Evening-type Subjects Research Articles

Association between sleep quality and habits of electronic media use among young adults with different circadian typology

Background: Circadian preference refers to individual differences for mental and physical activity in the morning and evening. We hypothesized, that inadvertent use of electronic media can cause circadian misalignment that influences sleeping habits and sleep quality of young adults. Aims and Objectives: The aim of the study was to investigate the effect of circadian preferences on sleeping habits and the association of electronic media use with sleep quality and sleep disturbances. Materials and Methods: A total of 188 subjects were enrolled and divided into three groups: Evening, intermediate, and morning chronotype based on the Morningness-Eveningness score. Electronic media use at bedtime and duration of use were assessed subjectively. Sleep quality and subjective sleep disturbances, daytime sleepiness, and chronotype were assessed by the Pittsburgh Sleep Quality Index, Epworth Sleepiness Score, and Morningness-Eveningness Questionnaire Self-assessment version, respectively. Results: The majority of subjects with the evening chronotypes suffered from poor sleep quality compared to other chronotypes and the difference was statistically significant. In evening-type subjects, electronic media use at bedtime, long sleep latency, short sleep duration, and daytime sleepiness were significantly associated with poor sleep quality with odds ratios of 2.34 (1.08–5.08), 11.42 (4.98–26.19), 8.54 (1.01–68.24), and 1.68 (1.03–2.73), respectively. Conclusion: The majority of evening-type subjects had poor sleep quality, altered sleeping habits, and electronic media use at bedtime is significantly associated with poor sleep quality. Hence, history regarding sleep habits and lifestyle, especially electronic media use, should be taken from young adults, who are coming to the outpatient department for other than sleep disorders, to prevent the development of health-related problems.

Physical activity and morningness: A helpful combination in improving the sleep quality of active Italian university students

ABSTRACT University students are commonly described as having worsened sleep quality, especially when inactive and Evening-type (E-type) subjects. This study aimed to examine the interactions between physical activity and chronotype on sleep quality among a sample of active Sports Science university students. In November 2019, 433 participants (mean age: 19.7 ± 1.56 years; 70% males) completed the Pittsburgh Sleep Quality Index, the Godin-Shepard Leisure-Time Physical Activity Questionnaire (tertiles categorisation), and the Morningness-Eveningness Questionnaire. Females and E-type slept significantly worse than males and Neither-(N-types) and Morning-types (M-types), respectively. However, there were no significant differences in sleep quality based on physical activity levels. The three-way ANOVA revealed that sleep quality in N- and E-types appeared to be independent of physical activity, whereas M-types showed an improvement in sleep classification with increased physical activity. Moderation analysis indicated that physical activity significantly moderated the relationship between chronotypes and sleep quality. Specifically, M-types demonstrated a more pronounced improvement in sleep quality with increasing physical activity compared to the other chronotypes. In conclusion, M-type university students derived the greatest benefits from physical activity in improving sleep quality. Conversely, physical activity seemed to have a limited impact on sleep quality among active E-type university students.

Associations Between Chronotype, Adherence to the Mediterranean Diet, and Attitude to Healthy Nutrition

Background. Chronotype is the attitude of a subject in determining the individual circadian preference in behavioral and biological rhythm associated with eating behaviors and health.
 Objective. The aim of this study was to evaluate the associations between chronotype, adherence to the Mediterranean diet, and attitudes to healthy nutrition in Turkish adults.
 Methods. A survey was conducted online using online platforms. A total of 1,197 volunteers between 18-65 years of age participated in our study. Participants’ adherence to the Mediterranean diet was assessed using the Mediterranean Diet Adherence Screener (MEDAS); their healthy eating attitude and chronotype were assessed using the Attitude Scale for Healthy Nutrition (ASHN) and the Morning-Evening Questionnaire (MEQ), respectively.
 Results. Most of the participants were classified as those with an intermediate chronotype. More than half of evening-type participants and nearly half of intermediate-type participants had poor Mediterranean diet adherence. In addition, the percentages of individuals with morning and evening chronotypes in the very low and moderate classification ranges were similar and lower than the percentages of those with an intermediate chronotype. Linear regression analysis revealed that participants with higher MEQ values had higher ASHN and MEDAS scores and a lower body mass index as compared to those with lower MEQ values.
 Conclusions. Chronotype was associated with Mediterranean diet adherence and healthy eating attitude. In particular, morning-type subjects showed higher adherence to the Mediterranean diet than intermediate- and evening-type subjects.

