Search Results (227)

Background/Objectives: Given the heterogeneous nature of long COVID, its treatment and management remain challenging. This study aimed to investigate whether poor pre-pandemic sleep quality, its deterioration during the peak of the pandemic, and circadian preference increase the risk of long COVID symptoms. Methods: An online survey was conducted between 9 October and 12 December 2022, with 384 participants who had recovered from COVID-19 at least three months prior to data collection. Participants were categorized based on the presence of at least one long COVID symptom. Logistic regression models assessed associations between sleep-related variables and long COVID symptoms. Results: Participants with long COVID symptoms reported significantly poorer sleep quality, higher perceived stress, greater somatic and cognitive pre-sleep arousal, and elevated levels of post-traumatic stress symptoms, anxiety, depression, and aggression. Fatigue (39.8%) and memory problems (37.0%) were the most common long COVID symptoms. Sleep deterioration during the pandemic peak was reported by 34.6% of respondents. Pre-pandemic poor sleep quality, its deterioration during the pandemic, and poor sleep at the time of the survey were all significantly associated with long COVID. An extreme morning chronotype consistently predicted long COVID symptoms across all models, while an extreme evening chronotype was predictive only when accounting for sleep quality changes during the pandemic. COVID-19 frequency, severity, financial impact, and somatic pre-sleep arousal were significant predictors in all models. Conclusions: Poor sleep quality before the pandemic and its worsening during the pandemic peak are associated with a higher likelihood of long COVID symptoms. These findings underscore the need to monitor sleep health during pandemics and similar global events to help identify at-risk individuals and mitigate long-term health consequences, with important clinical and societal implications. Full article

Transcranial direct current stimulation (tDCS) can modulate cortical excitability in a polarity-specific manner, yet identical protocols often produce inconsistent outcomes across sessions or individuals. This narrative review proposes that much of this variability arises from the brain’s intrinsic temporal landscape. Integrating evidence from chronobiology, sleep research, and non-invasive brain stimulation, we argue that tDCS produces reliable, polarity-specific after-effects only within a circadian–homeostatic “window of efficacy”. On the circadian (Process C) axis, intrinsic alertness, membrane depolarisation, and glutamatergic gain rise in the late biological morning and early evening, whereas pre-dawn phases are marked by reduced excitability and heightened inhibition. On the homeostatic (Process S) axis, consolidated sleep renormalises synaptic weights, widening the capacity for further potentiation, whereas prolonged wakefulness saturates plasticity and can even reverse the usual anodal/cathodal polarity rules. Human stimulation studies mirror this two-process fingerprint: sleep deprivation abolishes anodal long-term-potentiation-like effects and converts cathodal inhibition into facilitation, while stimulating at each participant’s chronotype-aligned (phase-aligned) peak time amplifies and prolongs after-effects even under equal sleep pressure. From these observations we derive practical recommendations: (i) schedule excitatory tDCS after restorative sleep and near the individual wake-maintenance zone; (ii) avoid sessions at high sleep pressure or circadian troughs; (iii) log melatonin phase, chronotype, recent sleep and, where feasible, core temperature; and (iv) consider mild pre-heating or time-restricted feeding as physiological primers. By viewing Borbély’s two-process model and allied metabolic clocks as adjustable knobs for plasticity engineering, this review provides a conceptual scaffold for personalised, time-sensitive tDCS protocols that could improve reproducibility in research and therapeutic gain in the clinic. Full article

Morningness-eveningness is usually assessed as either a trait or a state using either a morning–evening preference scale or sleep timing reported for free days, respectively. These assessments were implemented in numerous studies exploring the associations between morningness-eveningness and health, mood, and sleep problems. Evening types almost always had more problems than morning types. We examined these associations in university students with conflicting results of trait and state assessments of morningness-eveningness and tried to confirm their chronotype using a multidimensional chronotyping approach that recognizes four types other than morning and evening (lethargic, vigilant, napping, and afternoon). The conflicting trait and state assessments of morningness-eveningness were found in 141 of 1582 students. Multidimensional chronotyping supported morningness of morning types with late weekend sleep timing, and the associations with health, mood, and sleep problems resembled the associations of other morning types (i.e., these associations persisted despite late sleep timing). In contrast, evening types with early weekend sleep timing were more likely classified as lethargic or napping types rather than evening types. They did not resemble evening types in their associations with health, mood, and sleep problems (i.e., early sleep timing did not change these associations). Model-based simulations of the sleep–wake cycles of students with conflicting trait and state assessments suggested that their bedtimes cannot be solely determined by their biological clocks. On weekdays or weekends, mind-bedtime procrastination can lead to missing the bedtime signal from their biological clocks (i.e., self-deprivation of sleep or, in other words, voluntary prolongation of the wake phase of the sleep–wake cycle). Full article

