Extreme Morning Research Articles

EVENING PREFERENCE IS RELATED TO THE INCIDENCE OF DEPRESSIVE STATES INDEPENDENT OF SLEEP-WAKE CONDITIONS

Although evening preference has recently been identified as a risk factor for depression, it has not been substantiated whether evening preference is a direct risk factor for depressive states, or if it is associated secondarily through other factors, such as delayed sleep timing and shortened sleep duration. The objective of this study is to investigate associations in Japanese adult subjects between evening preference and incidence of depressive states, adjusting for various sleep parameters related to depressive states. The Morningness-Eveningness Questionnaire (MEQ), the Pittsburgh Sleep Quality Index (PSQI), and the Center for Epidemiologic Studies Depression Scale (CES-D) were administered to 1170 individuals (493 males/677 females; mean and range 38.5 and 20–59 yrs) to assess their diurnal preferences, sleeping states, and presence of depression symptoms. Subjects were classified into five chronotypes based on MEQ scores. Evening preference was associated with delayed sleep timing, shortened sleep duration, deteriorated subjective sleep quality, and worsened daytime sleepiness. Logistic regression analysis demonstrated that the extreme evening type (odds ratio [OR] = 1.926, p = .018) was associated with increased incidence of depressive states and that the extreme morning type (OR = 0.342, p = .038) was associated with the decreased incidence of depressive states, independent of sleep parameters, such as nocturnal awakening (OR = 1.844, p < .001), subjective sleep quality (OR = 2.471, p < .001), and daytime sleepiness (OR = 1.895, p = .001). However, no significant associations were observed between the incidence of depressive states and sleep duration, sleep timing, and sleep debt (levels of insufficient sleep). Although the findings of this study do not demonstrate a causative relationship between evening preference and depression, they do suggest the presence of functional associations between mood adjustment and biological clock systems that regulate diurnal preference. They also suggest that evening preference might increase susceptibility to the induction of mood disorders. (Author correspondence: mishima@ncnp.go.jp)

Association between CLOCK 3111T/C and preferred circadian phase in Korean patients with bipolar disorder

Genes associated with circadian rhythms have been suggested to play an important role in the pathophysiology of bipolar disorder. A single nucleotide polymorphism (SNP) in the 3′-flanking region of CLOCK (3111T/C; rs1801260) has been reported to be associated with sleep disturbances and an increased recurrence rate in patients with bipolar disorder. We examined the association of CLOCK 3111T/C with bipolar disorder in 260 patients and 350 controls in a Korean population. CLOCK 3111T/C showed significant allelic and genotypic associations with bipolar disorder ( P = 0.012, P = 0.033, respectively). Morningness/eveningness (M/E) was evaluated using the Composite Scale of Morningness (CSM) in 108 patients with bipolar disorder. In the subgroup analysis of the highest and lowest 25th percentile of M/E scores, significantly more C allele carriers were found among extreme evening types than among extreme morning types ( P = 0.041). After correcting for age, C allele carriers had lower M/E scores than those carrying the T/T genotype, but the association was not statistically significant. We also analyzed the association between age at onset (AAO) and CLOCK 3111T/C in the bipolar disorder group, and no association was found. Despite the relatively small sample sizes, these results support a possible role of the CLOCK 3111T/C SNP in bipolar disorder. Further studies with larger samples and more polymorphisms are necessary.

Daily light exposure profiles in older non‐resident extreme morning and evening types

Differences in daily light exposure profiles have been reported, with younger M-types shown to spend more time in bright light, especially in the morning, compared with E-types. This study aimed to investigate how patterns of daily light exposure in older non-resident M-types and E-types compare. Sleep diaries were kept during actigraphic measurement of activity and light using the Actiwatch-L for 14 days in 12 M-types [eight females, mean +/- standard deviation (SD) Horne-Ostberg Morning-Eveningness Questionnaire (HO MEQ) score 75.2 +/- 1.6] and 11 E-types (seven females, HO MEQ 41.5 +/- 4.8), over 60 years old, living in their own homes. Light data were log-transformed, averaged over each hour, and group x time analysis of covariance (ancova) performed with age as a covariate. M-types had significantly earlier bed and wake time than E-types, but there was no significant difference in sleep duration, sleep efficiency or time spent in bed between groups. Daily exposure to light intensity greater than 1000 lux was compared between the two groups, with no significant difference in the duration of exposure to >1000 lux between M-types and E-types. Twenty-four-hour patterns of light exposure show that M-types were exposed to higher light intensity at 06:00 h than E-types. Conversely, E-types were exposed to higher light intensity between 22:00 and 23:00 h than M-types. These findings show that differences in daily light exposure patterns found previously in younger M-types and E-types are also found in older M-types and E-types, but at an earlier clock-time, confirming the tendency to advance with ageing.

