Changes in serum TSH and free T4 during human sleep restriction

The interplay between subclinical hypothyroidism and poor sleep quality: A systematic review

BACKGROUND

The relationship between subclinical hypothyroidism (SHYPO) and sleep disturbances is still poorly investigated. This systematic review aims to critically appraise the existing literature to provide more insights in understanding whether SHYPO favors sleep disturbances or it is the sleep disturbance per se that affects the hypothalamus-pituitary-thyroid axis regulation.

METHODS

Original studies on sleep quality and duration in patients with SHYPO were searched in the PubMed/MEDLINE, Embase, Web of Science and Scopus databases. Two reviewers independently screened articles for inclusion, extracted data, and assessed the quality of included studies.

RESULTS

Eight studies, including 2916 patients with SHYPO and 18,574 healthy controls, were retrieved. An overall agreement (7 out of 8 studies), about a positive correlation between decreased sleep quality and/or duration and SHYPO was observed. Five studies investigated sleep quality through self-reported surveys; only two studies explored both subjective and objective assessment of sleep quality with actigraphy (n = 1) or polysomnography (n = 1); finally, one study assessed subjective evaluation of sleep quality through a single question regarding the number of sleeping hours. A high level of heterogeneity among studies was manifest due to differences in population source, sleep measure assessment and criteria for diagnosing SHYPO.

DISCUSSION

Overall, the existing literature data suggest a link between SHYPO and sleep disturbances, but further studies on larger populations of patients with homogeneous study designs and outcomes are warranted.

Multiplex influences on vigilance and biochemical variables induced by sleep deprivation

Introduction

Sleep loss and sleep deprivation (SD) cause deleterious influences on health, cognition, mood and behaviour. Nevertheless, insufficient sleep and SD are prevalent across many industries and occur in various emergencies. The deleterious consequences of SD have yet to be fully elucidated. This study aimed to assess the extensive influences of SD on physiology, vigilance, and plasma biochemical variables.

Methods

Seventeen volunteers were recruited to participate in a 32.5-h SD experiment. Multiple physiological and cognitive variables, including tympanic temperature, blood oxygen saturation (SaO2), and vigilance were recorded. Urinal/salivary samples were collected and subjected to cortisol or cortisone analysis, and plasma samples were subjected to transcriptomic analysis of circular RNA (circRNA) expression using microarray. Plasma neurotransmitters were measured by targeted metabolic analysis, and the levels of inflammatory factors were assessed by antibody microarray.

Results

The volunteers showed significantly increased sleepiness and decreased vigilance during SD, and the changes in circadian rhythm and plasma biochemistry were observed. The plasma calcium (p = 0.0007) was induced by SD, while ischaemia-modified albumin (IMA, p = 0.0030) and total bile acid (TBA, p = 0.0157) decreased. Differentially expressed circRNAs in plasma were identified, which are involved in multiple signaling pathways including neuronal regulation and immunity. Accordingly, SD induced a decrease in 3-hydroxybutyric acid (3OBH, p = 0.0002) and an increase in thyroxine (T4, p < 0.0001) in plasma. The plasma anti-inflammatory cytokine IL-10 was downregulated while other ten inflammatory factors were upregulated.

Conclusion

This study demonstrates that SD influences biochemical, physiological, cognitive variables, and the significantly changed variables may serve as candidates of SD markers. These findings may further our understanding of the detrimental consequence of sleep disturbance at multiple levels.

The Relationship Between Thyroid Dysfunction and Sleep Quality Among Population of Saudi Arabia

Purpose

Thyroid problems and sleep disturbances are common health problems that impact people of all ages, income levels, and genders. The clinical relationship between these conditions is still not well understood, despite their widespread occurrence. The main objectives of the study were to determine the prevalence of thyroid disorders and evaluate the relationship between them and sleep quality in the Saudi Arabian population.

Patients and Methods

The study employed an observational cross-sectional design and included a representative Saudi Arabian cohort. The Pittsburgh Sleep Quality Index (PSQI) was included in a digital self-administered survey that participants were asked to complete.

Results

There were 1044 responders in the study, most of whom (54%) were between the ages of 21 and 30. Female respondents made up 62% of the sample. Thyroid disorders were diagnosed in 9.2% of cases. A significant correlation was found (p=0.001 and p<0.001, respectively) between thyroid disorders and sleep disturbances as well as the use of sleep medications.

Conclusion

The study revealed a significant prevalence of poor sleep quality in the Saudi population as a whole, with thyroid disorder diagnosis and female gender emerging as independent risk factors. More extensive longitudinal studies in the area are desperately needed.