Background: Chronotype reflects individual variations in daily activity and sleep patterns, influenced by underlying circadian rhythms. While chronotype is often reduced to the morningness–eveningness spectrum, recent evidence suggests more diverse circadian typologies. Chronotype is linked to mental health, frequently associated with psychiatric disorders such as depression and suicide. This study aims to examine differences among six chronotypes (as defined by Single-Item Chronotyping) in mental health outcomes, including depression, anxiety, interpersonal relations, general functioning, suicidal behavior, and suicide acceptance. Methods: The study sample consisted of 306 young adults. Chronotype was determined using the Polish version of Single-Item Chronotyping (SIC). Mental health was assessed with the 30-item General Health Questionnaire (GHQ-30), which evaluates three dimensions: depression and anxiety, interpersonal relations, and general functioning. The Suicide Behavior Questionnaire (SBQ-R) measured past and potential future suicidal tendencies, while the Suicide Acceptance Questionnaire (SAQ) assessed attitudes toward the act of suicide. Results: The “daytime sleepy” and “moderately active” chronotypes were identified as at higher risk for mental health issues. These types exhibited greater levels of depression and anxiety, more general dysfunction, and a higher risk of suicidal behavior. The “daytime sleepy” type also experienced more interpersonal relationship difficulties compared to the “daytime active” type. Conclusions: Recognizing the “daytime sleepy” and “moderately active” types as risk factors highlights the importance of considering chronotype in mental health assessments. The SIC provides a concise method for monitoring circadian rhythm changes during treatment, facilitating tailored interventions such as modifying treatment schedules or lifestyle adjustments in alignment with an individual’s circadian rhythm. Full article

Background/Objectives: Numerous studies have documented the effect of human chronotypes on psychological well-being. This study aimed to examine the associations of chronotype subtypes and mental health among Spanish university students. Methods: Sociodemographic data were collected electronically using a self-administered questionnaire with Google Forms. In addition, participants completed The Morningness-Eveningness Questionnaire (MEQ) by Horne and Östberg, the Goldberg Anxiety and Depression Scale (GADS), and the Perceived Stress Scale (PSS). Results: Two hundred and eighty-nine students participated in the study. The most prevalent chronotype in the study sample was the intermediate (64.4%), followed by the evening (19.4%) and the morning (16.3%) chronotypes. Based on cut-off scores of the instruments used, the percentage of students with relevant symptoms of anxiety, depression and stress was high, 45.3%, 46.4% and 79.6%, respectively. Statistical analysis showed statistically significant differences between the total score of the Goldberg scale and the three chronotype categories, with higher scores in the evening group. A multivariate regression model analysis also identified a statistically significant correlation between the depression subscale and chronotype (R squared = 0.287) and between evening vs. morning chronotype (OR = 0.48; IC 95% [0.23–0.98]) and evening vs. intermediate chronotype (OR = 2.60; 95% CI [1.00–5.08]). In turn, the depression subscale showed a statistically significant correlation with the variables gender (OR = 2.22; 95% CI [1.03–4.76] being more frequent in women) and daily consumption of stimulant drinks (OR = 0.54; 95% CI [0.31–0.94]; being higher in people with lower consumption). The anxiety subscale showed a statistically significant correlation with chronotype (R squared = 0.309) and with evening vs. morning chronotype (OR = 0.46, 95% CI [0.22–0.94]). With respect to stress, there was a statistically significant correlation with gender (OR = 3.08, 95% CI [1.40–6.79], being more frequent in women), with chronotype (R squared = 0.141), and with evening vs. morning chronotype (OR = 0.34, 95% CI [0.16–0.72]). Conclusions: Our results suggest that students with an evening chronotype are more likely to suffer from mental health problems, and interventions to improve their mental health are necessary. Full article

