Daily rhythms of the sleep-wake cycle

The impact of strategic napping on peak expiratory flow and respiratory function in young elite athletes

Respiratory health is a critical determinant of athletic performance, and the utilization of restorative strategies, such as strategic napping, may offer a competitive edge to athletes. This study investigates the effects of nap duration on the respiratory function of young elite athletes who have achieved top rankings national competitions. Participants engage in three test sessions with varying nap durations: no nap (N0), a 25-minute nap (N25), and a 45-minute nap (N45), with a minimum 72-hour interval between sessions. Respiratory parameters including Forced Vital Capacity (FVC), Forced Expiratory Volume in one second (FEV1), FEV1/FVC ratio, Peak Expiratory Flow rate (PEF), Forced Expiratory Flow at 25-75% of FVC (FEF25-75%), and Forced Expiratory Time (FET) are assessed. Results reveal a significant enhancement in PEF values following a 45-minute nap (N45) compared to the no-nap control (N0) [F1 - 11=7.356, p =.004, ηp2 = 0.401, (95% CI for difference: -1.56 to - 0.056)], indicating a potential positive influence of napping on maximum expiratory flow rate and, consequently, athletes' respiratory performance. While no significant changes are observed in other respiratory parameters across different nap durations, these findings underscore the potential benefits of strategic napping in optimizing respiratory health in young elite athletes.

Sleep deprivation reduced LPS-induced IgG2b production by up-regulating BMAL1 and CLOCK expression

Sleep deprivation (SD) weakens the immune system and leads to increased susceptibility to infectious or inflammatory diseases. However, it is still unclear how SD affects humoral immunity. In the present study, sleep disturbance was conducted using an sleep deprivation instrument, and the bacterial endotoxin lipopolysaccharide (LPS) was used to activate the immune response. It was found that SD-pretreatment reduced LPS-induced IgG2b+ B cells and IgG2b isotype antibody production in lymphocytes of spleen. And, SD-pretreatment decreased the proportion of CD4+T cells, production of CD4+T cells derived TGF-β1 and its contribution in helping IgG2b production. Additionally, BMAL1 and CLOCK were selectively up-regulated in lymphocytes after SD. Importantly, BMAL1 and CLOCK deficiency contributed to TGF-β1 expression and production of IgG2b+ B cells. Thus, our results provide a novel insight to explain the involvement of BMAL1 and CLOCK under SD stress condition, and their roles in inhibiting TGF-β1 expression and contributing to reduction of LPS induced IgG2b production.

Stability of social jetlag and sleep timing into the second year of the Covid-19 pandemic: Results from a longitudinal study of a nationally representative adult sample in Ireland

The early phase of the COVID-19 pandemic has previously been associated with marked changes in sleep/wake timing arising from the imposition of society-wide infection mitigation measures. Such observations are considered of broader significance as they reveal the social pressures that sleep timing normally operates under. In order to assess how persistent such changes were as the COVID-19 pandemic developed, we assessed sleep timing and quality in a longitudinal study of a nationally-representative sample of Irish adults with data collected at two time-points (December 2021 and March 2021). Data on social jetlag and chronotype was derived from the micro Munich Chronotype Questionnaire from 830 and 843 participants who provided data in December 2020 and March 2021 respectively, of which 338 contributed data to both timepoints. Demographics and measures of insomnia symptoms, anxiety, depression and loneliness were also collected, and data was analysed both within-subjects and cross-sectionally within data waves. Social jetlag (the mismatch between sleep timing on "work" and "free" days) and other measures of sleep timing were stable across the two time-points, although insomnia symptoms improved slightly from December 2020 to March 2021. The mean social jetlag at both timepoints was ~ 30 minutes, considerably lesser than reported pre-pandemic levels in similar populations. Multiple regression analysis of cross-sectional data reveals that the timing of midsleep on "free" days was only a weak-to-moderate predictor of social jetlag, whilst hours worked per week was the strongest predictor of social jetlag. Requirement for "face-to-face" contact with the public at work and urban location of residence also emerged as predictors of social jetlag, although insomnia, anxiety and depression symptoms and loneliness rating did not. We conclude that sleep timing changes that occurred during the initial phase of the COVID-19 pandemic persisted into the second year of the pandemic, and these results further illustrate the key roles working practices and other social factors have in shaping social jetlag.

The influence of a permanent double-shift school start time on adolescent sleep and chronotype across different age groups

The main objective of this study was to explore the differences in sleep habits and chronotype across different age groups in Mexican adolescents attending a permanent double-shift school system. This cross-sectional study consisted of 1,969 (1,084 girls) students from public elementary, secondary, and high schools, as well as undergraduate university students from Mexico. Age range was 10-22 [15.33 ± 3.28 (mean ± SD)] years, 988 morning shift and 981 afternoon shift students. Questions regarding usual self-reported bedtime and rise time were collected, and from that, estimates for time in bed, midpoint of sleep, social jetlag, and chronotype were evaluated. Afternoon shift students reported later rise times, bedtimes, midpoint of sleep, and longer time in bed on school days than morning shift students, as well as less social jetlag. Overall, afternoon shift students reported a later chronotype than morning shift students. Peak lateness of chronotype in afternoon shift students was at age 15, with girls peaking at age 14 and boys at age 15. Meanwhile, morning shift students reported peak lateness of chronotype around age 20. In this study, adolescents from different age ranges attending an extremely delayed school start time reported adequate sleep compared with adolescents attending a fixed morning school start time. In addition, the analysis presented in this study seems to suggest that the peak of late chronotype may be influenced by school start times.

Dexmedetomidine Improved Sleep Quality in the Intensive Care Unit After Laryngectomy

Purpose

To examine whether nighttime dexmedetomidine infusion improved sleep quality in patients after laryngectomy.

Patients and Methods

Thirty-five post-laryngectomy patients admitted to the intensive care unit (ICU) were randomly assigned to a 9-h (from 2100 h on surgery day to 0600 h the morning after laryngectomy) dexmedetomidine (0.3 μg/kg/h continuous infusion) or placebo group. Polysomnography results were monitored during the dexmedetomidine infusion period. The percentage of stage 2 non-rapid eye movement (stage N2) sleep was the primary outcome measure.

Results

Thirty-five patients (18 placebo group; 17 dexmedetomidine group) had complete polysomnogram recordings. The percentage of stage N3 sleep was significantly increased in the dexmedetomidine infusion group (from median 0% (0 to 0) in placebo group to 0% (interquartile range, 0 to 4) in dexmedetomidine group (difference, -2.32%; 95% CI, -4.19 to -0.443; P = 0.0167)). Infusion had no effect on total sleep time, stage N1 or N2 sleep percentages, or sleep efficiency. It decreased muscle tensity and snore non-rapid eye movement. Subjective sleep quality improved. Hypotension incidence increased in the dexmedetomidine group, but significant intervention was not required.

Conclusion

Dexmedetomidine infusion improved overall patient sleep quality in the ICU after laryngectomy.

What daily factors affect the sleep habits of Japanese toddlers?

STUDY OBJECTIVES

Good sleep, especially during early childhood, is important for development. In Japan, the mean nocturnal sleep duration of toddlers is < 10 hours, and even if toddlers slept for > 11 hours/day, as recommended by the National Sleep Foundation, some of them showed late bedtime and late wake-up time or took long naps. Therefore, we provisionally assumed the minimal sleep conditions for Japanese toddlers, named Nenne-criteria, such as bedtime before 10:00 pm, nocturnal sleep duration of ≥ 9 hours, and < 1 average time of awakening after sleep onset, and investigated the important factors for good sleep.

METHODS

We analyzed cross-sectional data from online surveys describing the sleep-related behaviors of 2,124 toddlers and their caregivers. We compared the daily schedules that affect sleep between the Nenne-criteria-meet group and the not-meet group.

