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Abstract Study Objectives Individual circadian type is a ubiquitous trait defining sleep, with eveningness often associated with poorer sleep and mental health than morningness. However, it is unknown whether COVID-19 pandemic has differentially affected sleep and mental health depending on the circadian type. Here, the differences in sleep and mental health between circadian types are examined globally before and during the COVID-19 pandemic. Methods The sample collected between May and August 2020 across 12 countries/regions consisted of 19 267 adults with information on their circadian type. Statistical analyses were performed by using Complex Sample procedures, stratified by country and weighted by the number of inhabitants in the country/area of interest and by the relative number of responders in that country/area. Results Evening-types had poorer mental health, well-being, and quality of life or health than other circadian types during the pandemic. Sleep–wake schedules were delayed especially on working days, and evening-types reported an increase in sleep duration. Sleep problems increased in all circadian types, but especially among evening-types, moderated by financial suffering and confinement. Intermediate-types were less vulnerable to sleep changes, although morningness protected from most sleep problems. These findings were confirmed after adjusting for age, sex, duration of the confinement, or socio-economic status during the pandemic. Conclusions These findings indicate an alarming increase in sleep and mental health problems, especially among evening-types as compared to other circadian types during the pandemic.

Light spectra, an imperative zeitgeber, may differ in its chronobiological effects among chronotype ensuing differences in circadian pacesetting. With the increasing usage of colored lights in the environment, the effects of light wavelength on the electrical activity of the brain among chronotypes need to be investigated. Healthy participants (N=24) were recruited to morning, intermediate, and evening chronotype groups using the composite scale for morningness scores. They were exposed to randomized brief sessions of red, green, blue, and white light preceded by 15 min of darkness. EEG was recorded in all sessions. The power spectrum was estimated for alpha, beta, theta, and delta waves from different regions of the scalp and compared among the groups. The morning and evening chronotype had statistically significantly higher mean delta power than intermediate chronotype in colored light. Evening chronotype showed a statistically significantly higher mean beta power than the intermediate chronotype (p=0.013) in green light. Intermediate chronotype had statistically significantly higher mean alpha power than morning (p=0.029) and evening chronotype (p=0.009) in red light. The results show a significant effect of the spectral property of light on brain waves in chronotypes. The green light is more effective in alerting evening chronotypes. The finding of the present study may be applicable in research pertinent to brain imaging in chronotypes especially with red, green, and blue light exposure and chromotherapy-based interventions in affective and psychiatric conditions.

Sleep and mental health are intrinsically intertwined, but not every individual with problems sleeping develops a mental health disorder. This study examined the association among chronotypes, resilience, sleep quality and mental health symptoms amongst otherwise healthy individuals. Two hundred adults ( M age  = 27.75 ± 5.11, 68% female) with no previous diagnosis of mental illness were recruited and filled in a set of questionnaires measuring chronotypes, sleep quality, depression and anxiety symptoms. The findings from the path analysis showed that the morning type had a statistically significant direct effect on a range of sleep quality indices. These included better subjective sleep quality, shortened sleep latency, and fewer daytime dysfunctions, as well as a higher level of resilience. However, it did not significantly affect depression and anxiety symptoms. In addition, the morning type had statistically significant indirect effects on a higher level of resilience and fewer depression and anxiety symptoms through the mediating effect of sleep quality indices. Findings from this study support that morning type is associated with better resilience and psychological health, which is mediated through better sleep quality.

Previous studies on late-night digital media use and adolescent sleep have not considered how chronotype, a natural tendency to be awake or asleep at certain time, is associated with this relationship. Therefore, the nature of the relationship between late-night digital media use and sleep in different chronotypes remains still unknown. The sample consisted of 15–20-year-old Finnish adolescents ( n  = 1084, mean age = 16.9 years, SD = 0.93, 45.7% female). This study examined whether chronotype, measured as diurnal type and midpoint of sleep, was associated with the time of evening/night when digital media was used. Associations between the use of different forms of digital media and sleep quality, sleep duration and tiredness on school days were also investigated. Finally, the mediation effect of late-night digital media use to the relationship between chronotype and sleep was examined. Generalized linear models showed that evening chronotype, weekend midpoint of sleep, and the time of evening or night at which digital media was used were associated with more insufficient sleep and tiredness, lower sleep quality and shorter sleep duration on school days. The total use of all media forms, i.e., late-night digital media for music, movies/series, social media, and studying, were associated with shorter sleep duration and more insufficient sleep and daytime tiredness. Late-night social media use also mediated the association between diurnal type and sleep quality. Watching movies or listening to music late at night was the strongest mediator of the association between diurnal type and sleep and tiredness. The most prominent finding shows that of the all different media forms, watching movies or listening to music late at night were associated with increased daytime tiredness, whereas late social media use was associated with poor sleep quality. These interactions were pronounced especially for evening-types. The findings of the current study suggest that the negative effects of late-night media use are reflected especially in sleep quality and daytime tiredness among evening-types during adolescence.