Background: Evening chronotypes are increasingly recognized as being at elevated risk of psychological vulnerabilities, including sleep disturbances, mood disorders, and disordered eating. Body image, a central self-related construct, has been identified as a key factor influencing eating disorder (ED) risk. This study aimed to explore whether body image moderates the relationship between chronotype and the risk of developing an ED. Methods: A total of 165 adults (139 women; mean age = 35.45) completed validated self-report questionnaires assessing chronotype (Morningness–Eveningness Questionnaire), body image (Body Shape Questionnaire), and ED risk (EAT-26). Pearson correlations and moderation analyses (PROCESS macro and Model 1) were conducted with body image as a moderator of the association between chronotype and ED risk. Results: Eveningness was significantly associated with greater ED risk (r = −0.53, p < 0.001) and a more negative body image (r = −0.48, p < 0.001). Body image was a strong predictor of ED risk (r = 0.85, p < 0.001). Moderation analysis revealed a significant interaction between chronotype and body image (b = −0.006, SE = 0.0009, p < 0.001), indicating that the relationship between chronotype and ED risk was stronger among individuals with a more negative body image. Conclusions: These findings highlight the role of body image as a moderating factor in the link between chronotype and eating disorder vulnerability. Interventions aimed at improving body image, especially among evening chronotypes, may help mitigate ED risk. These results underscore the importance of integrating circadian and psychosocial factors in ED prevention and early intervention strategies. Full article

Background/Objectives: Obesity is a major contributor to cardiovascular disease, yet traditional risk assessment methods may overlook behavioral and circadian influences that modulate metabolic health. Chronotype, physical activity, sleep quality, eating speed, and breakfast habits have been increasingly associated with cardiometabolic outcomes. This study aims to evaluate the associations between these behavioral factors and both anthropometric and biochemical markers of cardiovascular risk among obese candidates for bariatric surgery. Methods: A cross-sectional study was conducted in a sample of 286 obese adults (78.3% females, mean 44.3 years, SD = 10.8, mean BMI = 42.5 kg/m², SD = 6.2) followed at a central Portuguese hospital. Chronotype (reduced Morningness–Eveningness Questionnaire), sleep quality (Pittsburgh Sleep Quality Index), physical activity (Godin–Shephard Questionnaire), eating speed, and breakfast skipping were assessed. Cardiovascular risk markers included waist-to-hip ratio (WHR), waist-to-height ratio, A Body Shape Index (ABSI), Body Roundness Index, atherogenic index of plasma (AIP), triglyceride–glucose index (TyG), and homeostatic model assessment for insulin resistance (HOMA-IR). Results: Men exhibited significantly higher WHR, ABSI, HOMA-IR, TyG, and AIP. Eveningness was associated with higher insulin (r = −0.168, p = 0.006) and HOMA-IR (r = −0.156, p = 0.011). Poor sleep quality was associated with higher body fat mass (r = 0.151, p = 0.013), total cholesterol (r = 0.169, p = 0.005) and LDL cholesterol (r = 0.132, p = 0.030). Faster eating speed was associated with a higher waist circumference (r = 0.123, p = 0.038) and skeletal muscle mass (r = 0.160, p = 0.009). Conclusions: Male sex, evening chronotype, and poor sleep quality were associated with more adverse cardiometabolic profiles in individuals with severe obesity. These findings support the integration of behavioral and circadian factors into cardiovascular risk assessment strategies. Full article

This study explored whether sleep duration, insomnia, social jetlag, and circadian preference predicted adolescents’ risk of anxiety and depression two years later. High school students initially aged 16–17 years were, in 2019 and 2021, invited to a web-based survey assessing sleep patterns, insomnia, circadian preference, anxiety, and depression. Sleep duration, insomnia, circadian preference, depression, and anxiety were assessed using the Munich ChronoType Questionnaire, the Bergen Insomnia Scale, the reduced Morningness–Eveningness Questionnaire, the Patient Health Questionnaire-9, and the Generalized Anxiety-Disorder 7, respectively. Analyses were conducted using logistic regression analyses. The analytic longitudinal sample comprised 1456 students (initial mean age 16.4 years; 61.4% girls). Short school night sleep duration, chronic insomnia, and more severe insomnia symptoms at baseline predicted greater risk of anxiety and depression at follow-up when controlled for anxiety and depression at baseline. Neither free night sleep duration nor social jetlag at baseline were related to the risk of anxiety and depression at follow-up. When circadian preference was investigated continuously, greater morningness at baseline predicted lower risk of anxiety and depression at follow-up. When circadian preference was investigated categorically, evening preference type was associated with higher risk of depression at follow-up than intermediate preference type, while the prospective risk of anxiety and depression otherwise did not differ in relation to circadian preference. The results attest to prospective associations between adolescent sleep problems at baseline and later risk of anxiety and depression. Full article

