Rhythm Of Core Temperature Research Articles

Is there a diurnal variation of COVID-19 patients warranting presentation to the health centre? A chronobiological observational cross-sectional study

Background The circadian clock regulates the function of the immune system, the replication of viruses, and the magnitude of infections. The aim of this study was to analyse whether hospital attendance in Coronavirus disease 2019 (COVID-19) patients presents a diurnal variation. Methods Data from the electronic medical records of 1094 COVID-19 patients who presented to a Health Centre in Qatar during the month of July 2020 was retrospectively analysed. The following demographic (i.e. time of day (TOD), sex, age), clinical (i.e. cycle threshold (CT), temperature, oxy-haemoglobin saturation and resting heart-rate), biochemical (i.e. uraemia, glycaemia and albuminia) and haematological (i.e. leukocytes, erythrocytes ad platelets) parameters were collected. Results Univariate analysis showed a significant effect of TOD on hospital admission (p < 0.001), with patients attending the health care centre more during the active behavioural phase (08h00-00h00) compared to the resting phase (00h00-08h00). COVID-19 infection blunted the circadian rhythms of core body temperature, neutrophils and leukocytes family and shifted the circadian rhythms of resting heart-rate and uraemia. Correlation analysis showed a near perfect negative correlation between the age of patients and the TOD (r=–0.97), with older patients attending the care centre earlier during the day. Conclusion COVID-19 infection affected the circadian rhythms of the host through disrupting the circadian rhythms of core temperature and innate immunity mediators. Old patients attend the health care centre earlier compared to younger ones. However, CT during polymerase chain reaction-test was unaffected by the TOD, which limits the conclusion that COVID-19 viral infection exhibits diurnal variation.

Estradiol treatment improves biological rhythms in a preclinical rat model of menopause

The perimenopausal transition at middle age is often associated with hot flashes and sleep disruptions, metabolic changes, and other symptoms. Whereas the mechanisms for these processes are incompletely understood, both aging (AG) and a loss of ovarian estrogens play contributing roles. Furthermore, the timing of when estradiol (E) treatment should commence and for how long are key clinical questions in the management of symptoms. Using a rat model of surgical menopause, we determined the effects of regimens of E treatment with differing time at onset and duration of treatment on diurnal rhythms of activity and core temperature and on food intake and body weight. Reproductively mature (MAT, ∼4 months) or AG (∼11 months) female rats were ovariectomized, implanted intraperitoneally with a telemetry device, and given either a vehicle (V) or E subcutaneous capsule implantation. Rats were remotely recorded for 10 days per month for 3 (MAT) or 6 (AG) months. To ascertain whether delayed onset of treatment affected rhythms, a subset of AG-V rats had their capsules switched to E at the end of 3 months. Another set of AG-E rats had their capsules removed at 3 months to determine whether beneficial effects of E would persist. Overall, activity and temperature mesor, robustness, and amplitude declined with AG. Compared to V treatment, E-treated rats showed (1) better maintenance of body weight and food intake; (2) higher, more consolidated activity and temperature rhythms; and (3) higher activity and temperature robustness and amplitude. In the AG arm of the study, switching treatment from V to E or E to V quickly reversed these patterns. Thus, the presence of E was the dominant factor in determining stability and amplitude of locomotor activity and temperature rhythms. As a whole, the results show benefits of E treatment, even with a delay, on biological rhythms and physiological functions.

Site and type of craniopharyngiomas impact differently on 24-hour circadian rhythms and surgical outcome. A neurophysiological evaluation.

This study aimed to quantify 24h body core temperature (BcT°) and sleep-wake cycle rhythm alterations in craniopharyngioma (CP) patients and to identify markers related to the postsurgical outcomes. Ten consecutive CP patients underwent neuroradiological, endocrinological and ophthalmological evaluations, 24h BcT° and sleep-wake cycle recordings before and after endoscopic endonasal surgery. The sample included four women and six men. Nocturnal sleep efficiency was pathologically reduced in eight patients before surgery. Seven out of ten patients presented one to three daytime naps. 24h BcT° rhythm was pathological in six out of ten cases. Post-surgery sleep efficiency normalized in four out of eight patients, whereas nine out of ten patients presented with two to six longer daytime naps. Diurnal naps were mainly present in patients showing pre-operative involvement of the third ventricle floor. 24h BcT° remained pathological in only one out of six cases, returned to normal in two and improved in three. 24h BcT° rhythm improved more in papillary CPs than in adamantomatous CPs. Our data confirmed that both CP and surgery frequently disrupt the sleep-wake cycle and BcT° rhythms. Tumour location and histotype may be related to a worse postsurgical outcome. Therefore, in-depth investigation including circadian monitoring is crucial for surgical outcome.

