Wrist temperature and cortisol awakening response in humans with social jetlag in the North

The discrepancy between biological and social rhythms known as social jetlag (SJL) is common in modern society and has a range of negative consequences for cognitive functioning, well-being and health. Social jetlag is typical for people with late chronotypes. As shown earlier, the prevalence of individuals with a late chronotype is higher among the residents of high latitudes. Therefore, a higher rate of detection of people with SJL should be expected in the North. In this study we assessed the detection rate of SJL among 62 young inhabitants of the European North of Russia (the Komi Republic), and the relationship between SJL, the circadian rhythm of the wrist temperature, and the cortisol awakening response (CAR). The detection rate of SJL was 65% among the people examined. A significant decrease in the amplitude (A) of circadian rhythm of wrist temperature: (β = ?0.34 (CI 95%: ?0.66 to ?0.33); F_1,60 = 10.4; p < 0.0001; η² = 0.31), an increased incidence of depression: No-SJL = 4.5%; SJL = 17.5% (H = 4.84; p < 0.05), and a tendency for an increase in CAR was also observed in the SJL group. There were sex differences in sensitivity to SJL. Females with SJL but not males had higher global seasonality scores (β = 0.51 (CI 95%: 0.21 to 0.81); F_1,33 = 10.9; p < 0.002; η² =0.24), shorter sleep duration (β = ?0.52 (CI 95%: ?0.82 to ?0.22); F_1,33 = 12.9; p < 0.001; η² = 0.28), worse sleep quality (β = 0.39 (CI 95%: 0.07 to 0.72); F_1,33 = 6.31; p < 0.017; η² = 0.16) and lower A of circadian rhythm of wrist temperature (β = ?0.18 (CI 95%: ?0.55 to 0.18); F_1,33 = 4.48; p < 0.043; η² = 0.13) compared with females without SJL. Thus, our data indicate that 40 of 62 participants of investigation had social jetlag. A decrease of the amplitude of the circadian rhythm of the wrist temperature appears to be an objective marker of SJL. Social jetlag had a strong negative impact on females but not on males.     

Chronotype,social jetlag,and time perspective

ABSTRACT

The phase of entrainment (chronotype) is known to be associated with time perspective (TP), suggesting that the state of circadian system is involved in the long-term planning of human life. However, little is known regarding the influence of circadian misalignment on long-term planning ability. The aim of this study was to investigate the association between social jetlag (SJL) and TP. A total of 1064 schoolchildren and university students (mean age ± standard deviation, 19.2 ± 2.9 years; range, 15–25 years; females, 71.7%) from four cities in the Russian Federation located between 56.9 and 61.7 degrees North completed the Munich ChronoType Questionnaire, the Pittsburgh Sleep Quality Index, the Seasonal Pattern Assessment Questionnaire, and Zimbardo Time Perspective Inventory. Study participants also indicated personal data (age, sex, height weight, place of residence, and achievements). A multiple regression analysis with stepwise inclusion of predictors in the model was performed to evaluate associations between time perspective characteristics (dependent variables) and predictor variables. The change in R² was used as the measure of effect size. Chronotype was found to be a moderate predictor of future TP (B = 0.034; ΔR² = 0.037). In addition, sleep quality was found to be a moderate predictor of past negative (B = 0.043; ΔR² = 0.074), present fatalistic (B = 0.021; ΔR² = 0.035), and deviation from balanced TP (B = 0.034; ΔR² = 0.066). Mood seasonality was a moderate predictor of present hedonistic TP (B = 0.016; ΔR² = 0.038), and social jetlag was a weak predictor of present fatalistic (B = 0.052; ΔR² = 0.019), future (B = ?0.033; ΔR² = 0.004), and deviation from balanced TP (B = 0.047; ΔR² = 0.012). In conclusion, this study found a weak but significant association between social jetlag and TP in adolescents and young adults.     