The fall of vulnerability to sleep disturbances in evening chronotypes when working from home and its implications for depression

Eveningness is distinctively associated with sleep disturbances and depression symptoms due to the misalignment between biological and social clocks. The widespread imposition of remote working due to the COVID-19 pandemic allowed a more flexible sleep schedule. This scenario could promote sleep and mental health in evening-type subjects. We investigated the effect of working from home on sleep quality/quantity and insomnia symptoms within the morningness-eveningness continuum, and its indirect repercussions on depressive symptomatology. A total of 610 Italian office workers (mean age ± standard deviation, 35.47 ± 10.17 years) and 265 remote workers (40.31 ± 10.69 years) participated in a web-based survey during the second contagion wave of COVID-19 (28 November–11 December 2020). We evaluated chronotype, sleep quality/duration, insomnia, and depression symptoms through validated questionnaires. Three moderated mediation models were performed on cross-sectional data, testing the mediation effect of sleep variables on the association between morningness-eveningness continuum and depression symptoms, with working modality (office vs. remote working) as moderator of the relationship between chronotype and sleep variables. Remote working was associated with delayed bedtime and get-up time. Working modality moderated the chronotype effect on sleep variables, as eveningness was related to worse sleep disturbances and shorter sleep duration among the office workers only. Working modality also moderated the mediation of sleep variables between chronotype and depression. The above mediation vanished among remote workers. The present study suggests that evening-type people did not show their characteristic vulnerability to sleep problems when working from home. This result could imply a reduction of the proposed sleep-driven predisposition to depression of late chronotypes. A working environment complying with individual circadian preferences might ensure an adequate sleep quantity/quality for the evening-type population, promoting their mental health.

Relationship between Dynamics of Physiological Signals and Subjective Quality of Life and Its Lifestyle Dependency.

In terms of preventive healthcare, how adopted lifestyle maintains healthy states or leads to pathological states is an essential issue. In this study, for the healthy subjects, their daily patterns of heart rate variability (HRV) and behavioral activity dynamics were analyzed in association with subjective quality of life (QOL), and how the relationship between the physiological signal dynamics and QOL is differentiated by the chronotype (sleep-wake pattern) was investigated. As a result, the morning type subjects were found to show higher sequential variation in R-R interval (rMSSD) and behavioral activity, and to have higher sleep quality and non-depressive tendency. Even the evening type subjects could have higher sleep quality under the condition that rMSSD shows a dip around early afternoon and keep a higher level of activity during the daytime, which may be due to realization of steady entrainment to the circadian time cues. Through this study, fundamental knowledge for preventive healthcare was obtained for us to help people's choice of an appropriate lifestyle for their health.

Heart Rate Variability in Sport Performance: Do Time of Day and Chronotype Play A Role?

A reliable non-invasive method to assess autonomic nervous system activity involves the evaluation of the time course of heart rate variability (HRV). HRV may vary in accordance with the degree and duration of training, and the circadian fluctuation of this variable is crucial for human health since the heart adapts to the needs of different activity levels during sleep phases or in the daytime. In the present review, time-of-day and chronotype effect on HRV in response to acute sessions of physical activity are discussed. Results are sparse and controversial; however, it seems that evening-type subjects have a higher perturbation of the autonomic nervous system (ANS), with slowed vagal reactivation and higher heart rate values in response to morning exercise than morning types. Conversely, both chronotype categories showed similar ANS activity during evening physical tasks, suggesting that this time of day seems to perturb the HRV circadian rhythm to a lesser extent. The control for chronotype and time-of-day effect represents a key strategy for individual training schedules, and, in perspective, for primary injury prevention.