Sleep regulation and host genetics

Due to the multifactorial and complex nature of rest, we focus on phenotypes related to sleep. Sleep regulation is a multifactorial process. In this chapter, we focus on those phenotypes inherent to sleep that are highly prevalent in the population, and that can be modulated by lifestyle, such as sleep quality and duration, insomnia, restless leg syndrome and daytime sleepiness. We, therefore, leave in the background those phenotypes that constitute infrequent pathologies or for which the current level of scientific evidence does not favour the implementation of practical approaches of this type. Similarly, the regulation of sleep quality is intimately linked to the regulation of the circadian rhythm. Although this relationship is discussed in the sections that require it, the in-depth study of circadian rhythm regulation at the molecular level deserves a separate chapter, and this is how it is dealt with in this volume.

Sensitivity to thyroid hormones is associated with sleep duration in the euthyroid population with depression degree lower than moderate

We collected thyroid-related hormone index levels, sleep duration, and other basic characteristics of the population with depression from the NHANES 2009-2012 cycles and evaluated the association of Thyroid-Stimulating Hormone Index (TSHI) with sleep duration in the euthyroid population with depression via different analysis methods. We found that the association between TSHI and sleep duration was only found in patients with depression degree < Moderate (score: 1-14) rather than > Moderate group. Among the populations with degree < Moderate (N = 1918), only 4 indexes (parametric Thyroid Feedback Quantile Index, PTFQI, Thyrotroph Thyroxine Resistance Index, TT4RI, Thyroid-Stimulating Hormone TSH, and TSHI) reflecting the sensitivity to thyroid hormones were related to the sleep duration, with a significant non-linear relationship after adjusting for potential confounders (all P < 0.05). Trend analysis indicated that with the level increase of these 4 indexes, the sleep duration increased (all P for trend < 0.001). Further, we found that TSHI was relatively more important among the 4 indexes. Sum up, sensitivity to thyroid hormones is associated with sleep duration in the euthyroid population with depression degree lower than Moderate. Poor sensitivity referred to a longer sleep duration.

The relationship between sleep duration and thyroid function in the adult US population: NHANES 2007-2012

OBJECTIVE

Sleep disturbance is a common problem in the general population. Sleep deprivation or dysfunction can have profound health consequences. However, how sleep duration is associated with thyroid function remains unclear. This study was thus developed to examine the association between sleep duration and thyroid function in the US adult population.

METHODS

A total of 8102 participants from the NHANES 2007-2012 dataset were included in this study. Weighted data analyses were conducted, and the link between sleep duration and thyroid function was probed using linear regression models with smoothed curve fitting. Stratified analyses were also performed.

RESULTS

Weighted mean (standard deviation) values for study variables were as follows: sleep duration 6.85 (0.02) hours, thyroid-stimulating hormone (TSH) 1.86 (0.03) mIU/ml, serum free T3 3.20 (0. 01) pg/mL, serum free T4 0.80 (0.01) ng/dL, serum total T3 115.12 (0.64) ng/dL, serum total T4 7.81 (0.04) ug/dL, TPOAb 16.20 (1.53) IU/mL, TgAb 5.75 (0.73) IU/mL, and Tg 15.11 (0.46) ng/mL. In unadjusted analyses, increased sleep duration was associated with higher serum TSH levels and decreased FT3 levels. After adjustment for potential confounders, a significant negative relationship was detected between sleep duration and FT3 levels in participants with ≤7 hours of sleep. When sleep duration exceeded 7 hours, no significant changes in FT3 levels were observed after further increases in sleep duration.

CONCLUSION

Increased sleep duration was related to decreased FT3 levels, primarily at short sleep durations, and this correlation was no longer evident when participants reached the recommended healthy sleep duration.

Sleep quality in patients with non-functioning pituitary adenoma: impact of replacement therapies with an emphasis on the time of hydrocortisone

PURPOSE

Sleep disturbances are widespread and associated with pituitary diseases, even those under long-term therapeutic management. The aim of this study was to investigate sleep quality in patients with non-functioning pituitary adenoma (NFPA) and determine the factors that might influence sleep quality, including the detailed features of replacement therapy.

METHODS

Eighty-two patients with NFPA and 82 age- and gender-matched control subjects were included. Pittsburgh Sleep Quality Index (PSQI), Hospital Anxiety and Depression Scale (HADS) and International Physical Activity Questionnaire (IPAQ) were used.