RESULTS

The Nenne-criteria-meet group showed better daytime behaviors than the not-meet group. Structural equation modeling on daily schedules revealed that, to increase sleep pressure at the appropriate time, it is important to restrict media viewing, play outdoors in the morning, have an early nap ending time, avoid hyperarousal-inducing behaviors before bedtime, maintain daily schedules regularly, and decrease social jetlag.

CONCLUSIONS

The Nenne-criteria are useful for screening Japanese toddlers who require intervention for sleep hygiene. To improve toddlers' sleep, it is important not only to guide the ideal bedtime but also to provide tips for improving daily schedules and to avoid suboptimal sleep-related behaviors.

CITATION

Murata E, Yoshizaki A, Fujisawa TX, Tachibana M, Taniike M, Mohri I. What daily factors affect the sleep habits of Japanese toddlers? J Clin Sleep Med. 2023;19(6):1089-1101.

Sleep-mediated regulation of reward circuits: implications in substance use disorders

Our modern society suffers from both pervasive sleep loss and substance abuse-what may be the indications for sleep on substance use disorders (SUDs), and could sleep contribute to the individual variations in SUDs? Decades of research in sleep as well as in motivated behaviors have laid the foundation for us to begin to answer these questions. This review is intended to critically summarize the circuit, cellular, and molecular mechanisms by which sleep influences reward function, and to reveal critical challenges for future studies. The review also suggests that improving sleep quality may serve as complementary therapeutics for treating SUDs, and that formulating sleep metrics may be useful for predicting individual susceptibility to SUDs and other reward-associated psychiatric diseases.

Factors Associated With Sleep Disturbance Amongst Youth With Bipolar Disorder

BACKGROUND

While sleep disturbances and their impact on functioning are well-established in adults with bipolar disorder (BD), little is known about this topic in youth.

OBJECTIVE

This study investigates the prevalence and correlates of sleep disturbance among youth with BD.

METHODS

The study included 103 youth (72 BD, 31 healthy controls [HC]), ages 14-20 years. Study measures included a semi-structured diagnostic interview and the Pittsburgh Sleep Quality Index (PSQI). PSQI yields a global score and 7 subscale scores. Analyses examined between group differences in PSQI scores, and correlates of PSQI within BD.

RESULTS

BD youth had significantly higher (worse) global sleep scores, and higher scores on 5/7 subscales (quality, latency, disturbance, sleep medication use, daytime dysfunction). In univariate analyses, poorer sleep quality was associated with higher lifetime and current depression severity, mixed mood state, self-reported affective lability, and borderline personality traits. Lifetime lithium treatment and euthymic mood state were associated with better sleep scores. In multivariate analyses, greater current depression severity and self-reported affective lability were most robustly associated with poor sleep quality.

CONCLUSIONS

Converging with data from adults, present findings indicate greater sleep disturbance among youth with BD versus HC. Also convergent with adults with BD, mood disturbance, whether depression severity or emotional lability, comprised the predominant correlates of sleep disturbance among youth with BD. Future research is warranted to better understand the temporal association between sleep disturbance and its correlates in youth with BD. Relatedly, interventions that address both mood and sleep disturbances may help improve overall functioning.

Development and Initial Validation of the Assessment of Sleep Environment (ASE): Describing and Quantifying the Impact of Subjective Environmental Factors on Sleep

The purpose of this study was to develop and test the reliability and validity of a 13-item self-report Assessment of Sleep Environment (ASE). This study investigates the relationship between subjective experiences of environmental factors (light, temperature, safety, noise, comfort, humidity, and smell) and sleep-related parameters (insomnia symptoms, sleep quality, daytime sleepiness, and control over sleep). The ASE was developed using an iterative process, including literature searches for item generation, qualitative feedback, and pilot testing. It was psychometrically assessed using data from the Sleep and Healthy Activity Diet Environment and Socialization (SHADES) study (N = 1007 individuals ages 22-60). Reliability was determined with an internal consistency and factor analysis. Validity was evaluated by comparing ASE to questionnaires of insomnia severity, sleep quality, daytime sleepiness, sleep control, perceived stress, and neighborhood disorder. The ASE demonstrated high internal consistency and likely reflects a single factor. ASE score was associated with insomnia symptoms (B = 0.09, p < 0.0001), sleep quality (B = 0.07, p < 0.0001), and sleep control (B = -0.01, p < 0.0001), but not daytime sleepiness. The ASE was also associated with perceived stress (B = 0.20, p < 0.0001) and neighborhood disorder (B = -0.01, p < 0.0001). Among sleep environment factors, only smell was not associated with sleep quality; warmth and safety were negatively associated with sleepiness; and of the sleep environment factors, only light/dark, noise/quiet, and temperature (warm/cool) were not associated with insomnia symptoms. The ASE is a reliable and valid measure of sleep environment. Physical environment (light, temperature, safety, noise, comfort, humidity, and smell) was associated with insomnia symptoms and sleep quality but not sleepiness.

Transcorneal Electrical Stimulation Induces Long-Lasting Enhancement of Brain Functional and Directional Connectivity in Retinal Degeneration Mice

To investigate neuromodulation of functional and directional connectivity features in both visual and non-visual brain cortices after short-term and long-term retinal electrical stimulation in retinal degeneration mice. We performed spontaneous electrocorticography (ECoG) in retinal degeneration (rd) mice following prolonged transcorneal electrical stimulation (pTES) at varying currents (400, 500 and 600 μA) and different time points (transient or day 1 post-stimulation, 1-week post-stimulation and 2-weeks post-stimulation). We also set up a sham control group of rd mice which did not receive any electrical stimulation. Subsequently we analyzed alterations in cross-frequency coupling (CFC), coherence and directional connectivity of the primary visual cortex and the prefrontal cortex. It was observed that the sham control group did not display any significant changes in brain connectivity across all stages of electrical stimulation. For the stimulated groups, we observed that transient electrical stimulation of the retina did not significantly alter brain coherence and connectivity. However, for 1-week post-stimulation, we identified enhanced increase in theta-gamma CFC. Meanwhile, enhanced coherence and directional connectivity appeared predominantly in theta, alpha and beta oscillations. These alterations occurred in both visual and non-visual brain regions and were dependent on the current amplitude of stimulation. Interestingly, 2-weeks post-stimulation demonstrated long-lasting enhancement in network coherence and connectivity patterns at the level of cross-oscillatory interaction, functional connectivity and directional inter-regional communication between the primary visual cortex and prefrontal cortex. Application of electrical stimulation to the retina evidently neuromodulates brain coherence and connectivity of visual and non-visual cortices in retinal degeneration mice and the observed alterations are largely maintained. pTES holds strong possibility of modulating higher cortical functions including pathways of cognition, awareness, emotion and memory.

Engineering digital biomarkers of interstitial glucose from noninvasive smartwatches

Prediabetes affects one in three people and has a 10% annual conversion rate to type 2 diabetes without lifestyle or medical interventions. Management of glycemic health is essential to prevent progression to type 2 diabetes. However, there is currently no commercially-available and noninvasive method for monitoring glycemic health to aid in self-management of prediabetes. There is a critical need for innovative, practical strategies to improve monitoring and management of glycemic health. In this study, using a dataset of 25,000 simultaneous interstitial glucose and noninvasive wearable smartwatch measurements, we demonstrated the feasibility of using noninvasive and widely accessible methods, including smartwatches and food logs recorded over 10 days, to continuously detect personalized glucose deviations and to predict the exact interstitial glucose value in real time with up to 84% and 87% accuracy, respectively. We also establish methods for designing variables using data-driven and domain-driven methods from noninvasive wearables toward interstitial glucose prediction.