Üniversite Öğrencilerinde Kronotipe Göre Besin Tüketiminin Değerlendirilmesi

Amaç: Bu çalışma, üniversite öğrencilerinin kronotiplerinin belirlenmesi ve kronotiplerine göre besin tüketimlerinin karşılaştırılması amacıyla planlanmış ve yürütülmüştür.
 Bireyler ve Yöntem: Çalışmaya yaşları 19-31 yıl arasında olan, 198 erkek (%24.5) ve 609 kadın (%75.5) olmak üzere toplam 807 üniversite öğrencisi dahil edilmiştir. Bireylere genel özelliklerinin, beslenme ve uyku alışkanlıklarının sorgulandığı bir anket formu ve kronotipin belirlenmesi için “İnsan Sirkadiyen Ritminde Sabahçıl ve Akşamcıl Tipleri Belirlemede Kendi Kendini Değerlendirme Formu” uygulanmıştır. Araştırmacılar tarafından bireylerin iki günlük besin tüketim kaydı alınmış, vücut ağırlığı ve boy uzunluğu ölçümleri standartlara uygun şekilde yapılmıştır. Bireylerin enerji ve besin ögelerinin önerilen günlük yeterli alım düzeylerini karşılama durumları Türkiye Beslenme Rehberi’ne (TÜBER, 2015) göre değerlendirilmiştir.
 Bulgular: Katılımcıların %23’ü sabahçıl (n= 186), %52.8’i ara (n= 426), %24.2’si ise akşamcıl (n= 195) kronotipe sahiptir. Sabahçıl tip bireylerin günlük su tüketimlerinin ara ve akşamcıl tip bireylerden anlamlı düzeyde daha fazla olduğu saptanmıştır (p=0.000). Bireyler antropometrik ölçümlerine göre değerlendirildiğinde sabahçıl bireylerin beden kütle indeksi (BKİ) değerlerinin akşamcıl tiplere göre (p=0.014) daha yüksek olduğu belirlenmiştir. Araştırmaya katılan sabahçıl bireylerde hafta içi sabah öğününü, hafta sonu ise öğle öğününü atlayanların oranı akşamcıl bireylere göre anlamlı düzeyde daha azdır (sırasıyla p=0.002, p=0.011). Akşamcıl bireylerin günlük enerjinin karbonhidrattan gelen yüzdesi sabahçıl bireylerden daha fazladır (p=0.043). Sabahçıl bireylerin ise günlük enerjinin yağdan gelen yüzdesi akşamcıl bireylere göre daha fazladır (p=0.020). Sabahçıl bireylerin günlük folik asit alım düzeyleri akşamcıl bireylere göre daha fazladır (p=0.018).
 Sonuç: Bu çalışmada üniversite öğrencilerinin farklı kronotipe sahip olmalarına rağmen besin tüketimlerinin benzer olduğu belirlenmiştir. Beslenme, uyku düzeni gibi etmenlerle karşılıklı etkileşim içerisinde bulunan kronotip, fizyolojik süreçlerde değişikliklere neden olabilir. Üniversite öğrencilerinin kronotiplerine göre beslenme durumları prospektif fizyolojik çalışmalar ile desteklenmelidir.

Association of a nonsynonymous polymorphism in PER 1 with diurnal preference in Korean adults

No nonsynonymous single-nucleotide polymorphism (SNP) in PER1 has been reported with respect to diurnal preference. We aimed to determine whether a functional polymorphism in PER1 is involved in diurnal preference. Forty-seven morning-type (MT, age: 44.57 ± 12.33 years), 59 neither-type (NT, age: 35.20 ± 9.53 years), and 50 evening-type (ET, age: 28.96 ± 8.03 years) subjects were included in the final analysis. A synonymous (PER1 2485 C/T, rs2735611) and nonsynonymous (PER1 2495 G/T, rs138577469) polymorphism at 10-bp away from the PER1 2485 C/T were investigated as candidate SNPs. For the PER1 2485C/T SNP, no significant genotype distribution was observed among the three groups. For the PER1 2495G/T, the MT group showed significantly higher genotype distribution, T allele frequency, and proportion of T allele-positive subjects when compared to the combined group of NT and ET. Our findings suggest that a nonsynonymous polymorphism in PER1, which has only been found in Korean adults, is associated with morning preference.

Chronotype influences response to antidepressant chronotherapeutics in bipolar patients

ABSTRACTPatient diurnal mood fluctuation, sleep characteristics and factors affecting sleep homeostasis predict antidepressant response to the combination of total sleep deprivation and light therapy (TSD + LT). In order to study if chronotype could influence response to TSD+LT, we considered 194 bipolar depressed patients. Severity of depression was rated with Hamilton Depression Rating Scale; perceived mood levels were assessed by a self-administered 10-cm visual analogue scale and chronotype was assessed using the Mornigness-Eveningness Questionnaire.More than 60% of patients resulted responders to treatment with chronotype influencing the antidepressant response with evening type subjects showing higher response rates.

Evening chronotype associates with obesity in severely obese subjects: interaction with CLOCK 3111T/C.