RESULTS

In the NFPA group, 57.3% of patients had decreased sleep quality, compared to 35.4% in the control group (p=0.005). Although there was no relationship between the presence of hydrocortisone replacement and sleep quality (p>0.05), a strong positive correlation was observed between PSQI and morning hydrocortisone replacement time in patients with secondary adrenal insufficiency (r=0.834, p<0.001). Diabetes insipidus was found to be significantly higher in the group with decreased sleep quality (p=0.01). Moreover, there was a negative correlation between PSQI and IGF-1 in patients with NFPA (r=-0.259, p=0.01). A multivariate logistic regression model revealed that depression score and free T4 level in the upper half of the normal limit influence the sleep quality of patients with NFPA.

CONCLUSION

Our study indicated the presence of depression, and a free T4 level in the upper half of the normal range have an impact on the sleep quality of patients with NFPA. The time of hydrocortisone replacement might be important factor for improved sleep quality in patients with secondary adrenal insufficiency.

Hyperthyroidism in Graves Disease Causes Sleep Disorders Related to Sympathetic Hypertonia

CONTEXT

It is well known that Graves disease (GD) causes sleep disorders (SDs). However, the characteristics and associated factors of SD and its clinical course post hyperthyroidism normalization remain unclear.

OBJECTIVE

To clarify the characteristics and associated factors of subjective SD and its clinical course after GD treatment.

METHODS

From November 2017 to October 2020, we enrolled 72 participants (22 newly diagnosed with GD with untreated hyperthyroidism, 20 previously diagnosed with GD with normal thyroid function, and 30 normal controls) with no other underlying SD-related diseases. We compared the groups at enrollment and conducted prospective observations after 12 months of treatment on participants with newly diagnosed GD. Main outcome measures were differences and changes in the Pittsburgh Sleep Quality Index (PSQI) global and component sleep quality scores.

RESULTS

PSQI global sleep quality scores (P = .036) and sleep disturbance scores (P = .011) were significantly different among the 3 groups, and were highest in the untreated hyperthyroidism group. Multiple regression analysis demonstrated that free thyroxine level, which was positively correlated with sympathetic tone (ST) as evaluated by pulse rate, and urinary total metanephrines was associated with poorer PSQI global sleep quality scores independently of other factors (P = .006). Prospective observation showed that PSQI global sleep quality scores (P = .018) and sleep disturbance scores (P = .011) significantly improved with thyroid function normalization and ST attenuation.

CONCLUSION

Hyperthyroidism caused by GD augmented ST and exacerbated subjective SD. Normalization of hyperthyroidism caused by GD improved subjective SD.

Impact of sleep patterns upon female neuroendocrinology and reproductive outcomes: a comprehensive review

Sleep is vital to human bodily function. Growing evidence indicates that sleep deprivation, disruption, dysrhythmia, and disorders are associated with impaired reproductive function and poor clinical outcomes in women. These associations are largely mediated by molecular-genetic and hormonal pathways, which are crucial for the complex and time sensitive processes of hormone synthesis/secretion, folliculogenesis, ovulation, fertilization, implantation, and menstruation. Pathologic sleep patterns are closely linked to menstrual irregularity, polycystic ovarian syndrome, premature ovarian insufficiency, sub/infertility, and early pregnancy loss. Measures of success with assisted reproductive technology are also lower among women who engage in shift work, or experience sleep disruption or short sleep duration. Extremes of sleep duration, poor sleep quality, sleep disordered breathing, and shift work are also associated with several harmful conditions in pregnancy, including gestational diabetes and hypertensive disorders. While accumulating evidence implicates pathologic sleep patterns in impaired reproductive function and poor reproductive outcomes, additional research is needed to determine causality and propose therapeutic interventions.

Relationship between the night shift work and thyroid disorders: A systematic review and meta-analysis

OBJECTIVES

The night shift workers were reported to have health consequences, ranging from mild, as cluster headache, to severe, as heart attacks and hormonal irregularities. This study is aimed to perform a systematic review and meta-analyze of the association between the night shift work and the thyroid disorders.

METHODS

We comprehensively searched eight databases, including PubMed and Google Scholar for the relevant articles. This systematic review and meta-analysis were conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-analysis (PRISMA) statement.

RESULTS

We finally included six papers involving 4074 participants. Four papers were eligible for meta-analysis involving 1864 night shift workers and 2017 day shift workers. We against found that thyroid stimulating hormone (TSH) is significantly higher in the night shift group compared to the day shift group.

