Evening Preference Research Articles

Children's time of day preference: age, gender and ethnic differences

Comprehensive data for children's time of day preference were collected with school children from 8 through 16 years of age ( n=989) using the Children's Morningness–Eveningness Preferences (CMEP) scale. Strong evidence was found that children's optimal time of day preference shifts toward evening at about 13 years of age. Additionally, gender and ethnic differences in time of day preference were also examined. There was no gender difference, but there was a tendency for ethnic differences among older children. An implication of these findings is that a mismatch between older children's time of time preferences and school start time may have a negative effect on their school performance and this effect could be greater for some ethnic groups than for others.

GENDER DIFFERENCES IN MORNINGNESS–EVENINGNESS PREFERENCE

Morningness–eveningness preference (morning-, intermediate-, evening-type) or circadian typology is the individual difference that most clearly explains the variations in the rhythmic expression of biological or behavioral patterns. The aim of this study was to analyze gender difference in morningness–eveningness preference using the Horne and Östberg questionnaire in the largest university student population selected so far (N=2135), with an age range 18–30 yr. Morningness–eveningness questionnaire (MEQ) score distribution closely correlated to the normal curve (range=17–78, mean=48.25; SD=10.11), with 338 (15.84%) morning-types, 1273 (59.62%) intermediate-types, and 524 (24.54%) evening-types. The men and women differed significantly in their mean scores (p<0.0001) and distribution per circadian typology (p<0.00001), with the men presenting a more pronounced eveningness preference. Three factors were identified by factor analysis: time of greatest efficiency (I), sleep time/sleep phase (II), awakening time/sleep inertia (III). The MEQ items sensitive to gender differences were essentially those included in factor I and factor II. The results are discussed in relation to recent models of circadian regulation of the sleep–wake cycle.

Is self-reported morbidity related to the circadian clock?

Morningness and eveningness preference, an endogenous component of the circadian clock, is characterized by an interindividual difference in circadian phase and requires of humans a specific timing of behavior. The biological rhythms of morning and evening types are consequently phase shifted with fixed socioeconomic constraints. The impact of this phase shift on health is widely debated. The purpose of the authors' study was to determine the influence of morningness/eveningness preference on self-reported morbidity and health in an active population. A total of 1165 nonshift workers of the French national electrical and gas company, enrolled in the GAZEL cohort and aged 51.3+/-3.3 years, were included in this study. They replied by mail with a completed questionnaire, including morningness/eveningness preference, self-reported morbidity, subjective sleep patterns, and daytime somnolence and sleeping schedules for 3 weeks, during the spring of 1997. Annual self-reported health impairments were assessed with the annual general questionnaire of the GAZEL cohort for 1997. After adjustment for age, sex, and occupational status, morningness-like and eveningness-like participants reported a specific worse self-reported morbidity. Whereas morningness was associated with worse sleep (p = 0.0001), eveningness was associated with feeling less energetic (p = 0.04) and physical mobility (p = 0.02). These relationships were observed even in good sleepers, except for physical mobility. After adjustment for confounding variables, eveningness-like participants reported more sleep (p = 0.0004) and mood (p = 0.00018) disorders than morningness-like participants. Morningness/eveningness preference was related to specific chronic complaints of insomnia: morningness was related with difficulty in maintaining sleep (p = 0.0005) and the impossibility to return to sleep in the early morning (p = 0.0001) (sleep phase-advance syndrome); eveningness was related to difficulty in initiating sleep (p = 0.0001) and morning sleepiness (p = 0.0001). In good sleepers, morningness was related with sleep phase-advance syndrome (p = 0.0001) and eveningness with morning sleepiness (p = 0.0001). In conclusion, the expression (phase advance or delay) of the circadian clock could be related to worse self-reported morbidity and health. These findings must be verified by further epidemiological studies, but they suggest that the impossibility to return to sleep in the early morning is not only associated with age.

PARENTAL ENFORCEMENT OF BEDTIME DURING CHILDHOOD MODULATES PREFERENCE OF JAPANESE JUNIOR HIGH SCHOOL STUDENTS FOR EVENINGNESS CHRONOTYPE

