Wide awake at bedtime? Effects of caffeine on sleep and circadian timing in male adolescents - A randomized crossover trial

Latent class analysis of the sleep quality of night shift nurses and impact of shift-related factors on the occupational stress and anxiety

AIMS

The objective of this study is to explore the various latent categories within the sleep quality of night shift nurses and to investigate whether shift-related factors predispose nurses to higher levels of occupational stress and anxiety.

DESIGN

This is a cross-sectional study.

METHODS

From November to December 2020, registered nurses from 18 tertiary hospitals and 16 secondary hospitals in Chongqing were selected through convenience sampling for this study. Latent class analysis was used to investigate the sleep quality of nurses working night shifts. Furthermore, univariate analysis and logistic multivariate analysis were utilized to identify the contributing factors to occupational stress and anxiety.

RESULTS

The four latent categories of Pittsburgh Sleep Quality Index for night shift nurses were identified as 'Low Sleep Disorder Group' (56.34%), 'Moderate Sleep Disorder Group' (37.27%), 'High Sleep Disorder Non-Reliant on Sleeping medication Group' (4.89%) and 'High Sleep Disorder Reliant on Sleeping medication Group' (1.50%). The results showed that having a night-shift frequency of 3-4 times per month, night-shift durations of 9-12 h, sleep time delay after night shift (≥2 h), total sleep time after night shift less than 4 h were shift-related factors that increased the levels of occupational stress and anxiety.

CONCLUSION

The sleep quality of night shift nurses demonstrates heterogeneity and can be classified into four latent categories. Higher frequency of night shifts, extended work hours and insufficient rest time are all associated with increased levels of occupational stress and anxiety.

IMPACT

By identifying the four latent categories of sleep quality among night shift nurses, this study sheds light on the relationship between sleep patterns and levels of occupational stress and anxiety. These findings have important implications for healthcare institutions in the management of nurse well-being and work schedules.

PATIENT OR PUBLIC CONTRIBUTION

No patient or public contribution.

Activation of the Hippocampal DRD2 Alleviates Neuroinflammation, Synaptic Plasticity Damage and Cognitive Impairment After Sleep Deprivation

Sleep loss is commonplace nowadays and profoundly impacts cognition. Dopamine receptor D2 (DRD2) makes a specific contribution to cognition, although the precise mechanism underlying how DRD2 affects the cognitive process after sleep deprivation remains unclear. Herein, we observed cognitive impairment and impaired synaptic plasticity, including downregulation of synaptophysin and PSD95, decreased postsynaptic density thickness, neuron complexity, and spine density in chronic sleep restriction (CSR) mice. We also observed downregulated hippocampal DRD2 and Cryab expression in the CSR mice. Meanwhile, NF-κB translocation from the cytoplasm to the nucleus occurred, indicating that neuroinflammation ensued. However, hippocampal delivery of the DRD2 agonist quinpirole effectively rescued these changes. In vitro, quinpirole treatment significantly decreased the release of proinflammatory cytokines in microglial supernatant, indicating a potential anti-neuroinflammatory effect of Drd2/Cryab/NF-κB in CSR mice. Our study provided the evidence that activation of the Drd2 may relieve neuroinflammation and improve sleep deprivation-induced cognitive deficits.

Does the timing of intake matter? Association between caffeine intake and depression: Evidence from the National Health and Nutrition Examination Survey

BACKGROUND

Recent research suggests that caffeine intake is associated with a reduced risk of depression. However, the relationship between caffeine intake during different periods of the day and depression is still unclear.

METHODS

This cross-sectional study analyzed noninstitutionalized adults from the National Health and Nutrition Examination Survey, with a weighted representation of approximately 218 million US adults. Covariate-adjusted sample-weighted regressions were used to examine associations between caffeine intake and depression in different periods.

RESULTS

Caffeine intake during non-early morning periods (outside of 5:00-8:00 AM) is associated with a high prevalence of depression (unadjusted OR: 1.08, 95%CI: 1.05-1.11; adjusted OR: 1.03, 95 % CI: 1.00-1.06). Participants who consumed caffeine in the early morning (5:00-8:00 AM) had a lower prevalence of depression compared to participants who did not consume caffeine in the early morning (unadjusted OR: 0.75, 95%CI: 0.67-0.85; adjusted OR: 0.86, 95 % CI: 0.75-0.99).

LIMITATIONS

Cross-sectional study could not determine the temporal association; patients with depression in this study were not clinically diagnosed with Major Depressive Disorder.

CONCLUSIONS

Among US adults, early morning caffeine consumers had a lower prevalence of depression than non-consumers; caffeine intake during non-early morning periods is associated with a high prevalence of depression. Our results may suggest the importance of caffeine intake time for depression.