CONCLUSIONS

The higher TSH among the night shift workers is attributed to disruption of the circadian rhythm and sleep/wake cycle, with subsequent eating disorders. We proposed that more attention should be paid to the working pattern and the related health consequences.

The Hypothalamic Pituitary Thyroid Axis and Sleep

Sleep has a bidirectional relationship with the hypothalamic-pituitary-thyroid (HPT) axis, and both these homeostatic processes are inter-dependent for robust physiological functioning. The quality and quantity of sleep influence the circadian pattern of TSH and thyroid hormone secretion. Short term sleep restriction significantly reduces the amplitude of nocturnal TSH secretion and may modulate active thyroid hormone secretion, likely through an increased sympathetic tone. Conversely, TSH and active thyroid hormone affect the quantity and architecture of sleep. For instance, low TSH values are permissive for slow wave sleep and maintenance of normal sleep architecture, while the hypo- or hyper-secretion of active thyroid hormones adversely affects the quality and quantity of sleep. Structural thyroid disorders may also be associated with an altered circadian clock - a phenomenon warranting further investigation. In this review, we aim to provide readers a comprehensive review on the associations between the HPT axis and sleep patterns.

The relationship between thyroid function tests and sleep quality: cross-sectional study

INTRODUCTION

The relationship between sleep and hormones have long been recognized. Studies indicated that sleep quality is one of the major modulatory effects on the endocrine system. In this study, we aimed to assess the serum concentration of thyroid hormones in individuals who suffered from low quality sleep.

MATERIAL AND METHODS

Based on the Pittsburgh Sleep Quality Index and ISMA Stress questionnaire, we divided 83 participants into two groups. Forty-one individuals with low quality sleep group and 42 with good quality sleep group, all from the male students of a medical school in Tehran, Iran, participated in this descriptive and cross-sectional study. Then, serum levels of thyroid hormones including free T₃, free T₄, and TSH were assessed and compared between two groups.

RESULTS

There were a significant increase in serum levels of FT₄ (p=0.01) and TSH (p=0.02). There were also meaningful correlations between sleep score and stress score (p=0.008) as well as stress score and FT₄ (p=0.03) in the case group.

CONCLUSIONS

The current study showed that thyroid function tests (T₄ and TSH) significantly rose in the poor sleep condition. We also found correlations between sleep score, stress score, and FT₄ in the poor sleep condition group that suggest low sleep quality can affect thyroid hormones.

Effects of sleep restriction on subjective and physiological variables in middle-aged Korean adults: an intervention study

BACKGROUND

Adequate sleep is crucial for normal functioning. However, most people, including middle-aged adults of reproductive age, show a marked reduction in their sleep duration. Thus, sleep is a major issue that should be addressed in health management. We investigated the effects of short-term sleep restriction on subjective parameters (sleepiness, stress, fatigue) and physiological parameters (cortisol, thyrotropin [TSH], thyroxine [T4], triiodothyronine [T3], C-reactive protein [CRP]) in middle-aged adults, the recovery of these parameters after rest, and the associations between parameters.

METHODS

A total of 118 healthy adults (59 men, 59 women), aged 35-44 years, and without sleep problems, were enrolled. Participants underwent a 4-h sleep restriction per day for 3 day at a hospital, and then returned to their daily lives to take four days of rest. A questionnaire and blood test were administered before and after sleep restriction, and after the recovery period, to assess subjective and physiological parameters.

RESULTS

After sleep restriction, sleepiness, fatigue, and stress significantly increased compared to baseline. Cortisol and TSH were elevated after sleep restriction, while T4, T3, and CRP were reduced compared to baseline. After the recovery phase, all parameters were restored to levels similar to baseline levels. Changes in each parameter were mutually associated; fatigue and sleepiness had the strongest association.

CONCLUSION

Our results suggest that even a short period of sleep restriction can have an adverse impact on psychological and physiological stress parameters in middle-aged adults, and that adequate rest and sleep are needed to restore them to normal levels.