The circadian clock orchestrates nearly every aspect of physiology, aligning metabolic processes with environmental cues, such as light and food intake. While the central pacemaker in the suprachiasmatic nucleus synchronizes peripheral clocks across key metabolic tissue, feeding behavior emerges as the dominant cue for peripheral clock alignment. This interaction reveals a crucial link between circadian biology and metabolism. Disruption of these processes, whether from shift work, irregular eating patterns or lifestyle misalignment, has been strongly associated with metabolic disorders, including obesity, insulin resistance and cardiometabolic diseases. Within the field of chrononutrition, strategies, such as time-restricted feeding (TRF), have gained attention for their potential to restore circadian alignment and improve metabolic health. However, translational gaps persist, as most mechanistic insights are derived from nocturnal murine models, limiting their applicability to diurnal human physiology. Moreover, human studies are confounded by interindividual variability in chronotype, behavioral patterns, and dietary compliance. This review explores the molecular underpinnings of zeitgeber signals and critically assesses the translational barriers to implementing chrononutrition across species. By integrating insights from both preclinical and clinical research, we aim to refine the potential of circadian-based dietary interventions for metabolic disease prevention and personalized nutrition. Full article

While morningness (a preference for rising earlier in the day) is associated with positive affect and life satisfaction, eveningness is correlated with negative emotionality, poor sleep, less self-control, and more procrastination. The current study investigated inter-relationships between morningness–eveningness; bedtime, academic, and exercise procrastination; mind wandering; sleep quality; self-control; and depressive symptoms. An online survey including questionnaire measures of these variables was completed by 306 university students (aged 18–51 years; mean = 20.36, SD = 4.001; 34 male). Morningness correlated with more self-control and better sleep quality—eveningness correlated with more bedtime, academic, and exercise procrastination; depressive symptoms; and mind wandering. All forms of procrastination negatively correlated with self-control and sleep quality, and positively correlated with depressive symptoms and mind wandering, although more strongly with spontaneous than deliberate mind wandering. Mediation effects were found—bedtime procrastination (BP) between eveningness and spontaneous mind wandering (MW); spontaneous MW between BP and sleep quality; sleep quality between BP and depressive symptoms; self-control between depressive symptoms and academic procrastination. A path model of these inter-relationships was developed. This study adds to a growing body of research indicating that interventions to reduce bedtime procrastination may bring about improvements in wellbeing and academic achievement. Full article

Modern elite football is becoming increasingly physically demanding, often requiring training and matches to be played at night. This schedule may disrupt circadian rhythms and melatonin secretion, thereby impairing sleep and recovery. This study investigated the effects of training time on melatonin secretion, circadian phase markers, and sleep parameters in elite youth soccer players. Forty male players (aged 16–18 years) from an elite Spanish youth football club were studied. Two groups followed the same training program but trained either in the morning (MT) or in the evening (ET). Salivary melatonin was measured at six time points to determine the mean levels, dim light melatonin onset (DLMO), amplitude, and acrophase. Chronotype, sleep quality (PSQI), and daytime sleepiness (ESS) were assessed using validated questionnaires. Dietary intake and anthropometric variables were also recorded. The MT group had higher mean melatonin levels (p = 0.026) and earlier DLMO (p = 0.023) compared to the ET group. Sleep quality was significantly better in the MT group (p < 0.001), despite shorter sleep duration (p = 0.014). No major differences in diet or anthropometry were observed. The chronotype had a secondary effect on the circadian markers. Evening training is associated with alterations in melatonin rhythms and reduced sleep quality, possibly due to light-induced chronodisruption. These findings highlight the importance of training timing as a modifiable factor in the chronobiology and recovery of athletes. Incorporating circadian principles into training schedules may optimize resting time and thus performance and long-term health in athletes. Full article

Background: high levels of stress have hazardous impacts on nurses’ health, well-being, job satisfaction, and abilities to cope with the job demands, which in turn may impact the provision of quality patient care, which is essential for universal health coverage. Aim: to investigate the relationship of perceived stress related to personality traits, chronotype, and eating behaviour among hospital and community nurses in Brunei. Methods: A cross-sectional survey on nurses from public hospitals and community health centres from all four districts in the country. The questionnaire included Perceived Stress Scale to measure stress levels, the brief Big Five Inventory to identify personality, the Morningness-Eveningness Questionnaire to identify chronotype, and the Sakata Eating Behaviour Questionnaire to identify eating behaviour. Subgroup analysis and partial least squares structural equation modelling were applied. Results: The structural equation model revealed that personality trait (β = 0.482) is the most salient and strongest factor contributing to perceived stress, followed by chronotype profile (β = 0.45), accounting for 71.4% of the variance explained for perceived stress. Whereas perceived stress (β = 0.719) is a factor affecting eating behaviour, which accounts for 51.6% of the variance explained for eating behaviour. Conclusions: This study revealed that neuroticism and evening chronotype are significant stress predictors. Stress affects eating habits, with stressed nurses showing poor eating patterns. Older and single nurses report higher stress. Full article