We examined the effect of home bedtime discipline during childhood on morningness and eveningness (M-E) preference by Japanese junior high school students. M-E was assessed by the M-E Questionnaire (MEQ) of Torsvall and Åkerstedt (the higher the score, the greater the preference for morningness), and parental determination of bedtime during childhood was ascertained using an original questionnaire. The average M-E score of adolescents living in urban Kochi City (mean ± SD; 15.10 ± 3.42) was significantly lower (P <. 01) than the score of those in suburban districts (16.14 ± 3.44). Overall, 43.1% of the junior high school students in Kochi City compared to 53.0% of the students living in suburban districts had their bedtime decided during childhood by parents (P <. 01). In Kochi City, the M-E score for boys (14.62 ± 3.51) was lower (P <. 01) than girls (15.53 ± 3.28). During childhood, parents decided the bedtime for 49% of the girls compared to 36.6% of the boys (P <. 01). Boys whose bedtime was not decided by parents during childhood had a somewhat stronger preference for eveningness (14.20 ± 3.53) (P <. 05) compared to those whose bedtime was decided by parents (15.12 ± 3.36). The results suggest bedtime discipline at home during childhood has an effect on adolescent chronotype, modulating the extent of shift to eveningness in Japanese junior high school boys in particular. (Chronobiology International, 18(5), 823–829, 2001)

A PEDIGREE OF ONE FAMILY WITH DELAYED SLEEP PHASE SYNDROME

The prevalence of delayed sleep phase syndrome (DSPS) has been estimated to be quite low. Although no genetic inheritance pattern has been described, it has been reported that close to 50% of DSPS patients have biological relatives with similar symptoms. A pedigree of one extended family with symptoms suggestive of DSPS has been identified. Morningnesseveningness questionnaires were administered to all first- and second-degree relatives of a proband identified with DSPS. A total of 51 (86%) questionnaires were returned, and 6 adult biological relatives of 27 (22%) showed a preference for eveningness, which is much higher than reported in the general population. Both the paternal and maternal branches contained affected individuals, suggesting the possibility of a bilineal mode of inheritance. While the trait did not obey simple Mendelian inheritance, the vertical patterns of transmission were consistent with either an autosomal dominant mode of inheritance with incomplete penetrance or a multifactorial mode of inheritance. These data provide some preliminary support to the notion that eveningness, and thus DSPS, may have a genetic component. The prevalence of symptoms suggestive of DSPS is higher in this family than reported in the general population. Case reports such as this support the utility of larger, more systematic studies. It is unclear whether this degree of familiarity is representative of that in the general population. (Chronobiology International, 18(5), 831–840, 2001)

Emergency medicine residents' shiftwork tolerance and preference.

To determine the shift lengths currently worked by emergency medicine (EM) residents and their shift length preferences, and to determine factors associated with EM residents' subjective tolerance of shiftwork. A survey was sent to EM-2 through EM-4 allopathic EM residents in May 1996. This questionnaire assessed the residents' shift length worked, shift length preferences, night shift schedules, and self-reported ability to overcome drowsiness, sleep flexibility, and morningness-eveningness tendencies. When providing shift length preferences, the residents were asked to assume a constant total number of hours scheduled per month. Seventy-eight programs participated, and 62% of 1,554 eligible residents returned usable surveys. Current shift lengths worked were 8 hours (12%), 10 hours (13%), 12 hours (37%), combinations of 8-hour, 10-hour, or 12-hour (34%) shifts, and other combinations (4%). Seventy-three percent of the respondents indicated that they preferred to work 8-hour or 10-hour shifts, and only 21% preferred a 12-hour shift. Shiftwork tolerance was recorded as: not well at all (2%), not very well (14%), fairly well (70%), and very well (14%). The EM residents' eveningness preference, ability to overcome drowsiness, sleep flexibility, younger age, and having no children at home were all associated with greater shiftwork tolerance. Emergency medicine residents generally tolerate shiftwork well and prefer 8-hour or 10-hour shift lengths compared with 12-hour shift lengths. Emergency medicine residencies with 12-hour shifts should consider changing residents' shifts to shorter shifts.

Influence of morningness-eveningness preference in the relationship between body temperature and performance: A diurnal study

The present paper is a study of the evolution of body temperature and performance during the walking part of the day and the relationship between these two variables in respect of Morningness- Eveningness preferences. On the basis of the scores obtained from the Horne and Östberg questionnaire, adapted and standardized for the Spanish population, three groups, each containing 8 subjects, were formed (Morning-types, Neither-types, Evening-types). Extraversion and sex were seen to be highly-influential, decisive factors. Two different tasks were tested: visual reaction time and verbal memory, and the correlation between the two was calculated. Each of the subjects was tested in six sessions spread out over the day. Our results show that Neither-type subjects are the least dispersed among the parameters studied, but they did not give intermediate values between extreme groups. The reaction time task reveals a certain correlation with temperature changes in Evening-types only. Monitoring of the memory task shows fluctuations unrelated to changes in temperature, and no characteristic group pattern appears from preference for a certain time of day. The correlation between the two tasks was not significant for any of the groups of subjects involved in the experiment.