Ana Adan

Circadian typology: a comprehensive review.

The interest in the systematic study of the circadian typology (CT) is relatively recent and has developed rapidly in the two last decades. All the existing data suggest that this individual difference affects our biological and psychological functioning, not only in health, but also in disease. In the present study, we review the current literature concerning the psychometric properties and validity of CT measures as well as individual, environmental and genetic factors that influence the CT. We present a brief overview of the biological markers that are used to define differences between CT groups (sleep–wake cycle, body temperature, cortisol and melatonin), and we assess the implications for CT and adjustment to shiftwork and jet lag. We also review the differences between CT in terms of cognitive abilities, personality traits and the incidence of psychiatric disorders. When necessary, we have emphasized the methodological limitations that exist today and suggested some future avenues of work in order to overcome these. This is a new field of interest to professionals in many different areas (research, labor, academic and clinical), and this review provides a state of the art discussion to allow professionals to integrate chronobiological aspects of human behavior into their daily practice.

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.

Circadian typology and individual differences. A review

Abstract This paper reviews studies which have dealt with the relationship between morningness-eveningness (circadian typology) and other individual differences such as age, sex, personality dimensions and work schedule of their subjects. It appeared that the changes in the morningness-eveningness preference covaried with the age related changes in the internal body clock. An older age was associated with morningness while younger subjects tended towards eveningness, the critical age for the circadian typology change was 50 years. Sex-related differences are too small to be reflected in the scores on circadian typology questionnaires, although women were ahead of men by 1 hr in their circadian rhythms. The results on work schedule proved its role as a synchronizer modifying the morningness factor. The morningness dimension and extraversion are probably related through the impulsivity subdimension, which is closely associated with brain activation. Further research is needed to clarify the relationship between morningness and other personality dimensions (neuroticism, psychoticism), because the results are inconclusive. The influence of circadian typology on the tolerance to shift work and life habits are also discussed. The results with regard to shift work revealed the importance of morningness in determining human tolerance and health complaints. As regards life habits, there were differences in various aspects related to carcadian typology especially psychoactive substances consumption.

Horne & Östberg morningness-eveningness questionnaire: A reduced scale

Abstract This study presents a reduced scale of Horne & Ostbergs Morningness-Eveningness questionnaire. The information collected from the questionnaire (adapted a nd standardized for the Spanish population), which was administered to a sample of subjects (N=908) with different work schedules and ages, was analysed according to multiple correspondences and cluster. The total scores and the 5 types considered in the Horne & Ostberg questionnaire and the reduced from correlate very closely. The special interest of the reduced questionnaire is twofold. On the one hand, there is its actual make-up: it only contains questions about Morningness, which helps to define this dimension better. On the other hand, it shows how information can be collected more easily for research, especially in the case of using broad samples of subjects. The results obtained from the reduced scale for the variables contemplated in our researches corroborate the primacy of work schedule and age. Extraversion correlates negatively with Morningness scores, while sex and neuroticism show no significant differences.

Transcultural Properties of the Composite Scale of Morningness: The Relevance of the “Morning Affect” Factor

Morningness scales have been translated into several languages, but a lack of normative data and methodological differences make cross‐cultural comparisons difficult. This study examines the psychometric properties and factor structure of the Composite Scale of Morningness (CSM) in samples from five countries: France (n=627), Italy (n=702), Spain (n=391), Thailand (n=503), and Australia (n=654). Strong national differences are identified. A quadratic relationship between age and CSM total score was apparent in the Australian data with a downward trend after age 35 yrs. There was no age effect in any sample in the range from 18 to 29 yrs. Factor analysis identified a three‐factor solution in all groups for both men and women. Tuckers congruence coefficients indicate that: (1) this solution is highly congruent between sexes in each culture, and (2) a morning affect factor is highly congruent between cultures. These results indicate there are national differences in factorial structure and that cut‐off scores used to categorize participants as morning‐ and evening‐types should be established for different cultural and age groups.

Reviewing the Psychometric Properties of Contemporary Circadian Typology Measures

The accurate measurement of circadian typology (CT) is critical because the construct has implications for a number of health disorders. In this review, we focus on the evidence to support the reliability and validity of the more commonly used CT scales: the Morningness-Eveningness Questionnaire (MEQ), reduced Morningness-Eveningness Questionnaire (rMEQ), the Composite Scale of Morningness (CSM), and the Preferences Scale (PS). In addition, we also consider the Munich ChronoType Questionnaire (MCTQ). In terms of reliability, the MEQ, CSM, and PS consistently report high levels of reliability (>0.80), whereas the reliability of the rMEQ is satisfactory. The stability of these scales is sound at follow-up periods up to 13 mos. The MCTQ is not a scale; therefore, its reliability cannot be assessed. Although it is possible to determine the stability of the MCTQ, these data are yet to be reported. Validity must be given equal weight in assessing the measurement properties of CT instruments. Most commonly reported is convergent and construct validity. The MEQ, rMEQ, and CSM are highly correlated and this is to be expected, given that these scales share common items. The level of agreement between the MCTQ and the MEQ is satisfactory, but the correlation between these two constructs decreases in line with the number of “corrections” applied to the MCTQ. The interesting question is whether CT is best represented by a psychological preference for behavior or by using a biomarker such as sleep midpoint. Good-quality subjective and objective data suggest adequate construct validity for each of the CT instruments, but a major limitation of this literature is studies that assess the predictive validity of these instruments. We make a number of recommendations with the aim of advancing science. Future studies need to (1) focus on collecting data from representative samples that consider a number of environmental factors; (2) employ longitudinal designs to allow the predictive validity of CT measures to be assessed and preferably make use of objective data; (3) employ contemporary statistical approaches, including structural equation modeling and item-response models; and (4) provide better information concerning sample selection and a rationale for choosing cutoff points.

