Chronotype and diurnal cortisol profile in working women: differences between work and leisure days

Individualized prediction of anxiety and depressive symptoms using gray matter volume in a non-clinical population

Machine learning is an emerging tool in clinical psychology and neuroscience for the individualized prediction of psychiatric symptoms. However, its application in non-clinical populations is still in its infancy. Given the widespread morphological changes observed in psychiatric disorders, our study applies five supervised machine learning regression algorithms-ridge regression, support vector regression, partial least squares regression, least absolute shrinkage and selection operator regression, and Elastic-Net regression-to predict anxiety and depressive symptom scores. We base these predictions on the whole-brain gray matter volume in a large non-clinical sample (n = 425). Our results demonstrate that machine learning algorithms can effectively predict individual variability in anxiety and depressive symptoms, as measured by the Mood and Anxiety Symptoms Questionnaire. The most discriminative features contributing to the prediction models were primarily located in the prefrontal-parietal, temporal, visual, and sub-cortical regions (e.g. amygdala, hippocampus, and putamen). These regions showed distinct patterns for anxious arousal and high positive affect in three of the five models (partial least squares regression, support vector regression, and ridge regression). Importantly, these predictions were consistent across genders and robust to demographic variability (e.g. age, parental education, etc.). Our findings offer critical insights into the distinct brain morphological patterns underlying specific components of anxiety and depressive symptoms, supporting the existing tripartite theory from a neuroimaging perspective.

Sleep Duration and Sarcopenia: An Updated Systematic Review and Meta-Analysis

OBJECTIVES

In adults, short and long sleep duration has been associated with sarcopenia risk. Studies have shown that various factors, including biological and psychological factors, could be the underlying cause of the association between aberrant sleep duration and sarcopenia risk. In this study, we have qualitatively and quantitatively summarized previously published studies on sleep duration to assess the relationship between sleep duration and sarcopenia risk in adults. This would aid in enhancing our understanding of recent advancements in this field and the association between sleep duration and sarcopenia risk.

DESIGN

Systematic review and meta-analysis.

SETTING AND PARTICIPANTS

In this review, we included studies evaluating the association between the duration of sleep and sarcopenia in adults in observational studies.

METHODS

Five electronic databases (PubMed, EMBASE, Cochrane Library, China National Knowledge Infrastructure, and Web of Science) were searched to April 20, 2023, to identify studies related to sarcopenia and sleep duration. Next, we calculated the odds ratios (ORs) for sarcopenia prevalence based on the adjusted data from individual studies. Statistical analyses were performed using Stata 11.0.

RESULTS

Sarcopenia prevalence was high (18%) in adults with long sleep duration. Our results showed a significant association between short duration of sleep and high sarcopenia prevalence in older adults (OR 1.2, 95% CI 1.02-1.41, I2 = 56.6%). Furthermore, a significant association was observed between all participants with long-duration sleep and high sarcopenia prevalence (OR 1.53, 95% CI 1.34-1.75, I2 = 56.8%). We also observed significant heterogeneity in the adjusted ORs.

CONCLUSIONS AND IMPLICATIONS

There was a correlation between sarcopenia and short or long sleep duration, especially in older adults. In adults with a long duration of sleep, sarcopenia prevalence was relatively high.

The diurnal course of salivary cortisol and alpha-amylase on workdays and leisure days in teachers and the role of social isolation and neuroticism

Teachers are among the occupational groups with the highest sick leave rates due to workplace stress and burnout symptoms. A substantial body of research has suggested social isolation and neuroticism to be related to physiological stress activity. However, the relationship between such characteristics and stress experiences has rarely been studied in conjunction with physiological stress indicators in the teachers' natural settings. Thus, the present study examines salivary cortisol and α-amylase as physiological stress indicators on teachers' work and leisure days and their relationship with social isolation. Furthermore, we test whether neuroticism moderates the relationship between social isolation and salivary biomarkers. Forty-two teachers completed questionnaires assessing social isolation (Trier Inventory for the Assessment of Chronic Stress) and neuroticism (Big-Five Inventory). Participants collected eight saliva samples on three days, two workdays, and one leisure day to measure the concentration of cortisol and α-amylase as biomarkers of the hypothalamic-pituitary-adrenal (HPA) axis and the autonomic nervous system (ANS), respectively. Results showed a significantly higher Cortisol Awakening Response (CAR) and diurnal cortisol slope (DCS) on workdays than on the leisure day but no significant differences regarding measures of α-amylase. We found a significant positive relationship between social isolation and the CAR on the leisure day but no association with the α-amylase measures. Furthermore, after controlling for confounders, social isolation was unrelated to neuroticism, and the latter did not moderate between social isolation and the CAR. Our findings suggest an association between social isolation and the HPA axis, i.e., the CAR, but do not support an association with the ANS, which would be indicated by the α-amylase assessments. Finally, our findings could not support an association of neuroticism with the HPA axis and ANS.

