Associations between chronotype,morbidity and mortality in the UK Biobank cohort

Later chronotype (i.e. evening preference) and later timing of sleep have been associated with greater morbidity, including higher rates of metabolic dysfunction and cardiovascular disease (CVD). However, no one has examined whether chronotype is associated with mortality risk to date. Our objective was to test the hypothesis that being an evening type is associated with increased mortality in a large cohort study, the UK Biobank. Our analysis included 433 268 adults aged 38–73 at the time of enrolment and an average 6.5-year follow-up. The primary exposure was chronotype, as assessed through a single self-reported question-defining participants as definite morning types, moderate morning types, moderate evening types or definite evening types. The primary outcomes were all-cause mortality and mortality due to CVD. Prevalent disease was also compared among the chronotype groups. Analyses were adjusted for age, sex, ethnicity, smoking, body mass index, sleep duration, socioeconomic status and comorbidities. Greater eveningness, particularly being a definite evening type, was significantly associated with a higher prevalence of all comorbidities. Comparing definite evening type to definite morning type, the associations were strongest for psychological disorders (OR 1.94, 95% CI 1.86–2.02, p = < 0.001), followed by diabetes (OR 1.30, 95% CI 1.24–1.36, p = < 0.001), neurological disorders (OR 1.25, 95% CI 1.20–1.30, p = < 0.001), gastrointestinal/abdominal disorders (OR 1.23, 95% CI 1.19–1.27, p = < 0.001) and respiratory disorders (OR 1.22, 95% CI 1.18–1.26, p = < 0.001). The total number of deaths was 10 534, out of which 2127 were due to CVD. Greater eveningness, based on chronotype as an ordinal variable, was associated with a small increased risk of all-cause mortality (HR 1.02, 95% CI 1.004–1.05, p = 0.017) and CVD mortality (HR 1.04, 95% CI 1.00–1.09, p = 0.06). Compared to definite morning types, definite evening types had significantly increased risk of all-cause mortality (HR 1.10, 95% CI 1.02–1.18, p = 0.012). This first report of increased mortality in evening types is consistent with previous reports of increased levels of cardiometabolic risk factors in this group. Mortality risk in evening types may be due to behavioural, psychological and physiological risk factors, many of which may be attributable to chronic misalignment between internal physiological timing and externally imposed timing of work and social activities. These findings suggest the need for researching possible interventions aimed at either modifying circadian rhythms in individuals or at allowing evening types greater working hour flexibility.     

Sleep quality and methylation status of core circadian rhythm genes among nurses and midwives

Poor sleep quality or sleep restriction is associated with sleepiness and concentration problems. Moreover, chronic sleep restriction may affect metabolism, hormone secretion patterns and inflammatory responses. Limited recent reports suggest a potential link between sleep deprivation and epigenetic effects such as changes in DNA methylation profiles. The aim of the present study was to assess the potential association between poor sleep quality or sleep duration and the levels of 5-methylcytosine in the promoter regions of PER1, PER2, PER3, BMAL1, CLOCK, CRY1 CRY2 and NPAS2 genes, taking into account rotating night work and chronotype as potential confounders or modifiers. A cross-sectional study was conducted on 710 nurses and midwives (347 working on rotating nights and 363 working only during the day) aged 40–60 years. Data from in-person interviews about sleep quality, chronotype and potential confounders were used. Sleep quality and chronotype were assessed using Pittsburgh Sleep Quality Questionnaire (PSQI) and Morningness–Eveningness Questionnaire (MEQ), respectively. Morning blood samples were collected. The methylation status of the circadian rhythm genes was determined via quantitative methylation-specific real-time PCR assays (qMSP) reactions using DNA samples derived from leucocytes. The proportional odds regression model was fitted to quantify the relationship between methylation index (MI) as the dependent variable and sleep quality or sleep duration as the explanatory variable. Analyses were carried out for the total population as well as for subgroups of women stratified by the current system of work (rotating night shift/day work) and chronotype (morning type/intermediate type/evening type). A potential modifying effect of the system of work or the chronotype was examined using the likelihood ratio test. No significant findings were observed in the total study population. Subgroup analyses revealed two statistically significant associations between a shorter sleep duration and 1) methylation level in PER2 among day workers, especially those with the morning chronotype (OR = 2.31, 95%CI:1.24–4.33), and 2) methylation level in CRY2 among subjects with the intermediate chronotype, particularly among day workers (OR = 0.52, 95%CI:0.28–0.96). The study results demonstrated a positive association between average sleep duration of less than 6 hours and the methylation level of PER2 among morning chronotype subjects, and an inverse association for CRY2 among intermediate chronotype subjects, but only among day workers. Both the system of work and the chronotype turned out to be important confounders and modifiers in a number of analyses, making it necessary to consider them as potential covariates in future research on sleep deficiency outcomes. Further studies are warranted to explore this under-investigated topic.     