Sleep-wake profiles and circadian rhythms of core temperature and melatonin in young people with affective disorders

While disturbances of the sleep-wake cycle are common in people with affective disorders, the characteristics of these disturbances differ greatly between individuals. This heterogeneity is likely to reflect multiple underlying pathophysiologies, with different perturbations in circadian systems contributing to the variation in sleep-wake cycle disturbances. Such disturbances may be particularly relevant in adolescents and young adults with affective disorders as circadian rhythms undergo considerable change during this key developmental period. This study aimed to identify profiles of sleep-wake disturbance in young people with affective disorders and investigate associations with biological circadian rhythms. Fifty young people with affective disorders and 19 control participants (aged 16–31 years) underwent actigraphy monitoring for approximately two weeks to derive sleep-wake cycle parameters, and completed an in-laboratory assessment including evening dim-light saliva collection for melatonin assay and overnight continuous core body temperature measurement. Cluster analysis based on sleep-wake cycle parameters identified three distinct patient groups, characterised by ‘delayed sleep-wake’, ‘disrupted sleep’, and ‘long sleep’ respectively. The ‘delayed sleep-wake’ group had both delayed melatonin onset and core temperature nadir; whereas the other two cluster groups did not differ from controls on these circadian markers. The three groups did not differ on clinical characteristics. These results provide evidence that only some types of sleep-wake disturbance in young people with affective disorders are associated with fundamental circadian perturbations. Consequently, interventions targeting endogenous circadian rhythms to promote a phase shift may be particularly relevant in youth with affective disorders presenting with delayed sleep-wake cycles.

0701 CIRCADIAN TAU DIFFERENCES IN BIOLOGICAL, BEHAVIOURAL AND SLEEPINESS RHYTHMS IN DELAYED SLEEP-WAKE PHASE DISORDER AND NON-24-HOUR SLEEP-WAKE RHYTHM DISORDER PATIENTS

In this study we investigated biological, sleepiness and behavioural rhythm period lengths (i.e., taus) of Delayed Sleep-Wake Phase Disorder (DSWPD), Non-24-Hour Sleep-Wake Rhythm Disorder (N24SWD) patients and healthy control sleepers. We also ran cross-correlation analyses between different rhythm variables to examine phase angle of entrainment. The aim was to explore if behavioural rhythms, in addition to the biological circadian rhythms contribute to misalignments of sleep timing symptomatic of DSWPD and N24SWD. Twenty-six DSWPD participants who met diagnostic criteria (17m, 9f, age: 21.85 ± 4.97 years) and 18 controls (10m, 8f, age: 23.72 ± 5.10 years) participated in an 80-hour modified constant routine. Additionally, 4 full-sighted patients (3m, 1f, age: 25.75 ± 4.99 years) were diagnosed with N24SWD and included as a discrete study group. A forced-desynchrony ultradian protocol of 1-hour ‘days’ in dim light, controlled conditions alternated 20-minute sleep opportunities with 40-minute enforced wakefulness. Subjective sleepiness ratings were recorded prior to every sleep opportunity and median reaction time (vigilance) was measured hourly. Amount of sleep obtained (sleep propensity) was derived from 20-minute sleep opportunities to quantify hourly objective sleepiness. Hourly core body temperature was recorded and salivary melatonin assayed to measure endogenous circadian rhythms. Rhythm data were curved using the 2-component cosine model. DSWPD and N24SWD patients had significantly longer melatonin and temperature taus compared to controls. There were no significant tau differences between groups as measured by subjective sleepiness, sleep propensity and vigilance rhythms. However, DSWPD patients showed a greater interval between maximum sleep propensity and minimum core body temperature. Their sleep propensity rhythms lagged core temperature rhythms by an hour more compared to controls’ sleep propensity and core temperature rhythms. The findings provide further evidence that delayed circadian rhythms in DSWPD may result from larger phase angles between core body temperature and sleep propensity. This interval may result in later sleep timing in DSWPD patients relative to their circadian timing thus masking their light exposure during a time that is critical to phase-advancing the circadian system. This project was funded by the Australian Research Council.