Objectives: Type 1 diabetes is characterized by hyperglycemic episodes influenced by diet, sleep quality, chronotype, and physical activity, among others. While aerobic exercise is known to improve glycemic control, its effect on blood glucose regulation remains underexplored. Thus, this case study aimed to evaluate the effects of a prolonged and differentiated indoor and outdoor exercise intervention on glycemic control in an individual with type 1 diabetes. Methods: The participant (age: 23 years; weight: 95 kg; height: 1.90 m; Body Mass Index: 26.3 kg/m²; waist to hip ratio: 0.98; basal metabolic rate: 2015 kcal; Heart Rate Maximum (HRmax): 197 beats·min⁻¹) completed two outdoor (~3800 m) and two indoor sessions with self-selected speed, in the initial 2 min stage, at a 0% grade slope. The grade increased by 2% at each stage during the uphill phase until reaching volitional fatigue, followed by a 2% decrease at each stage during the downhill phase until returning to a 0% grade. Blood pressure was assessed before and after each session. Daily nutrition intake, insulin intake, and blood glucose were continuously monitored. Dietary adherence (PREvención con DIeta MEDiterránea), sleep quality (Pittsburgh Sleep Quality Index), chronotype (Morningness–Eveningness Questionnaire), and physical activity levels (International Physical Activity Questionnaire) were assessed before each session. The Physical Activity Enjoyment Scale was used to measure enjoyment after each session. Results: The sessions were completed in ~44 and ~39 min with the participant achieving 84% (outdoor) and 96% (indoor) of their theoretical HRmax. The intervention resulted in glycemic improvements, with time spent in hyperglycemia (>250 mg/dL) decreasing from 56.46% to 0%, while time in the normal range (70–180 mg/dL) increased to 63.96%. A 47% reduction in insulin units showed that insulin sensitivity also improved. Conclusions: Despite differences in intensity, indoor and outdoor activities yielded comparable benefits, with outdoor activities being perceived as more enjoyable (outdoor: 28.5 ± 0.7; indoor: 24.0 ± 5.6) and positively impacting glycemic control, thus supporting the need for tailored strategies in diabetes management. Full article

Trail running has seen a surge in participants, including individuals with disabilities, particularly in ultratrail running (UTRs). Sleep–wake patterns are crucial for optimal performances in UTRs, which present unique physiological and behavioral challenges. This case study evaluated the sleep–wake cycle of a blind trail ultramarathoner (BTR) and his guide (GTR) before, during, and after an 80 km UTR. Two male participants (BTR: 54 years, BMI: 26.1 kg/m²; GTR: 48 years, BMI: 24.2 kg/m²) were assessed using validated questionnaires (MEQ, ESS, ISI, and PSQI) and actigraphy over 35 days. The BTR exhibited a morning chronotype (MEQ = 63), mild insomnia (ISI = 11), poor sleep quality (PSQI = 5), and prolonged sleep latency (>60 min), while the GTR showed an indifferent chronotype (MEQ = 52), good sleep quality (PSQI = 3), and shorter latency (10 min). Post-competition, both athletes experienced an increased total sleep time (TST): the BTR by 17.8% (05:32:00 vs. 04:25:00) and the GTR by 5.5% (07:01:00 vs. 06:39:00). The BTR demonstrated a greater Wakefulness after sleep onset (WASO 01:00:00 vs. 00:49:00) and awakenings (15.4 vs. 6.1). A time series analysis revealed greater variability in the BTR’s post-competition sleep efficiency and TST, while the GTR exhibited a greater stability of the circadian phase. These findings highlight the intricate sleep challenges faced by blind athletes, informing strategies to optimize recovery and performance. Full article

This narrative review explores the intricate relationship between circadian regulation and exercise performance, emphasizing the importance of aligning training strategies with the body’s natural physiological fluctuations. The three key mechanisms investigated are temperature, hormonal fluctuations, and diurnal chronotype—an individuals’ exhibition of enhanced physical or cognitive performance at specific times of day. Core body temperature variations impact exercise performance, suggesting strategic workout timing and intensity adjustments. Hormonal patterns (i.e., insulin, cortisol, testosterone) influence energy metabolism and muscle growth, informing tailored training plans. Diurnal chronotypes significantly affect performance, advocating for personalized training sessions based on individual preferences and entrained awakening. Integrating circadian mechanisms into training offers strategic advantages, guiding practitioners to design effective, personalized regimens, though we acknowledge relevant challenges and the need for further research. Full article