The association between sleep chronotype and obesity among black and white participants of the Bogalusa Heart Study

ABSTRACT

Research indicates that sleep duration and quality are inter-related factors that contribute to obesity, but few studies have focused on sleep chronotype, representing an individual’s circadian proclivity, nor assessed these factors in racially diverse middle-aged samples. We examined the associations between chronotype and obesity among black and white men and women participating in the Bogalusa Heart Study (BHS).

Body mass index (BMI) and sleep data were available for 1,197 middle-aged men and women (mean age 48.2 ± 5.3 years) who participated in the BHS 2013–2016. Based on the reduced Morningness-Eveningness Questionnaire’s cutoff values for chronotypes, we combined ‘definitely morning’ and ‘moderately morning’ types into ‘morning’ type, ‘definitely evening’ and ‘moderately evening’ types into ‘evening’ type and kept those who were “neither” type in a separate group. We used ‘morning’ type as the referent group. Obesity was defined as a BMI ≥ 30. Multivariable logistic regression models were used to examine associations adjusting for sex, age, education, smoking, alcohol use and drug use, depression, shift work, physical activity and sleep duration.

Evening chronotype, reported by 11.1% of participants, was associated with obesity after multi-variable adjustment, including shift work, physical activity and sleep duration (OR 1.67, 95% CI: 1.08–2.56). However, once stratified by race (black/white), this association was found only among white participants (OR = 1.91, 95% CI = 1.12–3.25) after full adjustment.

In our biracial, community-based population, evening chronotype was independently associated with obesity, specifically among white participants. Further research is needed to identify behavioral, endocrine, nutritional and genetic pathways which underlie these associations.     

Chronotype and postmenopausal breast cancer risk among women in the California Teachers Study

ABSTRACT

Chronotype is the behavioral manifestation of an individual’s underlying circadian rhythm, generally characterized by one’s propensity to sleep at a particular time during the 24 hour cycle. Evening chronotypes (“night owls”) generally suffer from worse physical and mental health compared to morning chronotypes (“morning larks”) – for reasons that have yet to be explained. One hypothesis is that evening chronotypes may be more susceptible to circadian disruption, a condition where the coordinated timing of biologic processes breaks down. The role of chronotype as an independent or modifying risk factor for cancer has not been widely explored. The objective of the current study was to evaluate the risk of breast cancer associated with chronotype in a case-control study nested within the California Teachers Study (CTS) cohort. The study population consisted of 39686 post-menopausal CTS participants who provided information on chronotype by completing a questionnaire in 2012–2013. 2719 cases of primary invasive breast cancer diagnosed from 1995/1996 through completion of the chronotype questionnaire were identified by linkage of the CTS to the California Cancer Registry. 36967 CTS participants who had remained cancer-free during this same time period served as controls. Chronotype was ascertained by responses to an abbreviated version of the Horne-Ostberg Morningness-Eveningness Questionnaire (MEQ) and was characterized into five categories: definite morning, more morning than evening, neither morning or evening, more evening than morning, definite evening. Multivariable unconditional logistic regression analyses were performed to estimate the odds ratios (ORs) and 95% confidence intervals (95% CIs) for each of the chronotypes, adjusted for established breast cancer risk factors. Compared to definite morning types, definite evening types had an increased risk of breast cancer with elevated ORs that were statistically significant in both the crude (OR = 1.24, 95% CI: 1.10–1.40) and fully-adjusted models (OR = 1.20, 95% CI: 1.06–1.35). The risk estimates in the fully-adjusted model for all other chronotypes did not significantly differ from one. These results suggest that evening chronotype may be an independent risk factor for breast cancer among a population of women who are not known to have engaged in any substantial night shift work. Further research in other populations of non-shift workers is warranted.     

Chronotype and energy intake timing in relation to changes in anthropometrics: a 7-year follow-up study in adults

Individuals with a later preference for the daily activities (evening types) tend to have unhealthier behaviors, which could increase their risk for obesity when compared those with an earlier preference (morning types). Furthermore, later food intake timing, another behavior more characteristic of evening types, has been associated with obesity. However, chronotype differences in the long-term weight change and the role of chronotype in the association between energy intake timing and obesity risk are not clear. To study this we first examined the independent associations of chronotype and energy intake timing with anthropometric changes and then whether chronotype modified the association between energy intake timing and obesity risk. Our data included 1097 Finns from DILGOM (DIetary Lifestyle and Genetic Determinants of Obesity and Metabolic syndrome) 2007 (baseline) and 2014 (follow-up) and from Findiet 2007. Chronotype was assessed with a shortened version of Horne and Östberg’s morningness–eveningness questionnaire. Energy intake timing (as percentages of the total energy intake in the morning/evening) was assessed with 48-h dietary recalls. Weight, body mass index (BMI), and waist circumference were based on measured and self-reported values. Analysis of co-variance and multivariable logistic regression models were used for statistical analyses. Evening typed women had greater weight gain (+ 2.3 kg vs. + 0.3 kg, P = 0.016) and increase in BMI (0.7 kg/m² vs. ?0.1 kg/m², P = 0.024) than morning typed women. After excluding participants with depression, these associations attenuated to non-significant. Compared to participants whose energy intake was proportionally lowest during evening, those with proportionally highest energy intake during evening were more likely with obesity (BMI≥ 30 kg/m²) after follow-up (OR 1.97, 95% CI 1.21–3.21, Ptrend = 0.042). Participants’ chronotype did not modify this association (Pinteract = 0.95). In conclusion, our findings indicated that evening energy intake may play a role in obesity regardless of the chronotype. Furthermore, evening typed women were more prone to increases in their anthropometrics, which seem to be at least partly explained by depression. Further studies of this topic are warranted.     

