Bimodal diurnal preference in undergraduate students is associated with negative health and sleep outcomes.

The bimodal preference is a fourth diurnal preference proposed by re-scoring the Morningness-Eveningness Questionnaire. The present work aimed to describe the prevalence of the bimodal preference in a sample of undergraduate students and to characterize the bimodal type in terms of their health and sleep-related outcomes. A web-based cross-sectional study conducted between September 2018 and March 2021 (convenience sampling method). The sample was composed of undergraduate students who completed an electronic form that included the Morningness and Eveningness Questionnaire, the Pittsburgh Sleep Quality Index, the Self-Compassion Scale, the Epworth Sleepiness Scale, the Hospital Anxiety and Depression Scale, and the World Health Organization Subjective Well-Being Index. The final sample consisted of 615 students (82% female, mean age: 23.4 ± 6.5 years), of whom 108 (18%) had positive bimodality indexes. Bimodal subjects comprised 48 students, 8% of the total sample. Bimodal subjects had poorer subjective sleep quality, more daytime sleepiness, lower subjective well-being, greater anxiety and depression symptoms, and lower self-compassion than morning and/or intermediate types; they did not differ from evening types. The description of bimodal diurnal preference in this population may be of interest for the design of academic policies more in line with the circadian reality of students.

Is evening chronotype associated with higher alcohol consumption? A systematic review and meta-analysis.

A broader understanding of whether and to what extent chronotype should be considered a risk factor for alcohol consumption is needed. The aim of this systematic review was to summarize the evidence on the association between evening chronotype and alcohol consumption. A systematic search of observational studies on this association was conducted in the PubMed, Scopus, Web of Science, Cochrane Library and PsycINFO databases up to April 30th, 2023. Random-effect models estimated the pooled odds ratio (OR) of alcohol consumption according to chronotype. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines and Quality Assessment tool for Observational Cohorts and Cross-sectional Studies from the National Heart, Lung and Blood Institute were followed. A total of 33 studies involving 28 207 individuals (age range: 18-93 years) were included in this review. Overall, most studies indicated a higher volume and frequency of alcohol consumption in evening-type individuals than in individuals with different chronotypes. Additionally, a meta-analysis including 13 studies showed that evening-type individuals were 41% more likely to consume alcohol than those with other chronotypes (OR = 1.41, 95% confidence interval: 1.16-1.66; I2 = 38.0%). Limitations of the present findings are the predominance of cross-sectional studies and varied definitions of alcohol consumption. The available evidence supports an association between the evening chronotype and alcohol consumption. The evening-type population, especially young adults, is a specific target for educational interventions for preventing or reducing alcohol consumption.PROSPERO number: CRD42022343778.

Factors that influence morningness-eveningness and daytime sleepiness: A cross-cultural comparison of Iranian and Brazilian adolescents.

As adolescents get older, they become more evening oriented and, because they are usually expected to wake early to attend school, they often present daytime sleepiness, which is associated with negative outcomes. It is still unclear if this is similar cross-culturally. Here, we studied morningness-eveningness and daytime sleepiness in early adolescence from two different developing nations (Brazil and Iran). A total sample of 697 Iranian and Brazilian early adolescents (9- to 15-year-old; 358 boys) from Tehran, Iran, and São Paulo, Brazil, varying in age and parental schooling (a proxy of socioeconomic status: SES) completed the Morningness-Eveningness Scale for Children (MESC) and the Pediatric Daytime Sleepiness Scale (PDSS) and reported their total sleep time on school nights. They also filled in the Pubertal Developmental Scale to determine their pubertal status. A negligible cross-cultural difference in morningness-eveningness was found, indicating that Brazilians showed a slight circadian-phase delay compared with Iranians throughout all tested ages. There was also seen a very slight increase in phase delay as early adolescents aged, indicative of more eveningness. However, there were no country differences in daytime sleepiness once total sleep time during school nights was controlled for, which was the only factor that affects PDSS scores.