Postoperative outcome of body core temperature rhythm and sleep-wake cycle in third ventricle craniopharyngiomas.

OBJECTIVE One of the more serious risks in the treatment of third ventricle craniopharyngiomas is represented by hypothalamic damage. Recently, many papers have reported the expansion of the indications for the endoscopic endonasal approach (EEA) to be used for these tumors as well. The aim of this study was to assess the outcome of sleep-wake cycle and body core temperature (BCT), both depending on hypothalamic control, in patients affected by craniopharyngiomas involving the third ventricle that were surgically treated via an EEA. METHODS All consecutive adult patients with craniopharyngiomas that were treated at one center via an EEA between 2014 and 2016 were prospectively included. Each patient underwent neuroradiological, endocrinological, and ophthalmological evaluation; 24-hour monitoring of the BCT rhythm; and the sleep-wake cycle before surgery and at follow-up of at least 6 months. RESULTS Ten patients were included in the study (male/female ratio 4:6, mean age 48.6 years, SD 15.9 years). Gross-total resection was achieved in 8 cases. Preoperative BCT rhythm was pathological in 6 patients. After surgery, these disturbances resolved in 2 cases, improved in another 3, and remained the same in 1 patient; also, 1 case of de novo onset was observed. Before surgery the sleep-wake cycle was pathological in 8 cases, and it was restored in 4 patients at follow-up. After surgery the number of patients reporting diurnal naps increased from 7 to 9. CONCLUSIONS The outcome of the sleep-wake cycle and BCT analyzed after EEA in this study is promising. Despite the short duration of the authors' experience, they consider these results encouraging; additional series are needed to confirm the preliminary findings.

Sleep Medication and Athletic Performance-The Evidence for Practitioners and Future Research Directions.

Sleep is a restorative circadian process underpinned by numerous interrelated biological processes (Brown et al., 2012; Goel et al., 2013; Zeitzer, 2013; Vyazovskiy and Delogu, 2014). Specifically, biological rhythms in core temperature, blood pressure, immune function as well as melatonin, and other hormones demonstrate an intricate relationship with sleep (Zisapel, 2007). Therefore, whilst sufficient sleep [7–9 h is recommended by the National Sleep Foundation (NSF) for adults (Hirshkowitz et al., 2015)] facilitates an optimal internal temporal order, an increased risk of poor quality of life, morbidity, and mortality (Zisapel, 2007) are seen with insufficient sleep (<6 h is not recommended by the NSF for adults), which is currently a concern in both the general population and athletes (Halson, 2015).

Melatonin concentrations and timing of seasonal reproduction in male mouse lemurs (Microcebus murinus) exposed to light pollution

Adverse effects of light at night are associated with human health problems and with changes in seasonal reproduction in several species. Owing to its role in the circadian timing system, melatonin production is suspected to mediate excess nocturnal light. To test this hypothesis, we examined the effect of light pollution on the timing of seasonal reproduction on a strict Malagasy long-day breeder, the nocturnal mouse lemur ( Microcebus murinus ). We randomly exposed 12 males in wintering sexual rest to moonlight or to a light-mimicking nocturnal streetlight for 5 weeks. We monitored urinary 6-sulfatoxymelatonin concentrations (aMT6s), plasma testosterone concentrations, and testis size, and we recorded daily rhythms of core temperature and locomotor activity. In males exposed to light pollution, we observed a significant decrease in urinary aMT6s concentrations associated with changes in daily rhythm profiles and with activation of reproductive function. These results showed that males entered spontaneous sexual recrudescence leading to a summer acclimatization state, which suggests that light at night disrupts perception of day length cues, leading to an inappropriate photoentrainment of seasonal rhythms.

