Acute effects of caffeine on attention: a comparison of non-consumers and withdrawn consumers

Caffeine and attentional control: improved and impaired performance in healthy older adults and Parkinson's disease according to task demands

INTRODUCTION

Caffeine is frequently consumed to boost goal-directed attention. These procognitive effects may occur due to the adenosine-mediated enhancement of monoamines, such as dopamine, after caffeine administration. As such, caffeine's beneficial effects may be altered in conditions such as Parkinson's disease (PD). However, whether caffeine improves cognition, and at what cost, has not been experimentally established in patients with neurodegenerative disease.

METHODS

Single-dose trials to probe cognitive effects of caffeine are often confounded by short-term caffeine abstinence which conflates caffeine's effects with treatment of withdrawal. Using a placebo controlled, blinded, randomised trial design, we assessed the effect of 100 mg of caffeine across well-established tasks (Choice reaction time, Stroop Task and Rapid Serial Visual Presentation Task; RSVP) that probe different aspects of attention in PD patients (n = 24) and controls (n = 44). Critically, participants withdrew from caffeine for a week prior to testing to eliminate the possibility that withdrawal reversal explained any cognitive benefit.

RESULTS

Caffeine administration was found to reduce the overall number of errors in patients and controls on the Stroop (p = .018, η²_p = .086) and Choice reaction time (p < . 0001, η²_p = .588) tasks, but there was no specific effect of caffeine on ignoring irrelevant information in the Stroop task. On the RSVP task, caffeine improved dual item accuracy (p = .037) but impaired single item accuracy (p = .044). Across all tasks, there was little evidence that caffeine has different effects in PD participants and controls.

CONCLUSION

When removing withdrawal effects as a factor, we demonstrate caffeine has beneficial effects on selective attention but is a double-edge sword for visual temporal attention and would need careful targeting to be clinically useful.

Bioactive Compounds and Traditional Herbal Medicine: Promising Approaches for the Treatment of Dementia

Dementia is a term that encompasses a group of clinical symptoms affecting memory, thinking and social abilities, characterized by progressive impairment of memory performance and cognitive functions. There are several factors involved in the pathogenesis and progression of dementia, such as old age, brain ischemia, toxin exposure, and oxidative stress. There are extensive similarities between dementia and Alzheimer's disease (AD) either in clinical manifestations or experimental animal models. AD is the most dominant form of dementia, characterized by the accumulation of beta-amyloid protein and cholinergic neurotransmission deficits in the brain. Currently available medications for the treatment of dementia, such as choline esterase inhibitors, N-methyl-D-aspartate (NMDA) antagonists (memantine), have short-term efficacy and only relieve symptoms rather than targeting the main underlying pathogenesis. Several animal studies and clinical trials are being conducted to provide a rational approach to these medicinal plants in the prevention or treatment of memory deficits. This review highlights the potential effects of medicinal plants and their derived lead molecules, and explains the related mechanisms and effects reviewed from published literature as major thrust aspects and hopeful strategies in the prevention or treatment of dementia.

EEG coherence during subjectively-rated psychological state variations

BACKGROUND

Neurofeedback training aims to develop awareness and control of psychological states in order to self-regulate brain activity and while used widely therapeutically, important questions remain unanswered. Central to these aims is an assumed association between the live EEG-based feedback and the subjective experience of a psychological state. To date, there is little evidence to support this relationship. Previous studies examining the association between an EEG index and subjective experience have explored only the presence or absence of the state, or merely assumed state variations. The current study aims to examine this association by considering how different levels of a psychological state (i.e., attention) are reflected in EEG coherence.

METHODS

Our approach aims to allow comparisons of EEG coherence between psychological states (attention vs. rest), and also within subjectively-rated levels of a psychological state (attention) through a purpose-designed questionnaire. Thirty healthy adult participants performed a resting eyes-open (REO) and attention modulation task, while 28 channels of EEG were recorded. Levels within the psychological state were subjectively-attested by participants on a trial-by-trial basis.

RESULTS

The main analyses examined the effect of subjectively-rated attention levels (SRALs) on EEG coherence, with results suggesting that high and low SRALs may be represented by: 1) different levels of alpha and theta coherence at anterior and posterior electrodes of the frontal lobe bilaterally, and 2) different levels of alpha coherence between central and parietal lobes, also bilaterally.

DISCUSSION

These findings provide partial, preliminary evidence for EEG correlates of SRALs. These findings may have implications for understanding underlying mechanisms of NFT, which is an underdeveloped area.