Rethinking the Conditions and Mechanism for Glymphatic Clearance

Critical studies that form the foundation of the glymphatic system and the clearance of metabolic by-products of unwanted proteins from the brain are reviewed. Concerns are raised about studying glymphatic flow in anesthetized animals and making assumptions about the whole brain based upon data collected from a cranial window on the cortex. A new model is proposed arguing that the flow of cerebral spinal fluid and parenchymal clearance in the perivascular system of unwanted proteins is regulated by circadian changes in brain temperature and blood flow at the level of the microvasculature.

Improvements in Sleep Quality Are Maintained at a Minimum of 2 Years Following Hip Arthroscopy for Femoroacetabular Impingement Syndrome

PURPOSE

To present the results of a mid-term follow-up study on sleep quality at a minimum of 2 years after hip arthroscopy for femoroacetabular impingement syndrome.

METHODS

Original inclusion criteria were consecutive patients undergoing primary hip arthroscopy for cam/pincer correction between March 1, 2017, and July 1, 2017, who did not respond to nonoperative management, whereas exclusion criteria were revision arthroscopy, gluteus medius repair, contralateral procedure during the follow-up period, and known sleep disorders. Patients who had followed up at 6 months were contacted at a minimum of 2 years following their surgery. In total, 37 of 55 (67.3%) were available for follow-up. New Pittsburgh Sleep Quality Index (PSQI) scores were obtained and compared with previously reported scores at preoperative and 6-month time points. The PSQI ranges from 0 to 21, with a score of ≥5 indicating poor sleep quality. Point biserial correlations and χ² tests of associations were used to investigate associations between demographics, preoperative patient-reported outcome measures, and the incidence of poor sleep quality at 2 years postoperatively.

RESULTS

Preoperatively, 94.5% of patients (52/55) had a PSQI of ≥5 with a mean PSQI score of 9.8 ± 4.2. Statistically significant improvements were observed at both 6 (PSQI: 2.2 ± 0.2, P < .001) and 24 months (PSQI: 4.3 ± 3.9) postoperatively compared to baseline (P < .001, both). The mean PSQIs at 2 years and 6 months postoperatively were not statistically different (P = .06). A total of 21.7% (10/46) of patients continued to experience poor sleep quality at 6 months postoperatively, whereas a total of 29.7% (11/37) did so at 2 years postoperatively (P = .36). No preoperative factors were associated with poor sleep quality (P > .05 all).

CONCLUSIONS

The early improvements in sleep quality observed 6 months postoperatively from an original small cohort were maintained at a mean 2.8-year follow-up in those who responded. However, approximately 30% of hip arthroscopy patients still experience poor sleep quality.

LEVEL OF EVIDENCE

IV, therapeutic case series.

Impact of Hours Awake and Hours Slept at Night on Radiologists' Mammogram Interpretations

OBJECTIVES

To examine whether radiologists' mammogram reading performance varies according to how long they have been awake ("hours awake") and the number of hours they slept ("hours slept") the night before a reading session.

METHODS

Retrospective data were retrieved from the BreastScreen Reader Assessment Strategy database. Malignancy-enriched mammographic readings were performed by 133 radiologists. Information on their hours awake and hours slept was collected. Analysis of covariance was performed to determine whether these two variables influenced radiologists' sensitivity, specificity, lesion sensitivity, receiver operating characteristic (ROC) curve, and jackknife alternative free-response ROC. Radiologists were divided into a more experienced and a less experienced groups (based on reading ≥2,000 and <2,000 mammogram readings per year, respectively).

RESULTS

The hours awake significantly influenced less experienced radiologists' lesion sensitivity (F_6,63 = 2.51; P = .03). Those awake for <2 hours had significantly lower lesion sensitivity than those awake for 8 to 10 hours (P = .01), and those awake for 4 to 6 hours had significantly lower lesion sensitivity than those awake for 8 to 10 hours (P = .002) and 10 to 12 hours (P = .02). The hours slept also influenced the ROC values of less experienced radiologists (F_1,68 = 4.96; P = .02). Radiologists with up to 6 hours of sleep had a significantly lower value (0.72) than those who had slept more than 6 hours (0.77). No statistically significant findings were noted for more experienced radiologists.

CONCLUSION

Inexperienced radiologists' performance may be influenced by the hours awake and hours slept before reading sessions.

Comfort driven design of innovative products: A personalized mattress case study

BACKGROUND

Human-centred design asks for wellbeing and comfort of the customer/worker when interacting with a product. Having a good perception-model and an objective method to evaluate the experienced (dis)comfort by the product user is needed for performing a preventive comfort evaluation as early as possible in the product development plan. The mattress of a bed is a typical product whose relevance in everyday life of people is under-evaluated. Fortunately, this behaviour is quickly changing, and the customer wants to understand the product he/she buys and asks for more comfortable and for scientifically assessed products. No guidelines for designing a personalized mattress are available in the literature.

OBJECTIVES

This study deals with the experience of designing an innovative product whose product-development-plan is focused on the customer perceived comfort: a personalized mattress. The research question is: which method can be used to innovate or create a comfort-driven human-centred product?

METHODS

Virtual prototyping was used to develop a correlated numerical model of the mattress. A comfort model for preventively assessing the perceived comfort was proposed and experimentally tested. Mattress testing sessions with subjects were organized, and collected data were compared with already tested mattresses. Brainstorming and multi-expert methods were used to propose, realize, and test an archetype of a new mattress for final comfort assessment.

RESULTS

A new reconfigurable mattress was developed, resulting in two patents. The mattress design shows that personalized products can be tuned according to the anthropometric data of the customer in order to improve the comfort experience during sleep.

CONCLUSIONS

A "comfort-driven design guideline" was proposed; this method has been based on the use of virtual prototyping, virtual optimization and physical prototyping and testing. It allowed to improve an existing product in a better way and to bring innovation in it.

Night-time Noise Levels and Patients’ Sleep Experiences in a Medical Assessment Unit in Northern England

Background:

Hospital in-patients need sleep so that restorative process and healing can take place. However, over one third of in-patients experience sleep disturbance, often caused by noise. This can compromise patients’ perceptions of care quality and cause physical and psychological ill health.

Aims:

To assess 1) in-patients sleep quality, quantity, reported sources of sleep disturbance and their suggestions for improvement 2) objectively measure decibel levels recorded at night.

Methods:

This descriptive study conducted in a Medical Assessment Unit used multi-methods; a semi-structured ‘sleep experience’ questionnaire administered to a purposive sample of in-patients; recording of night-time noise levels, on 52 consecutive nights, using two calibrated Casella sound level meters.

Results:

Patient ratings of ‘in-hospital’ sleep quantity (3.25; 2.72 SD) and quality (2.91; 2.56 SD) was poorer compared to ‘home’ sleep quantity (5.07; 2.81 SD) and quality (5.52; 2.79 SD). The difference in sleep quality (p<0.001) and quantity (p<0.001) ratings whilst in hospital, compared to at home, was statistically significant. Care processes, noise from other patients and the built environment were common sources of sleep disturbance. Participants’ suggestions for improvement were similar to interventions identified in current research. The constant noise level ranged from 38-57 decibels (equivalent to an office environment), whilst peak levels reached a maximum of 116 decibels, (equivalent to banging a car door one metre away).

Conclusion:

The self-rated patient sleep experience was significantly poorer in hospital, compared to home. Noise at night contributed to sleep disturbance. Decibel levels were equivalent to those reported in other international studies. Data informed the development of a ‘Sleep Smart’ toolkit designed to improve the in-patient sleep experience.