Premature birth and circadian preference in young adulthood: evidence from two birth cohorts

A preference for eveningness (being a “night owl”) and preterm birth (<37 weeks of gestation) are associated with similar adversities, such as elevated blood pressure, impaired glucose regulation, poorer physical fitness, and lower mood. Yet, it remains unclear if and how preterm birth is associated with circadian preference. The aim of this study was to assess this association across the whole gestation range, using both objective and subjective measurements of circadian preference.

Circadian preference was measured among 594 young adults (mean age 24.3 years, SD 1.3) from two cohorts: the ESTER study and the Arvo Ylppö Longitudinal Study. We compared 83 participants born early preterm (<34 weeks) and 165 late preterm (34 to <37 weeks) with those born at term (≥37 weeks, n = 346). We also compared very low birth weight (VLBW, <1500 g) participants with term-born controls. We obtained objective sleep data with actigraphs that were worn for a mean period of 6.8 (SD 1.4) nights. Our primary outcome was sleep midpoint during weekdays and weekend. The sleep midpoint is the half-way time between falling asleep and waking up, and it represents sleep timing. We also investigated subjective chronotype with the Morningness–Eveningness Questionnaire (MEQ) in 688 (n = 138/221/329) ESTER participants. The MEQ consists of 19 questions, which estimates the respondent to be of a “morning”, “evening,” or “intermediate” chronotype, based on the Morningness–Eveningness Score (MES). We analyzed the data from the actigraphs and the MES with three linear regression models, and analyzed distribution of the chronotype class with Pearson χ2.

There were no consistent differences across the study groups in sleep midpoint. As compared with those born at term, the mean differences in minutes:seconds and 95% confidence intervals for the sleep midpoint were: early preterm weekdays 11:47 (?8:34 to 32:08), early preterm weekend 4:14 (?19:45 to 28:13), late preterm weekdays ?10:28 (?26:16 to 5:21), and late preterm weekend ?1:29 (?20:36 to 17:37). There was no difference in sleep timing between VLBW-participants and controls either. The distribution of chronotype in the MEQ among all participants was 12.4% morningness, 65.4% intermediate, and 22.2% eveningness. The distribution of the subjective chronotype class did not differ between the three gestational age groups (p = 0.98). The linear regression models did not show any influence of gestational age group or VLBW status on the MES (all p > 0.5).

We found no consistent differences between adults born early or late preterm and those born at term in circadian preference. The earlier circadian preference previously observed in those born smallest is unlikely to extend across the whole range of preterm birth.     

Late chronotype and high social jetlag are associated with burnout in evening-shift workers: Assessment using the Chinese-version MCTQshift

Chronotypes are associated with shift work tolerance and sleep in shift workers, and sleep mediates the impact of shift work on mental health. However, the role of chronotype in the association between shift work and mental health has not been clarified. In this study, we aimed to examine the association between chronotype and burnout in shift workers, using the validated Munich ChronoType Questionnaire for shift workers (MCTQ^shift). A total of 288 shift workers with irregular shift frequencies were recruited and completed the Chinese-version MCTQ^shift and the Morningness–Eveningness Questionnaire (MEQ). Chronotypes were assessed by the calculation of corrected mid-sleep time (MSF_SC) from mid-sleep time on free days (MSF) based on their exact shift schedules. Another 26 evening-shift nurses were monitored with actigraphy for at least two consecutive evening shifts and the following two free days. Burnout was evaluated using the Copenhagen Burnout Inventory. We found that MSF^E_SC, MSF^E and mid-sleep time on workdays (MSW^E) had normal distributions and correlated significantly with MEQ scores (r = ? 0.47, ?0.45 and ?0.47, respectively; all p < 0.001). MSW was more closely correlated with actigraphy-derived mid-sleep time on the free day before workdays than that on workdays (r = 0.61 and 0.48, respectively, p < 0.05). Sleep duration was significantly longer on workdays among evening-shift workers who slept late on workdays than those who slept early (β = 0.59, p < 0.001). After demographic and work characteristics were adjusted for in linear regression models, late chronotype and high social jetlag were associated with burnout scores in evening-shift workers. In conclusion, the Chinese-version MCTQ^shift is a valid tool for chronotype assessment. Interventions to improve sleep in shift workers should be tailored to chronotype due to variations in sleep behavior. Late chronotype may be an inherent feature of mental health problems, because the association with burnout was significant in both day workers in previous studies and shift workers.     

