Dose-dependent pharmacokinetics and psychomotor effects of caffeine in humans

Acute effects of caffeine on threat-selective attention: moderation by anxiety and EEG theta/beta ratio

BACKGROUND

Spontaneous EEG theta/beta ratio (TBR) probably marks prefrontal cortical (PFC) executive control, and its regulation of attentional threat-bias. Caffeine at moderate doses may strengthen executive control through increased PFC catecholamine action, dependent on basal PFC function.

GOAL

To test if caffeine affects threat-bias, moderated by baseline frontal TBR and trait-anxiety.

METHODS

A pictorial emotional Stroop task was used to assess threat-bias in forty female participants in a cross-over, double-blind study after placebo and 200 mg caffeine.

RESULTS

At baseline and after placebo, comparable relations were observed for negative pictures: high TBR was related to low threat-bias in low trait-anxious people. Caffeine had opposite effects on threat-bias in low trait-anxious people with low and high TBR.

CONCLUSIONS

This further supports TBR as a marker of executive control and highlights the importance of taking baseline executive function into consideration when studying effects of caffeine on executive functions.

Pharmacological potential of methylxanthines: Retrospective analysis and future expectations

Methylated xanthines (methylxanthines) are available from a significant number of different botanical species. They are ordinarily included in daily diet, in many extremely common beverages and foods. Caffeine, theophylline and theobromine are the main methylxanthines available from natural sources. The supposedly relatively low toxicity of methylxanthines, combined with the many beneficial effects that have been attributed to these compounds through time, generated a justified attention and a very prolific ground for dedicated scientific reports. Methylxanthines have been widely used as therapeutical tools, in an intriguing range of medicinal scopes. In fact, methylxanthines have been/were medically used as Central Nervous System stimulants, bronchodilators, coronary dilators, diuretics and anti-cancer adjuvant treatments. Other than these applications, methylxanthines have also been hinted to hold other beneficial health effects, namely regarding neurodegenerative diseases, cardioprotection, diabetes and fertility. However, it seems now consensual that toxicity concerns related to methylxanthine consumption and/or therapeutic use should not be dismissed. Taking all the knowledge and expectations on the potential of methylxanthines into account, we propose a systematic look at the past and future of methylxanthine pharmacologic applications, discussing all the promise and anticipating possible constraints. Anyways, methylxanthines will still substantiate considerable meaningful research and discussion for years to come.

Reasons for Energy Drink Use and Reported Adverse Effects Among Adolescent Emergency Department Patients

OBJECTIVES

There is concern of energy drink use by adolescents. The objective of this study was to evaluate the energy drink consumption use, frequency, age of first use, reasons for use, influences of choice of brand, and adverse events recorded in a predominant Latino adolescent population.

METHODS

Subjects between the ages of 13 and 19 years utilizing emergency department services for any reason at a large county hospital answered a questionnaire about energy drink usage.

RESULTS

There were 192 subjects, of which 49% were male and 51% were female. Latino adolescents were 85% of the participants, although other ethnic groups participated including African American, white, and Asian. Reasons for use include 61% to increase energy, 32% as study aide, 29% to improve sports performance, and 9% to lose weight. Twenty-four percent reported using energy drinks with ethanol or illicit drugs including marijuana, cocaine, and methamphetamine. Adverse reactions were reported in 40% of the subjects including insomnia (19%), feeling "jittery" (19%), palpitations (16%), gastrointestinal upset (11%), headache (8%), chest pain (5%), shortness of breath (4%), and seizures (1%).

CONCLUSIONS

Both brand name and packaging influenced the choice of energy drink in most subjects. Forty percent reported at least 1 adverse effect. While most adverse effects were not severe, a small number are serious. In addition, we showed intentional ingestion with ethanol and illicit drugs. Of additional concern is that both brand and packaging seem to directly affect choice of energy drink consumed.

Caffeine and Insomnia in People Living With HIV From the Miami Adult Studies on HIV (MASH) Cohort

We explored the relationship between caffeine consumption, insomnia, and HIV disease progression (CD4+ T cell counts and HIV viral loads). Caffeine intake and insomnia levels were measured using the Modified Caffeine Consumption Questionnaire and the Pittsburgh Insomnia Rating Scale (PIRS) in 130 clinically stable participants who were living with HIV, taking antiretroviral therapy, and recruited from the Miami Adult Studies on HIV cohort. Linear regressions showed that caffeine consumption was significantly and adversely associated with distress score, quality-of-life score, and global PIRS score. Linear regression analyses also showed that global PIRS score was significantly associated with lower CD4+ T cell counts and higher HIV viral loads. Caffeine could have precipitated insomnia in susceptible people living with HIV, which could be detrimental to their disease progression states.