Evening chronotype as a bipolar feature among patients with major depressive disorder: the results of a pilot factor analysis

Objectives: The bipolar spectrum concept has resulted in a paradigm shift that has affected both the diagnosis and therapy of mood disorders, with bipolarity becoming an indicator of treatment resistance in depression. Evening circadian preference has also been linked to affective disorders. The aim of our study was to confirm the relationship between the severity of depressive symptoms, bipolar features, chronotype, and sleep quality among patients with major depressive disorder. Methods: A group of 55 individuals who were recruited from a mental health outpatient clinic completed the following psychometric tools: a Chronotype Questionnaire comprising morningness-eveningness (ME) and subjective amplitude of the rhythm (AM) scales, the Hypomania Checklist 32 (HCL-32), the Beck Depression Inventory (BDI) and the Pittsburgh Sleep Quality Index (PSQI). Results: Factor analysis identified two latent components, accounting cumulatively for 58% of variables: depressive symptoms (BDI and PSQI) and bipolarity (ME, AM, and HCL-32). After rotation, ME loading in the first factor increased the result to a significant level. The correlation between the two components was very low. Conclusions: Evening chronotype appears to be a bipolarity-related marker, with this relationship being independent of its link to depressive symptoms and sleep quality. Eveningness and high circadian rhythm amplitude may offer promise as diagnostic, prognostic, and therapeutic predictors.

COVID-19 Pandemic on Fire: Evolved Propensities for Nocturnal Activities as a Liability Against Epidemiological Control.

Humans have been using fire for hundreds of millennia, creating an ancestral expansion toward the nocturnal niche. The new adaptive challenges faced at night were recurrent enough to amplify existing psychological variation in our species. Night-time is dangerous and mysterious, so it selects for individuals with higher tendencies for paranoia, risk-taking, and sociability (because of security in numbers). During night-time, individuals are generally tired and show decreased self-control and increased impulsive behaviors. The lower visibility during night-time favors the partial concealment of identity and opens more opportunities for disinhibition of self-interested behaviors. Indeed, individuals with an evening-oriented chronotype are more paranoid, risk-taking, extraverted, impulsive, promiscuous, and have higher antisocial personality traits. However, under some circumstances, such as respiratory pandemics, the psychobehavioral traits favored by the nocturnal niche might be counter-productive, increasing contagion rates of a disease that can evade the behavioral immune system because its disease cues are often nonexistent or mild. The eveningness epidemiological liability hypothesis presented here suggests that during the COVID-19 pandemic, the evening-oriented psychobehavioral profile can have collectively harmful consequences: there is a clash of core tendencies between the nocturnal chronotype and the recent viral transmission-mitigating safety guidelines and rules. The pandemic safety protocols disrupt much normal social activity, particularly at night when making new social contacts is desired. The SARS-CoV-2 virus is contagious even in presymptomatic and asymptomatic individuals, which enables it to mostly evade our evolved contagious disease avoidance mechanisms. A growing body of research has indirectly shown that individual traits interfering with social distancing and anti-contagion measures are related to those of the nocturnal chronotype. Indeed, some of the social contexts that have been identified as superspreading events occur at night, such as in restaurants, bars, and nightclubs. Furthermore, nocturnal environmental conditions favor the survival of the SARS-CoV-2 virus much longer than daytime conditions. We compare the eveningness epidemiological liability hypothesis with other factors related to non-compliance with pandemic safety protocols, namely sex, age, and life history. Although there is not yet a direct link between the nocturnal chronotype and non-compliance with pandemic safety protocols, security measures and future empirical research should take this crucial evolutionary mismatch and adaptive metaproblem into account, and focus on how to avoid nocturnal individuals becoming superspreaders, offering secure alternatives for nocturnal social activities.

Environmental temperature as a mediator on the association between photoperiod at birth and chronotype.

The association between chronotypes and season of birth (SOB) remains an inconclusive issue due, in some extension, to the lack of investigations of mediation mechanisms. We evaluated the association of photoperiod at birth (PAB) with chronotypes and sleep duration in Brazil (n = 810), and the mediating effect of meteorological factors, sex, age and rs4753426 polymorphism in the melatonin receptor MTNR1B. Longer PAB was associated with a delayed mid-sleep phase with a suppressive effect of maximum environmental temperature. No significant interactions were identified for the other variables. These findings suggest that photoperiod and environmental temperature modulate chronotype development at early stages.

