furthermore, fatigue and sleep quality are potential pathways linking short and long sleep duration with SRH. Different dimensions of sleep interact in their association with health, and future research will benefit from an integrative approach.

Deep Learning for Identification of Acute Illness and Facial Cues of Illness.

Background: The inclusion of facial and bodily cues (clinical gestalt) in machine learning (ML) models improves the assessment of patients' health status, as shown in genetic syndromes and acute coronary syndrome. It is unknown if the inclusion of clinical gestalt improves ML-based classification of acutely ill patients. As in previous research in ML analysis of medical images, simulated or augmented data may be used to assess the usability of clinical gestalt. Objective: To assess whether a deep learning algorithm trained on a dataset of simulated and augmented facial photographs reflecting acutely ill patients can distinguish between healthy and LPS-infused, acutely ill individuals. Methods: Photographs from twenty-six volunteers whose facial features were manipulated to resemble a state of acute illness were used to extract features of illness and generate a synthetic dataset of acutely ill photographs, using a neural transfer convolutional neural network (NT-CNN) for data augmentation. Then, four distinct CNNs were trained on different parts of the facial photographs and concatenated into one final, stacked CNN which classified individuals as healthy or acutely ill. Finally, the stacked CNN was validated in an external dataset of volunteers injected with lipopolysaccharide (LPS). Results: In the external validation set, the four individual feature models distinguished acutely ill patients with sensitivities ranging from 10.5% (95% CI, 1.3-33.1% for the skin model) to 89.4% (66.9-98.7%, for the nose model). Specificity ranged from 42.1% (20.3-66.5%) for the nose model and 94.7% (73.9-99.9%) for skin. The stacked model combining all four facial features achieved an area under the receiver characteristic operating curve (AUROC) of 0.67 (0.62-0.71) and distinguished acutely ill patients with a sensitivity of 100% (82.35-100.00%) and specificity of 42.11% (20.25-66.50%). Conclusion: A deep learning algorithm trained on a synthetic, augmented dataset of facial photographs distinguished between healthy and simulated acutely ill individuals, demonstrating that synthetically generated data can be used to develop algorithms for health conditions in which large datasets are difficult to obtain. These results support the potential of facial feature analysis algorithms to support the diagnosis of acute illness.

Human sickness detection is not dependent on cultural experience.

Animals across phyla can detect early cues of infection in conspecifics, thereby reducing the risk of contamination. It is unknown, however, if humans can detect cues of sickness in people belonging to communities with whom they have limited or no experience. To test this, we presented Western faces photographed 2 h after the experimental induction of an acute immune response to one Western and five non-Western communities, including small-scale hunter-gatherer and large urban-dwelling communities. All communities could detect sick individuals. There were group differences in performance but Western participants, who observed faces from their own community, were not systematically better than all non-Western participants. At odds with the common belief that sickness detection of an out-group member should be biased to err on the side of caution, the majority of non-Western communities were unbiased. Our results show that subtle cues of a general immune response are recognized across cultures and may aid in detecting infectious threats.

Objective and Subjective Sleep in Rheumatoid Arthritis and Severe Seasonal Allergy: Preliminary Assessments of the Role of Sickness, Central and Peripheral Inflammation.

INTRODUCTION: Disturbed sleep in inflammatory disorders such as allergy and rheumatoid arthritis (RA) is common and may be directly or indirectly related to disease processes, but has not been well characterized in these patient groups, especially not with objective methods. AIM: The present study aimed to characterize objective and subjective sleep in patients with allergy or RA using sleep diaries, one-channel EEG and actigraphy. It also aimed to investigate if sleep measures were associated with central immune activation, assessed using translocator protein (TSPO) positron emission tomography, as well as cytokine markers of peripheral inflammation and disease-specific symptoms or general symptoms of sickness. METHODS: In total, 18 patients with seasonal pollen allergy, 18 patients with RA and 26 healthy controls were included in the study. Allergy patients and matched controls were assessed twice, in and out of pollen season, and RA patients and controls were assessed once. Sleep was recorded for approximately 1 week at each occasion. RESULTS: Patients with allergy had increased levels of slow-wave sleep during pollen season. In contrast, patients with RA had less SWS compared to healthy controls, while no differences were observed in sleep duration or subjective sleep quality. Across groups, neither proinflammatory cytokines, grey matter TSPO levels nor general sickness symptoms were associated with objective or subjective measures of sleep. Rhinitis, but not conjunctivitis, was correlated to worse subjective sleep and more slow wave sleep in allergy. Functional status, but not disease activity, predicted lower subjective sleep in RA. CONCLUSION: This study tentatively indicates that both patients with allergy and RA display sleep alterations but does not support inflammation as an independent predictor of the sleep disturbance across these patient groups.

Quantifying Cognitive Impairment After Sleep Deprivation at Different Times of Day: A Proof of Concept Using Ultra-Short Smartphone-Based Tests.

Cognitive functioning is known to be impaired following sleep deprivation and to fluctuate depending on the time of day. However, most methods of assessing cognitive performance remain impractical for environments outside of the lab. This study investigated whether 2-min smartphone-based versions of commonly used cognitive tests could be used to assess the effects of sleep deprivation and time of day on diverse cognitive functions. After three nights of normal sleep, participants (N = 182) were randomised to either one night of sleep deprivation or a fourth night of normal sleep. Using the Karolinska WakeApp (KWA), participants completed a battery of 2-min cognitive tests, including measures of attention, arithmetic ability, episodic memory, working memory, and a Stroop test for cognitive conflict and behavioural adjustment. A baseline measurement was completed at 22:30 h, followed by three measurements the following day at approximately 08:00 h, 12:30 h, and 16:30 h. Sleep deprivation led to performance impairments in attention, arithmetic ability, episodic memory, and working memory. No effect of sleep deprivation was observed in the Stroop test. There were variations in attention and arithmetic test performance across different times of day. The effect of sleep deprivation on all cognitive tests was also found to vary at different times of day. In conclusion, this study shows that the KWA's 2-min cognitive tests can be used to detect cognitive impairments following sleep deprivation, and fluctuations in cognitive performance relating to time of day. The results demonstrate the potential of using brief smartphone-based tasks to measure a variety of cognitive abilities within sleep and fatigue research.