Influence of sleep-wake cycle on body mass index in female shift-working nurses with sleep quality as mediating variable

This study investigated the relationship between the sleep-wake cycle and body mass index (BMI) of female shift-working nurses and examine the mediating effect of sleep quality on this relationship. We recruited a total of 147 female nurses working monthly rotating shifts at a teaching hospital in Taiwan from the day (n=63), evening (n=50), and night (n=34) shifts. Our research instruments utilized a questionnaire to collect demographic and work-related information, the Pittsburgh Sleep Quality Index (PSQI), and actigraphs to record sleep patterns for seven consecutive days. The sleep-wake cycles were then estimated using the dichotomy index (I<O). The I<O values were negatively associated with both BMI (β=-0.28, p=0.001) and PSQI scores (β=-0.29, p<0.001), the bootstrapping results indicated that the estimate of the indirect effect was -0.28, and the 95% confidence interval ranged from -0.68 to -0.05. For female shift-working nurses, sleep quality mediates the influence of the sleep-wake cycle on BMI, indicating that the maintenance of a regular sleep-wake cycle and good sleep quality could be important for female shift-working nurses.

Association between sleep-wake habits and use of health care services of middle-aged and elderly adults in China

OBJECTIVE

To examine the relationship between sleep-wake habits and the use of health care services.

RESULTS

The proportions of the participants who were "early to bed" and "late to bed" were 48.7% and 51.3%, respectively. In the full sample, compared with those who were early to bed and early to rise, participants who went to bed late were more likely to report physician visits (late to bed and early to rise: OR = 1.13, 95% CI: 1.08-1.19, late to bed and late to rise: OR = 1.27, 95% CI: 1.18-1.38, respectively). We found no significant association between sleep-wake habits and the number of hospitalization.

CONCLUSIONS

Those middle-aged and elderly people who stayed up late and got up late are more likely to visit the doctors than those who went to bed early and got up early.

METHODS

We obtained data from a cohort study of retired employees in China, and 36,601 (95.59%) involved in the present study. The participants were allocated into 4 sleep-wake habits groups: Early-bed/Early-rise, Early-bed/Late-rise, Late-bed/Early-rise, and Late-bed/Late-rise. We explored the association between sleep-wake habits with the number of physician visits and hospitalizations.

Using ambulatory assessment to measure dynamic risk processes in affective disorders

BACKGROUND

Rapid advances in the capability and affordability of digital technology have begun to allow for the intensive monitoring of psychological and physiological processes associated with affective disorders in daily life. This technology may enable researchers to overcome some limitations of traditional methods for studying risk in affective disorders, which often (implicitly) assume that risk factors are distal and static - that they do not change over time. In contrast, ambulatory assessment (AA) is particularly suited to measure dynamic "real-world" processes and to detect fluctuations in proximal risk for outcomes of interest.

METHOD

We highlight key questions about proximal and distal risk for affective disorders that AA methods (with multilevel modeling, or fully-idiographic methods) allow researchers to evaluate.

RESULTS

Key questions include between-subject questions to understand who is at risk (e.g., are people with more affective instability at greater risk than others?) and within-subject questions to understand when risk is most acute among those who are at risk (e.g., does suicidal ideation increase when people show more sympathetic activation than usual?). We discuss practical study design and analytic strategy considerations for evaluating questions of risk in context, and the benefits and limitations of self-reported vs. passively-collected AA.

LIMITATIONS

Measurements may only be as accurate as the observation period is representative of individuals' usual life contexts. Active measurement techniques are limited by the ability and willingness to self-report.

CONCLUSIONS

We conclude by discussing how monitoring proximal risk with AA may be leveraged for translation into personalized, real-time interventions to reduce risk.

Computational Modeling of the Effects of Sleep Deprivation on the Vigilance Decrement

OBJECTIVE

We developed a computational model of the effects of sleep deprivation on the vigilance decrement by employing the methods of system dynamics modeling.

BACKGROUND

Situations that require sustained attention for a prolonged duration can cause a decline in cognitive performance, the so-called vigilance decrement. One factor that should influence the vigilance decrement is fatigue in the form of sleep deprivation.

METHOD

We employed the methods of system dynamics modeling (numerical-integration techniques for modeling complex feedback systems) to create a computational model of the vigilance decrement. We then simulated the computational effects of sleep deprivation on the behavior of that model, using empirical data obtained from the literature for calibrating such effects.

RESULTS

Sleep deprivation of 2 hr over a 14-day period should produce an additional decline of 9% in detection performance over that found with the typical vigilance decrement, whereas 4 hr of sleep deprivation over 14 days should produce an additional decline of 14% in detection performance.

CONCLUSION

With respect to dual-process theory, it is through its deleterious effects on analytical cognition that sleep deprivation should impact the vigilance decrement.

APPLICATION

Such computational modeling may be advantageous for human-machine teaming by theoretically allowing a future autonomous software agent to anticipate the decline of human performance and compensate accordingly.

Feature Extraction and Evaluation for Driver Drowsiness Detection Based on Thermoregulation

Numerous reports state that drowsiness is one of the major factors affecting driving performance and resulting in traffic accidents. In the past, methods to detect driver drowsiness have been developed based on physiological, behavioral, and vehicular features. In this pilot study, we test the use of a new set of features for detecting driver drowsiness based on physiological changes related to thermoregulation. Nineteen participants successfully performed a driving simulation, while the temperature of the nose (Tnose) and wrist (Twrist) as well as the heart rate (HR) were monitored. On average, an initial increase in temperature followed by a gradual decrease was observed in drivers who experienced drowsiness. For non-drowsy drivers, no such trends were observed. In addition, HR decreased on average in both groups, yet the decrease in the drowsy group was more distinct. Next, a classification based on each of these variables resulted in an accuracy of 68.4%, 88.9%, and 70.6% for Tnose, Twrist, and HR, respectively. Combining the information of all variables resulted in an accuracy of 89.5%, meaning that ultimately the state of 17 out of 19 drivers was detected correctly. Hence, we conclude that the use of physiological features related to thermoregulation shows potential for future research in this field.

Pineal gland and schizophrenia: A systematic review and meta-analysis

Melatonin (MLT), the main hormone of the pineal gland (PG), is assumed to support initiation and maintenance of sleep, and a stable sleep-wake cycle, exerting antioxidative and neuroprotective actions. Evidence demonstrates that sleep and circadian rhythm abnormalities are very common in schizophrenia patients. Some imaging studies suggest structural abnormalities of the PG in these patients as well. We aimed to critically appraise the literature on PG imaging and melatonin secretion in schizophrenia patients, in comparison to matched healthy controls, and to review placebo-controlled trials of add-on exogenous MLT treatment in schizophrenia patients. In this systematic review, twenty-nine studies were included. Meta-analytical evaluation of data was possible only for MLT secretion finding that midnight plasma levels were significantly reduced in individuals with schizophrenia as compared to healthy controls (Hedge`s g = 1.32, p < 0.01). Imaging studies demonstrated greater prevalence of enlarged calcifications (>1 cm) of the PG (2 out of 2 computed tomography studies) and smaller PG volume (2 out of 3 magnetic resonance studies) compared with healthy controls. Anatomic and functional abnormalities of the PG were not associated with duration of illness or with treatment factors, maybe suggesting them to be primary characteristics of the disease and genetically based. Add-on MLT treatment leads to a modest improvement of objective and subjective sleep quality, of metabolic adverse effects of antipsychotics, and of tardive dyskinesia symptoms in schizophrenia patients. It remains to be established whether MLT treatment in prodromal phases of the disease could prevent neurostructural abnormalities.

Mind-wandering, or the allocation of attentional resources, is sleep-driven across childhood

Mind-wandering or the spontaneous, uncontrolled changes in the allocation of attention resources (lapses) may cause variability in performance. In childhood, the relationship between the activation state of the brain, such as in attentional performance, and sleep has not been explored in detail. We investigated the role of sleep in attentional performance, and explored the most important parameters of their relationship. We objectively measured momentary lapses of attention of 522 children and correlated them with sleep schedules. In the subgroup of young children (age 7.1 ± 0.6 years; 60.8% girls), increasing age, long sleep duration and assessment closer to the previous night’s sleep period was associated with impaired performance speed and consistency. From pre-adolescence (age 9.4 ± 0.8 years; 50.5% girls) onwards somno-typologies may develop. As a result, in adolescence (age 13.4 ± 1.2 years; 51.3% girls) not only sleep duration but also sleep midpoint and sleep regularity influence the individual speed and stability of attention. Across development, regularity of sleep, individual sleep midpoint and bedtime become increasingly important for optimal performance throughout the day. Attentional performance and sleep shared almost half of their variance, and performance was sleep-driven across childhood. Future studies should focus on intra- and inter-individual differences in sleep-wake behavior to improve performance or decrease mind-wandering in youth by targeting sleep habits.