Unveiling sleep mysteries: Sleep-wake cycle as a biological parameter of the circadian typology (Chronotype) / Revelando mistérios do sono: Ciclo sono-vigília como parâmetro biológico da tipologia circadiana (cronotipo)

The sleep-wake cycle that is circadian rhythm may have different patterns according to sex, environment and genetics determinants. This chronological cycle type, chronotype, may be populational expressed by the extremes, early or later going to bed and waking up, in a continuum. The first, the Morning-type individuals (the lark) and the later, the Evening types (the owl). Between the two extremes, there is the majority of these chronotypes ­ the intermediate ones. These patterns may be classified according to the questionnaires such as Horne and Ostberg Morningness/ Eveningness Questionnaire (MEQ) and the Munich Chrono Type Questionnaire (MCTQ). The rural population tends to be Morning-type, as well as children and younger women, more than men. The Morning person tends to be more healthy than the Evening ones who are more prone to diseases, as depression and metabolic syndrome. This basic knowledge may be helpful to patient's counseling and management: to avoid mismatch of circadian physiology and social duties / sleep. This circadian desynchrony can increase the risk of diseases, consequently there is a need to chrono-medicine into current treatment strategies.

O ciclo sono-vigília, que é um ritmo circadiano, pode ter padrões diferentes de acordo com os determinantes sexuais, ambientais e genéticos. Esse tipo de ciclo cronológico, cronótipo, pode ser expresso em termos populacionais pelos extremos, indo cedo ou mais tarde para a cama ou saindo dela, em um continuum. O primeiro, os indivíduos do tipo Manhã (a cotovia) e o posterior, os tipos da Tarde (a coruja). Entre os dois extremos, há a maioria desses cronotipos - os intermediários. Esses padrões podem ser classificados de acordo com questionários como o Horne e Ostberg Morningness/Eveningness Questionnaire (MEQ) e o Munich Chrono Type Questionnaire (MCTQ). A população rural tende a ser do tipo matutino, assim como crianças e mulheres mais jovens, mais que os homens.A pessoa da manhã tende a ser mais saudável do que as da noite, mais propensa a doenças, como depressão e síndrome metabólica. Esse conhecimento básico pode ser útil para o aconselhamento e tratamento dos pacientes: para evitar incompatibilidade entre a fisiologia circadiana e os deveres sociais / sono. Essa dessincronia circadiana pode aumentar o risco de doenças, consequentemente, é necessário a cronomedicina nas atuais estratégias de tratamento.

How do stress, sleep quality, and chronotype associate with clinically significant depressive symptoms? A study of young male military recruits in compulsory service

Objective: Although studies have shown an association between poor sleep and chronotype with psychiatric problems in young adults, few have focused on identifying multiple concomitant risk factors. Methods: We assessed depressive symptoms (Beck Depression Inventory [BDI]), circadian typology (Morningness-Eveningness Questionnaire [MEQ]), sleep quality (Pittsburgh Sleep Quality Index [PSQI]), perceived stress (Perceived Stress Scale [PSS]), social rhythm (Social Rhythm Metrics [SRM]), and salivary cortisol (morning, evening and night, n=37) in 236 men (all 18 years old). Separate analyses were conducted to understand how each PSQI domain was associated with depressive symptoms. Results: Depressive symptoms were more prevalent in individuals with higher perceived stress (prevalence ratio [PR] = 6.429, p < 0.001), evening types (PR = 2.58, p < 0.001) and poor sleepers (PR = 1.808, p = 0.046). Multivariate modeling showed that these three variables were independently associated with depressive symptoms (all p < 0.05). The PSQI items subjective sleep quality and sleep disturbances were significantly more prevalent in individuals with depressive symptoms (PR = 2.210, p = 0.009 and PR = 2.198, p = 0.008). Lower levels of morning cortisol were significantly associated with higher depressive scores (r = -0.335; p = 0.043). Conclusion: It is important to evaluate multiple factors related to sleep and chronotype in youth depression studies, since this can provide important tools for comprehending and managing mental health problems.