Caffeine in the management of patients with headache

Caffeinated headache medications, either alone or in combination with other treatments, are widely used by patients with headache. Clinicians should be familiar with their use as well as the chemistry, pharmacology, dietary and medical sources, clinical benefits, and potential safety issues of caffeine. In this review, we consider the role of caffeine in the over-the-counter treatment of headache. The MEDLINE and Cochrane databases were searched by combining “caffeine” with the terms “headache,” “migraine,” and “tension-type.” Studies that were not placebo-controlled or that involved medications available only with a prescription, as well as those not assessing patients with migraine and/or tension-type headache (TTH), were excluded. Compared with analgesic medication alone, combinations of caffeine with analgesic medications, including acetaminophen, acetylsalicylic acid, and ibuprofen, showed significantly improved efficacy in the treatment of patients with TTH or migraine, with favorable tolerability in the vast majority of patients. The most common adverse events were nervousness (6.5%), nausea (4.3%), abdominal pain/discomfort (4.1%), and dizziness (3.2%). This review provides evidence for the role of caffeine as an analgesic adjuvant in the acute treatment of primary headache with over-the-counter drugs, caffeine doses of 130 mg enhance the efficacy of analgesics in TTH and doses of ≥100 mg enhance benefits in migraine. Additional studies are needed to assess the relationship between caffeine dosing and clinical benefits in patients with TTH and migraine.

In-vitro examination of the positive inotropic effect of caffeine and taurine, the two most frequent active ingredients of energy drinks

Background

Our study aimed to evaluate changes in the contractile behavior of human myocardium after exposure to caffeine and taurine, the main active ingredients of energy drinks (EDs), and to evaluate whether taurine exhibits any inotropic effect at all in the dosages commonly used in EDs.

Methods

Myocardial tissue was removed from the right atrial appendages of patients undergoing cardiac surgery and prepared to obtain specimens measuring 4 mm in length. A total of 92 specimens were exposed to electrical impulses at a frequency of 75 bpm for at least 40 min to elicit their maximum contractile force before measuring the isometric contractile force (ICF) and duration of contraction (CD). Following this, each specimen was treated with either taurine (group 1, n = 29), or caffeine (group 2, n = 31) or both (group 3, n = 32). After exposure, ICF and CD measuring were repeated. Post-treatment values were compared with pre-treatments values and indicated as percentages.

Results

Exposure to taurine did not alter the contraction behavior of the specimens. Exposure to caffeine, in contrast, led to a significant increase in ICF (118 ± 03%, p < 0.01) und a marginal decrease in CD (95 ± 1.6%, p < 0.01). Exposure to a combination of caffeine and taurine also induced a statistically significant increase in ICF (124 ± 4%, p < 0.01) and a subtle reduction in CD (92 ± 1.4%, p < 0.01). The increase in ICF achieved by administration of caffeine was similar to that achieved by a combination of both caffeine and taurine (p = 0.2).

The relative ICF levels achieved by administration of caffeine and a combination of taurine and caffeine, respectively, were both significantly higher (p < 0.01) than the ICF resulting from exposure to taurine only.

Conclusion

While caffeine altered the contraction behavior of the specimen significantly in our in-vitro model, taurine did not exhibit a significant effect. Adding taurine to caffeine did not significantly enhance or reduce the effect of caffeine.

Review of Caffeine-Related Fatalities along with Postmortem Blood Concentrations in 51 Poisoning Deaths

Publications reporting concentrations of caffeine in postmortem blood were reviewed if the cause of death was attributed to overdosing (poisoning) with drugs. Age and gender of the deceased, the manner of death (accident, suicide or undetermined) and types of co-ingested drugs were evaluated in relation to the concentrations of caffeine in blood (N = 51). The mean age (±SD) of the victims was 39 ± 17.8 years (range 18-84 years) and most were female (N = 31 or 61%). The difference in mean age of males (42 ± 17.2 years) and females (37 ± 18.3 years) was not statistically significant (t = 0.811, P = 0.421). The mean (±SD), median and range of caffeine concentrations in postmortem blood were 187 ± 96 mg/L (180 mg/L) and 33-567 mg/L, respectively. The median concentration of caffeine in males (161 mg/L) was not significantly different from that of females (182 mg/L), z = 1.18, P = 0.235. There was no correlation between the age of the deceased and the concentration of caffeine in postmortem blood (R2 = 0.026, P > 0.05). Manner of death was classified as suicide in 51% of cases (median blood-caffeine 185 mg/L), accidental in 16% (median 183 mg/L) or undetermined in 33% (median 113 mg/L). The median concentration of caffeine in blood was lower when manner of death was undetermined compared with suicide or accidental (P = 0.023). Although other drugs, including ethanol, antidepressants, antipsychotics, benzodiazepines and/or ephedrine, were often identified in postmortem blood, the predominant psychoactive substance was caffeine. The deceased had ingested caffeine in tablet or powder form and it does not seem likely that toxic concentrations of caffeine can be achieved from over-consumption of caffeinated beverages alone.

