Stability of genetic influence on morningness–eveningness: A cross-sectional examination of South Korean twins from preadolescence to young adulthood

Medical Research Center, Seoul National University, Seoul, South Korea.
Journal of Sleep Research (Impact Factor: 3.35). 04/2007; 16(1):17-23. DOI: 10.1111/j.1365-2869.2007.00562.x
Source: PubMed


A cross-sectional twin design was used to study the developmental nature of genetic and environmental influences on morningness-eveningness (M-E). A total of 977 South Korean twin pairs aged 9-23 years completed 13 items of a Korean version of the Composite Scale through the telephone interview. The total sample was split into three age groups: preadolescents, adolescents, and young adults. Twin correlations did not vary significantly with age, suggesting that genetic influences on M-E are stable throughout the developmental span. Results of model-fitting analyses indicated that genetic and environmental factors explained, respectively, 45% and 55% of the variance in all three age groups. Environmental factors were primarily those factors that twins did not share as a consequence of their common rearing; family environmental factors in M-E were consistently near zero in all three age groups. The present study is the first to demonstrate genetic influences on M-E in preadolescent children as young as 9 years old. In spite of differences in culture and frequencies of genes between South Koreans and Caucasians, genetic and environmental influences on M-E found in the present sample were remarkably similar to those reported by previous studies on the basis of late adolescent and adult Caucasian twins.

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    • "The categorization of morning and evening types is typically achieved from self-report questionnaires: One of the most commonly used questionnaire for assessing M–E is the morningness scale developed by Smith, Reilly, and Midkiff (1989). Research has shown that the variance in M–E is accounted for about 50% percent by genetic factors (see, Hur, 2007), however other factors such as age (Randler, 2008a), gender (Adan & Natale, 2002), social (e.g., work schedules, life habits etc. . .), and environmental (climate, light, temperature or geographical latitude) play a significant role (for a review, see Adan et al., 2012; Cavallera & Giudici, 2008). "
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    Personality and Individual Differences 04/2015; 76. DOI:10.1016/j.paid.2014.12.020 · 1.95 Impact Factor
    • "The psychometric properties of the CSM [68] used in adolescent samples are sound. Most of the studies employing German samples reported Cronbach's alpha values > than 0.80 [53,56,57,59, 66,67,80–82], while four studies on South Korean, Turkish, German and Spanish adolescents [22] [33] [47] [61] showed values ranging between 0.61 and 0.78. We could not assess test-retest reliability through correlation analyses since these studies did not meet our inclusion criteria (see Table 1 and Supplementary Table 3). "
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    ABSTRACT: Purpose: To review the psychometric properties of the questionnaires commonly filled in by children and adolescents to measure circadian preference. Methods: We examined the Morningness-Eveningness Questionnaire for Children and Adolescents (MEQ-CA), the Morningness-Eveningness Scale for Children (MESC) and the Composite Scale of Morningness (CSM). We critically analyzed the reliability, in term of internal consistency (through the Cronbach’s alpha) and test-retest reliability (through the correlation coefficient), and the type of validation against external criteria (objective assessment of the sleep/wake cycle, body temperature, hormones and other questionnaires). Fifty studies that reported these data were included in the review: 7 studies used the MEQ-CA, 28 used the MESC and 15 used the CSM. Results: The percentage of studies reporting at least acceptable levels of internal consistency was high and similar between the three questionnaires. Evidence for test-retest reliability was scant, since only 3 studies were available; it was at least acceptable for the MESC (two studies with a time interval of 1 month), not acceptable for the MEQ-CA (one study with a time interval of 6 months), while no information was available for the CSM. As regards the validation evidence, the MEQ-CA has been validated by the highest number of external criteria (actigraphy, oral body temperature and other questionnaires), followed by the CSM (cortisol sampling and other questionnaires). The MESC has been validated only against self-report measures. Conclusions: The present state of the art would suggest the use of the MEQ-CA to assess circadian preference in children and adolescents.
    European Psychiatry 02/2015; DOI:10.1016/j.eurpsy.2015.01.006 · 3.44 Impact Factor
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    • "Individuals can be classified as morning, evening or neither, although criteria to classify children are lacking. Half the variance in circadian preferences is genetically determined [99] and the trait remains considerably stable during human development despite the marked shifts towards eveningness in adolescents [49]. Behavioural, emotional (including suicidality and drug abuse) and academic problems are worse in adolescents with evening types compared to morning or intermediate types [100e103]. "
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    ABSTRACT: The main aim of this paper is to consider relevant theoretical and empirical factors defining optimal sleep, and assess the relative importance of each in developing a working definition for, or guidelines about, optimal sleep, particularly in children. We consider whether optimal sleep is an issue of sleep quantity or of sleep quality. Sleep quantity is discussed in terms of duration, timing, variability and dose-response relationships. Sleep quality is explored in relation to continuity, sleepiness, sleep architecture and daytime behaviour. Potential limitations of sleep research in children are discussed, specifically the loss of research precision inherent in sleep deprivation protocols involving children. We discuss which outcomes are the most important to measure. We consider the notion that insufficient sleep may be a totally subjective finding, is impacted by the age of the reporter, driven by socio-cultural patterns and sleep-wake habits, and that, in some individuals, the driver for insufficient sleep can be viewed in terms of a cost-benefit relationship, curtailing sleep in order to perform better while awake. We conclude that defining optimal sleep is complex. The only method of capturing this elusive concept may be by somnotypology, taking into account duration, quality, age, gender, race, culture, the task at hand, and an individual’s position in both sleep–alert and morningness–eveningness continuums. At the experimental level, a unified approach by researchers to establish standardized protocols to evaluate optimal sleep across paediatric age groups is required.
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