A single dose of alcohol does not meaningfully alter circadian phase advances and phase delays to light in humans

Sleep-Related Predictors of Risk for Alcohol Use and Related Problems in Adolescents and Young Adults

PURPOSE

Growing evidence supports sleep and circadian rhythms as influencing alcohol use and the course of alcohol use disorder (AUD). Studying sleep/circadian-alcohol associations during adolescence and young adulthood may be valuable for identifying sleep/circadian-related approaches to preventing and/or treating AUD. This paper reviews current evidence for prospective associations between sleep/circadian factors and alcohol involvement during adolescence and young adulthood with an emphasis on the effects of sleep/circadian factors on alcohol use.

SEARCH METHODS

The authors conducted a literature search in PsycInfo, PubMed, and Web of Science using the search terms "sleep" and "alcohol" paired with "adolescent" or "adolescence" or "young adult" or "emerging adult," focusing on the title/abstract fields, and restricting to English-language articles. Next, the search was narrowed to articles with a prospective/longitudinal or experimental design, a sleep-related measure as a predictor, an alcohol-related measure as an outcome, and confirming a primarily adolescent and/or young adult sample. This step was completed by a joint review of candidate article abstracts by two of the authors.

SEARCH RESULTS

The initial search resulted in 720 articles. After review of the abstracts, the list was narrowed to 27 articles reporting on observational longitudinal studies and three articles reporting on intervention trials. Noted for potential inclusion were 35 additional articles that reported on studies with alcohol-related predictors and sleep-related outcomes, and/or reported on candidate moderators or mediators of sleep-alcohol associations. Additional articles were identified via review of relevant article reference lists and prior exposure based on the authors' previous work in this area.

DISCUSSION AND CONCLUSIONS

Overall, the review supports a range of sleep/circadian characteristics during adolescence and young adulthood predicting the development of alcohol use and/or alcohol-related problems. Although sleep treatment studies in adolescents and young adults engaging in regular and/or heavy drinking show that sleep can be improved in those individuals, as well as potentially reducing alcohol craving and alcohol-related consequences, no studies in any age group have yet demonstrated that improving sleep reduces drinking behavior. Notable limitations include relatively few longitudinal studies and only two experimental studies, insufficient consideration of different assessment timescales (e.g., day-to-day vs. years), insufficient consideration of the multidimensional nature of sleep, a paucity of objective measures of sleep and circadian rhythms, and insufficient consideration of how demographic variables may influence sleep/circadian-alcohol associations. Examining such moderators, particularly those related to minoritized identities, as well as further investigation of putative mechanistic pathways linking sleep/circadian characteristics to alcohol outcomes, are important next steps.

Sleep and circadian differences between light and heavy adult alcohol drinkers

Background

Numerous studies have reported that eveningness is associated with increased alcohol consumption. However, biological markers of circadian timing, such as dim light melatonin onset (DLMO) and circadian photoreceptor responsivity (post‐illumination pupil response, PIPR), have rarely been assessed in the context of habitual alcohol consumption. This study aimed to examine sleep, circadian timing, and photoreceptor responsivity in adult alcohol drinkers.

Methods

Participants (21 to 45 years) included 28 light and 50 heavy drinkers. The 8‐day study consisted of a week of adlib sleep monitored with wrist actigraphy, followed by a 9‐h laboratory session with a photoreceptor responsivity and circadian phase assessment.

Results

The heavy drinkers obtained on average 28 more minutes of sleep (p = 0.002) and reported more eveningness than the light drinkers (p = 0.029). There was a trend for a shorter DLMO‐midsleep interval (p = 0.059) in the heavy drinkers, reflecting a tendency for them to sleep at an earlier circadian phase. The PIPR in the heavy drinkers was significantly smaller than in the light drinkers (p = 0.032), suggesting reduced circadian photoreceptor responsivity in the heavy drinkers. A larger PIPR was significantly associated with a later DLMO in the light drinkers (r = 0.44, p = 0.019), but this relationship was absent in the heavy drinkers (r = −0.01, p = 0.94).

Conclusions

These results are consistent with earlier reports of more eveningness and a shorter DLMO‐midsleep interval being associated with heavier alcohol drinking. The novel finding of reduced circadian photoreceptor responsivity in heavy drinkers is consistent with prior rodent studies. Future studies should explore the impact of habitual alcohol consumption on other measures of circadian photoreceptor responsivity.

Circadian regulation of breath alcohol concentration

STUDY OBJECTIVES

The role of the circadian clock in regulating blood/breath alcohol levels after consuming alcohol is uncertain. Our goal was to evaluate the degree to which the circadian system regulates breath alcohol concentration (BrAC) pharmacokinetic parameters.

METHODS

Twenty healthy adults aged 21-30 years took part in a 4-day laboratory study. A 40-h constant routine procedure was used to assess circadian rhythms. Every 4 h, participants were given a fixed oral dose of alcohol with breathalyzer measurements taken every 5 min to construct BrAC curves. Sinusoidal models were used to test for circadian variation of the peak BrAC, the time to reach peak BrAC, the absorption rate, the elimination rate, and the time for BrAC to return to zero after alcohol was ingested.