Effects of night shifts in bipolar disorders and extreme morningness

Night work and shift work scenarios are increasing in modern society. Instability in the sleep-wake rhythm is an important risk factor for triggering episodes of bipolar disorder. Extreme chronotype has negative effects on shift work ("shift-worker syndrome"). Effects of night or shift work on patients with bipolar disorder and extreme chronotype are not well understood. A patient with bipolar II disorder and extreme morning type followed a stable work schedule for a significant period of time, maintaining a stable mood. After changing to a night-shift schedule, depressive symptoms developed. When the night-shift schedule was stopped, her mental state normalised. This case highlights the possibility of a sensitizing role of chronotype in triggering episodes of bipolar disorder after the sleep-wake rhythm has been disrupted by night work or shift work. The evaluation of a person's capability to perform night work or shift work should take into account psychiatric disorders and chronotype as well as physical conditions.

Staggered School Hours to Spread Peak Demand for Public Transport. Benefits and Costs

The author uses a case study of student transportation by public bus in Linkoping, Sweden, to discuss the possibility of public transportation peak demand spread through staggered school hours. The study found that introducing a staggered morning start for Linkoping's high schools can substantially reduce extreme morning peak at only one departure point on Linkoping's many lines. It demonstrated that bus service cost savings from the leveling out of the extreme morning peak could be of the same magnitude as costs for students resulting from a change in school hours. Staggered school hours could introduce other changes that could benefit the bus transportation system while reducing student costs. Cooperation between the public transportation authority and the high school headmasters is the biggest challenge.

Diurnal Variation in Energetic Arousal, Tense Arousal, and Hedonic Tone in Extreme Morning and Evening Types

The aim of the present study was to examine levels of energetic arousal (EA), tense arousal (TA), and hedonic tone (HT) in individuals with different circadian preferences. Subjects were males with extreme either morning (M‐type) or evening (E‐type) preferences (N=31), selected using the Morningness‐Eveningness Questionnaire cutoff points derived from the Polish population norms. They completed the UWIST Mood Adjective Check List every 1.5 h between 08:00 to 20:00 h in laboratory conditions. The obtained data showed higher levels of TA and lower levels of HT in E‐types over the whole day as compared to M‐types. As for EA, M‐types showed higher levels than E‐types between 08:00 to 17:00 h, but the two groups showed no differences during the later hours of the day. Both groups were found to exhibit similar diurnal patterns in TA and HT, and dissimilarity between M‐types and E‐types appeared in the daily course of EA. The results show the three‐dimensional model of mood is more advantageous in M‐types than in E‐types during the hours of typical human activity.

A silent polymorphism in the PER1 gene associates with extreme diurnal preference in humans

The three PERIOD proteins form a major negative feedback component of the molecular mechanism governing the periodicity of the vertebrate circadian clock. Genetic variations within the human PER2 and PER3 genes have been linked with diurnal preference and disorders of sleep timing. We screened the coding region of PER1, as well as the 5'- and 3'-untranslated regions and the promoter region, for polymorphisms. The T2434C polymorphism in exon 18, a synonymous substitution, associated with extreme diurnal preference. The C allele was more frequent in subjects with extreme morning preference (frequency=0.24) than in subjects with extreme evening preference (frequency=0.12). No significant association was observed between either allele and delayed sleep phase syndrome. This polymorphism may have a direct effect on RNA translatability, or be in linkage disequilibrium with another polymorphism which affects PER1 expression at the DNA, RNA, or protein level. This is the first reported association between a PER1 polymorphism and extreme diurnal preference. Functionally important polymorphisms in PER1 are rare, which may indicate that it is subject to more stringent selection pressure than the other PER genes.