Investigational therapies for the treatment of narcolepsy

INTRODUCTION

Narcolepsy is a chronic sleep disorder characterized by a pentad of excessive daytime sleepiness (EDS), cataplexy, sleep paralysis, hypnagogic/hypnopompic hallucinations, and disturbed nocturnal sleep. While non-pharmacological treatments are sometimes helpful, more than 90% of narcoleptic patients require a pharmacological treatment. Areas covered: The present review is based on an extensive Internet and PubMed search from 1994 to 2017. It is focused on drugs currently in development for the treatment of narcolepsy. Expert opinion: Currently there is no cure for narcolepsy, with treatment focusing on symptoms control. However, these symptomatic treatments are often unsatisfactory. The research is leading to a better understanding of narcolepsy and its symptoms. New classes of compounds with possible applications in the development of novel stimulant/anticataplectic medications are described. H3 receptor antagonists represent a new therapeutic option for EDS in narcolepsy. JZP-110, with its distinct mechanism of action, would be a new therapeutic option for the treatment of EDS in the coming years. In the future, hypocretin-based therapies and immune-based therapies, could modify the clinical course of the disease. However, more information would be necessary to completely understand the autoimmune process and also how this process can be altered for therapeutic benefits.

Energy Drinks and the Risk of Cardiovascular Disease: A Review of Current Literature

Energy drinks (EDs) are commonly used as a dietary supplement by young adolescents and adults. They are often used as a source of energy in order to enhance physical and mental performance. EDs contain a variety of substances, but caffeine is the main component. Safety has been the biggest concern associated with consuming EDs. Case reports, observational studies, and meta-analyses have been done in order to determine the effects of EDs on cardiovascular changes. The detrimental effects of EDs are cardiac arrhythmias, myocardial infarction, prolonged QT interval, aortic dissection, and death. In this article, we review case reports, observational studies, and meta-analyses of EDs and the risk of cardiovascular events and mortality. We also review active ingredients, pharmacokinetics, and the mechanism of action of EDs.

The Relationship Between Caffeine, Sleep, and Behavior in Children

STUDY OBJECTIVES

To examine caffeine consumption from various dietary sources in a cohort of Australian children and the relationship between caffeine consumption, sleep, and daytime behavior.

METHODS

Children aged 8 to 12 years and their parents/guardians completed a battery of questionnaires. Children completed a caffeine questionnaire while parents completed questionnaires regarding demographics, sleep, and behavior.

RESULTS

The final sample consisted of 309 children (mean ± standard deviation [SD] age 10.6 ± 1.3 years, male = 48%) and corresponding parent reports. On average a mean ± SD 10.2 ± 17.4 mg/day of caffeine was consumed with a range of zero to 151 mg/day. Of the children who consumed caffeine (87% of the sample), the largest contributor was coffee and tea; making up 41% of total caffeine intake, and sodas (soft drinks) contributed to 40% of caffeine intake. Total caffeine consumption was significantly associated with sleep routine (r = 0.152); morning tiredness (r = 0.129); restless sleep (r = 0.113); and internalizing behavioral problems (r = 0.128). Using path analysis, caffeine consumption was positively associated with morning tiredness (β = 0.111, P = .050) which was positively associated with internalizing behaviors (β = 0.432, P < .001). The addition of sleep routine and restless sleep to the model led to a complete mediation of caffeine consumption on morning tiredness, as well as a partial mediation of the association between morning tiredness and internal behaviors.

CONCLUSIONS

In 8- to 12-year-olds the primary sources of caffeine are coffee/tea and sodas. Overall mean caffeine consumption is small by adult standards but has an effect on behavior and sleep in children. The effect on behavior is mediated by disrupted sleep, indicating that caffeine is a contributor to sleep problems and related behavior in children.