Vitamin D and chronotype: is there any relationship in individuals with obesity?

PURPOSE

Chronotype is the attitude to perform most of the daily activities in the morning ("morning chronotype", MC) or in the evening ("evening chronotype", EC). The latter, as well as vitamin D deficiency, has been associated with an increased risk of obesity-related complications, likely through the promotion of insulin resistance. Therefore, we aimed to investigate whether there is any relationship between vitamin D (25-OH-D) and chronotype in individuals with obesity.

METHODS

In this cross-sectional study, we enrolled 59 individuals (43.1 ± 13 years; 17M/42F) with obesity. Anthropometric parameters, lifestyle habits, personal medical history, chronotype, insulin resistance, and 25-OH-D were assessed.

RESULTS

Individuals with EC presented significantly higher BMI than MC (p < 0.001), greater waist (p = 0.012), and hip circumferences (p = 0.001). Individuals with EC showed significantly lower insulin sensitivity (p = 0.017) and 25-OH-D than MC. In addition, the prevalence of vitamin D deficiency and impaired fasting glucose was significantly higher in EC than in MC. 25-OH-D directly correlated with chronotype score (r = 0.351; p = 0.019) whereas inversely with BMI (r = - 0.363; p = 0.016). The regression analysis showed that BMI was most tightly associated with 25-OH-D concentrations (β = - 0.323, p = 0.032), followed by chronotype score (β = 0.340, p = 0.042). Using chronotype score as the dependent variable, BMI significantly predicted a lower chronotype score (β = - 0.586, p < 0.001).

CONCLUSION

The present study showed that 25-OH-D, as well as chronotype, correlate independently with obesity.

Beyond sleep: A multidimensional model of chronotype

Chronotype can be defined as an expression or proxy for circadian rhythms of varied mechanisms, for example in body temperature, cortisol secretion, cognitive functions, eating and sleeping patterns. It is influenced by a range of internal (e.g., genetics) and external factors (e.g., light exposure), and has implications for health and well-being. Here, we present a critical review and synthesis of existing models of chronotype. Our observations reveal that most existing models and, as a consequence, associated measures of chronotype have focused solely or primarily on the sleep dimension, and typically have not incorporated social and environmental influences on chronotype. We propose a multidimensional model of chronotype, integrating individual (biological and psychological), environmental and social factors that appear to interact to determine an individual's true chronotype with potential feedback loops between these factors. This model could be beneficial not only from a basic science perspective but also in the context of understanding health and clinical implications of certain chronotypes as well as designing preventive and therapeutic approaches for related illnesses.

Chronotype, circadian rhythm, and psychiatric disorders: Recent evidence and potential mechanisms

The circadian rhythm is crucial for physiological and behavioral functions. Chronotype, which represents individual preferences for activity and performance, is associated with human health issues, particularly psychiatric disorders. This narrative review, which focuses on the relationship between chronotype and mental disorders, provides an insight into the potential mechanism. Recent evidence indicates that (1) the evening chronotype is a risk factor for depressive disorders and substance use disorders, whereas the morning chronotype is a protective factor. (2) Evening chronotype individuals with bipolar disorder tend to have more severe symptoms and comorbidities. (3) The evening chronotype is only related to anxiety symptoms. (4) The relationship between chronotype and schizophrenia remains unclear, despite increasing evidence on their link. (5) The evening chronotype is significantly associated with eating disorders, with the majority of studies have focused on binge eating disorders. Furthermore, the underlying mechanisms or influence factors are described in detail, including clock genes, brain characteristics, neuroendocrinology, the light/dark cycle, social factors, psychological factors, and sleep disorders. These findings provide the latest evidence on chronotypes and psychiatric disorders and serve as a valuable reference for researchers.