Sleep habits, circadian preferences and substance use in a Mexican population: the use of the Morningness-Eveningness-Stability-Scale improved (MESSi).

This study aimed to validate the Morningness-Eveningness-Stability-Scale improved (MESSi) in Mexico, analyzing the factor structure and sleep habits, combined with the proposal of cutoff values for the scales, and to assess the relationship with substance use. We applied the questionnaires through an online survey to a total sample of 510 Mexicans, aged 18-77 years (M = 27.79, SD = 10.24). The MESSi showed an acceptable fit and the Cronbach's alpha coefficients were good to satisfactory in the Mexican sample in every subscale: Morning Affect (MA, α = 0.90), Eveningness (EV, α = 0.88), Distinctness (DI, α = 0.80). In order to obtain a better interpretation of the MESSi subscales, we decided to propose cutoff points corresponding to the 25th-75th percentile. The categories were depicted as strong trait presence, intermediate trait presence and weak trait presence. When applying the cutoff points for the MESSi sub-scales, with Morning Affect (MA), strong-types went to bed and woke up earlier and had more sleep than weak-types during weekdays and weekends and reported less social jetlag. For Eveningness (EV), strong-types went to bed and woke up later than weak-types on weekdays and weekends. Also, strong-types had a shorter time in bed during weekdays but not on weekends and reported more social jetlag. Lastly, with Distinctness (DI), the results reported that those with a strong-type showed greater amplitude on weekdays and weekends. Furthermore, the MESSi scale found that evening people consumed more alcohol and tobacco. Our study supported the validity and reliability of the MESSi in a Mexican population and the relationship between eveningness and substance consumption. Furthermore, the proposed cutoff scores for the MESSi sub-scales add a novel approach for the measurement and interpretation of the scale.

The association between chronotype, food craving and weight gain in pregnant women.

BACKGROUND: This cross-sectional study investigated the association between chronotype, food craving and weight gain in pregnant women. METHODS: In total, 245 pregnant women attending the public health service in Brazil were included. Chronotype was derived from the time of mid-sleep time on free days, with a further correction for calculated sleep debt, and higher scores on this variable indicate a tendency to eveningness. A Food Craving Questionnaire Trait and State assessment was performed, and weight gain was calculated. Generalised linear models were used to determine the association between the variables under analysis. RESULTS: Evening types presented higher anticipation of relief from negative states and feelings as a result of eating as a usual behaviour compared to morning (P = 0.013) and non-evening types (P = 0.028); less intense desire to eat as a sporadic behaviour compared to morning (P = 0.012) and non-evening types (P = 0.009); and less anticipation of positive reinforcement that may result from eating as a sporadic behaviour than non-evening types (P = 0.022). We also found a significant association between chronotype score and anticipation of relief from negative states and feelings as a result of eating (P = 0.004); anticipation of positive reinforcement that may result from eating (P = 0.013) as a usual behaviour; weight gain during the early gestational period (P = 0.024); and intense desire to eat (P = 0.045) as a sporadic behaviour. CONCLUSIONS: We conclude that evening chronotype was associated with the food craving trait. Pregnant women who tend to eveningness are more likely to gain weight in the early gestational period.

Morningness-eveningness is not associated with academic performance in the afternoon school shift: Preliminary findings.

BACKGROUND: The effect of morningness-eveningness, sleep habits, and intelligence on academic performance has been studied in a fixed morning school shift. However, no studies have analysed these variables in an afternoon school shift and tested whether morningness-eveningness is related to academic performance beyond sleep habits and intelligence effects. AIMS: The psychometric properties of the Morningness-Eveningness Scale for Children (MESC) were analysed. Additionally, academic performance, sex, intelligence, sleep habits, and morningness-eveningness relationship in a morning and afternoon school shift were compared. SAMPLE: The sample consisted of 400 students at a secondary public school in Reynosa, Tamaulipas, in north-eastern Mexico (195 boys and 205 girls; mean ± SD: 13.85 ± 0.70 years old) attending a double-shift school system: 200 from the morning shift (99 boys and 101 girls) and 200 from the afternoon shift (96 boys and 104 girls). METHODS: The students completed the MESC as a measure of morningness-eveningness, a sleep habits survey, a test of academic performance, and the inductive reasoning subtest (R) of the Primary Mental Abilities battery. RESULTS: Adolescents in the two school shifts did not differ in academic performance and intelligence. In the afternoon shift, adolescents slept longer, reported less sleep deficit and social jet lag, and were more oriented to eveningness than adolescents in the morning shift. Sex (girls), sleep length, inductive reasoning, and morningness were associated with academic performance in the morning shift but only sex and intelligence in the afternoon shift. CONCLUSIONS: The role of morningness-eveningness in academic performance in the afternoon shift is examined.