Multiscale modeling reveals inhibitory and stimulatory effects of caffeine on acetaminophen-induced toxicity in humans

Acetaminophen (APAP) is a widely used analgesic drug that is frequently co-administered with caffeine (CAF) in the treatment of pain. It is well known that APAP may cause severe liver injury after an acute overdose. However, the understanding of whether and to what extent CAF inhibits or stimulates APAP-induced hepatotoxicity in humans is still lacking. Here, a multiscale analysis is presented that quantitatively models the pharmacodynamic (PD) response of APAP during co-medication with CAF. Therefore, drug-drug interaction (DDI) processes were integrated into physiologically based pharmacokinetic (PBPK) models at the organism level, whereas drug-specific PD response data were contextualized at the cellular level. The results provide new insights into the inhibitory and stimulatory effects of CAF on APAP-induced hepatotoxicity for crucially affected key cellular processes and individual genes at the patient level. This study might facilitate the risk assessment of drug combination therapies in humans and thus may improve patient safety in clinical practice.

Effects of caffeine on fractional flow reserve values measured using intravenous adenosine triphosphate

We investigated the effects of caffeine intake on fractional flow reserve (FFR) values measured using intravenous adenosine triphosphate (ATP) before cardiac catheterization. Caffeine is a competitive antagonist for adenosine receptors; however, it is unclear whether this antagonism affects FFR values. Patients were evenly randomized into 2 groups preceding the FFR study. In the caffeine group (n = 15), participants were given coffee containing 222 mg of caffeine 2 h before the catheterization. In the non-caffeine group (n = 15), participants were instructed not to take any caffeine-containing drinks or foods for at least 12 h before the catheterization. FFR was performed in patients with more than intermediate coronary stenosis using the intravenous infusion of ATP at 140 μg/kg/min (normal dose) and 170 μg/kg/min (high dose), and the intracoronary infusion of papaverine. FFR was followed for 30 s after maximal hyperemia. In the non-caffeine group, the FFR values measured with ATP infusion were not significantly different from those measured with papaverine infusion. However, in the caffeine group, the FFR values were significantly higher after ATP infusion than after papaverine infusion (P = 0.002 and P = 0.007, at normal and high dose ATP vs. papaverine, respectively). FFR values with ATP infusion were significantly increased 30 s after maximal hyperemia (P = 0.001 and P < 0.001 for normal and high dose ATP, respectively). The stability of the FFR values using papaverine showed no significant difference between the 2 groups. Caffeine intake before the FFR study affected FFR values and their stability. These effects could not be reversed by an increased ATP dose.

Low, but not high, dose caffeine is a readily available probe for adenosine actions

Caffeine is very widely used and knowledge of its mode of action can be used to gain an understanding of basal physiological regulation. This review makes the point that caffeine is - in low doses - an antagonist of adenosine acting at A₁, A_2A and A_2B receptors. We use published and unpublished data to make the point that high dose effects of caffeine are not only qualitatively different but have a different underlying mechanism. Therefore one must be careful in only using epidemiological or experimental data where rather low doses of caffeine are used to draw conclusions about the physiology and pathophysiology of adenosine.

Intralipid in acute caffeine intoxication: a case report

Caffeine is arguably the most widely used stimulant drug in the world. Here we describe a suicide attempt involving caffeine overdose whereby the patient's severe intoxication was successfully treated with the prompt infusion of Intralipid. A 19-year-old man was found in an agitated state at home by the volunteer emergency team about 1 h after the intentional ingestion of 40 g of caffeine (tablets). His consciousness decreased rapidly, followed quickly by seizures, and electrocardiographic monitoring showed ventricular fibrillation. Advanced life support maneuvers were started immediately, with the patient defibrillated 10 times and administered 5 mg epinephrine in total and 300 + 150 mg of amiodarone (as well as lidocaine and magnesium sulfate). The cardiac rhythm eventually evolved to asystole, necessitating the intravenous injection of epinephrine to achieve the return of spontaneous circulation. However, critical hemodynamic instability persisted, with the patient's cardiac rhythm alternating between refractory irregular narrow complex tachycardia and wide complex tachycardia associated with hypotension. In an attempt to restore stability we administered three successive doses of Intralipid (120 + 250 + 100 mg), which successfully prevented a severe cardiovascular collapse due to a supra-lethal plasma caffeine level (>120 mg/L after lipid emulsion). The patient survived without any neurologic complications and was transferred to a psychiatric ward a few days later. The case emphasizes the efficacy of intravenous lipid emulsion in the resuscitation of patients from non-local anesthetic systemic toxicity. Intralipid appears to act initially as a vehicle that carries the stimulant drug away from heart and brain to less well-perfused organs (scavenging mechanism) and then, with a sufficient drop in the caffeine concentration, possibly as a tonic to the depressed heart.