Sleep improves memory for the content but not execution of intentions in adolescents

OBJECTIVE

Sleep benefits prospective memory in young adults probably in part due to its well-established role in enhancing declarative memory, thereby facilitating retrieval of the intention content. In prior work on adolescents, we did not detect differences in prospective memory comparing five nights of sleep restriction and adequate sleep. Here, we examined whether this might be attributed to a limited role of sleep in benefiting the declarative content in this age group, and whether a sleep benefit on prospective memory would be uncovered with a shorter retention interval.

METHODS

A total of 59 adolescents (mean ± standard deviation: 16.55 ± 0.94 years) were instructed to remember to press a special key in response to two target words embedded in a semantic categorization task. Memory was tested after a 12-h retention interval, which included either overnight sleep (21:00-09:00, n = 29) or daytime wakefulness (09:00-21:00, n = 30).

RESULTS

We found no significant group difference in the percentage of target words correctly responded to (mean ± standard error of the mean for the sleep group: 32.76 ± 6.69%; wake group: 41.67 ± 7.61%, t = 0.88, p = 0.38). However, participants who slept recalled more target words compared to those who stayed awake (98.28 ± 1.72% vs. 86.67 ± 5.32%, t = 2.05, p < 0.05). In addition, a significantly greater proportion of sleep participants (n = 28 of 29) compared to wake participants (n = 24 of 30) recalled both target words correctly (χ² = 3.76, p < 0.05).

CONCLUSION

These findings suggest that during adolescence, sleep plays a more prominent role in improving memory for the content as compared to the execution of intentions.

Sex differences in sleep patterns and changes in 7th to 12th graders: a longitudinal follow-up study in Taiwan

Study Objectives

To assess the relationship between sex and the development of sleep patterns in adolescents from grade 7 to 12.

Methods

We analyzed longitudinal data from annual school-based assessments of sleep habits among secondary school students in northern Taiwan. Measures of sleep patterns included sleep length on weekdays and weekends as well as weekend-weekday difference (WndD), defined as the discrepancy in the time in bed (TIB) between weekdays and weekends. Growth curve models were used to assess sex differences in sleep patterns. Associations between other covariates and sleep patterns were also explored.

Results

We found shorter weekday TIB in girls compared with boys at all time points. In contrast, girls had longer weekend TIB than boys over time except in the 12th grade. WndD was also longer in girls than boys. All interaction terms between sex and time were insignificant, indicating that developmental change across time was not statistically different for boys and girls. Several other factors, namely, parental education, pubertal development, self-perceived health, weight status, depressive symptoms, academic stress, infrequent exercise, and substance use, were also found to be associated with sleep patterns.

Conclusions

Our findings show a sex difference in TIB both on weekdays and weekends. No sex difference was found in the development of sleep patterns over time.

Circadian Rhythms, Exercise, and Cardiovascular Health

Human circadian rhythmicity is driven by a circadian clock comprised of two distinct components: the central clock, located in the suprachiasmatic nucleus (SCN) within the hypothalamus, and the peripheral clocks, located in almost all tissues and organ systems in the body. Entrainment, or alignment, of circadian rhythmicity is dependent upon time of day and can occur through environmental influences such as light cues and physical activity exerted on skeletal muscle. Entrainment of the circadian clock through exercise has been reported to improve health by reducing risk of conditions such as cardiovascular disease (CVD), but further research is still needed. The purpose of this review is to discuss the effects exercise has on the regulation of circadian rhythmicity, specifically with respect to CVD risk factors – including hormonal levels, sleep/wake cycles, blood pressure, and heart rate. Additionally, the impact of exercise-induced circadian entrainment is discussed relative to hormone regulation, nocturnal blood pressure dipping, post-exercise hypotension, and overall cardiovascular health.

Relevance of a Mobile Internet Platform for Capturing Inter- and Intrasubject Variabilities in Circadian Coordination During Daily Routine: Pilot Study

Background

Experimental and epidemiologic studies have shown that circadian clocks’ disruption can play an important role in the development of cancer and metabolic diseases. The cellular clocks outside the brain are effectively coordinated by the body temperature rhythm. We hypothesized that concurrent measurements of body temperature and rest-activity rhythms would assess circadian clocks coordination in individual patients, thus enabling the integration of biological rhythms into precision medicine.

Objective

The objective was to evaluate the circadian clocks’ coordination in healthy subjects and patients through simultaneous measurements of rest-activity and body temperature rhythms.

Methods

Noninvasive real-time measurements of rest-activity and chest temperature rhythms were recorded during the subject’s daily life, using a dedicated new mobile electronic health platform (PiCADo). It involved a chest sensor that jointly measured accelerations, 3D orientation, and skin surface temperature every 1-5 min and relayed them out to a mobile gateway via Bluetooth Low Energy. The gateway tele-transmitted all stored data to a server via General Packet Radio Service every 24 hours. The technical capabilities of PiCADo were validated in 55 healthy subjects and 12 cancer patients, whose rhythms were e-monitored during their daily routine for 3-30 days. Spectral analyses enabled to compute rhythm parameters values, with their 90% confidence limits, and their dynamics in each subject.

Results

All the individuals displayed a dominant circadian rhythm in activity with maxima occurring from 12:09 to 20:25. This was not the case for the dominant temperature period, which clustered around 24 hours for 51 out of 67 subjects (76%), and around 12 hours for 13 others (19%). Statistically significant sex- and age-related differences in circadian coordination were identified in the noncancerous subjects, based upon the range of variations in temperature rhythm amplitudes, maxima (acrophases), and phase relations with rest-activity. The circadian acrophase of chest temperature was located at night for the majority of people, but it occurred at daytime for 26% (14/55) of the noncancerous people and 33% (4/12) of the cancer patients, thus supporting important intersubject differences in circadian coordination. Sex, age, and cancer significantly impacted the circadian coordination of both rhythms, based on their phase relationships.

Conclusions

Complementing rest-activity with chest temperature circadian e-monitoring revealed striking intersubject differences regarding human circadian clocks’ coordination and timing during daily routine. To further delineate the clinical importance of such finding, the PiCADo platform is currently applied for both the assessment of health effects resulting from atypical work schedules and the identification of the key determinants of circadian disruption in cancer patients.

Patterns and reliability of children's skin temperature prior to and during sleep in the home setting

The relationship between patterns of change in skin temperature and sleep is well recognized. In particular, there is a rapid rise in distal skin temperature (T_distal) and slower rise in proximal skin temperature (T_proximal) prior to sleep onset. The difference between T_distal and T_proximal is known as the distal-proximal gradient (DPG). Rise in DPG is known as a measure of distal vasodilation, which contributes to the drop in core body temperature (T_core) that is important to sleep onset and maintenance. Patterns of change in skin temperature before and during sleep are reported for neonates, infants, adults and elderly, however they are not known for school aged children. Therefore, the current observational study aimed to determine the patterns and reliability of skin temperatures (T_skin) and DPG in relation to sleep of school aged children in their home settings. Participants (22 children, aged 6-12) completed the Children's Sleep Habits Questionnaire and used Thermochron iButtons and actigraphy for four school nights in their typical sleep settings. There were evident patterns of T_skin change before and during sleep. In particular, T_distal was lower but rose more rapidly than T_proximal after reported bedtime and prior to sleep onset. This reflected a timely rise in DPG, and shows that distal vasodilation precedes sleep onset in school aged children. The measures of T_skin and sleep were practical for children in their home settings, and the observed patterns were consistent across consecutive school nights. Environmental and behavioural strategies that manage skin temperature before and during sleep should be explored for their potential as valuable components of treatment of childhood insomnia.