A Randomized, Crossover Study of the Acute Cognitive and Cerebral Blood Flow Effects of Phenolic, Nitrate and Botanical Beverages in Young, Healthy Humans

Background: In whole foods, polyphenols exist alongside a wide array of other potentially bioactive phytochemicals. Yet, investigations of the effects of combinations of polyphenols with other phytochemicals are limited. Objective: The current study investigated the effects of combining extracts of beetroot, ginseng and sage with phenolic-rich apple, blueberry and coffee berry extracts. Design: This randomized, double-blind, placebo-controlled crossover design investigated three active beverages in 32 healthy adults aged 18–49 years. Each investigational beverage comprised extracts of beetroot, ginseng and sage. Each also contained a phenolic-rich extract derived from apple (containing 234 mg flavanols), blueberry (300 mg anthocyanins) or coffee berry (440 mg chlorogenic acid). Cognition, mood and CBF parameters were assessed at baseline and then again at 60, 180 and 360 min post-drink. Results: Robust effects on mood and CBF were seen for the apple and coffee berry beverages, with increased subjective energetic arousal and hemodynamic responses being observed. Fewer effects were seen with the blueberry extract beverage. Conclusions: Either the combination of beetroot, ginseng and sage was enhanced by the synergistic addition of the apple and coffee berry extract (and to a lesser extent the blueberry extract) or the former two phenolic-rich extracts were capable of evincing the robust mood and CBF effects alone.

Can caffeine intake combined with aerobic exercise lead to improvement in attentional and psychomotor performance in trained individuals?

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Supplementation effect was found, suggesting distinct interaction mechanisms between attention and SRT (simple reaction time).

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The change in the SRT magnitude increased after 60 min from caffeine intake, and even more after exercise.

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The decrease in the SRT magnitude after caffeine intake and exercise suggests additional effects of caffeine on exercise.

To evaluate the acute effects of ingestion of 500 mg of caffeine in addition to aerobic exercise on the optimization of cognitive attention tasks and simple reaction time. Twenty men were randomly divided into two groups, caffeine (CAF) and placebo (PLA), and underwent cardiopulmonary exercise testing and cognitive testing (D2SLK, D2GZ, D2F% and TRS). Then, both ingested 500 mg of caffeine or placebo (double blind), and after 60 min performed a 30-minute continuous exercise session at 70 % VO2Max. Cognitive tests were repeated immediately after exercise, and after 30 min. D2SLK, D2GZ, D2F% and TRS scores were compared by repeated measures ANOVA. The magnitude of the effect was established, and it was considered meaningful p = 0.05. CAF is able to alter D2SLK and also reduce D2F% (0.001 - moderate effect, 0.82) and improve the task after 30 min of exercise (p = 0.014 - moderate effect 0.95). The TRS showed significant gains for the CAF group compared to PLA (0.000 - high effect 1.76). Caffeine induces significant effects in attention and reaction time domains independent of the effect of aerobic exercise.

Mental energy: plausible neurological mechanisms and emerging research on the effects of natural dietary compounds

Objective: Lack of mental energy is one of the leading reasons adults turn to dietary supplements, with three out of ten supplement users hoping to improve their energy level; even more consume caffeine-containing products for the same reason. Despite this interest from consumers, there is no consensus scientific definition of mental energy or sole validated instrument for measuring it. We performed this review to summarize main findings from research regarding the influence of natural dietary compounds on three aspects of mental energy: cognition (vigilance), motivation (to do mental work), and mood (feelings of energy and/or absence of feelings of fatigue).Methods: A narrative review of key papers.Results: In addition to caffeine, a number of other compounds, including the polyphenols, which are found in all plant-derived products, and the phytochemicals in culinary herbs and herbal products such as Panax ginseng and Ginkgo biloba, have been shown in animal models to modulate neurotransmitter activity potentially relevant to mental energy. Inadequate intake of B vitamins could also potentially have a negative effect on mental energy due to their role in overall energy production, as precursors of key cofactors in the citric acid cycle, as well as their role in brain function and neurotransmitter synthesis. Consumption of some of these products may have direct or indirect effects on one or more elements of mental energy.Conclusion: Large, prospective clinical trials of these products using appropriate, validated instruments designed to measure mental energy may be worthwhile if sufficient evidence exists to justify such trials.

The Acute Effects of Caffeinated Black Coffee on Cognition and Mood in Healthy Young and Older Adults

Cognitive and mood benefits of coffee are often attributed to caffeine. However, emerging evidence indicates behavioural effects of non-caffeine components within coffee, suggesting the potential for direct or synergistic effects of these compounds when consumed with caffeine in regular brewed coffee. The current randomised, placebo-controlled, double-blind, counterbalanced-crossover study compared the effects of regular coffee, decaffeinated coffee, and placebo on measures of cognition and mood. Age and sex effects were explored by comparing responses of older (61–80 years, N = 30) and young (20–34 years, N = 29) males and females. Computerised measures of episodic memory, working memory, attention, and subjective state were completed at baseline and 30 min post-drink. Regular coffee produced the expected effects of decreased reaction time and increased alertness when compared to placebo. When compared to decaffeinated coffee, increased digit vigilance accuracy and decreased tiredness and headache ratings were observed. Decaffeinated coffee also increased alertness when compared to placebo. Higher jittery ratings following regular coffee in young females and older males represented the only interaction of sex and age with treatment. These findings suggest behavioural activity of coffee beyond its caffeine content, raising issues with the use of decaffeinated coffee as a placebo and highlighting the need for further research into its psychoactive effects.