Clinical significance of social jetlag in patients with excessive daytime sleepiness

ABSTRACT

Social jetlag has recently attracted attention as the circadian misalignment between biological and social clocks. We aimed to examine social jetlag and its effect on daytime sleepiness and daily functions in patients with narcolepsy, behaviorally induced insufficient sleep syndrome (BIISS) and delayed sleep-wake phase disorder (DSPD). The levels of social jetlag (SJL_mid) and sleep-corrected social jetlag (SJL_sc) were calculated for each patient, and the effect of these social jetlag-related parameters on daytime sleepiness and daily functions were examined. Objective sleepiness measured by the mean sleep latency in the multiple sleep latency test, subjective sleepiness assessed by the Epworth sleepiness scale (ESS), health-related quality of life (HRQoL) assessed by the SF-8 health survey, and incidences of mistakes in daily activities, traffic accidents and near-miss events related to daytime sleepiness were compared among the narcolepsy (n = 39), BIISS (n = 87) and DSPD (n = 28) groups. Both SJL_mid and SJL_sc showed a negative correlation with physical HRQoL in patients with narcolepsy and a positive correlation with the ESS score in patients with DSPD. In patients with BIISS, SJL_sc reflected sleep loss rather than circadian misalignment; moreover, SJL_sc was not associated with daytime sleepiness and daily functions. Social jetlag was not associated with incidences of mistakes in daily activities, traffic accidents and near-miss events.

The state of social jetlag and its association with daily functions differed among the narcolepsy, BIISS and DSPD groups. Social jetlag represented sleep debt in BIISS, circadian misalignment in narcolepsy and both in DSPD. Our results thus show that the clinical manifestations and significance of social jetlag differ depending on the underlying sleep disorders.     

Association of chronotype and social jetlag with human non-verbal intelligence

The aim of this study was to evaluate the effects of chronotype and social jetlag (SJL) on intelligence. Subjects were aged 14–25 years (n = 1008). A significant effect of intelligence on academic performance, as measured by the Raven’s Standard Progressive Matrices test, was found (F_2,917 = 11.75, P < 0.0001, η² = 0.03). When SJL was less than 2 hours, the intelligence of people with late chronotype was found to be higher than that of subjects with early and intermediate chronotypes (F_2,305 = 3.12, P < 0.05, η² = 0.02). A negative effect of SJL on the results of intelligence testing was noted only in subjects with late chronotype (F_2,536 = 2.61, P < 0.05, η² = 0.02). Our data suggest that people with late chronotype have a higher level of intelligence, but these advantages disappear when SJL ≥2 hours.     

Effects of chronotype and time of day on mood responses to CrossFit training

Morningness-eveningness, time of day, and physical exercises have been shown to influence mood states. This study aimed to test whether impact of physical exercise on mood depends on time of day and chronotype. Ninety-four participants (age 32 ± 6 years; 34% females; weekly training volume 4 ± 1 hours) filled the Composite Scale of Morningness and reported their current mood using the UWIST Mood Adjective Checklist before and after a 60-min long CrossFit training session which took part in the morning (beginning at 6:30 or 7:45) or in the evening (beginning at 19:30 or 20:45). In this quasi-experiment the measurements were taken by the occasion of the participants’ usual training, in their preferred hours. There were only a few evening-types in the studied sample, while morning and intermediate chronotypes were over-represented. Participation in CrossFit training resulted in mood improvement consisting of increase in energetic arousal (η² = 0.29) and hedonic tone (η² = 0.47) and reduction of tense arousal (η² = 0.14), all significant at p = 0.001. Furthermore, CrossFit training during morning hours boosted mood in the intermediate/evening chronotype group to the levels observed in morning chronotypes (η² = 0.29, p < 0.05, for the three-way interaction effect). We conclude that participation in intense physical exercise, such as CrossFit training, may allow compensation for the negative effects of non-optimal time of day on experienced moods, particularly in the case of neither/evening-types.     

