Comparison of sleep timing of people with different chronotypes affected by modern lifestyle

Circadian rhythm is an endogenous rhythmic behavior of organisms which can be entrained by daily light–dark cycles.The timing of human sleep-cycle is regulated by endogenous circadian rhythm and homeostatic processes. Light exposure affects both sleep timing and circadian rhythm. Now humans can extend lighting time by turning on artificial lights and wake up time is usually triggered by alarm clocks to meet social schedules. This modern lifestyle is believed to be related with a temporal mismatch between sleep and circadian rhythmicity(social jet-lag) and insufficient sleep, which lead to ill mental and physical health outcomes. At present, the impacts of self-selection of light exposure and social constrains on sleep timing is far from clear. According to preferred sleep-wake schedule, there are three different chronotypes. In this paper, we apply a mathematical model to get a quantitative comparison of sleep timing of people with different chronotypes with the effects of modern light consumption and social constrains. The results show that the prolonged day light and evening light exposure both delay preferred sleep timing with the sleep duration almost unchanged. People of evening-type or with longer intrinsic periods are most expected to be vulnerable to evening light. Increasing light exposure can offset the effect of evening light to some extent, but it is most difficult for evening-type people. Social constrains cause the largest social jet-lag in people of evening-type, which increases with evening light intensity or intrinsic periods. Morning-type people's sleep symptoms worsens, while that of evening-type people improves with age. This study provides a theoretical reference for preventing and treating sleep disorder and social jet-lag for individuals with different chronotypes.

Chronotype and self-reported sleep,alertness,and mental health in U.S. sailors

Service members are at risk for sleep and psychological conditions affecting their readiness. Chronotype(“morningness”or “eveningness”) is strongly associated with sleep, health and performance. The objective of this study was to examine associations between validated measures of chronotype and sleep quality, daytime functioning, alertness,and symptoms of depression, anxiety, and post-traumatic stress disorder(PTSD) in US service members(n=298).Although predominantly young males(who skew toward eveningness in civilian populations), these Sailors skewed toward morningness(35.6% morning, 51.3% intermediate). Eveningness was associated with symptoms of depression and PTSD(P<0.01), less time in bed(P<0.05), more sleep disruption(P<0.01), and poorer daytime functioning and alertness(P<0.05). Evening types were less likely to consider sleep important for performance(P<0.05). To maximize service member readiness, schedules should be aligned with endogenous rhythms, whenever possible, and evening chronotypes may benefit from targeted interventions. Chronotype should be examined alongside health and readiness in service members.

Predictive Factors for Smartphone Dependence: Relationship to Demographic Characteristics, Chronotype, and Depressive State of University Students

We investigated factors contributing to smartphone dependence. To 196 medical university students, we administered a set of self-reporting questionnaires designed to evaluate demographic characteristics, smartphone dependence, chronotype, and depressive state. Smartphone dependence was evaluated using the Wakayama Smartphone-Dependence Scale (WSDS) with 3 subscales: Subscale 1, immersion in Internet communication;Subscale 2, using a smartphone for extended periods of time and neglecting social obligations and other tasks;Subscale 3, using a smartphone while doing something else and neglect of etiquette. Multiple regression analyses revealed that living in a family, eveningness, and presence of depression were associated with Subscale 1, that living in a family and eveningness were also associated with Subscale 2, and that being a man was associated with Subscale 3. These findings suggest that smartphone dependence can be predicted by factors such as gender, mode of residence, chronotype, or depressive state.

Chronotypes and affective disorders:A clock for mood?

Affective disorders are often accompanied by circadian rhythm disruption and the major symptoms of mental illness occur in a rhythmic manner.Chronotype,also known as circadian preference for rest or activity,is believed to exert a substantial influence on mental health.Here,we review the connection between chronotypes and affective disorders,and discuss the potential underlying mechanisms between these two phenomena.

Chronotype distribution in the Chinese population

Purpose:Individual chronotypes are reported to be closely associated with mood,health status,and even disease progression.However,no reports of chronotype distribution in the Chinese population have been made available to date.Methods:We performed a chronotype survey using the classic Morningness–Eveningness Questionnaire both online and offline.The webpage-based online survey was distributed via a social network application on mobile phones.The offline survey was distributed to local primary and middle schools.A total of 9476 questionnaires were collected,of which 8395 were valid.The mean age of the participants was 30.38±11.47 years,and 37.38%were male.Results:Overall,the Chinese chronotypes showed a near-normal distribution with a slight shift toward eveningness.When analyzed in different age groups,the overall Chinese population was shown to be"latest"in their early twenties.In the young population,two significant points of change in chronotype were identified at the ages of 10 and 16 years.The chronotype composition remained relatively stable during early adulthood(from 17 to 28 years of age).Conclusion:This study generated the first overview of chronotype distribution in the Chinese population and will serve as essential background data for future studies.

Sleep, circadian dysrhythmia, obesity and diabetes

Synchrony of biological processes with environmental cues developed over millennia to match growth, reproduction and senescence. This entails a complex interplay of genetic, metabolic, chemical, light, hormonal andhedonistic factors across life forms. Sleep is one of the most prominent rhythms where such a match is established. Over the past 100 years or so, it has been possible to disturb the synchrony between sleep-wake cycle and environmental cues. Development of electric lights, shift work and continual accessibility of the internet has disrupted this match. As a result, many noncommunicable diseases such as obesity, insulin resistance, type 2 diabetes, coronary artery disease and malignancies have been attributed in part to such disruption. In this presentation a review is made of the origin and evolution of sleep studies, the pathogenic mediators for such asynchrony, clinical evidence and relevance and suggested management options to deal with the disturbances.

Genetically predicted insomnia causally increases the risk of erectile dysfunction

Sleep has attracted extensive attention due to its significance in health.However,its association with erectile dysfunction(ED)is insufficiently investigated.To investigate the potential causal links between sleep traits(insomnia,sleep duration,and chronotype)and ED,this study was performed.The single-nucleotide polymorphisms(SNPs)associated with insomnia,sleep duration,and chronotype were retrieved from previous genome-wide association studies(GWAS).A conventional two-sample Mendelian randomization(MR)was used to estimate the causal links between sleep traits and ED.The summary statistics of ED were from individuals of European ancestry(6175 cases vs 217630 controls).As shown by the random effect inverse-variance-weighting(IVW)estimator,genetically predicted insomnia was causally associated with a 1.15-fold risk of ED(95%confidence interval:1.07-1.23,P<0.001).Sleep duration and morningness were not causally associated with ED,as indicated by the IVW(all P>0.05).These findings were consistent with the results of sensitivity analyses.Based on genetic data,this study provides causal evidence that genetically predicted insomnia increases the risk of ED,whereas sleep duration and chronotype do not.