Cold exposure and/or fasting modulate the relationship between sleep and body temperature rhythms in mice

We assessed the relationship between core temperature (Tc) and sleep rhythms in mice, and examined the effects of ambient temperature and fasting. Tc, electroencephalograms (EEG), electromyograms (EMG), and spontaneous activity in male ICR mice (n=9) were measured by telemetry for 3days under a 12:12h dark–light cycle. Mice were fed or fasted at an ambient temperature (Ta) of 27°C or 20°C for the final 30h of the experiment. The vigilance state was categorized into a wake state, rapid-eye movement (REM) sleep, and non-REM (NREM) sleep, and the total sleep time (TST) was assessed. Relationships between Tc and TST, NREM periods, and REM sleep were estimated using Pearson's correlation coefficient. During cold exposure, Tc decreased during the dark and light phases, and TST and the periods of NREM and REM sleep decreased during the dark phase. Throughout the fasting period, Tc also decreased during the dark and light phases. Furthermore, the decrease in Tc was augmented when fasting and cold were combined. TST and NREM sleep periods decreased in the light and dark phases, respectively, whereas REM sleep periods decreased in both phases. Negative linear correlations (r=−0.884 to −0.987) were observed between Tc and TST, NREM sleep periods, and REM sleep periods, except for Tc and REM sleep periods where fasting and cold conditions were combined. The correlations between sleep and Tc rhythms were well maintained during cold exposure and fasting. However, when cold and fasting were combined, REM sleep and Tc rhythms were desynchronized.

The Effect of Dietary Nitrate Supplementation on Maximal Cycling Power

Muscle shortening velocity and power increase in the presence of nitric oxide (NO). NO bioavailability increases after consuming foods rich in dietary nitrate. There is a very high concentration of nitrate in concentrated beetroot juice. PURPOSE: The purpose of this study was to determine if beetroot juice can increase maximal cycling power compared to a nitrate-depleted beetroot juice placebo. METHODS: In this double-blind, crossover study, acute changes in maximal cycling power were determined after beetroot juice supplementation or consumption of a placebo. During each of four visits, seven trained athletes (n=5 cyclists, 2 alpine skiers) performed four bouts of maximal cycling (∼3s) using an inertial load cycle ergometer immediately before, then 2.5h after consuming a bolus (140ml) of either nitrate-rich (∼11.2mmol) beetroot juice or a nitrate-depleted placebo. A 2x2 Repeated Measures ANOVA was used to assess main effects of time (pre- vs. post-drink) and treatment (beetroot juice vs. placebo), and the interaction between time and treatment (α=0.05). RESULTS: There was a main effect for time (p=0.002), but not for treatment (p=0.14). There was a trend toward an interaction between time and treatment (p=0.11). Specifically, there was a greater increase in maximal power from pre- to post-beetroot juice supplementation (1071±321W vs 1134±339W) compared to the increase observed in the placebo trial (1117±315W vs. 1154±322W). CONCLUSIONS: The main effect for time was a somewhat unexpected finding. All pre-drink trials happened early in the morning (before 8:00 am), and the post-drink trials happened mid-morning (∼9:00-10:45 am). Therefore, our results may have been confounded by the circadian rhythm in core temperature and muscle power. Nevertheless, there was still a trend toward increased maximal power after beetroot juice supplementation in trained athletes compared to the observed increase after consuming the placebo. These findings warrant more research to determine if indeed dietary nitrate can increase maximal cycling power.

Effects of light pollution on seasonal estrus and daily rhythms in a nocturnal primate

Mammals use variations in the length of day to anticipate environmental changes and time their reproduction. Light pollution, which affects day length perception, could lead to changes in biological functions. To explore the effects of light pollution on seasonal reproduction, we conducted an experimental study on a strict long-day breeder, the nocturnal gray mouse lemur (Microcebus murinus). Twelve females were randomly exposed to either a moonlight treatment or a light pollution treatment for 5 weeks during the transition from a short- to long-day photoperiod. Daily rhythms of locomotor activity and core temperature were recorded, and the occurrence of estrus and urinary 17-β-estradiol concentrations were monitored. In females exposed to light pollution, the first seasonal estrus occurred while they were still in a short-day photoperiod, 2 weeks earlier than in females exposed to moonlight. Moreover, the daily rhythms profiles of females exposed to light pollution showed significant changes that mimicked long-day acclimatization. This study demonstrates that light pollution can affect daily rhythms and the timing of seasonal estrus in a primate and suggests that functional changes in the circadian system may underlie the adverse effects of light pollution that are observed in wildlife.