Would you say “yes” in the evening? Time-of-day effect on response bias in four types of working memory recognition tasks

Across a wide range of tasks, cognitive functioning is affected by circadian fluctuations. In this study, we investigated diurnal variations of working memory performance, taking into account not only hits and errors rates, but also sensitivity (d’) and response bias (c) indexes (established by signal detection theory). Fifty-two healthy volunteers performed four experimental tasks twice – in the morning and in the evening (approximately 1 and 10 h after awakening). All tasks were based on Deese–Roediger–McDermott paradigm version dedicated to study working/short-term memory distortions. Participants were to memorize sets of stimuli characterized by either conceptual or perceptual similarity, and to answer if they recognized subsequent stimulus (probe) as an “old” one (i.e. presented in the preceding memory set). The probe was of three types: positive, negative or related lure. In two verbal tasks, memory sets were characterized by semantic or phonological similarity. In two visual tasks, abstract objects were characterized by a number of overlapping similarities or differed in only one detail. The type of experimental material and the participants’ diurnal preference were taken into account. The analysis showed significant effect of time of day on false alarms rate (F_(1,50) = 5.29, p = 0.03, η_p² = 0.1) and response bias (F_(1,50) = 11.16, p = 0.002, η_p² = 0.18). In other words, in the evening participants responded in more liberal way than in the morning (answering “yes” more often). As the link between variations in false alarms rate, response bias and locus coeruleus activity was indicated in literature before, we believe that our data may be interpreted as supporting the hypothesis that diurnal fluctuations in norepinephrine release have effect on cognitive functioning in terms of decision threshold.     

Exploring the role of circadian clock gene and association with cancer pathophysiology

ABSTRACT

Most of the processes that occur in the mind and body follow natural rhythms. Those with a cycle length of about one day are called circadian rhythms. These rhythms are driven by a system of self-sustained clocks and are entrained by environmental cues such as light-dark cycles as well as food intake. In mammals, the circadian clock system is hierarchically organized such that the master clock in the suprachiasmatic nuclei of the hypothalamus integrates environmental information and synchronizes the phase of oscillators in peripheral tissues.

The circadian system is responsible for regulating a variety of physiological and behavioral processes, including feeding behavior and energy metabolism. Studies revealed that the circadian clock system consists primarily of a set of clock genes. Several genes control the biological clock, including BMAL1, CLOCK (positive regulators), CRY1, CRY2, PER1, PER2, and PER3 (negative regulators) as indicators of the peripheral clock.

Circadian has increasingly become an important area of medical research, with hundreds of studies pointing to the body’s internal clocks as a factor in both health and disease. Thousands of biochemical processes from sleep and wakefulness to DNA repair are scheduled and dictated by these internal clocks. Cancer is an example of health problems where chronotherapy can be used to improve outcomes and deliver a higher quality of care to patients.

In this article, we will discuss knowledge about molecular mechanisms of the circadian clock and the role of clocks in physiology and pathophysiology of concerns.     

Effect of different light regimes on fitness of two species of Drosophila montium subgroup

Most organisms possess “biological chronometers” in the form of circadian clocks. Organism possessing circadian clock gains fitness advantage in two ways, by synchronizing its behavior through physiological process and secondly by coordinating its internal metabolic process. Environmental manipulations of circadian clocks have been shown to affect many life-history-related traits. Life-history traits are important components of fitness. To enhance individual fitness, organism has to synchronize the physiology with the surrounding environment. The present investigations were made to understand whether rhythm changes affect fitness of two co-existing species of montium a subgroup of Drosophila. The stocks were maintained at 20 ± 1 °C with 75% RH. Fitness such as fecundity, male lifetime fertility, female lifetime fertility, and longevity was assessed in LD (light/dark), LL (continuous light), and DD (continuous dark) for 15 and 30th generations. Fecundity was assessed in 25 pairs of flies for 20 days, and fertility and longevity was assessed in 10 pairs of flies until lifetime. The result revealed differential effect of light regimes on the two different species of Drosophila. Although the two species are related, effect of the three light regimes, LD, LL, and DD on them was different. It is evident that these two species although genetically related exhibit different responses to different light regimes.     