The aim of the paper is to review the current evidence on the impact of ‘the timing of energy intake’ on the risk of developing obesity and obesity-related metabolic diseases. The prevalence of obesity is currently increasing worldwide thus becoming a severe health burden for most countries. Indeed, obesity represents a risk factor for several non-communicable diseases such as cancer, type 2 diabetes, dyslipidaemia, CVD and overall mortality. In order to treat obesity, several pharmacological approaches have been developed and are indicated for subjects with obesity with a BMI ≥ 30 kg/m 2 or ≥ 27 kg/m 2 and obesity-related comorbidities. For severe obesity (BMI ≥ 40 kg/m 2 ), bariatric surgery represents a promising approach. The most common bariatric surgical procedures are represented by the Roux-en-Y gastric bypass, laparoscopic adjustable band, laparoscopic gastric sleeve and biliopancreatic diversion with duodenal switch. Both anti-obesity pharmacological and surgical treatments require change in lifestyle. When a nutritional plan is established, attention is usually paid to macronutrient composition and energy intake, while ‘the time of food’ is not taken into account. Chronotype, which is the attitude of a subject to carry out most of their daily activities in the first (morning chronotype) or second half (evening chronotype) of the day, has been reported to have a role in the pathogenesis of obesity and obesity-related cardiometabolic diseases as well as eating speed. Thus, adopting a physiological timing of energy intake could be an additional strategy to potentiate the current anti-obesity approaches.

PurposeMisalignment between sleep opportunity and chronotype preference during adolescence may affect sleep and mental health. The aim of this study was to objectively evaluate sleep duration and social jetlag (SJL) to observe if there is a relationship with anxiety, depression, or chronotype.MethodsCommunity based cohort study (n = 65) was conducted in Northern Europe. Participants recorded their sleep during the regular school schedule for 3 school nights and 2 free nights with FDA-cleared/EU Medical Device Directive (CE-02862) compliant home sleep test. They also completed validated questionnaires to assess (Morningness Eveningness Questionnaire; MEQ), sleepiness (Epworth Sleepiness Scale; ESS), and insomnia (Insomnia Severity Index; ISI), anxiety (General Anxiety Disorder-7; GAD-7), and depression symptoms (Beck’s Depression Inventory-II; BDI-II). Data were collected during the last week of February and the first 2 weeks of March, 2023.ResultsAverage sleep duration on school nights was 7 h, 15 min, with 18% of participants on average sleeping ≥ 8 h. Average sleep onset was significantly later on free nights (1 hour, 47 minutes; p < 0.0001) causing a high prevalence of moderate-severe SJL, in 71% of participants.Evening chronotypes (prevalence 15.4%) fell asleep later on free nights, causing them to have significantly more SJL (2 hours, 58 minutes) than morning chronotypes (1 hour, 32 minutes) and intermediary chronotypes (1 hour, 36 minutes). Evening chronotypes also had more severe insomnia (ISI + 4.4, p = 0.006; + 4.0, p = 0.001) and greater depressive symptoms (BDI-II + 21.6, p < 0.0001; + 17.1, p < 0.0001). A significant negative correlation was observed between MEQ scores and ESS (r =  − 0.287; p = 0.001), ISI (r =  − 0.343, p < 0.0001), GAD-7 (r =  − 0.185, p < 0.0001), BDI-II (r =  − 0.501, p = 0.0001), and suicidal thoughts (r =  − 0.294, p = 0.017).ConclusionAdolescents are sleep-deprived and have a high prevalence of SJL that is positively correlated with depressive symptoms and evening chronotype. That evening chronotypes have shorter sleep duration, more severe SJL, and significantly more sleepiness and insomnia, anxiety, and depressive symptoms may indicate possible benefits in identifying this group with the aim to assist them in improving their sleep habits with potentially positive effects on mental health.