RESULTS

A significant circadian rhythm was detected for group-averaged peak BrAC values and the time for BrAC to return to zero, but not other BrAC variables. Peak BrAC values were lowest in the evening near the peak of the core body temperature rhythm and nadir of the salivary cortisol rhythm. Peak BrAC values increased during the night and reached their highest levels in the morning and afternoon. The time needed for BrAC to return to zero was also longest in the late morning and afternoon.

CONCLUSION

The circadian system modulates some BrAC pharmacokinetic parameters. In normally entrained individuals, taking the same oral dose of alcohol at different times of day can result in different BrAC responses. These findings have potential implications for alcohol-related accidents and alcohol toxicity.

Disrupted diurnal oscillation of gut-derived Short chain fatty acids in shift workers drinking alcohol: Possible mechanism for loss of resiliency of intestinal barrier in disrupted circadian host

Microbiota derived short chain fatty acids (SCFAs) are produced by fermentation of nondigestible fiber, and are a key component in intestinal barrier homeostasis. Since the microbiome has diurnal fluctuations, we hypothesized that SCFAs in humans have a diurnal rhythm and their rhythmicity would be impacted by the host central circadian misalignment (night shift work) which would make intestinal barrier more susceptible to disruption by alcohol. To test this hypothesis, we studied 3 groups of subjects: patients with alcohol use disorder, but no liver disease (AD), healthy day workers (DW), and night workers (NW). All subjects were studied at baseline and then in DW and NW subjects after moderate daily alcohol (0.5 g/kg) for 7 days. Gut-derived plasma SCFAs showed a significant circadian oscillation by cosinor analysis in DW; however, SCFA in the AD and NW subjects lost 24-hour rhythmicity. Decrease in SCFA correlated with increased colonic permeability. Both chronic and moderate alcohol consumption for 1 week caused circadian disruption based on wrist actigraphy and urinary melatonin. Our study shows that (1) gut-derived plasma SCFAs have a diurnal rhythm in humans that is impacted by the central clock of the host; (2) moderate alcohol suppresses SCFAs which was associated with increased colonic permeability; and (3) less invasive urinary 6-SM correlated and rest-activity actigraphy correlated with plasma melatonin. Future studies are needed to examine the role circadian misalignment on gut derived SCFAs as possible mechanism for loss of intestinal barrier resiliency to injurious agents like alcohol.

Sleep and circadian risk factors for alcohol problems: a brief overview and proposed mechanisms

Disturbances in sleep and circadian rhythms may be important, albeit underappreciated, risk factors for the initiation of alcohol use and the escalation of alcohol problems. In this review, we first describe sleep and circadian changes during adolescence and young adulthood. Second, we explain how these sleep/circadian changes intersect with onset and escalation of alcohol use. Third, we briefly note how alcohol use (whether acute or chronic) affects sleep and circadian rhythms. Finally, we articulate a conceptual model containing two mechanistic pathways-broadly positive and negative reinforcement-linking sleep/circadian factors to alcohol involvement before listing key areas we believe are ripe for further inquiry.

Circadian misalignment and weekend alcohol use in late adolescent drinkers: preliminary evidence

Alcohol use accelerates during late adolescence, predicting the development of alcohol use disorders (AUDs) and other negative outcomes. Identifying modifiable risk factors for alcohol use during this time could lead to novel prevention approaches. Burgeoning evidence suggests that sleep and circadian factors are cross-sectionally and longitudinally linked to alcohol use and problems, but more proximal relationships have been understudied. Circadian misalignment, in particular, is hypothesized to increase the risk for AUDs, but almost no published studies have included a biological measure of misalignment. In the present study, we aimed to extend existing research by assessing the relationship between adolescent circadian misalignment and alcohol use on a proximal timeframe (over two weeks) and by including three complementary measures of circadian alignment. We studied 36 healthy late (18-22 years old, 22 females) alcohol drinkers (reporting ≥1, standard drink per week over the past 30 days) over 14 days. Throughout the study, participants reported prior day's alcohol use and prior night's sleep each morning via smartphone and a secure, browser-based interface. Circadian phase was assessed via the dim light melatonin onset (DLMO) in the laboratory on two occasions (Thursday and Sunday nights) in counterbalanced order. The three measures of circadian alignment included DLMO-midsleep interval, "classic" social jet lag (weekday-weekend difference in midsleep), and "objective" social jet lag (weekday-weekend difference in DLMO). Multivariate imputation by chained equations was used to impute missing data, and Poisson regression models were used to assess associations between circadian alignment variables and weekend alcohol use. Covariates included sex, age, Thursday alcohol use, and Thursday sleep characteristics. As predicted, greater misalignment was associated with greater weekend alcohol use for two of the three alignment measures (shorter DLMO-midsleep intervals and larger weekday-weekend differences in midsleep), while larger weekday-weekend differences in DLMO were associated with less alcohol use. Notably, in contrast to expectations, the distribution of weekday-weekend differences in DLMO was nearly equally distributed between individuals advancing over the weekend and those delaying over the weekend. This unexpected finding plausibly reflects the fact that college students are not subject to the same systematically earlier weekday schedules observed in high school students and working adults. These preliminary findings support the need for larger, more definitive studies investigating the proximal relationships between circadian alignment and alcohol use among late adolescents.