A randomized,double-blind and placebo-controlled crossover trial on the effect of l-ornithine ingestion on the human circadian clock

ABSTRACT

In mammals, daily physiological events are regulated by the circadian rhythm, which comprises two types of internal clocks: the central clock and peripheral clocks. Circadian rhythm plays an important role in maintaining physiological functions including the sleep-wake cycle, body temperature, metabolism and organ functions. Circadian rhythm disorder, which is caused, for example, by an irregular lifestyle or long-haul travel, increases the risk of developing disease; therefore, it is important to properly maintain the rhythm of the circadian clock. Food and the circadian clock system are known to be closely linked. Studies on rodents suggest that ingesting specific food ingredients, such as the flavonoid nobiletin, fish oil, the polyphenol resveratrol and the amino acid L-ornithine affects the circadian clock. However, there are few reports on the foods that affect these circadian clocks in humans. In this study, therefore, we examined whether L-ornithine affects the human central clock in a crossover design placebo-controlled human trial. In total, 28 healthy adults (i.e. ≥20 years) were randomly divided into two groups and completed the study protocol. In the 1st intake period, participants were asked to take either L-ornithine (400 mg) capsules or placebo capsules for 7 days. After 7 days’ interval, they then took the alternative test capsules for 7 days in the 2nd intake period. On the final day of each intake period, saliva was sampled at various time points in the dim light condition, and the concentration of melatonin was quantified to evaluate the phase of the central clock. The results revealed that dim light melatonin onset, a recognized marker of central circadian phase, was delayed by 15 min after ingestion of L-ornithine. Not only is this finding an indication that L-ornithine affects the human central clock, but it also demonstrates that the human central clock can be regulated by food ingredients.     

Peripheral clock system circadian abnormalities in Cushing’s disease

ABSTRACT

In Cushing’s syndrome, the cortisol rhythm is impaired and can be associated with the disruption in the rhythmic expression of clock genes. In this study, we evaluated the expression of CLOCK, BMAL1, CRY1, CRY2, PER1, PER2, PER3 genes in peripheral blood leukocytes of healthy individuals (n = 13) and Cushing’s disease (CD) patients (n = 12). Participants underwent salivary cortisol measurement at 0900 h and 2300 h. Peripheral blood samples were obtained at 0900 h, 1300 h, 1700 h, and 2300 h for assessing clock gene expression by qPCR. Gene expression circadian variations were evaluated by the Cosinor method. In healthy controls, a circadian variation in the expression of CLOCK, BMAL1, CRY1, PER2, and PER3 was observed, whereas the expression of PER1 and CRY2 followed no specific pattern. The expression of PER2 and PER3 in healthy leukocytes presented a late afternoon acrophase, similarly to CLOCK, whereas CRY1 showed night acrophase, similarly to BMAL1. In CD patients, the circadian variation in the expression of clock genes was lost, along with the abolition of cortisol circadian rhythm. However, CRY2 exhibited a circadian variation with acrophase during the dark phase in patients. In conclusion, our data suggest that Cushing’s disease, which is characterized by hypercortisolism, is associated with abnormalities in the circadian pattern of clock genes. Higher expression of CRY2 at night outlines its putative role in the cortisol circadian rhythm disruption.     

Relationships between chronotype,social jetlag,sleep, obesity and blood pressure in healthy young adults

Sleep disturbances, chronotype and social jetlag (SJL) have been associated with increased risks for major chronic diseases that take decades to develop, such as obesity, metabolic syndrome and cardiovascular disease. Potential relationships between poor sleep, chronotype and SJL as they relate to metabolic risk factors for chronic disease have not been extensively investigated. This prospective study examined chronotype, SJL and poor sleep in relation to both obesity and elevated blood pressure among healthy young adults.

SJL and objective sleep measures (total sleep time, sleep onset latency, wake after sleep onset and sleep efficiency) were derived from personal rest/activity monitoring (armband actigraphy) among 390 healthy adults 21–35 years old. Participants wore the device for 6–10 days at 6-month intervals over a 2-year period (n = 1431 repeated observations). Chronotypes were categorized into morning, intermediate and evening groups using repeated measures latent class analysis. Means of SJL and sleep measures among latent chronotype groups were compared using partial F-tests in generalized linear mixed models. Generalized linear mixed models also were used to generate odds ratios (ORs) with 95% confidence intervals (CIs) examining the relationship between repeated measures of chronotype, SJL, sleep and concurrent anthropometric outcome measures (body mass index, percentage of body fat, waist-to-hip ratio, waist-to-height ratio), systolic blood pressure and diastolic blood pressure.