The aim of this study was to evaluate the association between chronotype, stress, sleep and social jetlag (SJL) in Bulgarian sports students. In total, 29 male and female university students were surveyed using the Horne-Ostberg morningness-eveningness questionnaire, smart watch for measuring the peripheral skin temperature, perceived stress scale (PSS), Pittsburgh sleep quality index (PSQI) and a self-report questionnaire to determine SJL. It was determined that 2 students were morning type (MT), 7 were evening type (ET) and 20 were intermediate type (IT). Temperature measurements confirmed that. Mann-Whitney U test showed an association between stress scores and gender groups, PSQI scores showed association with PSS groups, chronotype and SJL. Females were more stressed than males. Students with high SJL levels (n = 7) were ET (n = 5). In our sample ET (n = 7) were more than MT (n = 2). Usually athletes tend to be MT. Age has a great influence in chronotype expression. ET perceived more stress and experienced more frequent daytime dysfunction than MT and IT. Collectively, these results suggest that stress levels are higher when imbalance exists between more than one circadian rhythm disruption indicators. Also training schedules should be arranged when taking into account circadian preferences.

Individuals with severe mental illness (SMI) have increased risk of physical comorbidities, linked to worse outcomes such as greater psychopathology, frailty, and neurocognitive impairment. Mechanisms underlying this burden remain unclear. This study examined whether frailty and psychopathology predict evening chronotype, especially in SMI with comorbidities. A longitudinal study assessed 165 participants at two time points over one year: schizophrenia ( = 30), bipolar disorder ( = 42), major depressive disorder ( = 35), and healthy controls ( = 58). The SMI group ( = 107) was divided into SMI with comorbidities (SMI-C; = 47) and without (SMI; = 60). Measures included psychopathology, frailty, chronotype, neurocognitive and functional performance, and hematological biomarkers. Neurocognitive and functional impairments were greater in SMI groups than controls ( = 10.3-31.4; < 0.0001; η² = 0.12-0.34). The SMI-C group showed worse frailty than controls at T1 ( = 4.3; < 0.01; η² = 0.05) and than SMI at T2 ( = 8.5; < 0.0001; η² = 0.12), and elevated MCV/MCH ( = 3.8-9.4; < 0.05-0.0001; η² = 0.04-0.11). Chronotype distribution did not differ. Frailty and psychopathology predicted chronotype in SMI ( < 0.05-0.01); in controls, frailty and performance did so (p < 0.05). Psychopathological and hematological profiles are associated with chronotype and may help identify subgroups for chronobiology-informed interventions. These findings support more personalized treatment approaches.

Sleep has attracted extensive attention due to its significance in health. However, its association with erectile dysfunction (ED) is insufficiently investigated. To investigate the potential causal links between sleep traits (insomnia, sleep duration, and chronotype) and ED, this study was performed. The single-nucleotide polymorphisms (SNPs) associated with insomnia, sleep duration, and chronotype were retrieved from previous genome-wide association studies (GWAS). A conventional two-sample Mendelian randomization (MR) was used to estimate the causal links between sleep traits and ED. The summary statistics of ED were from individuals of European ancestry (6175 cases vs 217 630 controls). As shown by the random effect inverse-variance-weighting (IVW) estimator, genetically predicted insomnia was causally associated with a 1.15-fold risk of ED (95% confidence interval: 1.07-1.23, P < 0.001). Sleep duration and morningness were not causally associated with ED, as indicated by the IVW (all P > 0.05). These findings were consistent with the results of sensitivity analyses. Based on genetic data, this study provides causal evidence that genetically predicted insomnia increases the risk of ED, whereas sleep duration and chronotype do not.

The current study used daily assessments of sleep to examine stability and change in sleep chronotype in adolescents and their parents. The study assessed adolescent sleep chronotype according to age, gender, and parent chronotype, and evaluated its associations with emotional and behavioral problems in youth. Participants included of 417 Mexican American adolescents ( M age = 16.0 years, Range = 13.9–20.0) and 403 caregivers, who reported bed and wake times daily for 2 consecutive weeks at two time points spaced 1 year apart. In addition, adolescents completed established self-report questionnaires of emotional and behavioral problems. Chronotype was computed as the midsleep point from bed to wake time on free days, correcting for sleep debt accumulated across scheduled days. Multilevel modeling showed a curvilinear association between adolescent age and chronotype, with a peak eveningness observed between ages 16 to 17. Adolescent and parent chronotypes were contemporaneously correlated, but each was only moderately stable over the 1-year period. Later adolescent chronotype was contemporaneously associated with more substance use in all adolescents. Individual development and the family context shape sleep chronotype in adolescents and parents. Sleep chronotype is implicated in adolescent behavioral health.