Development of Late Circadian Preference: Sleep Timing From Childhood to Late Adolescence.

OBJECTIVES: To assess differences relating to circadian preference in objectively measured sleep patterns from childhood to adolescence over a 9-year period. We hypothesized there is developmental continuity in sleep timing and duration according to circadian preference. STUDY DESIGN: Young participants (N = 111, 65% girls) from a community-based birth cohort underwent sleep actigraphy at mean ages 8.1 (SD = 0.3), 12.3 (SD = 0.5), and 16.9 (SD = 0.1) years. A short version of Morningness-Eveningness Questionnaire was administered in late adolescence. At each follow-up, sleep midpoint, duration, wake after sleep onset, sleep efficiency, and weekend catch-up sleep were compared between those reporting morning, intermediate, and evening preferences in late adolescence. RESULTS: Mixed model analyses indicated that sleep timing was significantly earlier among morning types compared with evening types at all ages (P values < .04). The mean differences in sleep midpoint between morning and evening types increased from a mean of 19 minutes (age 8), 36 minutes (age 12), to 89 minutes (age 17). The largest change occurred from age 12 to 17 years. Sleep duration, wake after sleep onset, sleep efficiency, and catch-up sleep did not differ according to circadian preference. CONCLUSIONS: This study found significant continuity in sleep timing from childhood to adolescence over 9 years, indicating that late circadian preference reported in late adolescence begins to manifest in middle childhood. Further studies are needed to establish whether sleep timing has its origins at an even earlier age.

Chronotype and anxiety are associated in patients with chronic primary insomnia

Objective: To assess the interaction of chronotype with anxiety in patients with chronic primary insomnia. Methods: Sixty-four patients (50 women) with mean age 43.9±8.1 years were investigated with the Horne and Östberg Morningness-Eveningness Questionnaire (MEQ) and State-Trait Anxiety Inventory (STAI). Results: Significant negative correlations of chronotype-MEQ score with STAI state-anxiety (r = -0.40, p < 0.05), STAI trait-anxiety (r = -0.40, p < 0.05), and STAI pre-sleep state anxiety (r = -0.30, p < 0.05) were observed. Eveningness preference was associated with higher trait, state, and pre-sleep state anxiety. Conclusions: These results suggest that chronotype may be an important parameter to identifying the origin and significance of a vicious anxiety-insomnia-depression cycle in patients with chronic primary insomnia.

Re-examining sleep׳s effect on motor skills: How to access performance on the finger tapping task?

Here our goal was to determine the magnitude of sleep-related motor skill enhancement. Performance on the finger tapping task (FTT) was evaluated after a 90 min daytime nap (n=15) or after quiet wakefulness (n=15). By introducing a slight modification in the formula used to calculate the offline gains we were able to refine the estimated magnitude of sleep׳s effect on motor skills. The raw value of improvement after a nap decreased after this correction (from ~15% to ~5%), but remained significantly higher than the control. These results suggest that sleep does indeed play a role in motor skill consolidation.

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±5.7 kg/m(2), 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.