Sleep latency ≥12 min was associated with increased odds of a high waist-to-height ratio (OR = 1.37; CI: 1.03–1.84). Neither chronotype nor SJL was independently associated with anthropometric outcomes or with blood pressure. Relationships between poor sleep and anthropometric outcomes or blood pressure varied by chronotype. Morning types with total sleep time <6 h, sleep efficiency <85% or wake after sleep onset ≥60 min were more likely to have an increased percentage of body fat, waist-to-hip ratio and waist-to-height ratio relative to those with an intermediate chronotype. Similarly, sleep latency ≥12 min was associated with increased odds of elevated systolic blood pressure (OR = 1.90; CI: 1.15–3.16, p_interaction = 0.02) among morning versus intermediate chronotypes. No relationships between poor sleep and obesity or elevated blood pressure were observed among evening chronotypes.

The results from this study among healthy young adults suggest that poor sleep among morning types may be more strongly associated with obesity and elevated blood pressure relative to those with an intermediate (neutral) chronotype. Sleep-related metabolic alterations among different chronotypes warrant further investigation.     

A Comparative Study of the Non-acidic Chemically Mediated Antifoulant Properties of Three Sympatric Species of Ascidians Associated with Seagrass Habitats

In this study, the mechanical properties of biofilms formed at the surface of nano-filtration (NF) membranes from a drinking water plant were analysed. Confocal laser scanning microscopy observations revealed that the NF biofilms formed a dense and heterogeneous structure at the membrane surface, with a mean thickness of 32.5 ± 17.7 μm. The biofilms were scraped from the membrane surface and analysed in rotation and oscillation experiments with a RheoStress 150 rotating disk rheometer. During rotation analyses, a viscosity decrease with speed of shearing characteristic of rheofluidification was observed (η = 300 Pa s for ý = 0.3 s^?1). In the oscillation analyses with a sweeping of frequency (1–100 Hz), elasticity (G′) ranged from 3000 to 3500 Pa and viscosity (G″) from 800 to 1200 Pa. Creep curves obtained with an application of a shear stress of 30 Pa were viscoelastic in nature. The G ₀ and η values were, respectively, 1.4 ± 0.3 × 10³ Pa and 3.3 ± 0.65 × 10⁶ Pa s. The relationship between the characteristics of NF biofilms and the flow conditions encountered during NF is discussed.     

Cyclic Presence and Absence of Conspecifics Alters Circadian Clock Phase But Does Not Entrain the Locomotor Activity Rhythm of the Fruit Fly Drosophila melanogaster

Circadian clocks use a wide range of environmental cues, including cycles of light, temperature, food, and social interactions, to fine-tune rhythms in behavior and physiology. Although social cues have been shown to influence circadian clocks of a variety of organisms including the fruit fly Drosophila melanogaster, their mechanism of action is still unclear. Here, the authors report the results of their study aimed at investigating if daily cycles of presence and absence (PA) of conspecific male visitors are able to entrain the circadian locomotor activity rhythm of male hosts living under constant darkness (DD). The results suggest that PA cycles may not be able to entrain circadian locomotor activity rhythms of Drosophila. The outcome does not change when male hosts are presented with female visitors, suggesting that PA cycles of either sex may not be effective in bringing about stable entrainment of circadian clocks in D. melanogaster. However, in hosts whose clock phase has already been set by light/dark (LD) cycles, daily PA cycles of visitors can cause measurable change in the phase of subsequent free-running rhythms, provided that their circadian clocks are labile. Thus, the findings of this study suggest that D. melanogaster males may not be using cyclic social cues as their primary zeitgeber (time cue) for entrainment of circadian clocks, although social cues are capable of altering the phase of their circadian rhythms. (Author correspondence: vsharma@jncasr.ac.in, vksharmas@gmail.com)     

Phase resetting of circadian peripheral clocks using human and rodent diets in mouse models of type 2 diabetes and chronic kidney disease