Comparing three morningness scales: Age and gender effects, structure and cut-off criteria

OBJECTIVE To add to the validity of the French version of the Composite Scale of Morningness (CSM) by comparing its structure with that of the Morningness-Eveningness Questionnaire (MEQ), the most widely used scale to measure circadian typology. Second, to compare the cut-off criteria used to transform the continuous scores into categorical chronotypes. Third, to further test the effects of age and gender on morningness scores. The rMEQ, a shortened version of the MEQ, is also considered. METHODS Four hundred and fifty-six students served as volunteer subjects and filled the CSM and the MEQ. RESULTS There was no effect of gender, and the CSM and MEQ scores correlated above (+) 0.90 in both genders. Regarding age, morningness was stable before age 35 and increased afterwards. We replicated the three-factor structure of the CSM previously reported in five different cultures. The MEQ is longer and counted a fourth factor while the first three factors were quite identical to those extracted from the CSM. This comparative study emphasizes the recurrent problem of cut-off scores: the available values for both instruments result in a very poor concordance of chronotypes. CONCLUSIONS Belonging to the evening-type is regarded as a risk factor for sleep disorders and its positive predictive value should be correctly assessed. Hence, normative scores standardized in such a way they reflect the effects of age, gender and culture are needed for the total score and the factor scores. To this extent, T-scores (with a mean of 50 and standard deviation of 10) would be suitable, and normative tables for French subjects (N = 1598) are given as supplemental data.

RELATIONSHIP BETWEEN CIRCADIAN TYPOLOGY AND FUNCTIONAL AND DYSFUNCTIONAL IMPULSIVITY

The present study explores the relationships between functional and dysfunctional impulsivity factors, circadian typology, and sex. A sample of 850 university students (396 men) aged between 18 and 33 yrs of age completed the Dickmans Impulsivity Inventory (DII) and reduced morningness–eveningness questionnaire (rMEQ). Factorial analysis showed a dimensional clustering with satisfactory item saturation for both dimensions of impulsivity, especially in men and evening-type. Men presented higher values than women for functional and dysfunctional impulsivity, while morning-type subjects obtained lower scores in dysfunctional impulsivity than the neither- and evening-types. An interactive effect between circadian typology and sex was obtained for dysfunctional impulsivity. Higher scores in men for dysfunctional impulsivity were found in neither- and evening-types, while no significant differences were obtained between men and women in the morning-type group. The morning-type typology can be considered a protective factor for impulse control disorders, especially in men, but further research is needed on the clinical and neurobiological implications of our results. (Author correspondence: aadan@ub.edu).

CIRCADIAN TYPOLOGY AND TEMPERAMENT AND CHARACTER PERSONALITY DIMENSIONS

The purpose of the present study is to explore the relationships between circadian typology and Cloninger’s model of the seven dimensions of personality, taking into account the possible sex interactions. This model considers four temperament dimensions (viz., HA, harm avoidance; NS, novelty seeking; RD, reward dependence; and PS, persistence) and three character dimensions (viz., SD, self-directedness; C, cooperativeness; and ST, self-transcendence). A sample of 862 university students (500 women), between 18 and 30 (21.94 ± 2.64) yrs of age completed the short versions of the Temperament and Character Inventory (TCI-56) and the reduced Morningness-Eveningness Questionnaire (rMEQ). Women showed higher values for HA, RD, and C, while men showed higher values for NS. Evening-type subjects had higher NS but lower HA, PS, and SD scores. Moreover, circadian typology modulated the sex differences in HA and NS, and only evening-type men showed a lower HA score and higher NS score. Circadian typology is related to Cloninger’s model of Temperament and Character personality dimensions. Future studies should further examine possible implications, regarding both the vulnerability of developing psychopathological disorders and the prognosis of response to different treatments. (Author correspondence: aadan@ub.edu)

Influence of Circadian Typology on Drug Consumption, Hazardous Alcohol use, and Hangover Symptoms

Few studies have focused on the influence of circadian typology on drug use, and none has considered the use of illegal drugs and hazardous alcohol consumption. This study analyzes the influence of circadian typology on several types of drug consumption (habitual or sporadic), hangover symptoms (past 12 mos), and, more specifically, hazardous alcohol consumption of young adults. Five hundred seventeen university students (173 males), between 17 and 30 yrs of age, answered the Composite Scale of Morningness (CSM), the Alcohol Use Disorders Identification Test (AUDIT), and a self-referred questionnaire on drug consumption during the previous month and on the prevalence of different hangover symptoms during the previous year. Our results confirm a higher prevalence of consumption of addictive substances, both legal (nicotine and cola drinks) and illegal (cannabis and ecstasy), in evening- compared to morning- and neither-type subjects (p < .001 in all cases). Evening-type subjects also obtained a higher total score on the AUDIT (p < .001) and showed a greater prevalence in the subscales of potential alcohol problems (p < .02), as well as more frequent different hangover symptoms (learning difficulties, thirst, tiredness, headaches, sensorial hypersensitivity, anxiety, and irritability; p < .04 in all cases) compared with morning- and neither-type subjects, except for sensorial hypersensitivity and anxiety, for which the evening-type did not differ from the neither-type. Our results provide substantial evidence that the evening circadian typology is a risk factor for the development of drug consumption and that it should be taken into account both in preventive and treatment approaches. Moreover, the data regarding hazardous alcohol use and hangover symptoms emphasize the need to include circadian typology in future studies on the pattern of heavy episodic drinking. (Author correspondence: gprat@ub.edu)