Association between Sleep Duration and Subclinical Thyroid Dysfunction Based on Nationally Representative Data

Background: Sleep duration is an identified risk factor for adverse health outcomes. As the endocrine system is closely intertwined with sleep duration and quality, the association between endocrine dysfunction and sleep has been evaluated. Thyroid function, particularly that related to thyrotropin (TSH), is also known to be influenced by the sleep/awake status and circadian rhythm. Additionally, a link between sleep duration and autoimmunity, which is a common cause of thyroid dysfunction, has been suggested; however, depending on the sleep deprivation method used in studies, the effects of sleep on thyroid function vary. The relationship between subclinical thyroid dysfunction and sleep duration is poorly documented. Thus, to elucidate the impact of sleep on thyroid function, we investigated the association of subclinical thyroid dysfunction with sleep duration using representative data from the sixth Korea National Health and Nutrition Examination Survey, conducted from 2013 to 2015. Methods: In all, 4945 participants (2543 male and 2402 female) were included after excluding subjects using the following criteria: <19 years of age, free T4 level outside the normal range, history of thyroid disease, or incomplete data. The population was classified into three groups: short sleeper (<7 h/day), normal sleeper (7–8 h/day), and long sleeper (>8 h/day). The odds ratio (OR) for subclinical hypothyroidism or hyperthyroidism according to sleep duration was evaluated. Results: The short, normal, and long sleeper groups consisted of 2097, 2514, and 334 subjects, respectively. On multiple logistic regression analysis, compared to normal sleepers, short sleepers showed a significantly increased risk of subclinical hyperthyroidism (OR 1.37, 95% confidential interval (CI) 1.02–1.84, p = 0.036), while the risk of subclinical hypothyroidism in short sleepers was not elevated. Comparing long sleepers to normal sleepers, the OR for subclinical hyperthyroidism and hypothyroidism was 1.79 (95% CI 1.12–2.86, p = 0.015) and 1.91 (95% CI 1.03–3.53, p = 0.039), respectively. Conclusions: Both shorter and longer sleep durations were associated with an increase in the risk of subclinical thyroid dysfunction compared to the optimal sleep duration. This analysis of representative population data shows that sleep duration could intertwine with thyroid function resulting in increased risk of subclinical thyroid dysfunction.

The interplay between neuroendocrine and sleep alterations following traumatic brain injury

BACKGROUND

Sleep and endocrine disruptions are prevalent after traumatic brain injury (TBI) and are likely to contribute to morbidity.

OBJECTIVE

To describe the interaction between sleep and hormonal regulation following TBI and elucidate the impact that alterations of these systems have on cognitive responses during the posttraumatic chronic period.

METHODS

Review of preclinical and clinical literature describing long-lasting endocrine dysregulation and sleep alterations following TBI. The bidirectional relationship between sleep and hormones is described. Literature describing co-occurrence between sleep-wake disturbances and hormonal dysregulation will be presented. Review of literature describing cognitive effects of seep and hormones. The cognitive and functional impact of sleep disturbances and hormonal dysregulation is discussed within the context of TBI.

RESULTS/CONCLUSIONS

Sleep and hormonal alterations impact cognitive and functional outcome after TBI. Diagnosis and treatment of these disturbances will impact recovery following TBI and should be considered in the post-acute rehabilitative setting.

Sleep deprivation and obesity in adults: a brief narrative review

Background/aims

Obesity and sleep deprivation are two epidemics that pervade developed nations. Their rates have been steadily rising worldwide, especially in the USA. This short communication will explore the link between the two conditions and outline the proposed mechanisms behind their relationship.

Methods

Studies on the topic of sleep and obesity were reviewed, and findings were used to develop a theoretical model for the biological link between short sleep duration and obesity.

Results

Individuals who regularly slept less than 7  hours per night were more likely to have higher average body mass indexes and develop obesity than those who slept more. Studies showed that experimental sleep restriction was associated with increased levels of ghrelin, salt retention and inflammatory markers as well as decreased levels of leptin and insulin sensitivity.

Conclusions

There may be a link between obesity and sleep deprivation. We recommend further investigations are to elucidate the potential mechanisms.

Constant light alters serum hormone levels related to thyroid function in male CD-1 mice

Disruptions to the circadian rhythm can lead to altered metabolism. Modification of thyroid function may be a reason why circadian misalignment may contribute to future metabolic disorders. We investigated whether circadian disruption through constant light (LL) can lead to variations in hormone levels associated with thyroid function. Mice were exposed to LL or a 12:12 Light:Dark (LD) cycle for 6 weeks; then glucose tolerance and thyroid hormone levels were measured at ZT 6 and ZT 18. There was day/night variation in glucose tolerance, but LL had no effect. LL reduced TSH, increased fT4, and abolished day/night variation in fT3 and leptin. These findings illustrate that LL alters thyroid-related hormones, providing evidence of a link between circadian disruption and thyroid function.