A Review of Energy Drinks and Mental Health, with a Focus on Stress, Anxiety, and Depression

Background: Concerns have been expressed regarding the potential for caffeinated energy drinks to negatively affect mental health, and particularly so in young consumers at whom they are often targeted. The products are frequently marketed with declarations of increasing mental and physical energy, providing a short-term boost to mood and performance. Although a certain amount of evidence has accumulated to substantiate some of these claims, the chronic effects of energy drinks on mental health also need to be addressed.

Methods: To review the relevant literature, PubMed and PsycINFO were searched for all peer-reviewed articles published in English that addressed associations between energy drink use and mental health outcomes. Case reports were also considered, though empirical studies investigating acute mood effects were excluded as a review of such articles had recently been published. Fifty-six articles were retrieved: 20 of these (along with eight more identified through other means) were included in the current review, and, because the majority addressed aspects of stress, anxiety, and depression, particular focus was placed on these outcomes.

Results: Though a number of null findings (and one negative relationship) were observed, the majority of studies examined reported positive associations between energy drink consumption and symptoms of mental health problems.

Conclusions: Though the findings imply that energy drink use may increase the risk of undesirable mental health outcomes, the majority of research examined utilized cross-sectional designs. In most cases, it was therefore not possible to determine causation or direction of effect. For this reason, longitudinal and intervention studies are required to increase our understanding of the nature of the relationships observed.

Chronic caffeine treatment enhances the resilience to social defeat stress in mice

Strong evidence has shown that caffeine exerts antidepressant-like effects in chronic stress situations by increasing dopamine levels. However, whether caffeine mediates the dopaminergic system and interferes with the resilience to social defeat stress in mice is unknown. The aim of this study is to investigate the role of caffeine in the behavioral responses to social defeat stress and the possible regulatory role of the dopaminergic system. Mice experienced chronic social defeat stress for 10 days. Caffeine was administered intraperitoneally before, during and after social defeat stress. The time spent in interaction zone, social interaction ratio and sucrose preference test was used to measure the social avoidance and anhedonia in mice. The results showed that chronic pretreatment with caffeine for 14 days and for 10 days during stress reversed the avoidance of social behavior and anhedonia induced by social defeat stress in mice, suggesting the enhancement of the resilience to social defeat stress induced by caffeine. However, neither the treatment with caffeine only during the social defeat stress for 10 days nor the treatment with acute caffeine after defeat stress altered the resilience to stress. Furthermore, chronic caffeine treatment did not affect the normal locomotor activity and the desperate behavior in naïve mice. Moreover, the antagonism of dopamine D1 receptor and not D2 receptor reversed the effect of caffeine on the social avoidance and depressive-like behavior. Finally, pretreatment with higher doses of caffeine did not affect the behavioral response to social defeat stress. Taken together, our findings provide new insight into the effects of caffeine on social avoidance and anhedonia in mice. In addition, our results illustrated the value of measuring changes in depressive-like behavior before and after social defeat stress to determine the potential treatment of caffeine on depression through the regulation of dopaminergic system.

Caffeine: cognitive and physical performance enhancer or psychoactive drug?

Caffeine use is increasing worldwide. The underlying motivations are mainly concentration and memory enhancement and physical performance improvement. Coffee and caffeine-containing products affect the cardiovascular system, with their positive inotropic and chronotropic effects, and the central nervous system, with their locomotor activity stimulation and anxiogenic-like effects. Thus, it is of interest to examine whether these effects could be detrimental for health. Furthermore, caffeine abuse and dependence are becoming more and more common and can lead to caffeine intoxication, which puts individuals at risk for premature and unnatural death. The present review summarizes the main findings concerning caffeine’s mechanisms of action (focusing on adenosine antagonism, intracellular calcium mobilization, and phosphodiesterases inhibition), use, abuse, dependence, intoxication, and lethal effects. It also suggests that the concepts of toxic and lethal doses are relative, since doses below the toxic and/or lethal range may play a causal role in intoxication or death. This could be due to caffeine’s interaction with other substances or to the individuals' preexisting metabolism alterations or diseases.

Caffeine consumption and self-assessed stress, anxiety, and depression in secondary school children

Previous research suggests that effects of caffeine on behaviour are positive unless one is investigating sensitive groups or ingestion of large amounts. Children are a potentially sensitive subgroup, and especially so considering the high levels of caffeine currently found in energy drinks. The present study used data from the Cornish Academies Project to investigate associations between caffeine (both its total consumption, and that derived separately from energy drinks, cola, tea, and coffee) and single-item measures of stress, anxiety, and depression, in a large cohort of secondary school children from the South West of England. After adjusting for additional dietary, demographic, and lifestyle covariates, positive associations between total weekly caffeine intake and anxiety and depression remained significant, and the effects differed between males and females. Initially, effects were also observed in relation to caffeine consumed specifically from coffee. However, coffee was found to be the major contributor to high overall caffeine intake, providing explanation as to why effects relating to this source were also apparent. Findings from the current study increase our knowledge regarding associations between caffeine intake and stress, anxiety, and depression in secondary school children, though the cross-sectional nature of the research made it impossible to infer causality.