Relevance of chronotype for eating patterns in adolescents

During adolescence, a shift from morningness to eveningness occurs, yet school continues to start early in the morning. Hence, adolescents are at risk for social jetlag, i.e. a discrepancy between biological and social timing. It remains to be determined whether chronotype associates with daily and daytime-specific eating patterns during this potentially critical period. Therefore, the aim of the present study was to investigate whether chronotype is decisive for daily eating patterns [total energy intake (TEI, kcal), total macronutrient intake (% of TEI), eating occasion frequency (n/day), meal frequency (n/day), snack frequency (n/day), duration of nightly fasting], or daytime-specific eating patterns [morning (before 11 am) energy intake (% of TEI), morning macronutrient intake (% of morning energy intake), regular breakfast skipping (no morning energy intake at least on 2 of 3?days, yes/no), evening (after 6 pm) energy intake (% of TEI), evening macronutrient intake (% of evening energy intake), regular dinner skipping (no evening energy intake at least on 2 of 3?days, yes/no)] in German adolescents. Chronotype was assessed by use of the Munich Chronotype Questionnaire and is defined as the midpoint of sleep corrected for sleep-debt accumulated over the workweek (the later the midpoint of sleep, the later the chronotype). A total of 223 participants (10–18?years) provided 346 questionnaires and concurrent 3-day weighed dietary records. Associations between chronotype and eating patterns were analyzed cross-sectionally using multivariable linear and logistic mixed-effects regression models. Adolescents with earlier and later chronotypes did not differ in their daily eating patterns. With respect to daytime-specific eating patterns, 1?h delay in chronotype was associated with 4.0 (95% CI 2.5–6.6) greater odds of regular breakfast skipping (p < 0.0001). In addition, later chronotype was associated with higher evening energy intake (p = 0.0009). In conclusion, our data show that a later chronotype among adolescents is associated with a shift of food consumption toward later times of the day. Hence, adolescents’ eating patterns appear to follow their internal clock rather than socially determined schedules.     

Relationships between chronotype,social jetlag,sleep, obesity and blood pressure in healthy young adults

Sleep disturbances, chronotype and social jetlag (SJL) have been associated with increased risks for major chronic diseases that take decades to develop, such as obesity, metabolic syndrome and cardiovascular disease. Potential relationships between poor sleep, chronotype and SJL as they relate to metabolic risk factors for chronic disease have not been extensively investigated. This prospective study examined chronotype, SJL and poor sleep in relation to both obesity and elevated blood pressure among healthy young adults.

SJL and objective sleep measures (total sleep time, sleep onset latency, wake after sleep onset and sleep efficiency) were derived from personal rest/activity monitoring (armband actigraphy) among 390 healthy adults 21–35 years old. Participants wore the device for 6–10 days at 6-month intervals over a 2-year period (n = 1431 repeated observations). Chronotypes were categorized into morning, intermediate and evening groups using repeated measures latent class analysis. Means of SJL and sleep measures among latent chronotype groups were compared using partial F-tests in generalized linear mixed models. Generalized linear mixed models also were used to generate odds ratios (ORs) with 95% confidence intervals (CIs) examining the relationship between repeated measures of chronotype, SJL, sleep and concurrent anthropometric outcome measures (body mass index, percentage of body fat, waist-to-hip ratio, waist-to-height ratio), systolic blood pressure and diastolic blood pressure.

Sleep latency ≥12 min was associated with increased odds of a high waist-to-height ratio (OR = 1.37; CI: 1.03–1.84). Neither chronotype nor SJL was independently associated with anthropometric outcomes or with blood pressure. Relationships between poor sleep and anthropometric outcomes or blood pressure varied by chronotype. Morning types with total sleep time <6 h, sleep efficiency <85% or wake after sleep onset ≥60 min were more likely to have an increased percentage of body fat, waist-to-hip ratio and waist-to-height ratio relative to those with an intermediate chronotype. Similarly, sleep latency ≥12 min was associated with increased odds of elevated systolic blood pressure (OR = 1.90; CI: 1.15–3.16, p_interaction = 0.02) among morning versus intermediate chronotypes. No relationships between poor sleep and obesity or elevated blood pressure were observed among evening chronotypes.

The results from this study among healthy young adults suggest that poor sleep among morning types may be more strongly associated with obesity and elevated blood pressure relative to those with an intermediate (neutral) chronotype. Sleep-related metabolic alterations among different chronotypes warrant further investigation.     