Deprivation of plasma estradiol level affects circadian rhythms of body core and tail skin temperature in female rats

PurposeWe aimed to assess the effect of estradiol on daily changes of thermoregulatory responses of the tail vasculature in ovariectomized rats.MethodsFemale Wistar rats (n=10, age of 8‐12 wk) were bilaterally ovariectomized, and placed a telemetry device for the measurements of body core temperature (Tcore) and spontaneous activity (ACT) in the abdominal cavity. Temperature of the tail surface (Ttail) was estimated by thermography. Two silicon tubes containing 17β‐estradiol (E2, 50mg) were subcutaneously placed in one group (n=5, E2 (+)), and empty tubes were placed in the other group (n=5, E2 (‐)). The tubes were removed 10 days after the surgery. Tcore, ACT, and Ttail were measured a day before and 14 days after the removal of the tubes (PRE and Day 14, respectively). Regression analysis was conducted for the relationship between the daily values of Tcore and Ttail.ResultsOn the PRE, Tcore was higher (P&lt;0.05) in the E2 (‐) group than in the E2 (+) group at 12:30‐17:00 (37.2±0.2°C and 36.5±0.2°C, respectively). Ttail was higher (P&lt;0.05) in the E2 (‐) group than the E2 (+) group at 20:00‐0:30 (33.4±0.3°C and 31.2±0.6°C, respectively). The regression slope for Ttail and Tcore was greater (P&lt;0.05) in the E2 (‐) group than in the E2 (+) group on the PRE (1.41±0.34 and 0.60±0.16, respectively). On Day 14, in the E2 (‐) group, circadian rhythms of Tcore and Ttail remained unchanged from those on the PRE. Tcore and Ttail were higher than those on PRE at 14:30‐18:30 and 19:00‐18:30, respectively. The regression slope was greater (P&lt;0.05) than that of the PRE.ConclusionA reduction of estradiol affects circadian rhythms of Tcore and Ttail. Moreover, a lack of estradiol may decrease the ability in thermoregulatory response of the tail vasculature.

Heterothermy in large mammals: inevitable or implemented?

Advances in biologging techniques over the past 20 years have allowed for the remote and continuous measurement of body temperatures in free-living mammals. While there is an abundance of literature on heterothermy in small mammals, fewer studies have investigated the daily variability of body core temperature in larger mammals. Here we review measures of heterothermy and the factors that influence heterothermy in large mammals in their natural habitats, focussing on large mammalian herbivores. The mean 24 h body core temperatures for 17 species of large mammalian herbivores (>10 kg) decreased by ∼1.3°C for each 10-fold increase in body mass, a relationship that remained significant following phylogenetic correction. The degree of heterothermy, as measured by the 24 h amplitude of body core temperature rhythm, was independent of body mass and appeared to be driven primarily by energy and water limitations. When faced with the competing demands of osmoregulation, energy acquisition and water or energy use for thermoregulation, large mammalian herbivores appear to relax the precision of thermoregulation thereby conserving body water and energy. Such relaxation may entail a cost in that an animal moves closer to its thermal limits for performance. Maintaining homeostasis requires trade-offs between regulated systems, and homeothermy apparently is not accorded the highest priority; large mammals are able to maintain optimal homeothermy only if they are well nourished, hydrated, and not compromised energetically. We propose that the amplitude of the 24 h rhythm of body core temperature provides a useful index of any compromise experienced by a free-living large mammal and may predict the performance and fitness of an animal.

Diurnal variation of cognitive performance and perceived difficulty in dart-throwing performance in 9–10-year-old boys

The aim of this study was to investigate variations in cognitive performance and difficulty perception in 9–10-year-old boys. Fifteen healthy boys (Age = 9.8 ± 0.4 years; Height = 146 ± 5.2 cm; Body mass = 34.2 ± 2.9 kg) performed three cognitive tasks, the reaction time (RT), the trail-making test, TMT (to evaluate flexibility), and the barrage tests (to evaluate selective attention [SA]). The tests were performed at 07:00 and 17:00 h. The results demonstrated that oral temperature, RT, and flexibility were significantly higher at 17:00 h than at 07:00 h. A significant main effect of diurnal variation was found for RT (t = 3.075, p = 0.008), SA (t = 2.43, p = 0.029), and executive function (TMT, Parts A and B) (t = 5.86, p < 0.001; t = 4.85, p < 0.001, respectively). However, these rhythms of cognitive performance were not correlated with the rhythm of core temperature at 07:00 h. In conclusion perceived difficulty was correlated with executive function in situations with higher level of difficulties.