The hypothalamic-pituitary-thyroid axis and personality in a sample of healthy subjects

Thyroid hormones influence various brain pathologies, including psychiatric disorders. However, the relationship between these hormones and the psychological state in the normal, non-clinical population is poorly understood. We aimed to test whether serum levels of thyroid hormones are associated with personality in the healthy population. Thyrotropin (TSH), free T3 (FT4), total and free T4 (TT4 and FT4) concentrations were measured in the blood of 104 healthy participants (44% men) aged 18-59 (M=35±9). Personality traits were assessed using the revised short versions of the Temperament and Character Inventory (TCI-140) and the NEO Five-Factor Inventory (NEO-FFI). The data were analysed by correlational, regression, extreme groups and graphical techniques, which showed significant correlations between inter-individual variations in serum thyroid hormone levels and specific aspects of personality. In particular, high serum TSH was strongly associated with higher Persistence and Self-Directedness, and negatively correlated with Harm Avoidance on the TCI-140 and Neuroticism on the NEO-FFI, thus representing a more adaptive personality profile. Furthermore, increased FT4 was associated with lower Reward-Dependence, and increased TT4 was associated with lower Cooperativeness, representing a deficit in social attachment. Our data indicate that the relationship between thyroid hormones and personality in the healthy population might be rather more complex than the results obtained in clinical samples suggest.

Longer sleep is associated with lower BMI and favorable metabolic profiles in UK adults: Findings from the National Diet and Nutrition Survey

Ever more evidence associates short sleep with increased risk of metabolic diseases such as obesity, which may be related to a predisposition to non-homeostatic eating. Few studies have concurrently determined associations between sleep duration and objective measures of metabolic health as well as sleep duration and diet, however. We therefore analyzed associations between sleep duration, diet and metabolic health markers in UK adults, assessing associations between sleep duration and 1) adiposity, 2) selected metabolic health markers and 3) diet, using National Diet and Nutrition Survey data. Adults (n = 1,615, age 19–65 years, 57.1% female) completed questions about sleep duration and 3 to 4 days of food diaries. Blood pressure and waist circumference were recorded. Fasting blood lipids, glucose, glycated haemoglobin (HbA1c), thyroid hormones, and high-sensitivity C-reactive protein (CRP) were measured in a subset of participants. We used regression analyses to explore associations between sleep duration and outcomes. After adjustment for age, ethnicity, sex, smoking, and socioeconomic status, sleep duration was negatively associated with body mass index (-0.46 kg/m² per hour, 95% CI -0.69 to -0.24 kg/m², p < 0.001) and waist circumference (-0.9 cm per hour, 95% CI -1.5 to -0.3cm, p = 0.004), and positively associated with high-density lipoprotein cholesterol (0.03 mmol/L per hour, 95% CI 0.00 to 0.05, p = 0.03). Sleep duration tended to be positively associated with free thyroxine levels and negatively associated with HbA1c and CRP (p = 0.09 to 0.10). Contrary to our hypothesis, sleep duration was not associated with any dietary measures (p ≥ 0.14). Together, our findings show that short-sleeping UK adults are more likely to have obesity, a disease with many comorbidities.

Estimating individual optimal sleep duration and potential sleep debt

In this study, we hypothesized that dynamics of sleep time obtained over consecutive days of extended sleep in a laboratory reflect an individual's optimal sleep duration (OSD) and that the difference between OSD and habitual sleep duration (HSD) at home represents potential sleep debt (PSD). We found that OSD varies among individuals and PSD showed stronger correlation with subjective/objective sleepiness than actual sleep time, interacting with individual's vulnerability of sleep loss. Furthermore, only 1 h of PSD takes four days to recover to their optimal level. Recovery from PSD was also associated with the improvement in glycometabolism, thyrotropic activity and hypothalamic-pituitary-adrenocortical axis. Additionally, the increase (rebound) in total sleep time from HSD at the first extended sleep would be a simple indicator of PSD. These findings confirmed self-evaluating the degree of sleep debt at home as a useful clinical marker. To establish appropriate sleep habits, it is necessary to evaluate OSD, vulnerability to sleep loss, and sleep homeostasis characteristics on an individual basis.