Sleep quality,chronotype and metabolic syndrome components in bipolar disorders during the remission period: Results from the FACE-BD cohort

Data on sleep or circadian abnormalities and metabolic disturbances in euthymic bipolar disorders are scarce and based on small sample sizes. The aim of this study was to explore the associations between sleep disturbances, chronotype and metabolic components in a large sample of euthymic patients with bipolar disorders (BD). From 2009 to 2015, 752 individuals with bipolar disorders from the FACE-BD cohort were included and assessed for sleep quality, chronotype and metabolic components. The Structured Clinical Interview for DSM-IV Axis I Disorders (SCID) was used to confirm the diagnosis of BD. Subjective sleep quality was measured with the Pittsburgh Sleep Quality Index and chronotype with the Composite Scale of Morningness. Sociodemographic and clinical characteristics, psychotropic treatment, psychiatric comorbidities and blood samples were collected. In our sample, 22.4% of individuals with BD presented with a metabolic syndrome, 53.7% had sleep disturbances, 25.4% were considered as having an evening chronotype and 12.6% as having a morning chronotype. Independently of potential confounders, euthymic patients with sleep disturbances had a higher abdominal circumference, and patients with evening chronotype had a significantly higher level of triglycerides. There was an association between evening chronotype and an increased atherogenic index of plasma (OR = 4.8, 95%CI = 1.6–14.7). Our findings contribute the scant literature on the relationship between sleep quality, chronotype and cardiometabolic components in euthymic individuals with BD and highlight the need to improve quality of sleep and patient education about healthier sleep-hygiene practices.     

Morningness-eveningness scores predict outcomes differentially for depressed patients attending morning vs. afternoon day treatment streams

ABSTRACT

At the Center for Addiction and Mental Health (CAMH) Integrated Day Treatment (IDT) program, each patient attends either a morning stream or an afternoon stream, but not both. We examined whether subjective chronotype, or the time of day an individual prefers to be most active and alert, predicted treatment outcomes differentially in depressed patients attending the morning vs. afternoon IDT streams. The Horne-Östberg Morningness-Eveningness Questionnaire (MEQ) was administered before IDT treatment to 203 consecutive patients experiencing a major depressive episode. Multiple regression was used to predict change in depression and quality of life scores based on treatment stream (morning or afternoon), baseline MEQ scores and the treatment stream by MEQ interaction. The treatment stream by MEQ interaction was a highly significant predictor of both depression and quality of life change scores. Post-hoc analyses based on established MEQ categories revealed that definite evening chronotypes had significantly better responses in the morning stream than did morning chronotypes, and significantly worse responses in the afternoon stream relative to moderate evening or neutral chronotypes. There were insufficient morning chronotypes in the afternoon stream to assess clinical responses for this subgroup. In the morning stream only, there was a significant positive correlation between the change in MEQ scores after four weeks of IDT treatment (i.e. a shift to greater morningness) and the decrease in depression scores (r = .36, p = .003), consistent with a therapeutic phase advance in circadian rhythms. In sum, these preliminary data suggest that definite evening chronotypes may have the greatest relative benefit from attending the morning vs. afternoon IDT stream. As patients currently select which IDT stream they will attend, future work based on randomized treatment assignment and using passive actigraphy to assess circadian phase is currently planned to extend these preliminary findings.     

Association of possible sleep bruxism in children with different chronotype profiles and sleep characteristics

Sleep bruxism (SB) in children has been associated with several sleep characteristics, which may alter their sleep pattern. This change affects the internal biological clock and consequently the chronotype profile. The aim of this study was to evaluate the existence of an association between possible SB in children with specific chronotype profiles and sleep characteristics. The study included 207 parents/guardians of children aged between 3 and 12 years who were waiting for their children’s dental treatment at the Pediatric Dentistry Clinic of the Federal University of Rio de Janeiro, Brazil. A questionnaire on the socio-demographic characteristics of parents and children as well as on the features of the children’s sleep was applied. In addition, the CIRENS scale (Circadian Energy Scale) was completed by the parents to identify the children’s chronotype. A chi-squared test was used to determine the association between possible SB, the chronotype, and sleep characteristics. A multiple logistic regression model was implemented to observe the influence of chronotype, age, and other independent variables on the possible SB. The logistic regression model demonstrated that nocturnal agitation (p = 0.009; OR = 3.42) and nightmares (p = 0.045; OR = 3.24) were associated with possible SB in children. Although no significant association (p = 0 .089) between the chronotype profile and possible SB was observed in the 3 to 5 years age group, a proportional difference was observed between the chronotype categories in this age group—12.5% of children with SB had a morning type, while 26.4% had an intermediate type and 47.8% an evening type compared to those without possible SB. Nocturnal agitation and nightmares were associated with possible SB. In addition, young children with an evening chronotype had a tendency toward possible SB.     