Effects of feet warming using bed socks on sleep quality and thermoregulatory responses in a cool environment

Background

As a way of helping to sleep in winter, methods of warming the feet through footbaths or heating pads before bedtime are tried. In particular, bed socks are popular during winter sleeping in Korea, but scientific evidence about the physiological effects of bed socks on sleep quality is rarely reported. The purpose of this study was to evaluate the effect of feet warming using bed socks on sleep quality and thermoregulatory responses during sleep in a cool environment.

Methods

Six young males (22.7 ± 2.0 years in age, 175.6 ± 3.5 cm in height, and 73.1 ± 8.5 kg in body weight) participated in two experimental conditions (with and without feet warming) in a random order. The following variables on sleep quality using a wrist actigraphy were measured during a 7-h sleep at an air temperature of 23 °C with 50% RH: sleep-onset latency, sleep efficiency, total sleep time, number of awakenings, wake after sleep onset, average awakening length, movement index, and fragmentation index. Heart rate and rectal and skin temperatures were monitored during the 7-h sleep. Questionnaire on sleep quality was obtained after awakening in the morning.

Results

The results showed that sleep-onset latency was on average 7.5 min shorter, total sleep time was 32 min longer, the number of awakenings was 7.5 times smaller, and sleep efficiency was 7.6% higher for those wearing feet-warming bed socks during a 7-h sleep than control (no bed socks) (all P < 0.05). Also, their foot temperature was maintained on average 1.3 °C higher and the value in the distal-proximal skin temperature gradient was higher for those wearing feet warming bed socks when compared to the control condition (P < 0.05). However, there were no significant differences in heart rate, rectal and mean skin temperature, or in the questionnaire-based subjective evaluations between the two conditions.

Conclusions

Feet warming using bed socks during sleep in a cool environment had positive effects on sleep quality by shortened sleep onset, lengthened sleep time, and lessened awakenings during sleep but had no significant influence on core body temperature. These results imply that sleep quality could be improved by manipulation of the foot temperature throughout sleeping.

Suvorexant in Elderly Patients with Insomnia: Pooled Analyses of Data from Phase III Randomized Controlled Clinical Trials

OBJECTIVE

Suvorexant is an orexin receptor antagonist approved for treating insomnia at doses of 10-20 mg. Previously reported phase III results showed that suvorexant was effective and well-tolerated in a combined-age population (elderly and nonelderly adults). The present analysis evaluated the clinical profile of suvorexant specifically in the elderly.

METHODS

Prespecified subgroup analyses of pooled 3-month data from two (efficacy) and three (safety) randomized, double-blind, placebo-controlled, parallel-group trials. In each trial, elderly (≥65 years) patients with insomnia were randomized to suvorexant 30 mg, suvorexant 15 mg, and placebo. By design, fewer patients were randomized to 15 mg. Patient-reported and polysomnographic (subset of patients) sleep maintenance and onset endpoints were measured.

RESULTS

Suvorexant 30 mg (N = 319) was effective compared with placebo (N = 318) on patient-reported and polysomnographic sleep maintenance, and onset endpoints at Night 1 (polysomnographic endpoints)/Week 1 (patient-reported endpoints), Month 1, and Month 3. Suvorexant 15 mg (N = 202 treated) was also effective across these measures, although the onset effect was less evident at later time points. The percentages of patients discontinuing because of adverse events over 3 months were 6.4% for 30 mg (N = 627 treated), 3.5% for 15 mg (N = 202 treated), and 5.5% for placebo (N = 469 treated). Somnolence was the most common adverse event (8.8% for 30 mg, 5.4% for 15 mg, 3.2% for placebo).

CONCLUSION

Suvorexant generally improved sleep maintenance and onset over 3 months of nightly treatment and was well-tolerated in elderly patients with insomnia (clinicaltrials.gov; NCT01097616, NCT01097629, NCT01021813).

Factors influencing brown fat activation in FDG PET/CT: a retrospective analysis of 15,000+ cases

OBJECTIVE

Brown fat can exhibit high uptake of fluorine-18 fludeoxyglucose (¹⁸F-FDG) on positron emission tomography (PET) and interferes with interpretation of the scan. The goal of this study was to identify factors that may influence brown adipose tissue (BAT) activation.

METHODS

A retrospective study of ¹⁸F-FDG PET scans was performed using a database of 15,109 PET/CT reports. BAT activation reported by nuclear medicine physicians and factors influencing BAT activation were gathered. The data were analyzed using in-house software.

RESULTS

The total reported BAT activation was 3.6%. BAT activation was reported significantly more often in patients who were female (p < 0.0001), younger (p < 0.0001), with lower body mass index (p < 0.0001), with lower blood glucose levels (p = 0.01), indicated for breast cancer (p = 0.004), not administered chemotherapy recently before the scan (p < 0.0001) and shown to have BAT activation in a previous scan (p < 0.0001). BAT activation was also reported significantly more for lower outdoor temperatures (p < 0.0001) and for late morning scans than for afternoon (p = 0.005) and early morning (p = 0.001) scans.

CONCLUSION

This retrospective study of 15,109 scans highlights multiple factors contributing to BAT activation on ¹⁸F-FDG PET. The identification of new factors influencing BAT and confirmation of previously identified factors with a larger data set can be used to more accurately identify patients at risk for BAT activation so that prevention strategies can be implemented. Advances in knowledge: This study presents new factors associated with higher incidence of BAT activation, such as time of day, previous BAT activation and breast cancer. Conversely, recent chemotherapy was associated with reduced incidence of BAT activation.

Adopted youth and sleep difficulties

Sleep is a critical component of healthy development for youth, with cascading effects on youth’s biological growth, psychological well-being, and overall functioning. Increased sleep difficulties are one of many disruptions that adopted youth may face throughout the adoption process. Sleep difficulties have been frequently cited as a major concern by adoptive parents and hypothesized in the literature as a problem that may affect multiple areas of development and functioning in adopted youth. However, there is limited research exploring this relationship. Using a biopsychosocial framework, this paper reviews the extant literature to explore the development, maintenance, and impact of sleep difficulties in adopted youth. Finally, implications for future research and clinical interventions are outlined.

Low-dose Dexmedetomidine Improves Sleep Quality Pattern in Elderly Patients after Noncardiac Surgery in the Intensive Care Unit

Background

Patients admitted to the intensive care unit (ICU) after surgery often develop sleep disturbances. The authors tested the hypothesis that low-dose dexmedetomidine infusion could improve sleep architecture in nonmechanically ventilated elderly patients in the ICU after surgery.

Methods

This was a pilot, randomized controlled trial. Seventy-six patients age 65 yr or older who were admitted to the ICU after noncardiac surgery and did not require mechanical ventilation were randomized to receive dexmedetomidine (continuous infusion at a rate of 0.1 μg kg−1 h−1; n = 38) or placebo (n = 38) for 15 h, i.e., from 5:00 pm on the day of surgery until 8:00 am on the first day after surgery. Polysomnogram was monitored during the period of study-drug infusion. The primary endpoint was the percentage of stage 2 non–rapid eye movement (stage N2) sleep.

Results

Complete polysomnogram recordings were obtained in 61 patients (30 in the placebo group and 31 in the dexmedetomidine group). Dexmedetomidine infusion increased the percentage of stage N2 sleep from median 15.8% (interquartile range, 1.3 to 62.8) with placebo to 43.5% (16.6 to 80.2) with dexmedetomidine (difference, 14.7%; 95% CI, 0.0 to 31.9; P = 0.048); it also prolonged the total sleep time, decreased the percentage of stage N1 sleep, increased the sleep efficiency, and improved the subjective sleep quality. Dexmedetomidine increased the incidence of hypotension without significant intervention.