Chronotype: a review of the advances, limits and applicability of the main instruments used in the literature to assess human phenotype / Cronotipo: uma revisão dos avanços, limites e aplicabilidade dos principais instrumentos utilizados na literatura para avaliar o fenótipo humano

The study of circadian typology differences has increased in the last few years. As a result, new instruments have been developed to estimate the individual circadian phase of temporal human behavior, also referred as chronotype. The current review was conducted to evaluate the differences among the questionnaires most frequently used to assess chronotype: the Morningness-Eveningness Questionnaire (MEQ), the Composite Scale of Morningness (CSM), and the Munich Chronotype Questionnaire (MCTQ). Each instrument evaluates a different aspect of chronotype. MEQ is considered to evaluate the phase preferences of individual behavior over a 24-hour day, while MCTQ measures the phase of sleep positions for both free and work days. CSM is similar to MEQ, but is more sensitive to measure shift work. The concept of chronotype has been used to refer to phase positions or phase preferences in the literature reviewed. Most of the time this is a consequence of different interpretations: it is not clear whether phase preferences are a direct manifestation of the individual’s internal clock or a result of external cues, e.g., social interaction (including the alarm clock). Also, phase preferences are not uniform throughout life. Therefore, a single assessment, not taking age into consideration, will not accurately describe the sample. We suggest that MCTQ is the best instrument for investigators dealing with desynchronization and as an instrument for sleep phase. Conversely, if the goal is to assess characteristics that change under specific situations - chronotype -, the MEQ should be used

O estudo das diferenças de tipologia circadiana tem aumentado nos últimos anos. Como resultado, novos instrumentos têm sido desenvolvidos para estimar as preferências interindividuais de fase circadiana, denominada de cronotipo, responsável pela organização temporal do processo de regulação do organismo. O objetivo desta revisão foi avaliar as diferenças dos principais questionários utilizados para avaliar cronotipos: o Questionário de Matutinidade e Vespertinidade (Morningness-Eveningness Questionnaire, MEQ), o Composite Scale of Morningness (CSM) e o Questionário de Cronotipo de Munique (Munich Chronotype Questionnaire, MCTQ). Cada instrumento avalia um aspecto diferente dos cronotipos. Considera-se que o MEQ avalia as preferências de fase do comportamento individual ao longo de um dia de 24 horas, ao passo que o MCTQ mede a posição da fase de sono tanto em dias livres como em dias de trabalho. O CSM é semelhante ao MEQ, mas é mais sensível para ser utilizado em indivíduos que realizam trabalho em turnos. O conceito de cronotipo tem sido utilizado para se referir a posições de fase ou preferências de fase na literatura revisada. Na maioria das vezes, isso é consequência de diferentes interpretações: não está claro se as preferências de fase são uma manifestação direta do relógio interno do indivíduo ou um resultado de sinais externos, como por exemplo, interação social (incluindo o uso de despertador). Além disso, as preferências de fase não são uniformes ao longo da vida. Sendo assim, uma única avaliação, sem levar em consideração a idade do indivíduo nos escores utilizados nessas escalas, não descreverá a amostra com precisão. Sugerimos, através desta revisão, que o MCTQ deve ser considerado como instrumento para investigações que lidam com dessincronização e como instrumento de medida de fase de sono. Por outro lado, se o objetivo é avaliar características que mudam em determinadas situações - cronotipo -, o MEQ deve ser utilizado

Interactions of polymorphisms in different clock genes associated with circadian phenotypes in humans.

Several studies have shown that mutations and polymorphisms in clock genes are associated with abnormal circadian parameters in humans and also with more subtle non-pathological phenotypes like chronotypes. However, there have been conflicting results, and none of these studies analyzed the combined effects of more than one clock gene. Up to date, association studies in humans have focused on the analysis of only one clock gene per study. Since these genes encode proteins that physically interact with each other, combinations of polymorphisms in different clock genes could have a synergistic or an inhibitory effect upon circadian phenotypes. In the present study, we analyzed the combined effects of four polymorphisms in four clock genes (Per2, Per3, Clock and Bmal1) in people with extreme diurnal preferences (morning or evening). We found that a specific combination of polymorphisms in these genes is more frequent in people who have a morning preference for activity and there is a different combination in individuals with an evening preference for activity. Taken together, these results show that it is possible to detect clock gene interactions associated with human circadian phenotypes and bring an innovative idea of building a clock gene variation map that may be applied to human circadian biology.