Chronotype and Breast Cancer Risk in a Cohort of US Nurses

The aim of this study was to examine the relation between chronotype and breast cancer risk. We analyzed the association between chronotype (definite morning type, probable morning type, probable evening type, definite evening type, or neither morning nor evening type) and breast cancer risk among 72 517 women in the Nurses’ Health Study II (NHS II). Chronotype was self-reported in 2009, and 1834 breast cancer cases were confirmed among participants between 1989 and 2007; a 2-yr lag period was imposed to account for possible circadian disruptions related to breast cancer diagnosis. Age- and multivariable-adjusted logistic regression was used to estimate odds ratios (ORs) and 95% confidence intervals (CIs). Participants who self-reported as neither morning nor evening type had a 27% increased risk of breast cancer (multivariable-adjusted OR?=?1.27, 95% CI?=?1.04–1.56), compared with definite morning types. None of the other chronotypes were significantly associated with breast cancer risk (multivariable-adjusted OR?=?0.99, 95% CI?=?0.87–1.12 for probable morning versus definite morning types; OR?=?0.96, 95% CI?=?0.84–1.09 for probable evening versus definite morning types; and OR?=?1.15, 95% CI?=?0.98–1.34 for definite evening versus definite morning types). Overall, chronotype was not associated with breast cancer risk in our study. A modestly increased risk among neither morning nor evening types may indicate circadian disruption as a potentially underlying mechanism; however, more studies are needed to confirm our results.     

The influences of sleep duration,chronotype, and nightwork on the ovarian cycle

ABSTRACT

Despite research indicating that sleep disorders influence reproductive health, the effects of sleep on reproductive hormone concentrations are poorly characterized. We prospectively followed 259 regularly menstruating women across one to two menstrual cycles (the BioCycle Study, 2005–2007), measuring fasting serum hormone concentrations up to eight times per cycle. Women provided information about daily sleep in diaries and chronotype and night/shift work on a baseline questionnaire. We evaluated percent differences in mean hormone concentrations, the magnitude of shifts in the timing and amplitude of hormone peaks, and the risk for sporadic anovulation associated with self-reported sleep patterns and night/shift work. We estimated chronotype scores – categorizing women below and above the interquartile range (IQR) as “morning” and “evening” chronotypes, respectively. For every hour increase in daily sleep duration, mean estradiol concentrations increased by 3.9% (95% confidence interval [CI] 2.0, 5.9%) and luteal phase progesterone by 9.4% (CI 4.0, 15.2%). Receiving less than 7 hours of sleep per day was associated with slightly earlier rises in peak levels for several hormones. Women reporting night/shift work (n = 77) had lower testosterone relative to women employed without night/shift work (percent difference: ?9.9%, CI ?18.4, ?0.4%). Women with morning chronotypes (n = 47) had earlier rises in estradiol during their cycles and potentially an earlier rise in luteinizing hormone. Compared to those who had intermediate chronotypes, women with evening chronotypes (n = 42) had a later luteinizing hormone peak of borderline statistical significance. A reduced risk for sporadic anovulation was suggested, but imprecise, for increasing hours of daily sleep leading up to ovulation (risk ratio 0.79, CI 0.59, 1.06), while an imprecise increased risk was observed for women with morning chronotypes (risk ratio 2.50, CI 0.93, 6.77). Sleep-related hormonal changes may not greatly alter ovarian function in healthy women, but have the potential to influence gynecologic health.     

Chronotype and depressive symptoms in students: An investigation of possible mechanisms

ABSTRACT

Individuals with an evening chronotype are at increased risk of experiencing emotional problems, including depressive symptoms. However, the mechanisms underlying these associations remain unclear. The present study aimed to determine whether poor sleep quality, substance use and cognitive emotion regulation difficulties – which have been implicated in the etiology of depression – mediate the relationship between chronotype and depressive symptoms in a student sample, which was assessed cross-sectionally and after 1 year. A total of 742 Dutch students (75% women, mean age 21.4 ± 2.9 years) completed the Quick Inventory of Depressive Symptomatology, the Morningness-Eveningness Questionnaire, the Pittsburgh Sleep Quality Index, a questionnaire assessing alcohol, caffeine, tobacco and cannabis use, the Cognitive Emotion Regulation Questionnaire and the Behavioral Inhibition/Activation Scale. A subsample (n = 115) was assessed 1 year later with the same questionnaires. Cross-sectional analyses showed that evening chronotype was associated with more depressive symptoms, adjusted for age and gender (β = ?0.082, p = 0.028). The relationship between eveningness and depressive symptoms was mediated by sleep quality, alcohol consumption and the cognitive emotion regulation strategies of self-blame and positive reappraisal. In longitudinal analyses, eveningness at baseline predicted more depressive symptoms at follow-up, adjusted for age and gender (β = ?0.29, p = 0.002); after additional adjustment for baseline depressive symptoms, chronotype remained a significant predictor of depressive symptoms at T2 (β = ?0.16, t = ?2.01, p = 0.047). Only poor sleep quality at follow-up was a significant mediator of this relationship. Even though the effect is small in terms of explained variance, eveningness is related to depressive symptoms and this relationship is mediated by poor sleep quality, also in a prospective design. Self-blame and reduced positive reappraisal are correlated with eveningness. Further research is needed to assess the efficacy of chronotherapeutic interventions for the prevention of depression, in addition to sleep education and cognitive approaches.     