Conclusions

In nonmechanically ventilated elderly patients who were admitted to the ICU after noncardiac surgery, the prophylactic low-dose dexmedetomidine infusion may improve overall sleep quality.

Sleep patterns as a predictor for length of stay in a psychiatric intensive care unit

Systematic evaluations of the relationship between sleep patterns and length of stay in psychiatric intensive care units (PICUs) are lacking. The aims of the present study were to explore if sleep duration or night-to-night variations in sleep duration the first nights predict length of stay in a PICU. Consecutive patients admitted to a PICU were included (N=135) and the nurses registered the time patients were observed sleeping. In the three first nights, the mean sleep duration was 7.5 (±3.2)h. Sleep duration the first night correlated negatively with the length of stay for patients with schizophrenia. The mean difference in sleep duration from night one to night two were 3.3 (±3.0)h and correlated with length of stay for the whole group of patients, but especially for patients with schizophrenia. Patients of all diagnostic groups admitted to a PICU had pronounced intra-individual night-to-night variations in sleep duration. Stabilizing night-to-night variations of sleep duration might be a major goal in treatment.

Sleep Quality and Associated Factors in Older Turkish Adults With Hypertension: A Pilot Study

PURPOSE

The purpose of this study was to evaluate sleep quality and to explore its associations with participant characteristics, anemia, excessive daytime sleepiness, and physical activity in older Turkish adults with hypertension.

METHOD

This cross-sectional study included 128 adults aged 60 years or older with hypertension. Data were collected by using a personal information form, the Pittsburgh Sleep Quality Index, the Epworth Sleepiness Scale, and the International Physical Activity Questionnaire. Anemia was assessed by hemoglobin levels.

RESULTS

Eighty-one patients (63.3%) reported poor sleep quality. Anemia was present in 35.2% of the patients (defined as hemoglobin <13 g/dL for males and <12 g/dL for females). Female gender, the presence of anemia, and low levels of physical activity were associated with poor sleep quality. Conclusion/Implication: The majority of the participants had poor sleep quality. Better understanding of risk factors associated with poor sleep quality may contribute to more effective interventions to improve health and well-being.

The rest-activity rhythm and physical activity in early-onset dementia

BACKGROUND

A substantial part of elderly persons with dementia show rest-activity rhythm disturbances. The rest-activity rhythm is important to study in people with early-onset dementia (EOD) for rest-activity rhythm disturbances are predictive of institutionalization, and caregivers of young patients suffer from high distress.

OBJECTIVE

The aim of this study was to study (1) whether EOD patients have more rest-activity rhythm disturbances compared with cognitively intact adults; and (2) which factors contribute to a disturbed rhythm.

METHODS

We included 61 patients with EOD [mean age 61.9 (4.9) y, 41 (67%) men] and 68 cognitively intact adults [mean age 61.6 (4.5) y, 28 (41%) men]. Rest-activity rhythm was assessed by actigraphy.

RESULTS

EOD patients tended to have higher intradaily variability [0.46 (0.16) and 0.39 (0.10), P=0.03]. EOD patients also lay for a longer time in bed [time in bed: 08:49 (0:51) h and 08:07 (0:47) h, P<0.001] and needed more time to fall asleep [sleep onset latency: 23 (22) min and 15 (15) min, P=0.02]. Disturbances in the rest-activity rhythm were predicted by a low level of physical activity, use of antidepressants and central nervous system neurological medications, and being male.

CONCLUSIONS

EOD patients showed more variability in the rest-activity rhythm compared with cognitively intact adults. The main predictor for rest-activity rhythm disturbances was a low level of physical activity.

Effects of resistance exercise timing on sleep architecture and nocturnal blood pressure

Short sleep duration and poor quality of sleep have been associated with health risks including cardiovascular disease, diabetes, and obesity. Prior research has suggested that regular aerobic exercise improves the quality of sleep; however, less is known regarding resistance exercise (RE) and how RE may affect sleep architecture. The purpose of this study was to investigate the acute effects of timing of RE on sleep architecture and nocturnal blood pressure. College-aged subjects engaged in 5 laboratory visits. Visits 1 (C) and 2 provided a non-RE control day and established the 10-repetition maximum on each of 9 RE machines, respectively. During visits 3-5, the subjects reported at 0700 hours (7A), 1300 hours (1P), and 1900 hours (7P) in a randomized order to perform 30 minutes of RE. Ambulatory blood pressure and sleep-monitoring devices were worn during sleep after C, 7A, 1P, and 7P. Time to fall asleep was significantly different between RE conditions 7A and 1P and between 7A and 7P. All exercise conditions exhibited significantly fewer times woken than the non-RE control day, with 7P resulting in significantly less time awake after initially falling asleep as compared with C. Although timing of RE does not seem to statistically impact sleep stages or nocturnal blood pressure, these data indicate that engaging in RE at any time of the day may improve quality of sleep as compared with no RE. Resistance exercise may offer additional benefits regarding the ability to fall asleep and stay asleep to populations with osteoporosis, sarcopenia, anxiety, or depression.

Ontogeny and aging of the distal skin temperature rhythm in humans

In circadian terms, human ontogeny is characterized by the emergence of a daily pattern, from a previous ultradian pattern, for most variables during the first 6 months of life. Circadian aging in humans is characterized by a phase advance, accompanied by rhythm fragmentation and flattening. Despite an expanding body of literature focused on distal skin temperature, little information is available about the ontogeny and practically nothing about age-related changes in this rhythm. Thus, the aim was to evaluate the degree of maturation and aging of the circadian pattern of distal skin temperature to identify those parameters that are modified throughout life and could be used to differentiate subjects according to their age. For this, distal skin temperature was measured in 197 volunteers (55 % women), including babies aged 15 days (30 subjects), 1 month (28 subjects), 3 months (31 subjects), and 6 months (10 subjects); young adults aged 19 years (37 subjects); middle-aged persons aged 46 years (27 subjects); older people aged 72 (34 subjects). Circadian system maturation was associated with an increase in amplitude and a reduction in skin temperature during sleep. During adulthood, women showed a more robust pattern (lower fragmentation, and higher night-time temperature, amplitude, circadian function index, and first harmonic relative power); however, these differences were lost with aging, a period of life that was consistently associated with a phase advance of the rhythm. In summary, distal skin temperature pattern can be used as a robust variable to discern between different ages throughout the life.

Theory of Inpatient Circadian Care (TICC): A Proposal for a Middle-Range Theory

The circadian system controls the daily rhythms of a variety of physiological processes. Most organisms show physiological, metabolic and behavioral rhythms that are coupled to environmental signals. In humans, the main synchronizer is the light/dark cycle, although non-photic cues such as food availability, noise, and work schedules are also involved. In a continuously operating hospital, the lack of rhythmicity in these elements can alter the patient’s biological rhythms and resilience. This paper presents a Theory of Inpatient Circadian Care (TICC) grounded in circadian principles. We conducted a literature search on biological rhythms, chronobiology, nursing care, and middle-range theories in the databases PubMed, SciELO Public Health, and Google Scholar. The search was performed considering a period of 6 decades from 1950 to 2013. Information was analyzed to look for links between chronobiology concepts and characteristics of inpatient care. TICC aims to integrate multidisciplinary knowledge of biomedical sciences and apply it to clinical practice in a formal way. The conceptual points of this theory are supported by abundant literature related to disease and altered biological rhythms. Our theory will be able to enrich current and future professional practice.