Chronotype has been related to obesity and metabolic disturbances. However, little is known about the relationship between circadian preferences and genetic background in CLOCK genes with obesity and weight loss among severely obese patients after bariatric surgery. The research goals were (1) to examine whether evening chronotype is related to obesity and weight loss evolution in severely obese followed during 6 years after bariatric surgery and (2) to examine potential interactions between circadian preferences and CLOCK 3111T/C for obesity in this population. Participants (n=252, 79% female; age (mean±s.d.): 52±11 years; body mass index (BMI): 46.4±6.0 kg m-2) were grouped into evening and morning types. Obesity and weight loss parameters, energy and macronutrients intake, energy expenditure, chronotype, meal timing, sleep duration and CLOCK genotype were studied. Evening-type subjects showed significantly higher initial body weight (P=0.015) and BMI (P=0.014) than morning types. Moreover, evening-type, when compared with morning types, lost less weight (percentage of excess weight loss) after bariatric surgery (P=0.015). Weight-loss progression between the two chronotype groups differed significantly from the fourth year after the bariatric surgery toward a higher weight regain among evening types (P<0.05). We also detected a significant interaction between CLOCK 3111T/C SNP and chronotype for body weight at baseline (P<0.001). Specifically, among carriers of the risk allele C, evening types showed higher body weight than morning types (P=0.012). In addition, CLOCK 3111T/C SNP significantly associated with obesity and sleep duration in the older subjects. Evening chronotype is associated with higher obesity in severely obese subjects and with lower weight loss effectiveness after bariatric surgery. In addition, circadian preferences interact with CLOCK 3111T/C for obesity. The circadian and genetic assessment could provide tailored weight loss recommendations in subjects who underwent bariatric surgery.

Association between morningness/eveningness, addiction severity and psychiatric disorders among individuals with addictions

Studies have shown that Evening-Type (ET) subjects used more stimulating and sedative substances, and presented more psychiatric disorders than Morning-Type (MT) subject. However, there is a lack of data on the chronotype of patients with addiction. The aim of our study was to describe chronotype and associated factors in a sample of outpatients beginning treatment for addiction. Subjects were assessed with the Morningness–Eveningness questionnaire of Hörne & Ostberg, the Addiction Severity Index and the Mini International Neuropsychiatric Interview. In the 333 subjects with an addiction, 20% were MT and 32% were ET. When comparing ET to MT, multivariate analysis showed that ET was significantly associated with poly-problematic addiction, non-substance addictions, cannabis addiction, and mood disorders, but not with severity of addiction. MT was associated with antisocial personality disorder. Results suggested that chronotype was associated with specific addiction pattern and psychiatric disorders.

Temporal sleep patterns in adults using actigraph

The aim of the present study was to characterize the temporal patterns of sleep and wakefulness in a sample of the adult subjects from São Paulo city. All subjects filled the Morningness/Eveningness Questionnaire (MEQ) and wore an actigraph for at least three consecutive days. A total of 359 subjects were considered for the analyses. The mean age was 43±14 years, the mean body mass index was 26.7±5.7kg/m2, and 60% were female. The mean MEQ score was 58.0±10.7. The sleep pattern evaluated by the actigraphic analyses showed that 92% had a monophasic sleep pattern, 7% biphasic, and 1% polyphasic sleep pattern. Cluster analysis, based on time to sleep onset, sleep efficiency, sleep latency, and total sleep time, was able to identify three different groups denominated: morning type, evening type, and undefined type. Morning type subjects were more frequent, older, and had higher MEQ scores than evening type subjects. Our results showed that the actigraph objectively assessed the sleep-wake cycle and was able to discriminate between morning and evening type individuals. These findings suggest that the actigraph could be a valuable tool for assessing temporal sleep patterns, including the circadian preferences.

Eveningness and insomnia: independent risk factors of nonremission in major depressive disorder.

It is unclear whether there is an association between chronotype and nonremission of depression, and whether the association is related to the confounding effect of insomnia. A cohort of patients with major depressive disorder were assessed for chronotype (by Morningness-Eveningness Questinnaire [MEQ]), depressive symptoms, insomnia severity and clinical outcomes in a naturalistic follow-up study. Of the 253 recruited subjects (age 50.8 ± 10.2 y; female: 82.6%; response rate 90.0%), 19.4%, 56.1% and 24.5% patients were classified as eveningness, intermediate, and morningness, respectively. Evening-type subjects had higher insomnia severity, more severe depressive symptoms, and higher suicidality. Eveningness was associated with nonremission of depression with an odds ratio (OR) of 3.36 (95% confidence interval [CI] 1.35-8.34, P < 0.01), independent of insomnia severity. In addition, insomnia was an independent significant factor in contributing to nonremission of depression (OR = 1.12; 95% CI 1.05-1.19, P < 0.001). The independent association of eveningness with nonremission of depression suggested a significant underpinning of circadian involvement in major depressive disorder. Our findings support the need for a comprehensive assessment of sleep and circadian disturbances as well as integration of sleep and chronotherapeutic intervention in the management of depression.