Sleep duration and sarcopenia in adults aged ≥ 65 years from low and middle-income countries

BACKGROUND

Sleep duration may influence risk for sarcopenia but studies on this topic are scarce, especially from low and- middle-income countries (LMICs). Thus, the aim of the present study was to investigate the association between sleep duration and sarcopenia among adults aged ≥ 65 years from five LMICs (China, Ghana, India, Russia, South Africa).

METHODS

Cross-sectional, community-based data from the WHO study on global ageing and adult health (SAGE) were analysed. Sarcopenia was defined as having low skeletal muscle mass (SMM) and weak handgrip strength, while severe sarcopenia was defined as having low SMM, weak handgrip strength, and slow gait speed. Self-reported sleep duration in the past two nights were averaged and classified as ≤ 6, > 6 to ≤ 9, and ≥ 9 h/day. Multivariable logistic regression analysis was conducted.

RESULTS

Data on 13,210 adults aged ≥ 65 years [mean (SD) age 72.6 (11.3) years; 55.0% females] were analyzed. In the overall sample, compared to > 6 to ≤ 9 h/day of sleep duration, > 9 h/day was associated with 1.70 (95% CI 1.15-2.51) and 1.75 (95% CI 1.08-2.84) times higher odds for sarcopenia and severe sarcopenia, respectively. No significant associations were observed among males, but associations were particularly pronounced among females [i.e., OR = 2.19 (95% CI 1.26-3.81) for sarcopenia, and OR = 2.26 (95% CI 1.20-4.23) for severe sarcopenia].

CONCLUSIONS

Long sleep duration was associated with an increased odds of sarcopenia and severe sarcopenia in LMICs, particularly in females. Future studies should investigate whether addressing long sleep duration among females can lead to lower risk for sarcopenia onset in LMICs.

Evening chronotype is associated with severe NAFLD in obesity

BACKGROUND/OBJECTIVES

Chronotype, i.e., the individual attitude to carry out the daily activities at a certain time of the day, has been reported to play a role in metabolic diseases. Thus, the aim of our study was to investigate the association of non-alcoholic fatty liver disease (NAFLD) with chronotype categories in individuals with obesity.

SUBJECTS/METHODS

In this cross-sectional study, participants underwent to anthropometric, biochemical, and the Visceral Adiposity Index (VAI) assessment. Chronotype categories were assessed by the Horne-Ostberg Morningness-Eveningness Questionnaire (MEQ). The following indirect indices of NAFLD were calculated: Liver Fat Equation (LFE), Hepatic Steatosis Index (HSI) and Index of Non-alcoholic steatohepatitis (ION).

RESULTS

The study population consisted of 87 participants (40.3 ± 12.3 years; BMI 45.6 ± 6.3 kg/m²; 64F/23M). According to the chronotype score, 31.0% were morning (MC), 36.8% were intermediate (IC), and 32.2% evening chronotype (EC). Individuals with IC were significantly younger than those with MC and EC (p = 0.002 and p = 0.047, respectively). EC presented significantly higher BMI (p < 0.001), waist circumference (p = 0.007), and hip circumference (p = 0.001) than MC. Moreover, EC had higher BMI (p < 0.001) and waist circumference (p = 0.011) than IC. All participants presented NAFLD (HSI ≥ 36 and LFE ≥ 5). Nevertheless, only individuals with EC were above the threshold of non-alcoholic steatohepatitis evaluated as ION index (ION ≥ 50). Individuals with EC presented significantly higher VAI (p = 0.036), LFE (p = 0.034), HSI (p < 0.001) and ION (p = 0.014) than MC, also after the adjustment for age, gender, and BMI.

CONCLUSION

EC is associated with more severe NAFLD independently of age, gender, and BMI than MC and IC in individuals with obesity.