Sensitization and Tolerance Following Repeated Exposure to Caffeine and Alcohol in Mice

BACKGROUND

Energy drinks are popular mixers with alcohol. While energy drinks contain many ingredients, caffeine is an important pharmacologically active component and is generally present in larger amounts than in other caffeinated beverages. In these studies, we investigated the hypothesis that caffeine would influence the effects of alcohol (ethanol [EtOH]) on conditioned taste aversion (CTA), ataxia, and locomotor activity (LA) after repeated exposure.

METHODS

Four groups of mice were exposed by oral gavage twice daily to vehicle, EtOH (4 g/kg), caffeine (15 mg/kg), or the EtOH/caffeine combination. CTA to saccharin and ataxia in the parallel rod task was evaluated after 8 or 16 gavages, respectively, using EtOH (1 to 3 g/kg) or EtOH/caffeine (3 mg/kg + 2 g/kg) challenges. In addition, LA was evaluated initially and after repeated exposure to oral gavage of these drugs and doses.

RESULTS

Repeated oral gavage of EtOH produced significant locomotor sensitization, with those mice increasing total distance traveled by 2-fold. The locomotor response to caffeine, while significantly greater than vehicle gavage, did not change with repeated exposure. On the other hand, repeated gavage of caffeine/EtOH combination produced a substantial increase in total distance traveled after repeated exposure (~4-fold increase). After repeated EtOH exposure, there was significant tolerance to EtOH in the CTA and parallel rod tests. However, neither a history of caffeine exposure nor including caffeine influenced EtOH-induced CTA. Interestingly, a history of caffeine exposure increased the ataxic response to the caffeine/EtOH combination and appeared to reduce the ataxic response to high doses of EtOH.

CONCLUSIONS

The data support the general hypothesis that repeated exposure to caffeine influences the response to EtOH. Together with previously published work, these data indicate that caffeine influences some EtOH-related behaviors, notably locomotion and ataxia, but appears not to influence the expression of conditioned behaviors.

Caffeine Awareness in Children: Insights from a Pilot Study

STUDY OBJECTIVES

Caffeine, a commonly consumed psychoactive substance, can have significant effects on sleep. Caffeine intake among children is increasing, mainly in the form of sodas. However, adolescent caffeine consumers may lack knowledge about the caffeine content in common beverages. If true, this very fact may hamper the assessment of the effects of caffeine consumption on sleep in children if such assessments are a priori dependent on responders being able to reliably distinguish between caffeinated and noncaffeinated beverages. This preliminary study investigated adolescents' caffeine knowledge and intake at a Cleveland-area public middle school.

METHODS

Seventh- and eighth-grade students were surveyed using: (1) the Caffeine Literacy and Sleep Study (CLASS), a 15-question pilot instrument designed to assess caffeine knowledge and intake by type, quantity and timing, as well as sleep habits; and (2) the Cleveland Adolescent Sleepiness Questionnaire (CASQ), a validated survey measuring excessive daytime sleepiness in adolescents. These questionnaires were distributed and collected during a specified class period.

RESULTS

Of the 635 seventh- and eighth-grade students who attended school on the day of the study, 555 (87%) participated. Lack of knowledge about caffeine content of particular drinks was noted in seventh and eighth graders of both sexes with nearly 29% unaware that their favorite drinks contain caffeine and more than 50% unable to correctly identify the drinks with the most caffeine. A low percentage of students correctly identified light-colored sodas lacking caffeine: 7-Up (24.1%), Sierra Mist (38.9%), ginger ale (39.8%), Sprite (39.8%), and Fresca (53.7%). The percentages of students correctly identifying caffeinated light-colored beverages were: Arizona Green Tea (43.5%), Mello Yellow (50.9%), and A&W cream soda (67.6%). However, Mountain Dew was correctly identified by most (93.5%) as caffeinated.

CONCLUSIONS

Students were not consistently able to identify caffeine content or lack thereof in some common beverages. The results of this pilot study show that caffeine literacy in adolescents warrants further investigation and educational intervention.