A relationship among circadian typology, sensation seeking and impulsivity

The purpose of the present study is to explore the relationships among circadian typology, sensation seeking, impulsivity, and sex. A sample of 709 university students (380 women) aged 18–32 (22.24 ± 3.16) years completed the Sensation Seeking Scale form-V, the Dickman’s Impulsivity Inventory and the reduced Morningness–Eveningness Questionnaire. Men showed higher scores for thrill and adventure seeking, disinhibition, boredom susceptibility and sensation seeking ( p p = .017). Evening-type subjects had significantly higher dysfunctional impulsivity and experience seeking than morning-type, and higher disinhibition and sensation seeking total score than morning- and neither-type subjects ( p

Personality, sleep habits and sleep problems in a representative sample of Italian eighth grade students

In the present study the relationships between personality traits (Big Five factors, Impulsivity and Circadian Preference), sleep habits and sleep problems were evaluated in a representative sample of Italian eighth grade students. Participants ( N = 3391; 50.6% females, mean age: 13.8 ± 5 years) completed a modified version of School Sleep Habits Survey developed by Carskadon and coworkers to measure sleep habits during school days and weekends, daytime sleepiness, sleep problems, and circadian preference. In addition, students completed self report measures of Impulsivity and the Big Five factors. Boys reported more sleep related problems than females. Big five factors and circadian preferences influenced sleep habits and total sleep time in both school days and weekends. Low conscientiousness and high impulsivity were associated with daytime sleepiness, Circadian preference and Impulsivity were the best predictors of self-reported sleep/wake problems, indicating a higher prevalence of sleep complaints in impulsive and evening-type subjects.

Circadian typology and depressive disorders. A non negligible association

Circadian typology (morning, neither and evening-type) is an individual difference related to several aspects of mental health. We present a comprehensive review of the findings published about circadian typology, major depressive disorder and seasonal affective disorder. Circadian typology is related to begin, course, remission and relapse of major depressive disorder and seasonal affective disorder. Evening-type subjects have a higher prevalence of depressive symptomatology and suicidal ideation, showing more severe symptoms than morning- and neither-type with the same diagnostic, suggesting that this typology could represent a risk factor for the development of psychopathology. These individual differences may be explained by three factors: Clock gene polymorphisms, social jet lag and personality traits. Chronobiological therapy (behavioral habits, pharmacological therapy with melatonin and light therapy) has demonstrated hopeful results applied to depressive disorders when circadian rhythmicity is altered. Circadian typology should be taken into account in prevention programs and treatment of depressive disorders.

Circadian typology is related to Cloninger’s model of personality and dysfunctional impulsivity

The purpose of this study is to explore the relationships among circadian typology, Cloninger’s model of personality, functional and dysfunctional impulsivity factors, and sex. A sample of 709 university students (382 women) aged 18–32 (22.25 ± 3.16) years completed the reduced Morningness–Eveningness Questionnaire, the short version of the Temperament and Character Inventory and the Dickman’s Impulsivity Inventory. Women showed significantly higher values for harm avoidance, reward dependence, persistence, self-directedness, and cooperativeness ( p <. 045). Evening-type subjects had significantly higher dysfunctional impulsivity and novelty seeking scores than morning-type ( p <. 037), while morning-type had higher persistence scores than evening and neither-type ( p <. 005). Taken together, dysfunctional impulsivity, circadian typology and sex are good predictors for persistence. Circadian typology is related to several dimensions of Cloninger’s model of personality, as well as to dysfunctional impulsivity, and this should be taken into account in future studies and healthy programs.

Reliability and validity of the Korean version of Morningness–Eveningness Questionnaire in adults aged 20–39 years