Night work, chronotype and cortisol at awakening in female hospital employees

To examine the effect of night shift on salivary cortisol at awakening (C1), 30 min later (C2), and on the cortisol awakening response (CAR, the difference between C2 and C1). We compared shift and non-shift workers with a focus on the impact of worker chronotype. Our study included 66 shift-working females (mean age = 37.3 years, SD = 10.2) and 21 non-shift working females (mean age = 47.0 years, SD = 8.9). The shift workers collected their saliva samples at C1 and C2 on each two consecutive day shifts and night shifts. Non-shift workers collected their samples on two consecutive day shifts. We applied linear mixed-effects models (LMM) to determine the effect of night shift on CAR and log-transformed C1 and C2 levels. LMMs were stratified by chronotype group. Compared to non-shift workers, shift workers before day shifts (i.e. after night sleep) showed lower cortisol at C1 (exp [Formula: see text]=0.58, 95% CI 0.42, 0.81) but not at C2. In shift workers, the CARs after night shifts (i.e. after day sleep) were lower compared to CARs before day shifts ([Formula: see text]= - 11.07, 95% CI - 15.64, - 6.50). This effect was most pronounced in early chronotypes (early: [Formula: see text]= - 16.61, 95% CI - 27.87, - 5.35; intermediate: [Formula: see text]= - 11.82, 95% CI - 18.35, - 5.29; late: [Formula: see text]= - 6.27, 95% CI - 14.28, 1.74). Chronotype did not modify the association between night shift and CAR. In our population of shift workers, there was a mismatch between time of waking up and their natural cortisol peak at waking up (CAR) both during day and night shift duties.

Psychological state during pregnancy is associated with sleep quality: preliminary findings from MY-CARE cohort study

Psychological distress during pregnancy may increase the risk of adverse maternal and infant outcomes. Past studies have demonstrated the association between circadian disturbances with psychological health. However, the roles of chronotype and social jetlag on psychological state during pregnancy are yet to be identified. We aimed to examine the psychological state in pregnant women and its relations to chronotype, social jetlag (SJL), sleep quality and cortisol rhythm. The current study included a subsample of participants from an ongoing cohort study. A total of 179 primigravidas (mean age 28.4 ± 4.0 years) were recruited. Chronotype and sleep quality during the second trimester were assessed using the Morning-Eveningness Questionnaire (MEQ) and Pittsburgh Sleep Quality Index (PSQI), respectively. SJL was calculated based on the difference between mid-sleep on workdays and free days. Psychological state of participants was evaluated using the Depression, Anxiety, and Stress Scale-21 (DASS-21). Subsamples (n = 70) provided salivary samples at 5 time points over a 24 h period during the second trimester for cortisol assay. A higher proportion of pregnant women experienced moderate to severe anxiety symptoms (n = 77, 43.0%), followed by depressive (n = 17, 9.5%) and stress (n = 14, 7.8%) symptoms. No association was observed between chronotype and psychological distress during pregnancy. There was no significant difference in cortisol rhythms in relation to psychological distress. SJL and sleep quality were significantly associated with stress symptoms among pregnant women in the second trimester. Poor sleep quality, particularly daytime dysfunction (β = 0.37, p = .006) and sleep disturbances (β = 0.23, p = .047), were significantly associated with psychological distress (depressive, anxiety and stress symptoms) during the second trimester. The findings suggest that sleep is a potential modifiable lifestyle factor that can be targeted to improve psychological health among pregnant women.

Sleep duration and sarcopenia risk: a systematic review and dose-response meta-analysis

PURPOSE

Present systematic literature review and dose-response meta-analysis were carried out to evaluate the association between sleep duration and sarcopenia risk.

METHODS

Related studies were found by searching ISI Web of science databases, Scopus, and PubMed, up to May, 2019. Data were available from four studies. A total odds ratio of 17551 participants in these studies was pooled for the current study.

RESULTS

Pooled outcomes from random effects model demonstrated that lowest category of sleep duration (under 6 h) versus reference category (6-8 h) was significantly related with increased risk of sarcopenia (OR: 1.71 95% CI, 1.11, 2.64). Pooled OR also indicated that highest category (more than 8 h) of sleep duration versus reference category (6-8 h) was significantly associated with increased risk of sarcopenia (OR: 1.52 95% CI, 1.23, 1.88). Moreover, subgroup analysis by sex showed that women were affected by both short and long sleep while men were only affected by long sleep duration. The nonlinear dose-response meta-analysis revealed a U-shaped association between sleep duration and the risk of sarcopenia, with a nadir at 8 h per day. The linear dose-response meta-analysis illustrated that the risk of sarcopenia did not change significantly nor for a 0.5-h increment neither for 1-h increment in sleep duration per day.

CONCLUSION

The outcomes from this meta-analysis indicate that the public should be made aware of the negative consequences of long and short sleep for sarcopenia especially among women. Further studies should now be undertaken to establish possible links between risk of sarcopenia and sleep duration.