The midpoint of sleep on working days: a measure for chronodisruption and its association to individuals' well-being

There is consistent evidence suggesting a relationship between individuals' sleep-wake rhythms and well-being. The indiscriminate demands from daily working routines, which do not respect this individual physiological rhythm, might be mediating this phenomenon. The aim of the present study was to evaluate the relationship between the characteristics of sleep routines during working days and psychological well-being. This was a cross-sectional study on 825 individuals from rural communities from southern Brazil. The study protocol included a questionnaire on demographic characteristics, working routines, health complaints, and habits; the Munich Chronotype Questionnaire for sleep-wake rhythm and; the WHO-Five well-being index. Since sex has been shown to affect sleep circadian rhythm and well-being, analysis was performed on men and women separately. In the proposed hierarchical regression models, different factors contributed to well-being according to sex. Among men, sleep-wake and work-related variables did not predict well-being scores. Among women, later midpoints of sleep on working days (B = -1.243, SE B = 0.315, β = -0.220), working more days per week (B = -1.507, SE B = 0.494, β = 0.150), having longer working journeys (B = -0.293, SE B = 0.105, β = -0.166), earlier working journey midpoints (B = 0.465, SE B = 0.222, β = 0.115), and being exposed to less sunlight (B = 0.140, SE B = 0.064, β = 0.103) predicted worse well-being. For the subgroup of women with days free from work, we have found a correlation between later midpoints of sleep during the week with worse well-being (Pearson's r = -0.159, p = 0.045) while the same relationship was not significantly observed with the midpoint of sleep on non-working days (Pearson's r = -0.153, p = 0.054). Considering WHO-Five as categorical, based on proposed clinical cut-offs, among women working 7-d/week, those with worst well-being (WHO-Five < 13) had the latest midpoint of sleep (F = 4.514, p = 0.012). Thus, the midpoint of sleep on working days represents the interaction between individuals' sleep-wake behavior and working routines. It plays an important role as a stress factor and may be a useful alternative variable related to chronodisruption.

Influence of light at night on melatonin suppression in children

CONTEXT

The sensitivity of melatonin to light suppression is expected to be higher in children because children have large pupils and pure crystal lenses. However, melatonin suppression by light in children remains unclear.

OBJECTIVE

We investigated whether light-induced melatonin suppression in children is larger than that in adults.

METHODS

Thirty-three healthy primary school children (mean age, 9.2 ± 1.5 y) and 29 healthy adults (mean age, 41.6 ± 4.7 y) participated in two experiments. In the first experiment, salivary melatonin concentrations in 13 children and 13 adults were measured at night under a dim light (<30 lux) and a moderately bright light (580 lux) in an experimental facility. Pupil diameters were also measured under dim light and bright light. In the second experiment, melatonin concentrations in 20 children and 16 adults were measured under dim light in the experimental facility and under room light at home (illuminance, 140.0 ± 82.7 lux).

RESULTS

In experiment 1, the melatonin concentration was significantly decreased by exposure to moderately bright light in both adults and children. Melatonin suppression was significantly larger in children (88.2%; n = 5) than in adults (46.3%; n = 6; P < .01), although the data for some participants were excluded because melatonin concentrations had not yet risen. In experiment 2, melatonin secretion was significantly suppressed by room light at home in children (n = 15; P < .05) but not in adults (n = 11).

CONCLUSION

We found that the percentage of melatonin suppression by light in children was almost twice that in adults, suggesting that melatonin is more sensitive to light in children than in adults at night.

The circadian timing system in clinical oncology

The circadian timing system (CTS) controls several critical molecular pathways for cancer processes and treatment effects over the 24 hours, including drug metabolism, cell cycle, apoptosis, and DNA damage repair mechanisms. This results in the circadian time dependency of whole-body and cellular pharmacokinetics and pharmacodynamics of anticancer agents. However, CTS robustness and phase varies among cancer patients, based on circadian monitoring of rest- activity, body temperature, sleep, and/or hormonal secretion rhythms. Circadian disruption has been further found in up to 50% of patients with metastatic cancer. Such disruption was associated with poor outcomes, including fatigue, anorexia, sleep disorders, and short progression-free and overall survival. Novel, minimally invasive devices have enabled continuous CTS assessment in non-hospitalized cancer patients. They revealed up to 12-hour differences in individual circadian phase. Taken together, the data support the personalization of chronotherapy. This treatment method aims at the adjustment of cancer treatment delivery according to circadian rhythms, using programmable-in-time pumps or novel release formulations, in order to increase both efficacy and tolerability. A fixed oxaliplatin, 5-fluorouracil and leucovorin chronotherapy protocol prolonged median overall survival in men with metastatic colorectal cancer by 3.3 months as compared to conventional delivery, according to a meta-analysis (P=0.009). Further analyses revealed the need for the prevention of circadian disruption or the restoration of robust circadian function in patients on chronotherapy, in order to further optimize treatment effects. The strengthening of external synchronizers could meet such a goal, through programmed exercise, meal timing, light exposure, improved social support, sleep scheduling, and the properly timed administration of drugs that target circadian clocks. Chrono-rehabilitation warrants clinical testing for improving quality of life and survival in cancer patients.

Thoracic surface temperature rhythms as circadian biomarkers for cancer chronotherapy

The disruption of the temperature circadian rhythm has been associated with cancer progression, while its amplification resulted in cancer inhibition in experimental tumor models. The current study investigated the relevance of skin surface temperature rhythms as biomarkers of the Circadian Timing System (CTS) in order to optimize chronotherapy timing in individual cancer patients. Baseline skin surface temperature at four sites and wrist accelerations were measured every minute for 4 days in 16 patients with metastatic gastro-intestinal cancer before chronotherapy administration. Temperature and rest-activity were recorded, respectively, with wireless skin surface temperature patches (Respironics, Phillips) and an actigraph (Ambulatory Monitoring). Both variables were further monitored in 10 of these patients during and after a 4-day course of a fixed chronotherapy protocol. Collected at baseline, during and after therapy longitudinal data sets were processed using Fast Fourier Transform Cosinor and Linear Discriminant Analyses methods. A circadian rhythm was statistically validated with a period of 24 h (p < 0.05) for 49/61 temperature time series (80.3%), and 15/16 rest-activity patterns (93.7%) at baseline. However, individual circadian amplitudes varied from 0.04 °C to 2.86 °C for skin surface temperature (median, 0.72 °C), and from 16.6 to 146.1 acc/min for rest-activity (median, 88.9 acc/min). Thirty-nine pairs of baseline temperature and rest-activity time series (75%) were correlated (r > |0.7|; p < 0.05). Individual circadian acrophases at baseline were scattered from 15:18 to 6:05 for skin surface temperature, and from 12:19 to 15:18 for rest-activity, with respective median values of 01:10 (25-75% quartiles, 22:35-3:07) and 14:12 (13:14-14:31). The circadian patterns in skin surface temperature and rest-activity persisted or were amplified during and after fixed chronotherapy delivery for 5/10 patients. In contrast, transient or sustained disruption of these biomarkers was found for the five other patients, as indicated by the lack of any statistically significant dominant period in the circadian range. No consistent correlation (r < |0.7|, p ≥ 0.05) was found between paired rest-activity and temperature time series during fixed chronotherapy delivery. In conclusion, large inter-patient differences in circadian amplitudes and acrophases of skin surface temperature were demonstrated for the first time in cancer patients, despite rather similar rest-activity acrophases. The patient-dependent coupling between both CTS biomarkers, and its possible alteration on a fixed chronotherapy protocol, support the concept of personalized cancer chronotherapy.

Sleep disorders in older adults

Sleep pattern changes are considered normal as individuals age. However, changes in sleep patterns can ultimately affect the quality of life of many older adults. In addition, many sleep conditions are associated with an increase in morbidity and mortality. It is essential for clinicians to recognize sleep changes to lead to appropriate treatment. This article will focus on the assessment and interventions of sleep disorders in older adults.