Purinergic Signaling in Neuron-Astrocyte Interactions, Circadian Rhythms, and Alcohol Use Disorder

Alcohol use disorder (AUD) is a debilitating condition marked by cyclic patterns of craving, use, and withdrawal. These pathological behaviors are mediated by multiple neurotransmitter systems utilizing glutamate, GABA, dopamine, ATP, and adenosine. In particular, purines such as ATP and adenosine have been demonstrated to alter the phase and function of the circadian clock and are reciprocally regulated by the clock itself. Importantly, chronic ethanol intake has been demonstrated to disrupt the molecular circadian clock and is associated with altered circadian patterns of activity and sleep. Moreover, ethanol has been demonstrated to disrupt purinergic signaling, while dysfunction of the purinergic system has been implicated in conditions of drug abuse such as AUD. In this review, we summarize our current knowledge regarding circadian disruption by ethanol, focusing on the reciprocal relationship that exists between oscillatory neurotransmission and the molecular circadian clock. In particular, we offer detailed explanations and hypotheses regarding the concerted regulation of purinergic signaling and circadian oscillations by neurons and astrocytes, and review the diverse mechanisms by which purinergic dysfuction may contribute to circadian disruption or alcohol abuse. Finally, we describe the mechanisms by which ethanol may disrupt or hijack endogenous circadian rhythms to induce the maladaptive behavioral patterns associated with AUD.

Drosophila: An Emergent Model for Delineating Interactions between the Circadian Clock and Drugs of Abuse

Endogenous circadian oscillators orchestrate rhythms at the cellular, physiological, and behavioral levels across species to coordinate activity, for example, sleep/wake cycles, metabolism, and learning and memory, with predictable environmental cycles. The 21st century has seen a dramatic rise in the incidence of circadian and sleep disorders with globalization, technological advances, and the use of personal electronics. The circadian clock modulates alcohol- and drug-induced behaviors with circadian misalignment contributing to increased substance use and abuse. Invertebrate models, such as Drosophila melanogaster, have proven invaluable for the identification of genetic and molecular mechanisms underlying highly conserved processes including the circadian clock, drug tolerance, and reward systems. In this review, we highlight the contributions of Drosophila as a model system for understanding the bidirectional interactions between the circadian system and the drugs of abuse, alcohol and cocaine, and illustrate the highly conserved nature of these interactions between Drosophila and mammalian systems. Research in Drosophila provides mechanistic insights into the corresponding behaviors in higher organisms and can be used as a guide for targeted inquiries in mammals.

Circadian-Based Therapies for Circadian Rhythm Sleep-Wake Disorders

This review summarizes recent developments relevant to the treatment of circadian rhythm sleep-wake disorders. The clinical practice guidelines for the treatment of intrinsic circadian rhythm sleep-wake disorders is described, followed by recent treatment studies for delayed sleep-wake phase disorder, non-24 hour sleep-wake disorder, irregular sleep-wake disorder and shift work. New methods to estimate circadian phase, including home saliva collection to estimate the dim light melatonin onset, circadian questionnaires and general rules to guide light and exogenous melatonin treatments are described. New developments in light treatment are detailed, including light flashes during sleep and wearable light devices. Substances such as caffeine and alcohol, and devices such as electronic tablets are also considered for their potential to shift circadian timing. Finally, an update on melatonin supplements in the US is discussed, along with the controversy surrounding the use of melatonin supplements in patients with prediabetes or diabetes.

Night workers with circadian misalignment are susceptible to alcohol-induced intestinal hyperpermeability with social drinking

Alcohol-induced intestinal hyperpermeability (AIHP) is a known risk factor for alcoholic liver disease (ALD), but only 20-30% of heavy alcoholics develop AIHP and ALD. The hypothesis of this study is that circadian misalignment would promote AIHP. We studied two groups of healthy subjects on a stable work schedule for 3 mo [day workers (DW) and night workers (NW)]. Subjects underwent two circadian phase assessments with sugar challenge to access intestinal permeability between which they drank 0.5 g/kg alcohol daily for 7 days. Sleep architecture by actigraphy did not differ at baseline or after alcohol between either group. After alcohol, the dim light melatonin onset (DLMO) in the DW group did not change significantly, but in the NW group there was a significant 2-h phase delay. Both the NW and DW groups had no change in small bowel permeability with alcohol, but only in the NW group was there an increase in colonic and whole gut permeability. A lower area under the curve of melatonin inversely correlated with increased colonic permeability. Alcohol also altered peripheral clock gene amplitude of peripheral blood mononuclear cells in CLOCK, BMAL, PER1, CRY1, and CRY2 in both groups, and inflammatory markers lipopolysaccharide-binding protein, LPS, and IL-6 had an elevated mesor at baseline in NW vs. DW and became arrhythmic with alcohol consumption. Together, our data suggest that central circadian misalignment is a previously unappreciated risk factor for AIHP and that night workers may be at increased risk for developing liver injury with alcohol consumption.