Association between chronotype and body mass index: The role of C-reactive protein and the cortisol response to stress

BACKGROUND

Chronotype influences several physiological systems, including the immune system and the hypothalamus-pituitary-adrenal (HPA)-axis. Previous research has shown that evening chronotype is associated with adverse metabolic health outcomes and obesity. However, the exact mechanisms underlying the observed differences in metabolic function between "morning" and "evening" types remain to be explored.

OBJECTIVE

To investigate the relationship of chronotype with inflammatory and neuroendocrine stress markers and to explore their mediating and moderating roles in the association between chronotype and body mass index (BMI).

METHODS

Twenty-eight healthy young adults (50% women), mean age 23.8 ± 3.3 (SD) years, underwent a standardized laboratory stress test (Trier Social Stress Test, TSST). Concentrations of plasma C-reactive protein (CRP) at baseline and of salivary cortisol before and after the onset of the stressor were analyzed. Heart rate was measured continuously. Chronotype was assessed with the Morningness-Eveningness Questionnaire (MEQ).

RESULTS

Lower MEQ scores (i.e. evening tendency) were associated with higher BMI (r = -.40, p < .05), elevated CRP concentrations (r = -.42, p < .05) and higher cortisol responses to acute stress (r = -.53, p < .01). The relationship between MEQ score and BMI was mediated by CRP concentrations (b = -0.03, CI 95%: -0.08 to -0.007, p < .05). In addition, we observed a moderating effect of the cortisol stress response on this mediated relationship (b = 0.005, CI 95%: 0.0002 to 0.01, p < .05), such that the mediated relationship was stronger in individuals with a higher cortisol response.

CONCLUSION

Enhanced pro-inflammatory state and a higher cortisol response to stress may underlie the effect of evening chronotype on obesity risk and adverse metabolic health outcomes.

Sex differences in stress and immune responses during confinement in Antarctica

Background

Antarctica challenges human explorers by its extreme environment. The effects of these unique conditions on the human physiology need to be understood to best mitigate health problems in Antarctic expedition crews. Moreover, Antarctica is an adequate Earth-bound analogue for long-term space missions. To date, its effects on human physiology have been studied mainly in male cohorts though more female expeditioners and applicants in astronaut training programs are selected. Therefore, the identification of sex differences in stress and immune reactions are becoming an even more essential aim to provide a more individualized risk management.

Methods

Ten female and 16 male subjects participated in three 1-year expeditions to the German Antarctic Research Station Neumayer III. Blood, saliva, and urine samples were taken 1–2 months prior to departure, subsequently every month during their expedition, and 3–4 months after return from Antarctica. Analyses included cortisol, catecholamine and endocannabinoid measurements; psychological evaluation; differential blood count; and recall antigen- and mitogen-stimulated cytokine profiles.

Results

Cortisol showed significantly higher concentrations in females than males during winter whereas no enhanced psychological stress was detected in both sexes. Catecholamine excretion was higher in males than females but never showed significant increases compared to baseline. Endocannabinoids and N-acylethanolamides increased significantly in both sexes and stayed consistently elevated during the confinement. Cytokine profiles after in vitro stimulation revealed no sex differences but resulted in significant time-dependent changes. Hemoglobin and hematocrit were significantly higher in males than females, and hemoglobin increased significantly in both sexes compared to baseline. Platelet counts were significantly higher in females than males. Leukocytes and granulocyte concentrations increased during confinement with a dip for both sexes in winter whereas lymphocytes were significantly elevated in both sexes during the confinement.

Conclusions

The extreme environment of Antarctica seems to trigger some distinct stress and immune responses but—with the exception of cortisol and blood cell counts—without any major relevant sex-specific differences. Stated sex differences were shown to be independent of enhanced psychological stress and seem to be related to the environmental conditions. However, sources and consequences of these sex differences have to be further elucidated.

Hypothalamic-pituitary-adrenal axis differentially responses to morning and evening psychological stress in healthy subjects

Aim

The hypothalamic‐pituitary‐adrenal (HPA) axis responds to changing environmental demands including psychological stressors. The aim of the present study was to assess whether the time of day effects on the acute response of HPA axis activity to acute psychological stress.