[Sleep duration and metabolism]

Sleep duration has gradually diminished during the last decade while obesity and type 2 diabetes have become epidemics. Experimental sleep curtailment leads to increased appetite, hormonal disturbances and, especially, insulin resistance. Numerous epidemiological studies have therefore examined whether habitual short sleep is associated with obesity and type 2 diabetes. A large majority of cross-sectional studies have confirmed an association between short, and also long sleep duration and obesity in adults more than in the elderly. Short sleep is strongly associated to obesity in children and adolescents. Prospective studies, including studies in children, are not conclusive with regard to the effect of short sleep on the incidence of obesity. Both short and long sleep durations are associated with diabetes, but only short sleep duration seems predictive of future diabetes. Insomnia seems to be a strong contributor to short sleep duration but the association of insomnia with obesity is not clear. Insomnia is associated with type 2 diabetes and also predictive of a higher incidence. Other studies have shown that short sleep duration and insomnia are associated with, and sometime predictive of, other components of the metabolic syndrome, especially hypertension and the risk of coronary disease. The treatment of short sleep duration and insomnia with regard to their effects on the metabolic syndrome merits further study.

Novel loci associated with usual sleep duration: the CHARGE Consortium Genome-Wide Association Study

Usual sleep duration is a heritable trait correlated with psychiatric morbidity, cardiometabolic disease and mortality, although little is known about the genetic variants influencing this trait. A genome-wide association study (GWAS) of usual sleep duration was conducted using 18 population-based cohorts totaling 47 180 individuals of European ancestry. Genome-wide significant association was identified at two loci. The strongest is located on chromosome 2, in an intergenic region 35- to 80-kb upstream from the thyroid-specific transcription factor PAX8 (lowest P=1.1 × 10(-9)). This finding was replicated in an African-American sample of 4771 individuals (lowest P=9.3 × 10(-4)). The strongest combined association was at rs1823125 (P=1.5 × 10(-10), minor allele frequency 0.26 in the discovery sample, 0.12 in the replication sample), with each copy of the minor allele associated with a sleep duration 3.1 min longer per night. The alleles associated with longer sleep duration were associated in previous GWAS with a more favorable metabolic profile and a lower risk of attention deficit hyperactivity disorder. Understanding the mechanisms underlying these associations may help elucidate biological mechanisms influencing sleep duration and its association with psychiatric, metabolic and cardiovascular disease.

Sleep, sleep disturbance, and fertility in women

Sleep and sleep disturbances are increasingly recognized as determinants of women's health and well-being, particularly in the context of the menstrual cycle, pregnancy, and menopause. At present, however, little is known about whether fertility is affected by sleep quantity and quality. That is, to what degree, and by what mechanisms, do sleep and/or its disturbances affect fertility? The purpose of this review is to synthesize what is known about sleep disturbances in relation to reproductive capacity. A model is provided, whereby stress, sleep dysregulation, and circadian misalignment are delineated for their potential relevance to infertility. Ultimately, if it is the case that sleep disturbance is associated with infertility, new avenues for clinical intervention may be possible.

Contribution of daily and seasonal biorhythms to obesity in humans

While the significance of obesity as a serious health problem is well recognized, little is known about whether and how biometerological factors and biorhythms causally contribute to obesity. Obesity is often associated with altered seasonal and daily rhythmicity in food intake, metabolism and adipose tissue function. Environmental stimuli affect both seasonal and daily rhythms, and the latter are under additional control of internal molecular oscillators, or body clocks. Modifications of clock genes in animals and changes to normal daily rhythms in humans (as in shift work and sleep deprivation) result in metabolic dysregulation that favours weight gain. Here, we briefly review the potential links between biorhythms and obesity in humans.

Assessment of sleep quality in post-graduate residents in a tertiary hospital and teaching institute

OBJECTIVES

To evaluate subjective sleep quality, day-time sleepiness, prevalence of substance use, satisfaction with life among residents at our institute. To evaluate association of sleep qualitywith satisfaction with life and day-time sleepiness. To compare the findings between residents in clinical and para-clinical departments.

MATERIALS AND METHODS

Eighty-four residents filled questionnaires to obtain socio-demographic information and use of substance (s). Pittsburgh Sleep Quality Index (PSQI), Epworth Sleepiness Scale (ESS), and Satisfaction With Life scale (SWLS) were also used. Association between sleep quality and sleepiness and satisfaction with life was evaluated. From the data collected, comparisons were made between the clinical and para-clinical department residents.

RESULTS

A significant number of residents belonging to the clinical faculty were poorsleepers; reported high levels of abnormal day-time sleepiness and less satisfaction with life compared to residents in para-clinical faculties. The differences in correlation between sleepiness and satisfaction with life with sleep quality among the two groups were not found to be significant. A larger percentage of clinical residents reported use of at least one substance during the residency period compared to the para-clinical residents.