Clinical Neurobiology of Sleep and Wakefulness

OBJECTIVE

This article focuses on novel neuronal mechanisms of sleep and wakefulness and relates basic science developments with potential translational implications in circadian neurobiology, pharmacology, behavioral factors, and the recently integrated potential pathways of sleep-related motor inhibition.

LATEST DEVELOPMENTS

During the past decade, remarkable advances in the molecular biology of sleep and wakefulness have taken place, opening a promising path for the understanding of clinical sleep disorders. Newly gained insights include the role of astrocytes in sleep brain homeostasis through the glymphatic system, the promotion of memory consolidation during states of reduced cholinergic activity during slow wave sleep, and the differential functions of melatonin receptors involving regulation of both circadian rhythm and sleep initiation. Ongoing investigations exploring sleep and circadian rhythm disruptions are beginning to unlock pathophysiologic aspects of neurologic, psychiatric, and medical disorders.

ESSENTIAL POINTS

An understanding of sleep and circadian neurobiology provides coherent and biologically credible approaches to treatments, including the identification of potential targets for neuromodulation.

[Sleepiness among adolescents: etiology and multiple consequences]

Over the past century a dramatic decline in sleep duration among adolescents, such as more than one hour of sleep loss per night, has been reported. A debt in sleep duration could lead to sleep deprivation, a major risk factor associated with daytime sleepiness. Sleepiness refers to the inability to maintain an adequate level of alertness during the day which may result in more or less being able to control falling asleep at inappropriate times. This literature review updates on sleepiness regarding its characteristics, etiology and consequences on adolescents. Studies revealed that from 25 % to 78 % of adolescents had reported sleepiness. Its manifestations may include heavy lids, yawns, difficulties to concentrate and emotional irritability. In addition, while it is recommended that adolescents under 18 years-old should sleep from eight to ten hours a night, only 63 % of them actually do so. The etiology of sleep deprivation and sleepiness in this population can be explained by various biological and societal factors. First, the sleep-wake cycle of adolescents shows a biological shift from the beginning of pubertal maturation, described as a perfect storm. It refers to a social jetlag by going to sleep and waking up later and accumulating a sleep debt during weekdays which they try to reimburse during weekends. This phenomenon can be explained by physiological changes such as a slower accumulation of sleep pressure. In addition to this perfect storm, environmental and societal factors contribute to the social jetlag and reduce sleep duration in adolescents. Screen exposure before bedtime can delay sleep and wake onset, which is a risk factor for sleeping debt. Substance use such as caffeine, cigarettes or electronic vaporizer, ADHD or freely available medication, alcohol, cannabis use or drug consumption could further disrupt sleep-wake cycle by stimulating, depressing or otherwise disrupting the central nervous system. Early, before 8:30 am, class start times have been associated with chronic sleep deprivation, higher level of sleepiness and delayed melatonin peak secretion. Adolescents working or doing extracurricular occupations for more than 20hours a week are more at risk for reduced sleep duration and sleepiness. Parental supervision about sleep during the weekdays were associated with more appropriate bedtime. Adolescents from low socio-demographic characteristics and from minority ethnic groups have reported displaying a shorter sleep duration. Finally, sleep disorders of a physiological origin such as narcolepsy, sleep apnea or restless legs syndrome, may explain the sleep deprivation and sleepiness. Sleep deprivation and sleepiness in adolescents have consequences on their health. Cognitive functioning, such as problem solving, attention or memory, as well as school performance, can be compromised by sleep deprivation and sleepiness. At the psychological level, adolescents reporting sleepiness are more prone to display mental health problems: associations were found between sleepiness and subjective perception of depression, anxiety, somatic complaints as well as with antisocial behaviors. Finally, 68 % of 16 year-old adolescents reported they drove a car, and the reported sleepiness could lead to road accidents due to reduced attentional functioning, reaction time and decision-making abilities. In the United-States, from 7 % to 16.5 % of deadly accidents were related to driving while drowsy. Highlighting etiology and problems associated with sleep deprivation and sleepiness in adolescents could guide researchers and clinicians towards the development of possible interventions. Public health measures and knowledge transfer programs regarding modifiable psychosocial and societal factors associated with sleep-wake bioregulation could increase awareness in parents as well as in political and societal decision makers.

Impact of daily caffeine intake and timing on electroencephalogram-measured sleep in adolescents

STUDY OBJECTIVES

Caffeine use is ubiquitous among adolescents and may be harmful to sleep, with downstream implications for health and development. Research has been limited by self-reported and/or aggregated measures of sleep and caffeine collected at a single time point. This study examines bidirectional associations between daily caffeine consumption and electroencephalogram-measured sleep among adolescents and explores whether these relationships depend on timing of caffeine use.