Method

We studied 27 healthy young subjects. The subjects were participated two experiments as follows. In the first experiment, subjects were instructed to keep their regular sleep schedule for 2 weeks which were measured by using a wrist‐worn activity monitor. Afterward, to evaluate a diurnal rhythm of salivary cortisol, eight saliva samples were collected during waking period every 2 hours from when the subjects woke up. In the second experiment, the subjects were randomly assigned to two groups. The Trier Social Stress Test (TSST) was performed either in the morning (n = 14) or in the evening (n = 13). We measured diurnal rhythm of salivary cortisol and stress response of salivary cortisol and heart rate by the TSST. Morning and evening tests were started at 2 hours and 10 hours after woke up, respectively.

Results

All subjects showed a normal diurnal rhythm of salivary cortisol concentration, with a peak in the morning immediately after awaking and a minimum in the evening. The salivary cortisol response after the TSST was significantly increased from the prestress level in the morning but not in the evening.

Conclusion

The HPA response to acute psychological stress was more pronounced in the morning than in the evening, correlating with the circadian regulation of cortisol synthesis.

The aim of the present study was to examine whether the HPA axis differentially responses to morning and evening psychological stressor in healthy subjects. Here, we could demonstrate that the HPA axis activity response to acute psychological stressor is higher in the morning than in the evening, relating with circadian rhythm of salivary cortisol concentration.

Shiftwork and Diurnal Salivary Cortisol Patterns Among Police Officers

OBJECTIVE

To investigate associations between shiftwork and diurnal salivary cortisol among 319 police officers (77.7% men).

METHODS

Information on shiftwork was obtained from the City of Buffalo, NY electronic payroll records. Saliva was collected using Salivettes at seven time points and analyzed for free cortisol concentrations (nmol/L) using a chemiluminescence immunoassay. Mean slopes and areas under the curve were compared across shift schedule using analysis of variance (ANOVA)/analysis of covariance (ANCOVA).

RESULTS

Officers working primarily on the night shift had a significantly shallower slope. Mean slope (nmol/L/minutes) of the cortisol curve varied significantly across shifts (day: -0.00332 ± 0.00017, afternoon: -0.00313 ± 0.00018, night: -0.00257 ± 0.0002); adjusted P = 0.023.

CONCLUSIONS

Our results suggest that night shiftwork is a workplace factor that may alter the response of the hypothalamic-pituitary-adrenal (HPA) axis to the circadian cues responsible for the pattern of the diurnal cortisol curve.

Poor sleep quality and later sleep timing are risk factors for osteopenia and sarcopenia in middle-aged men and women: The NEO study

CONTEXT

Sleep deprivation has detrimental metabolic consequences. Osteopenia and sarcopenia usually occur together and increase risk of fractures and disease. Results from studies linking sleep parameters to osteopenia or sarcopenia are scarce and inconsistent.

OBJECTIVE

To examine the associations of sleep parameters with osteopenia and sarcopenia, considering the influence of sex and menopause.

DESIGN, SETTING AND PARTICIPANTS

Cross-sectional analysis of 915 participants (45-65 years, 56% women, BMI 26 (range: 18-56) kg/m2) in the Netherlands Epidemiology of Obesity (NEO) study, a population-based cohort study. Sleep duration, quality, and timing were assessed with the Pittsburgh Sleep Quality Index (PSQI); bone mineral density and relative appendicular muscle mass were measured by DXA scans. Linear and logistic regressions were performed to associate sleep parameters to bone mineral density, relative appendicular muscle mass, osteopenia (t-score between -1 and -2.5) and sarcopenia (1 SD below average muscle mass).

RESULTS

After adjustment for confounding factors, one unit increase in PSQI score (OR and 95% CI, 1.09, 1.03-1.14), declined self-rated sleep quality (1.76, 1.03-3.01), sleep latency (1.18, 1.06-1.31), and a one hour later sleep timing (1.51, 1.08-2.11), but not sleep duration (1.05, 0.90-1.23), were associated with osteopenia. PSQI score (1.10, 1.02-1.19) was also associated with sarcopenia; OR's of sleep latency and later mid-sleep time with sarcopenia were 1.14 (0.99-1.31) and 1.54 (0.91-2.61), respectively. Associations were somewhat stronger in women and varied per menopausal status.

CONCLUSIONS

These results suggest that decreased sleep quality and a later sleep timing are risk factors for osteopenia and sarcopenia in middle aged individuals.