Light Pollution Modifies the Expression of Daily Rhythms and Behavior Patterns in a Nocturnal Primate

Among anthropogenic pressures, light pollution altering light/dark cycles and changing the nocturnal component of the environment constitutes a threat for biodiversity. Light pollution is widely spread across the world and continuously growing. However, despite the efforts realized to describe and understand the effects of artificial lighting on fauna, few studies have documented its consequences on biological rhythms, behavioral and physiological functions in nocturnal mammals. To determine the impacts of light pollution on nocturnal mammals an experimental study was conducted on a nocturnal primate, the grey mouse lemur Microcebus murinus. Male mouse lemurs (N = 8) were exposed 14 nights to moonlight treatment and then exposed 14 nights to light pollution treatment. For both treatments, chronobiological parameters related to locomotor activity and core temperature were recorded using telemetric transmitters. In addition, at the end of each treatment, the 14th night, nocturnal and feeding behaviors were explored using an infrared camera. Finally, throughout the study, body mass and daily caloric food intake were recorded. For the first time in a nocturnal primate, light pollution was demonstrated to modify daily rhythms of locomotor activity and core temperature especially through phase delays and increases in core temperature. Moreover, nocturnal activity and feeding behaviors patterns were modified negatively. This study suggests that light pollution induces daily desynchronization of biological rhythms and could lead to seasonal desynchronization with potential deleterious consequences for animals in terms of adaptation and anticipation of environmental changes.

The Relationship between Thermoregulation and REM Sleep Behaviour Disorder in Parkinson’s Disease

BackgroundThis study explored the relationship between symptoms of rapid eye movement sleep behaviour disorder, thermoregulation and sleep in Parkinson’s Disease.MethodsThe study group comprised 12 patients with Parkinson’s Disease and 11 healthy age-matched controls. We investigated markers of thermoregulation (core-body temperature profile), circadian rhythm (locomotor actigraphy) and sleep (polysomnography).ResultsThe mesor (the mean value around which the core temperature rhythm oscillates) of the core-body temperature in patients with Parkinson’s Disease was significantly lower than that of controls. In addition, the nocturnal fall in CBT (the difference between the mesor and the nadir temperature) was also significantly reduced in PD patients relative to controls. Furthermore, in patients the reduction in the amplitude of their core-body temperature profile was strongly correlated with the severity of self-reported rapid eye movement sleep behaviour disorder symptom, reduction in the percentage of REM sleep and prolonged sleep latency. By contrast, these disturbances of thermoregulation and sleep architecture were not found in controls and were not related to other markers of circadian rhythm or times of sleep onset and offset.ConclusionsThese findings suggest that the brainstem pathology associated with disruption of thermoregulation in Parkinson’s disease may also contribute to rapid eye movement sleep behavioural disorder. It is possible that detailed analysis of the core-body temperature profile in at risk populations such as those patients with idiopathic rapid eye movement sleep behaviour disorder might help identify those who are at high risk of transitioning to Parkinson’s Disease.

Diurnal variations on cognitive performances in handball goalkeepers

The purpose of this study was to examine the effects of the time of day on the cognitive performances of the handball’s goalkeeper (GK) in terms of attention and reaction time (RT). The protocol involved 12 healthy GK volunteer males (age: 18.5 ± 1.7 years, level of experience: 8.3 ± 2.4 years, height: 1.80 ± 5.8 cm, weight: 79 ± 4.2 kg). They performed three cognitive tasks, i.e. the RT test, the Stroop test, and the barrage test at 08:00, 12:00, 16:00, 20:00 h, and midnight to evaluate simple RT, and selective (SA) and constant (CA) attention. Resting oral temperature was measured at the beginning of each test session. The results showed a significant time-of-day effect on RT, SA, and CA. Whereas, RT was higher (slower) at midnight, SA and CA were the highest (best) at 08:00 h. Likewise, the core temperature was time-of-day dependent with the highest values observed at 16:00 h. Therefore, cognitive performances of GK are time-of-day-dependent with the highest values observed in the morning for SA and CA, and at midnight for RT. However, these rhythmicities are not in phase with the rhythm of core temperature. Therefore, the activities that require better cognitive performance should be programed in the morning.