The Circadian Energy Scale (CIRENS): Two Simple Questions for a Reliable Chronotype Measurement Based on Energy

This study presents the Circadian Energy Scale (CIRENS), a very short and simple chronotype measurement tool based on energy. The CIRENS consists of two introspective questions about the usual energy level (very low, low, moderate, high, or very high, scored 1 to 5) in the morning and in the evening. The difference between energy level scores (?4 to 4) felt by respondents in the evening and morning defines the chronotype score and classification. A concurrent validity analysis of the CIRENS with the widely used Horne and Östberg Morningness-Eveningness Questionnaire (MEQ) was conducted using a sample of 225 college students, and with MSFsc, a sleep-based chronotype assessment tool based on the Munich Chronotype Questionnaire (MCTQ), using a sample of 34,530 subjects (18–83 yrs, 27% males). This large sample was collected in a Web survey for behavioral correlates of the CIRENS with variables previously associated with chronotype differences. The correlation of the CIRENS chronotype score was r?=??.70 with the MEQ and r?=?.32 with the MSFsc. CIRENS chronotype scores declined with age and were not affected by sex. Both CIRENS and MSFsc chronotype scores were related to differences in tobacco, caffeine, and cola soft-drink consumption (all higher in evening types). The CIRENS provides a simple chronotype index and a measure of absolute energy throughout the day and seems to be a reliable chronotype assessment tool that may be useful both clinically and for large-scale studies. (Author correspondence: diogorlara@gmail.com)     

The association between chronotype and perceived academic stress to depression in medical students

Depression is a multifactorial illness that is highly prevalent among medical students (MS). Chronotypes, which reflect circadian preference in humans, as well as academic stress have been associated with depression in different populations. However, it is not known how chronotype and stress might alone or in combination, associate with depression in MS. Thus, we aimed to evaluate the association between stress, chronotype and depression in MS. In a cross-sectional study, we evaluated a total of 1068 medical students from a public Medical School in Mexico City. The Patient Health Questionnaire-9 (PHQ-9) was used to evaluate depressive symptom severity and the presence of a current depressive episode with a cutoff score of 10 or higher. The Morning-Evening Questionnaire (MEQ) was used to establish chronotype and the Academic Stress Inventory was used to measure perceived academic stress (PAS). We observed that depressive symptom severity was higher in non-morning chronotypes and moderate/severe PAS groups. A factorial ANOVA showed an association between PAS groups and depressive symptom severity. Linear regression showed an association between depressive symptom severity and variables such as PAS scores (p = 0.001), family history of depression (p = 0.001), gender (p = 0.001) and academic year (p = 0.029). Logistic regression analysis showed that evening chronotype (OR: 2.3, 95% CI: 1.2–4.3, p = 0.01) and severe PAS (OR: 4.4, 95% CI: 2.8–7.0, p = 0.0001) were associated with depression. Further, MS with the combination of severe PAS and morning (OR: 5.9, 95% CI: 1.6–22.2, p = 0.01), intermediate (OR: 7.5, 95% CI: 2.3–24.4, p = 0.001) or evening (OR: 10.6, 95% CI: 2.8–40.0, p = 0.001) chronotypes showed a greater association with depression than any PAS or chronotype group alone. Being female, perceiving restricted or limited economic resources, having severe scores of academic stress, and evening chronotype were associated with an increased probability to suffer a current depressive episode. Collectively, these results show that chronotype and PAS are factors associated with depression in MS, and when combined promote this association. Our results might aid in early identification of MS susceptible to depression. Future research could focus on the implementation of simple, low cost preventive strategies, such as chronotype-oriented academic schedules.     