METHODS

Ninety-eight adolescents aged 11-17 (mean =14.38, standard deviation = 1.77; 50% female) participated in 7 consecutive nights of at-home sleep electroencephalography and completed a daily diary querying morning, afternoon, and evening caffeine use. Linear mixed-effects regressions examined relationships between caffeine consumption and total sleep time, sleep-onset latency, sleep efficiency, wake after sleep onset, and time spent in sleep stages. Impact of sleep indices on next-day caffeine use was also examined.

RESULTS

Increased total caffeine consumption was associated was increased sleep-onset latency (β = .13; 95% CI = .06, .21; P < .001) and reduced total sleep time (β = -.17; 95% confidence interval [CI] = -.31, -.02; P = .02), sleep efficiency (β = -1.59; 95% CI = -2.51, -.67; P < .001), and rapid eye movement sleep (β = -.12; 95% CI = -.19, -.05; P < .001). Findings were driven by afternoon and evening caffeine consumption. Reduced sleep efficiency was associated with increased afternoon caffeine intake the following day (β = -.006; 95% CI = -.012, -.001; P = .01).

CONCLUSIONS

Caffeine consumption, especially afternoon and evening use, impacts several aspects of adolescent sleep health. In contrast, most sleep indicators did not affect next-day caffeine use, suggesting multiple drivers of adolescent caffeine consumption. Federal mandates requiring caffeine content labeling and behavioral interventions focused on reducing caffeine intake may support adolescent sleep health.

CITATION

Lunsford-Avery JR, Kollins SH, Kansagra S, Wang KW, Engelhard MM. Impact of daily caffeine intake and timing on electroencephalogram-measured sleep in adolescents. J Clin Sleep Med. 2022;18(3):877-884.

Too Jittery to Sleep? Temporal Associations of Actigraphic Sleep and Caffeine in Adolescents

Caffeine consumption has been linked to poor sleep health in adolescents, but it is unknown whether poor sleep predicts caffeine consumption, and/or whether caffeine consumption predicts poor sleep, particularly when sleep is measured objectively. Data were collected from a micro-longitudinal sub-study of the age 15 wave of the Fragile Families and Child Wellbeing Study (n = 589). Adolescents wore an actigraphy device and completed daily surveys for ~1 week. Daily surveys assessed subjective sleep quality and caffeinated beverage consumption (0 = no caffeine, 1 = any caffeine). Separate mixed models assessed whether actigraphy-measured sleep duration, timing, maintenance efficiency, and subjective quality predicted next-day caffeinated beverage consumption within and between adolescents. Variability (standard deviation) of sleep duration and timing, sleep regularity index, and social jetlag were tested as additional between-person predictors. Lagged models tested whether daily caffeinated beverage consumption predicted sleep that night (n = 458). Adolescents with more variable sleep duration and midpoint had higher average odds of consuming caffeinated beverages compared to others. After adolescents consumed ≥1 caffeinated beverage, they had later sleep onset that night and wake time the next morning than usual versus when they did not consume caffeine. Curbing caffeinated beverage consumption may aid in the maintenance of regular sleep schedules and advance sleep timing in adolescents.

Sleepiness is a signal to go to bed: data and model simulations

Study Objectives

Assess the validity of a subjective measure of sleepiness as an indicator of sleep drive by quantifying associations between intraindividual variation in evening sleepiness and bedtime, sleep duration, and next morning and subsequent evening sleepiness, in young adults.

Methods

Sleep timing and sleepiness were assessed in 19 students in late autumn and late spring on a total of 771 days. Karolinska Sleepiness Scales (KSS) were completed at half-hourly intervals at fixed clock times starting 4 h prior to participants’ habitual bedtime, and in the morning. Associations between sleepiness and sleep timing were evaluated by mixed model and nonparametric approaches and simulated with a mathematical model for the homeostatic and circadian regulation of sleepiness.

Results

Intraindividual variation in evening sleepiness was very large, covering four or five points on the 9-point KSS scale, and was significantly associated with subsequent sleep timing. On average, a one point higher KSS value was followed by 20 min earlier bedtime, which led to 11 min longer sleep, which correlated with lower sleepiness next morning and the following evening. Associations between sleepiness and sleep timing were stronger in early compared to late sleepers. Model simulations indicated that the directions of associations between sleepiness and sleep timing are in accordance with their homeostatic and circadian regulation, even though much of the variance in evening sleepiness and details of its time course remain unexplained by the model.

Conclusion

Subjective sleepiness is a valid indicator of the drive for sleep which, if acted upon, can reduce insufficient sleep.