The endogenous circadian temperature period length (tau) in delayed sleep phase disorder compared to good sleepers

The currently assumed aetiology for delayed sleep phase disorder (DSPD) is a delay of the circadian system. Clinicians have sought to use bright light therapy, exogenous melatonin or chronotherapy to correct the disorder. However, these treatments have achieved unreliable outcomes for DSPD patients and, as such, one suggestion has been that the disorder may be caused by a longer than normal circadian rhythm period length (i.e. tau). The present study investigated this premise using a 78-h ultradian, ultra-short sleep-wake cycle. This constant bedrest routine was used to simulate a series of 1-h long 'days' by alternating 20-min sleep opportunities and 40min of enforced wakefulness. Thirteen participants were recruited for the study including, six people diagnosed with DSPD according to the International Classification of Sleep Disorders-2 [mean age=22.0, standard deviation (SD)=3.3] and seven good sleepers (mean age=23.1, SD=3.9) with normal sleep timing. The DSPD participants' core temperature rhythm tau (mean=24h 54min, SD=23min) was significantly longer (t=-2.33, P=0.04, Cohen's d=1.91) than the good sleepers' (mean 24h 29min, SD=16min). The temperature rhythm of the DSPD participants delayed more rapidly (i.e. >25minday(-1) ) than the good sleepers'. These findings provide an explanation for the difficulty that DSPD patients have in phase advancing to a more conventional sleep time and their frequent relapse following treatment. The outcomes of this study support a vigorous and continued application of chronobiological and behavioural therapies to entrain DSPD patients to their desired earlier sleep times.

Non-invasive monitoring of core body temperature rhythms over 72 h in 10 bedridden elderly patients with disorders of consciousness in a Japanese hospital: A pilot study

The purpose of this study was to elucidate the body core temperature rhythms of bedridden elderly patients with disorders of consciousness (DOC) in a Japanese hospital using a simple, non-invasive, deep-body thermometer. We measured body core temperature on the surface of abdomen in 10 bedridden elderly patients with DOC continuously over 72h. A non-heated core body temperature thermometer was used. The cycle of the body core temperature rhythm was initially derived by using the least squares method. Then, based on that rhythm, the mean, amplitude, and times of day of the highest and lowest body temperatures during the optimum cycle were determined using the cosinor method. We found a 24-h cycle in seven of the 10 patients. One patient had a 6-h, one a 12-h, and one a 63-h cycle. The mean value of the cosine curve in the respective optimum cycles was 36.48±0.34°C, and the amplitude was 0.22±0.09°C. Of the seven subjects with 24-h cycles, the highest body temperature occurred between 12:58 and 14:44h in four. In addition to 24-h cycles of core temperature rhythm, short cycles of 12 and 6-h and a long cycle of 63-h were seen. In order to understand the temperature rhythms of bedridden elderly patients with DOC, it is necessary to monitor their core body temperatures, ideally using a simple, non-invasive device. In the future, it will be important to investigate the relationship of the core temperature rhythm to nursing care and living environment.

Effect of time of day and partial sleep deprivation on the reaction time and the attentional capacities of the handball goalkeeper

The aim of this study was to investigate the effects of the time of day and partial sleep deprivation on cognitive performances (i.e., attention and reaction time [RT]) of the handball goalkeeper (GK). The protocol involved 12 healthy GK volunteer males (age: 18.5 ± 1.7 years, level of experience: 8.3 ± 2.4 years, height: 1.80 ± 5.8 cm; body-mass: 79 ± 4.2 kg). They performed three cognitive tasks, i.e. the RT test, the Stroop test, and the barrage test, respectively, to evaluate the RT, the selective attention (SA), and the constant attention (CA) following the two situations of partial sleep deprivation, i.e. in the beginning (SDB) and the end (SDE) of the night, and a reference night which is a full night of habitual sleep. Resting oral temperature was measured at the beginning of each test session. Each of the three experimental conditions was separated by a 72-h period. The analysis of variance revealed a significant sleep deprivation × test-time effect on the RT, the SA, and the CA. These variables decreased significantly from morning to afternoon for all three experimental conditions. It seems that the RT is more affected by SDE than SDB (p < 0.05; −41% vs. 49% after SDE and SDB, respectively); however, SA and CA are more affected by SDB than SDE (p < 0.05; 63% vs. 47% for SA and 39% vs. 29% for CA after SDB and SDE, respectively). Furthermore, the partial sleep deprivation causes a phase advance of the core temperature. In addition, cognitive performances are not in phase with the rhythm of core temperature for all three experimental conditions. In conclusion, the partial sleep deprivation negatively affect cognitive performances in the handball goalkeeper.