A single‐nucleotide polymorphism in the 5′‐untranslated region of the hPER2 gene is associated with diurnal preference

The PERIOD2 (PER2) gene is a key component of the molecular mechanism that generates circadian rhythms in mammals. A missense mutation in the human PER2 gene has previously been linked to advanced sleep phase syndrome (ASPS). We have investigated three other single-nucleotide polymorphisms in the hPER2 gene, one downstream of the transcription start site (C-1228T), one in exon 2 in the 5'-untranslated region (5'-UTR) (C111G), and one missense mutation (G3853A) causing a glycine to glutamine substitution in the predicted protein. Subjects selected from a group of 484 volunteers for extreme morning or evening preference, or intermediate diurnal preference were genotyped with regard to the three polymorphisms (n=35 for each group). Whereas allele frequencies for the other two polymorphisms did not differ significantly between any of the groups, the 111G allele frequency was significantly higher in subjects with extreme morning preference (0.14) than in subjects with extreme evening preference (0.03) (Fisher's exact test, two-sided P value=0.031, odds ratio=5.67). No significant difference in 111G allele frequency was observed between either of these groups and subjects with intermediate diurnal preference. Computer prediction indicated that the C111G polymorphism, which occurs 12 bases upstream from the translation start codon, might alter the secondary structure of the transcript. The PER2 111G allele associates with morning preference and is a potential candidate allele for ASPS.

Evaluating two morningness scales with item response theory

Using a student sample ( n=692) and an organization sample ( n=180), we scrutinized two morning–evening orientation scales using item response theory (IRT) methods. We used IRT to compare the measurement precision of the Composite Scale (CS) and the Early/Late Preferences Scale (PS). The CS had slightly higher measurement precision at all ranges of orientations, except for extreme morning and evening orientations for which the PS had slightly higher precision. IRT item-level statistics were also computed to try to understand how morning-orientation items functioned. Items that asked questions about morning activities tended to be more discriminating indicators of morning-orientation than items that asked about evening or peak performance activities. Items that involved unpleasant activities were less frequently endorsed than items that involved neutral or enjoyable activities. Implications for measurement of morning–evening orientation are discussed.

Researchers Identify Best Times For Effective Light Therapy

Researchers Identify Best Times For Effective Light Therapy

Psychometric comparison of two circadian rhythm questionnaires and their relationship with personality

Two questionnaires for the measurement of individual differences in circadian phase position (morningness-eveningness) were psychometrically evaluated and compared: the widely used Morningness-Eveningness Questionnaire (MEQ) by Horne and Östberg ( International Journal of Chronobiology, 4, 97–110, 1976) and the Marburger questionnaire by Moog ( Night and shift work: biological and social aspects. Oxford: Pergamon Press, 1981). Further instruments given to the sample (113 undergraduate students) were the EPI and a 2-week sleep/waking diary. In addition, two groups of extreme morning and evening types measured their own oral temperature throughout several days. Both circadian rhythm questionnaires proved reliable and valid (with respect to sleep/waking behaviour and oral temperature), although some deficiences were found for the MEQ with regard to its multidimensionality, skewness of distributions and a negative correlation with neuroticism. In line with previous research, a weak negative relationship of morningness-eveningness with extraversion was observed for both questionnaires. Impulsivity, rather than sociability, seemed to be the component responsible for this association. Effects of sex and age were only partially in line with previous findings.

Circadian rhythms of food intake and oral temperature in "morning" and "evening" groups of individuals.

The most marked ‘ morning ’ and ‘evening ’ types in a psychology class were identified by means of a questionnaire, and asked to record their oral temperatures and food intakes throughout the day during a 4-week and a 4-day period respectively. The morning group had its mean circadian temperature maximum 5 h earlier than the evening group, and had its cumulative food intake distribution curve 1¾ h ahead of the evening group. After adjusting the food distributions by 1¾ h in the time base to get a least-square fit, significant differences between the distributions remained. It is suggested that morning types have a more autonomous 24-hour-periodicity than evening types. It is concluded that the questionnaires have the power to discriminate extreme morning and evening types of individuals in terms of oral temperature and food intake. Food intake seems to be a sensitive enough measure to be included in studies of inter-individual differences of circadian rhythms.