The expression rhythms of clock genes, such as Per1, Per2, Bmal1, and Rev-erb α, in mouse peripheral clocks, are entrained by a scheduled feeding paradigm. In terms of food composition, a carbohydrate-containing diet is reported to cause strong entrainment through insulin secretion. However, it is unknown whether human diets entrain peripheral circadian clocks. In this study, we used freeze-dried diets for type 2 diabetes (DB) and chronic kidney disease (CKD), as well as low-carbohydrate diets. After 24 h of fasting, PER2::LUC knock-in mice were given access to food for 2 days during inactive periods, and bioluminescence rhythm was then measured using an in vivo imaging system. AIN-93M, the control mouse diet with a protein:fat:carbohydrate (PFC) ratio of 14.7:9.5:75.8, caused a significant phase advance (7.3 h) in the liver clock compared with that in 24 h fasted mice, whereas human diets caused significant but smaller phase advances (4.7–6.2 h). Compared with healthy and high fat/sucrose-induced DB mice, adenine-induced CKD mice showed attenuation of a phase-advance with a normal diet. There were no significant differences in phase-advance values between human diets (normal, DB, and CKD). In addition, a normal-carbohydrate diet (PFC ratio of 20.3:23.3:56.4) and a low-carbohydrate diet (PFC ratio of 36.4:42.9:20.7) caused similar phase advances in peripheral clocks. The present results strongly suggest that scheduled feeding with human diets can cause phase advances in the peripheral clocks of not only healthy, but also DB and CKD mice. This discovery provides support to the food-induced entrainment of peripheral clocks in human clinical trials.     

Social rhythm and other chronobiological findings in juvenile myoclonic epilepsy

We evaluated the correlation between chronobiological variables and characteristics of juvenile myoclonic epilepsy. Sample: 17 individuals epileptic outpatients and respective controls. Instruments: The Social Rhythm Metric for social zeitgebers, lux meter, and an ACT10^® thermistor for activity–rest rhythm, light exposure, and peripheral body temperature. Regularity scores showed an inverse correlation with age at disease onset (r = ?0.5; p < 0.05), but not with disease duration or stabilization time. A significant intergroup difference was recorded for mean diurnal peripheral temperature (p < 0.01) and activity amplitude (= 0.06). There was a correlation between activity and temperature means in both groups. These results underscore the relationship between epilepsy and the biological clock on a physiological level. Epilepsy, in turn, is influenced by the circadian rhythm, indicating the potential involvement of the body’s internal clock in the development of the disease or the seizure recurrence pattern.     

Narrow-band ultraviolet B (NB UV-B) exposures improve mood in healthy individuals differently depending on chronotype

ABSTRACT

The evening chronotype is associated with psychological symptoms such as depressed mood, while skin exposure to ultraviolet radiation (UVR) may affect mood and behavior through neural and humoral routes. This pilot study aimed to investigate the impact of whole-body narrow-band (NB) UV-B exposure on current mood state and circulating 25-hydroxyvitamin D3 (25(OH)D₃), interleukin-6 (IL-6), cortisol and β-endorphin (β-END) levels in healthy participants. Here, eleven healthy women received full-body NB UV-B exposures on four afternoons, and the chronotype was assessed with a shortened version of Horne and Östberg’s Morningness-Eveningness Questionnaire (MEQ). Perceived mood was evaluated using the Visual Analogue Scale (VAS), and serum 25(OH)D₃, IL-6, cortisol and β-END concentrations were monitored daily. Decreasing VAS values showed mood to improve significantly over the five days after the four suberythematous NB UV-B exposures (p = .038), and the more the circadian preference was inclined toward eveningness, the greater the improvement in the mood dimension of wellbeing (p = .021). Baseline mood state was correlated with baseline 25(OH)D₃ (r = ?0.54, 95% CI: ?0.86 to ?0.09) and with baseline cortisol (r = ?0.57, 95% CI: ?0.87 to ?0.04). During the NB UV-B exposures, 25(OH)D₃ increased significantly, as expected, and IL-6 declined significantly by ?0.35 (95% CI: ?0.69 to ?0.07) pg/mL from the initial values of 1.12 ± 0.66 pg/mL (p = .025). In conclusion, in our pilot study, NB UV-B exposure improved mood, especially among those with evening preference for their daily activities, as well as circulating 25(OH)D₃ levels, whereas circulating IL-6 levels decreased.

Abbreviations: UVR: Ultraviolet radiation; NB UV-B: narrow-band UV-B; VAS: Visual Analogue Scales; β-END: β-endorphin; IL-6: Interleukin-6