No Enhancement of 24-Hour Visuomotor Skill Retention by Post-Practice Caffeine Administration

Caffeine is widely consumed throughout the world and appears to indirectly facilitate learning and memory through effects on attention and motivation. Animal work indicates that post-training caffeine administration augments inhibitory avoidance memory, spatial memory, and object memory. In humans, post-training caffeine administration enhances the ability to discern between familiar images and new, similar images. However, the effect of post-training caffeine administration on motor memory has not been examined. Therefore, we tested two groups of low caffeine consumers (average weekly consumption ≤500 mg) in a double-blind, placebo-controlled study involving acquisition of a continuous isometric visuomotor tracking skill. On Day 1, subjects completed 5 blocks (150 repetitions) of training on the continuous isometric visuomotor skill and subsequently ingested either 200 mg of caffeine or placebo. On day 2, subjects completed an additional 5 blocks of training. Day 1 mean performance and performance variability were both similar between groups, suggesting that both groups acquired the motor skill similarly. For mean performance on Day 2, patterns of re-learning, mean performance learning magnitudes, mean performance learning rates, and mean performance retention magnitudes were all similar between groups. For performance variability on Day 2, there was a small trend towards increased variability in the caffeine group during re-learning, but performance variability learning magnitudes and performance variability retention magnitudes did not differ between groups. Because motor skill acquisition can also be conceptualized as a reduction in performance variability, these results suggest that there may be a small negative effect of post-practice caffeine administration on memory of a newly-learned visuomotor skill. Overall, we found no evidence to suggest that post-training caffeine administration enhances 24-hour retention of a newly-learned continuous visuomotor skill, and these results support the notion that memory-enhancing effects of post-training caffeine ingestion may be task-specific.

Sleep is more sensitive to high doses of caffeine in the middle years of life

During the middle years of life, sleep becomes more fragile and its sensitivity to psychostimulants may increase. This study evaluated the effects of 200 mg and 400 mg of caffeine on sleep in young and middle-aged adults. The sleep of 22 young (23.5 ± 1.9 years) and 24 middle-aged (51.7 ± 11.5 years) adults was recorded using polysomnography in two conditions (placebo and caffeine) in a double-blind cross-over design. Compared to placebo, caffeine increased sleep latency, shortened total sleep duration and reduced sleep efficiency. At the higher dose, these effects were more pronounced in middle-aged than in young adults. Furthermore, the higher dose of caffeine increased absolute stage 1 sleep in young adults, whereas it decreased absolute stage 2 sleep in middle-aged adults. Caffeine also induced dose-dependent increases in relative stage 1 sleep and reductions in absolute and relative slow wave sleep and absolute rapid eye movement sleep in both age groups. There was no dose- or age-related modulation of the effects of caffeine on quantified electroencephalographic measures. These results indicate that, compared to young adults, middle-aged adults are generally more sensitive to the effects of a high dose of caffeine on sleep quantity and quality.

Pharmacological treatment of sleep disorders and its relationship with neuroplasticity

Sleep and wakefulness are regulated by complex brain circuits located in the brain stem, thalamus, subthalamus, hypothalamus, basal forebrain, and cerebral cortex. Wakefulness and NREM and REM sleep are modulated by the interactions between neurotransmitters that promote arousal and neurotransmitters that promote sleep. Various lines of evidence suggest that sleep disorders may negatively affect neuronal plasticity and cognitive function. Pharmacological treatments may alleviate these effects but may also have adverse side effects by themselves. This chapter discusses the relationship between sleep disorders, pharmacological treatments, and brain plasticity, including the treatment of insomnia, hypersomnias such as narcolepsy, restless legs syndrome (RLS), obstructive sleep apnea (OSA), and parasomnias.

The combined effect of caffeine and ornithine on the mood of healthy office workers

Caffeine is widely consumed and well known for stimulating the central nervous system. When developing new foods and beverages that contain caffeine, it is important to explore the potential synergistic effects of consuming amino acids and other food ingredients with caffeine on humans. Given the physiological pathways affected by the amino acid ornithine, consumption of ornithine with caffeine may have synergistic effects. The purpose of the present study was to examine the effect of consuming caffeine with ornithine in humans. The study used a randomized, placebo-controlled, double-blinded crossover design. The subjects were all healthy office workers who ingested the placebo, 100 mg caffeine, or 100 mg caffeine plus 200 mg ornithine in the morning and completed questionnaires about their mood. Office workers who consumed the combination of caffeine and ornithine had higher mood ratings 8 h after consumption than office workers who consumed caffeine alone. The results of the present study suggest that there is a unique synergistic effect between caffeine and ornithine on the mood of healthy office workers and that ornithine may potentiate the effects of caffeine.