Associations of common noncommunicable medical conditions and chronic diseases with chronotype in a population-based health examination study

Chronotype is an emerging predictor of health and longevity, and understanding its influence on chronic diseases is important for constructing conceptual models of long-term pathways to health. We assessed the associations of chronotype with health status in the general Finnish adult population. Our population-based data were derived from the National FINRISK 2012 study and consisted of 4414 participants, aged 25–74?years, living in Finland. As part of their health examination, participants were asked about their circadian preference to the daily activities (morningness–eveningness) and a diagnosis or treatment for a set of common noncommunicable medical conditions and chronic diseases during the past 12?months. We found that there were 1935 (43.8%) morning types (MTs) and 595 (13.5%) evening types (ETs) and that 1884 (42.7%) were intermediates. As compared with the MTs, the ETs had significantly greater odds for depression (OR = 2.44, 95% CI = 1.52–3.90, p < 0.001) and other mental disorders (OR = 5.18, 95% CI = 2.32–11.52, p < 0.001). The odds were also increased for gallstones, and chronic obstructive pulmonary disease, but these did not remain significant after controlling for multiple testing. Responses to the single-item subjective estimation on the chronotype yielded the association of the definitely evening type of persons with the diagnosis or treatment of cardiac insufficiency (OR = 1.99, 95% CI = 1.02–3.88, p = 0.044) that was corroborated as the greater the eveningness score was, the more common the diagnosis or treatment of cardiac insufficiency was (β = 0.92, 95% CI = 0.85–0.98, p = 0.013). This exploratory study adds further support to the role of evening chronotype in chronic disease risk, albeit underlying mechanisms remain to be elucidated.     

Convergent and construct validity and test–retest reliability of the Caen Chronotype Questionnaire in six languages

ABSTRACT

Chronotype questionnaires provide a simple and time-effective approach to assessing individual differences in circadian variations. Chronotype questionnaires traditionally focused on one dimension of chronotype, namely its orientation along a continuum of morningness and eveningness. The Caen Chronotype Questionnaire (CCQ) was developed to assess an additional dimension of chronotype that captures the extent to which individual functioning varies during the day (amplitude). The aim of this study was to provide a multilanguage validation of the CCQ in six world regions (Arabic, Dutch, German, Italian, Portuguese and Spanish). At Time 1, a total of 2788 participants agreed to take part in the study (Arabic, n = 731; Dutch, n = 538; German, n = 329; Italian, n = 473; Portuguese, n = 361; Spanish, n = 356). Participants completed an assessment of the CCQ together with the Morningness-Eveningness Questionnaire (MEQ; Horne & Ostberg 1976) as well as questions related to factors theoretically related to chronotype (age, shift work, physical activity, sleep parameters and coffee consumption). One month later, participants again completed the CCQ. Results showed that the two-factor structure (morningness-eveningness and amplitude) of the CCQ could be replicated in all six languages. However, measurement invariance could not be assumed regarding the factor loadings across languages, meaning that items loaded more on their factors in some translations than in others. Test–retest reliability of the CCQ ranged from unacceptable (German version) to excellent (Dutch, Portuguese). Convergent validity was established through small–medium effect size correlations between the morningness-eveningness dimension of the CCQ and the MEQ. Taken together, our findings generally support the use of the translated versions of the CCQ. Further validation work on the CCQ is required including convergent validation against physiological markers of sleep, health and well-being.     

The relationship between chronotype,sleep disturbance,severity of fibromyalgia,and quality of life in patients with fibromyalgia

ABSTRACT

Patients with fibromyalgia (FM) report high levels of sleep disturbance and chronic diffuse musculoskeletal pain. These patients experience diminished quality of life (QoL) due to pain and other comorbidities. Chronotype preferences have been suggested as a potential factor connecting increased severity of FM, sleep disturbances, and poor overall QoL. The present study is the first study examining the possible association between chronotype preferences, sleep disturbance, severity of FM, and QoL in patients with FM.

One hundred drug-free patients diagnosed with FM participated in this cross-sectional study. Of them, 79 (79%) were females and 21 (21%) were males. The mean age was 41.65 ± 9.17 years (range: 21–62 years). The severity of FM symptoms, chronotype preferences, and QoL was evaluated using the Fibromyalgia Impact Questionnaire (FIQ), Morningness-Eveningness Questionnaire (MEQ), and World Health Organization Questionnaire on Quality of Life: Short Form (WHOQOL-BREF). The participants’ anxiety/depressive symptoms and sleep problems were assessed using the Hospital Anxiety and Depression Scale (HADS) and Pittsburgh Sleep Quality Index (PSQI).

The participants were classified according to their MEQ scores as evening type (score: 16–41), neither type (score: 42–58), and morning type (score: 59–86). It was found that there were significant differences in the FIQ score between the three groups (p < .001). It was determined that the total PSQI score was significantly higher in the evening type than the other two types (p < .05). It was found that there were significant differences in the general health, physical health, psychological, and environmental domain scores of the WHOQOL-BREF between the three groups (p < .05). It was detected that there were significant correlations between MEQ scores, WHOQOL-BREF subscale scores, FIQ scores, HADS-A and HADS-D scores, and PSQI scores. According to hierarchical regression analysis, eveningness preference explained an additional 21.9% of the variation in FM severity, thereby causing a statistically significant change in R-squared.

Our results indicated that eveningness preference was directly related to increased FM symptom severity and poorer QoL. Based on these findings, neglecting to take chronotype preference into account may not result in optimal response to standard treatment for some patients with FM.