CONCLUSIONS

Poor sleep quality is perceived greatly by the resident doctors in our public hospital, especially among clinical faculties. Interventions are thus necessary in order to ensure adequate sleep among them.

Nuclear receptors and their selective pharmacologic modulators

Nuclear receptors are ligand-activated transcription factors and include the receptors for steroid hormones, lipophilic vitamins, sterols, and bile acids. These receptors serve as targets for development of myriad drugs that target a range of disorders. Classically defined ligands that bind to the ligand-binding domain of nuclear receptors, whether they are endogenous or synthetic, either activate receptor activity (agonists) or block activation (antagonists) and due to the ability to alter activity of the receptors are often termed receptor "modulators." The complex pharmacology of nuclear receptors has provided a class of ligands distinct from these simple modulators where ligands display agonist/partial agonist/antagonist function in a tissue or gene selective manner. This class of ligands is defined as selective modulators. Here, we review the development and pharmacology of a range of selective nuclear receptor modulators.

Partial sleep restriction modulates secretory activity of thyrotropic axis in healthy men

Sleep and endocrine function are known to be closely related, but studies on the effect of moderate sleep loss on endocrine axes are still sparse. We examined the influence of partial sleep restriction for 2 days on the secretory activity of the thyrotropic axis. Fifteen healthy, normal-weight men were tested in a balanced, cross-over study. Serum concentrations of thyrotrophin (TSH), free triiodothyronine (fT3) and free thyroxine (fT4) were monitored at 1-h intervals during a 15-h daytime period (08:00-23:00 h) following two nights of restricted sleep (bedtime 02:45-07:00 h) and two nights of regular sleep (bedtime 22:45-07:00 h), respectively. Serum concentrations of fT3 (P < 0.026) and fT4 (P = 0.089) were higher after sleep restriction than regular sleep, with a subsequent blunting of TSH concentrations in the evening hours of the sleep restriction condition (P = 0.008). These results indicate profound alterations in the secretory activity of the thyrotropic axis after 2 days of sleep restriction to ~4 h, suggesting that acute partial sleep loss impacts endocrine homeostasis, with potential consequences for health and wellbeing.

Partial sleep deprivation and energy balance in adults: an emerging issue for consideration by dietetics practitioners

During the past 30 years, rates of partial sleep deprivation and obesity have increased in the United States. Evidence linking partial sleep deprivation, defined as sleeping <6 hours per night, to energy imbalance is relevant to weight gain prevention and weight loss promotion. With a majority of Americans overweight or obese, weight loss is a recommended strategy for reducing comorbid conditions. Our purpose was to review the literature regarding the role of partial sleep deprivation on energy balance and weight regulation. An inverse relationship between obesity and sleep duration has been demonstrated in cross-sectional and prospective studies. Several intervention studies have tested mechanisms by which partial sleep deprivation affects energy balance. Reduced sleep may disrupt appetitive hormone regulation, specifically increasing ghrelin and decreasing leptin and, thereby, influence energy intake. Increased wakefulness also may promote food intake episodes and energy imbalance. Energy expenditure may not be greatly affected by partial sleep deprivation, although additional and more accurate methods of measurements may be necessary to detect subtle changes in energy expenditure. Body weight loss achieved by reduced energy intake and/or increased energy expenditure combined with partial sleep deprivation may contribute to undesirable body composition change with proportionately more fat-free soft tissue mass lost compared with fat mass. Evaluating sleep patterns and recommending regular, sufficient sleep for individuals striving to manage weight may be prudent.

Interacting epidemics? Sleep curtailment, insulin resistance, and obesity

In the last 50 years, the average self-reported sleep duration in the United States has decreased by 1.5-2 hours in parallel with an increasing prevalence of obesity and diabetes. Epidemiological studies and meta-analyses report a strong relationship between short or disturbed sleep, obesity, and abnormalities in glucose metabolism. This relationship is likely to be bidirectional and causal in nature, but many aspects remain to be elucidated. Sleep and the internal circadian clock influence a host of endocrine parameters. Sleep curtailment in humans alters multiple metabolic pathways, leading to more insulin resistance, possibly decreased energy expenditure, increased appetite, and immunological changes. On the other hand, psychological, endocrine, and anatomical abnormalities in individuals with obesity and/or diabetes can interfere with sleep duration and quality, thus creating a vicious cycle. In this review, we address mechanisms linking sleep with metabolism, highlight the need for studies conducted in real-life settings, and explore therapeutic interventions to improve sleep, with a potential beneficial effect on obesity and its comorbidities.