Effects of blue light and caffeine on mood

RATIONALE

Both short wavelength (blue) light and caffeine have been studied for their mood enhancing effects on humans. The ability of blue light to increase alertness, mood and cognitive function via non-image forming neuropathways has been suggested as a non-pharmacological countermeasure for depression across a range of occupational settings.

OBJECTIVES

This experimental study compared blue light and caffeine and aimed to test the effects of blue light/placebo (BLU), white light/240-mg caffeine (CAF), blue light/240-mg caffeine (BCAF) and white light/placebo (PLA), on mood.

METHODS

A randomised, controlled, crossover design study was used, in a convenience population of 20 healthy volunteers. The participants rated their mood on the Swedish Core Affect Scales (SCAS) prior to and after each experimental condition to assess the dimensions of valence and activation.

RESULTS

There was a significant main effect of light (p = 0.009), and the combination of blue light and caffeine had clear positive effects on core effects (ES, ranging from 0.41 to 1.20) and global mood (ES, 0.61 ± 0.53).

CONCLUSIONS

The benefits of the combination of blue light and caffeine should be further investigated across a range of applications due to the observed effects on the dimensions of arousal, valence and pleasant activation.

Duration of activity and mode of action of modafinil: Studies on sleep and wakefulness in humans

The duration of activity of modafinil was investigated in healthy male volunteers in two double-blind crossover studies. Mode of action was explored using a statistical model concerned with the relationship between total sleep duration and that of rapid eye movement (REM) sleep. Nocturnal sleep (23:00-07:00) followed by next-day performance (09:00-17:00) was studied in 12 subjects administered 100, 200, 300 mg modafinil and placebo, 0.5 h before bedtime. Performance overnight (19:00-08:45) followed by sleep (09:15-15:15) was studied in nine subjects administered 100, 200, 300, 400 mg modafinil, 300 mg caffeine and placebo at 22:15. Modafinil dose-dependently reduced sleep duration (nocturnal: 200 mg, p<0.05; 300 mg, p<0.001; morning: 300 and 400 mg, p<0.05) and REM sleep (nocturnal: 300 mg; morning: 400 mg; p<0.05). The statistical model revealed that reduced REM sleep was due to alerting activity, with no evidence of direct suppression of REM sleep, suggesting dopaminergic activity. Enhanced performance with modafinil during overnight work varied with dose (200 mg>100 mg; 300, 400 mg>200, 100 mg, caffeine). However, in the study of next-day performance, the enhancement was attenuated at the highest dose (300 mg) by the greater disturbance of prior sleep. These findings indicate that modafinil has a long duration of action, with alerting properties arising predominantly from dopaminergic activity.

Dose-dependent model of caffeine effects on human vigilance during total sleep deprivation

Caffeine is the most widely consumed stimulant to counter sleep-loss effects. While the pharmacokinetics of caffeine in the body is well-understood, its alertness-restoring effects are still not well characterized. In fact, mathematical models capable of predicting the effects of varying doses of caffeine on objective measures of vigilance are not available. In this paper, we describe a phenomenological model of the dose-dependent effects of caffeine on psychomotor vigilance task (PVT) performance of sleep-deprived subjects. We used the two-process model of sleep regulation to quantify performance during sleep loss in the absence of caffeine and a dose-dependent multiplier factor derived from the Hill equation to model the effects of single and repeated caffeine doses. We developed and validated the model fits and predictions on PVT lapse (number of reaction times exceeding 500 ms) data from two separate laboratory studies. At the population-average level, the model captured the effects of a range of caffeine doses (50-300 mg), yielding up to a 90% improvement over the two-process model. Individual-specific caffeine models, on average, predicted the effects up to 23% better than population-average caffeine models. The proposed model serves as a useful tool for predicting the dose-dependent effects of caffeine on the PVT performance of sleep-deprived subjects and, therefore, can be used for determining caffeine doses that optimize the timing and duration of peak performance.

Treatment of menstrual migraine: utility of control of related mood disturbances

Menstrual migraine (MM) has a prevalence in the general population of approximately 7%, although it seems to be much higher within the population of females with migraine. Episodes of MM have been reported to be longer, more intense, more disabling, less responsive to acute therapy and more prone to recurrence than those of other types of migraine. MM is demonstrated to have a bi-directional link to affective illnesses such as premenstrual dysphoric disorder and depression. There is clinical and pathophysiological evidence suggesting that the relationship between MM and affective disorders could be linked to ovarian hormones. The aim of this review is to analyze treatment strategies in patients with co-existent MM and affective disorders.