Paradoxical diurnal cortisol changes in neonates suggesting preservation of foetal adrenal rhythms

Studies suggested the presence of foetal adrenal rhythms of cortisol, which are entrained in antiphase to maternal rhythms. In contrast, neonates are thought to have no adrenal rhythm until 2-3 months after birth. To test the hypothesis that a foetal-type adrenal rhythm is preserved after birth, saliva samples were collected from 65 preterm/term infants during hospital stay (30-40 weeks corrected age) at 10:00 and 19:00 h. Cortisol levels were assessed for their diurnal difference and dependence on antenatal/postnatal clinical variables. Cortisol levels were lower during periods 15-28 days and >28 days than ≤5 days of life. Lower cortisol was associated with pregnancy-induced hypertension (PIH), gestational age <28 weeks, and mechanical ventilation after birth. Higher cortisol was associated with vaginal delivery and non-invasive ventilation support at saliva collection. PIH and non-invasive mechanical ventilation at saliva collection were associated with cortisol levels even after adjustment for postnatal age. Cortisol levels were higher in the evening than in the morning, which was unassociated with gestational and postnatal age. Higher cortisol levels in the evening suggest the preservation of a foetal-type diurnal rhythm. Cortisol levels are associated with intrinsic and extrinsic variables, such as PIH, delivery mode, gestational age, and respiratory conditions.

A lack of consistent evidence for cortisol dysregulation in premenstrual syndrome/premenstrual dysphoric disorder

Although decades of research has examined the association between cortisol regulation and premenstrual syndrome/premenstrual dysphoric disorder (PMS/PMDD), no review exists to provide a general set of conclusions from the extant research. In the present review we summarize and interpret research that has tested for associations between PMS/PMDD and cortisol levels and reactivity (n=38 original research articles). Three types of studies are examined: correlational studies, environmental-challenge studies, and pharmacological-challenge studies. Overall, there was very little evidence that women with and without PMS/PMDD demonstrate systematic and predictable mean-level differences in cortisol, or differences in cortisol response/reactivity to challenges. Methodological differences in sample size, the types of symptoms used for diagnosis (physical and psychological vs. only affective), or the type of cortisol measure used (serum vs. salivary), did not account for differences between studies that did and did not find significant effects. Caution is recommended before accepting the conclusion of null effects, and recommendations are made that more rigorous research be conducted, considering symptom-specificity, within-person analyses, and multiple parameters of cortisol regulation, before final conclusions are drawn.

[Stress among nurses: an examination of salivary cortisol levels on work and day off]

The present study evaluates the use of salivary cortisol concentration as a physiological index of the stress level among nurses on their work day and day off and correlates it with the questionnaire used to measure occupational stress in nurses (Inventário de Estresse em Enfermeiros - IEE). This is a comparative, cross-sectional descriptive study in which sociodemographic data, IEE results and salivary cortisol levels were used. Fifty-seven nurses participated in the study (80.7% females and a mean age of 37.1 years old). The IEE average score was 124.5. The average cortisol level was 564.1 ng/m on work day and 354.1 ng/mL on day off. Nurses who had double workdays presented high values of salivary cortisol during the work day (638.1 ng/mL). In conclusion, salivary cortisol identified the nurses' stress level, and differences were found between a work day and day off. On the nurses' day off, their salivary cortisol levels and stress scores were lower.

Circadian typology: a comprehensive review

The interest in the systematic study of the circadian typology (CT) is relatively recent and has developed rapidly in the two last decades. All the existing data suggest that this individual difference affects our biological and psychological functioning, not only in health, but also in disease. In the present study, we review the current literature concerning the psychometric properties and validity of CT measures as well as individual, environmental and genetic factors that influence the CT. We present a brief overview of the biological markers that are used to define differences between CT groups (sleep-wake cycle, body temperature, cortisol and melatonin), and we assess the implications for CT and adjustment to shiftwork and jet lag. We also review the differences between CT in terms of cognitive abilities, personality traits and the incidence of psychiatric disorders. When necessary, we have emphasized the methodological limitations that exist today and suggested some future avenues of work in order to overcome these. This is a new field of interest to professionals in many different areas (research, labor, academic and clinical), and this review provides a state of the art discussion to allow professionals to integrate chronobiological aspects of human behavior into their daily practice.