Morningness–Eveningness (ME) can be defined by the difference in individual diurnal preference observed from general behavioral patterns including sleep habits. The Horne & Östberg Morningness–Eveningness Questionnaire (MEQ) has been used for classifying ME types. We examined the reliability of a Korean version of the MEQ (Korean MEQ) and verified its validity by comparing responses on the Korean MEQ to objectively-recorded sleep–wake rhythms. After translating and back translating the MEQ from English into Korean, we examined the internal consistency of 19 items of the Korean MEQ in 91 subjects, and the test–retest reliability in 21 subjects who took the Korean MEQ twice, 4 weeks apart. The Korean MEQ was then administered to 1022 young adult subjects. A subset of 46 morning, neither, and evening type subjects took part in a validation study in which their rest-activity timing was collected by actigraphy for 7 days. Cosinor analyses on these data were done to obtain the acrophase and amplitude of the sleep–wake rhythm. Cronbach’s alpha of the total scores from the Korean MEQ was 0.77, and the test–retest reliability intra-class correlation coefficient was 0.90 (p < 0.0001). There was a significant negative correlation between Korean MEQ score and reported sleep–wake timing among the entire cohort (p < 0.0001). There was a significant difference in bedtime and wake time (on both work and free days), and in the mean sleep–wake rhythm acrophase, between ME types (p < 0.01). In this study, the validity of the Korean MEQ was verified by illustrating the difference in acrophases of the sleep–wake rhythm between the ME types in young adults.

Relationships Among Circadian Typology, Psychological Symptoms, and Sensation Seeking

Recently, attention has been focused on the relationship among circadian typology, psychiatric symptoms, and personality traits. This study analyzes the influence of circadian typology on psychological distress, and the sensation-seeking personality trait. Five hundred seventeen college students (173 males), aged 17 to 30, answered the Composite Scale of Morningness (CSM), the General Health Questionnaire 28-item version (GHQ-28), and the Sensation Seeking Scale-V (SSS-V). The evening-type subjects in our sample scored higher than the neither- and morning- type in the GHQ-28 total score, as well as in the four subscales that composed it (Psychosomatic Symptoms, Anxiety and Insomnia, Social Dysfunction, and Severe Depression) (p < 0.02 in all cases). The evening-type subjects also had a larger proportion of psychiatric cases than the other two circadian typologies (p < 0.0001 in all cases). Moreover, the evening-type subjects obtained higher scores in the SSS-V total score and in the subscales of Disinhibition and Boredom Susceptibility (p < 0.001 in all cases). A positive correlation was observed between the GHQ-28 and the SSS-V total scores in the total sample, but only for the evening-type group (r = 0.217; p < 0.027). In the evening group, several relations were also found between the subscales of the GHQ-28 and the subscales of the SSS-V (r > 0.206; p < 0.036). All these data point to a relationship between evening-type subjects and the level of psychological distress and the sensation-seeking personality trait. They also suggest that eveningness could be related to developing psychological distress and personality traits that could, in turn, be related to developing other problems, such as drug consumption.

Time Course of Neurobehavioral Alertness During Extended Wakefulness in Morning- and Evening-Type Healthy Sleepers

The aim of the study was to evaluate the influence of chronotype (morning-type versus evening-type) living in a fixed sleep-wake schedule different from one's preferred sleep schedules on the time course of neurobehavioral performance during controlled extended wakefulness. The authors studied 9 morning-type and 9 evening-type healthy male subjects (21.4 ± 1.9 yrs). Before the experiment, all participants underwent a fixed sleep-wake schedule mimicking a regular working day (bedtime: 23:30 h; wake time: 07:30 h). Then, following two nights in the laboratory, both chronotypes underwent a 36-h constant routine, performing a cognitive test of sustained attention every hour. Core body temperature, salivary melatonin secretion, objective alertness (maintenance of wakefulness test), and subjective sleepiness (visual analog scale) were also assessed. Evening-types expressed a higher level of subjective sleepiness than morning types, whereas their objective levels of alertness were not different. Cognitive performance in the lapse domain remained stable during the normal waking day and then declined during the biological night, with a similar time course for both chronotypes. Evening types maintained optimal alertness (i.e., 10% fastest reaction time) throughout the night, whereas morning types did not. For both chronotypes, the circadian performance profile was correlated with the circadian subjective somnolence profile and was slightly phase-delayed with melatonin secretion. Circadian performance was less correlated with circadian core body temperature. Lapse domain was phase-delayed with body temperature (2–4 h), whereas optimal alertness was slightly phase-delayed with body temperature (1 h). These results indicate evening types living in a fixed sleep-wake schedule mimicking a regular working day (different from their preferred sleep schedules) express higher subjective sleepiness but can maintain the same level of objective alertness during a normal waking day as morning types. Furthermore, evening types were found to maintain optimal alertness throughout their nighttime, whereas morning types could not. The authors suggest that evening-type subjects have a higher voluntary engagement of wake-maintenance mechanisms during extended wakefulness due to adaptation of their sleep-wake schedule to social constraints. (Author correspondence: jack.taillard@gmail.com)