Interactions of polymorphisms in different clock genes associated with circadian phenotypes in humans

Several studies have shown that mutations and polymorphisms in clock genes are associated with abnormal circadian parameters in humans and also with more subtle non-pathological phenotypes like chronotypes. However, there have been conflicting results, and none of these studies analyzed the combined effects of more than one clock gene. Up to date, association studies in humans have focused on the analysis of only one clock gene per study. Since these genes encode proteins that physically interact with each other, combinations of polymorphisms in different clock genes could have a synergistic or an inhibitory effect upon circadian phenotypes. In the present study, we analyzed the combined effects of four polymorphisms in four clock genes (Per2, Per3, Clock and Bmal1) in people with extreme diurnal preferences (morning or evening). We found that a specific combination of polymorphisms in these genes is more frequent in people who have a morning preference for activity and there is a different combination in individuals with an evening preference for activity. Taken together, these results show that it is possible to detect clock gene interactions associated with human circadian phenotypes and bring an innovative idea of building a clock gene variation map that may be applied to human circadian biology.

Caracterização e distribuição de cronotipos no sul do Brasil: diferenças de gênero e estação de nascimento / Characterization and distribution of chronotypes in southern Brazil: gender and season of birth differences

OBJETIVO: Investigar a tipologia circadiana e as diferenças de gênero em universitários do sul do Brasil. MÉTODOS: Voluntários (736) de 17 a 49 anos preencheram a versão brasileira do Questionário de Cronotipo (QC), tradução do Morningness-eveningness Questionnaire (MEQ) de Horne e Õstberg. Medidas de tendência central e dispersão e curva de distribuição dos escores do QC (Kolmogorov-Smirnov) foram calculadas de acordo com gênero (teste t de Student), idade, estação de nascimento e desconforto com o horário de verão (qui-quadrado). RESULTADOS: Foram incluídos 648 indivíduos (36 por cento homens, 64 por cento mulheres), com perdas de 12 por cento por questionários incorretos. A distribuição dos escores do QC evidenciou uma curva normal (amplitude = 18-77; média = 46,6; desvio-padrão = 10,8). Nesta amostra, 32 por cento foram vespertinos, 54 por cento intermediários e 14 por cento matutinos. As médias do QC foram significativamente diferentes (p = 0,003): homens (44,9 ± 10,8) comparados com mulheres (47,5 ± 10,7) e 70 por cento dos que nasceram na primavera e no verão foram vespertinos (p = 0,015), sem associação gênero-estação do ano. CONCLUSÃO: Homens e nascidos na primavera-verão evidenciaram preferência pela vespertinidade, não havendo diferença de gênero com relação à estação de nascimento. Nossos resultados estão de acordo com estudos realizados no hemisfério norte que mostraram, também, uma associação entre a estação de nascimento e o cronotipo.

OBJECTIVE: To analyze circadian typology (diurnal preference) and gender differences in a university student population from Southern Brazil. METHODS: Seven hundred and thirty six university student volunteers, with an age range 17-49 years, filled the Brazilian version of the Chronotype Questionnaire (CQ), the portuguese translation of the Horne and Õstberg's Morningness-Eveningness Questionnaire (MEQ). Central and dispersion tendencies measures and CQ scores distribution curve (Kolmogorov-Smirnov) were calculated according to gender (Student t), age, birth season, and daylight-saving time discomfort (qui-square). RESULTS: Six hundred and fourty eight individuals (36 percent men; 64 percent women) were included in this study, with 12 percent of losses due to incorrect questionnaires. CQ score distribution was correlated to the normal curve (range=18-77; mean=46.6; s.d.=10.8). In this sample, 32 percent were evening-types; 54 percent were intermediate-types, and 14 percent were morning-types. CQ means were significatively different (p=0.003) when males (44.9±10.8) were compared to females (47.5±10.7), and 70 percent of those born during spring and summer were evening-types (p=0.015).There was no gender-by-season association. CONCLUSIONS: Men, and Individuals born in spring and summer, presented eveningness preference, without gender-birth season interaction. Our results are also in agreement with studies performed in the Northern Hemisphere, which showed an association between birth season and diurnal preference.