Effects of caffeine on reaction time are mediated by attentional rather than motor processes

BACKGROUND

Caffeine has a well-established effect on reaction times (RTs) but the neurocognitive mechanisms underlying this are unclear.

METHODS

In the present study, 15 female participants performed an oddball task after ingesting caffeine or a placebo, and electroencephalographic data were obtained. Single-trial P3b latencies locked to the stimulus and to the response were extracted and mediation models were fitted to the data to test whether caffeine's effect on RTs was mediated by its effect on either type of P3b latencies.

RESULTS

Stimulus-locked latencies showed clear evidence of mediation, with approximately a third of the effect of caffeine on RTs running through the processes measured by stimulus-locked latencies. Caffeine did not affect response-locked latencies, so could not mediate the effect.

DISCUSSION

These findings are consistent with caffeine's effect on RTs being a result of its effect on perceptual-attentional processes, rather than motor processes. The study is the first to apply mediation analysis to single-trial P3b data and this technique holds promise for mental chronometric studies into the effects of psychopharmacological agents. The R code for performing the single trial analysis and mediation analysis are included as supplementary materials.

Systematic Review and Meta-analysis of the Effects of Caffeine in Fatigued Shift Workers: Implications for Emergency Medical Services Personnel

BACKGROUND

Emergency Medical Services (EMS) workers may experience fatigue as a consequence of shift work. We reviewed the literature to determine the impact of caffeine as a countermeasure to fatigue in EMS personnel and related shift workers.

METHODS

We employed the GRADE methodology to perform a systematic literature review and search multiple databases for research that examined the impact of caffeine on outcomes of interest, such as patient and EMS personnel safety. For selected outcomes, we performed a meta-analysis of pooled data and reported the pooled effect in the form of a Standardized Mean Difference (SMD) with corresponding 95% confidence intervals.

RESULTS

There are no studies that investigate caffeine use and its effects on EMS workers or on patient safety. Four of 8 studies in shift workers showed that caffeine improved psychomotor vigilance, which is important for performance. Caffeine decreased the number of lapses on a standardized test of performance [SMD = 0.75 (95% CI: 0.30 to 1.19), p = 0.001], and lessened the slowing of reaction time at the end of shifts [SMD = 0.52 (95% CI: 0.19 to 0.85); p = 0.002]. Finally, 2 studies reported that caffeine reduced sleep quality and sleep duration.

CONCLUSIONS

Although the quality of evidence was judged to be low to moderate, when taken together, these studies demonstrate that caffeine can improve psychomotor performance and vigilance. However, caffeine negatively affects sleep quality and sleep duration. More systematic, randomized studies need to be conducted in EMS workers in order to address the critical outcomes of health and safety of EMS personnel and patients. The risk/benefit ratio of chronic caffeine use in shift workers is currently unknown.

Acute Tension-Type Headaches Are Associated with Impaired Cognitive Function and More Negative Mood

BACKGROUND/AIMS

Research has shown that migraine is often associated with memory problems. There have, however, been few studies of tension-type headache (TTH) and cognition. People who report frequent headaches often report high levels of negative affect. However, less is known about the acute effects of TTH on mood. To address these gaps in our knowledge, two studies examined the effects of acute TTH on -cognitive performance and mood.

METHODS

Both studies involved one group of participants completing a battery of tasks when they had a TTH and when they had no headache. Another group (the control) was headache free on both occasions. Duration of the headache was >30 min and <4 h. In the "no headache" condition, the participants were headache free for at least 24 h. In the first study, 12 participants (6 with TTH and 6 controls) completed a computerized battery measuring mood and aspects of cognition. In the second study, 22 participants (7 TTH, 5 after TTH, and 10 controls) completed paper and pencil mood and cognitive tasks.

RESULTS

In the first study, having a headache was associated with an increase in negative affect both before and after the tasks. Three performance tasks showed impairments when the participants had headaches: logical reasoning was slower and less accurate; retrieval from semantic memory was slower; and reaction times in the categorical search task were slower. Results from the second study confirmed the global increase in negative affect when the person has a TTH. The results confirmed the impairments in the logical reasoning and semantic processing tasks, and also showed that those with a TTH had greater psychomotor slowing and were more easily distracted. Effects did not continue after the headache had gone.

CONCLUSION

Two small-scale studies have shown that TTH is associated with negative affect and impaired cognitive function. It is now of interest to determine whether OTC treatment can remove these effects.

Caffeine: Friend or Foe?

The debate on the safety of and regulatory approaches for caffeine continues among various stakeholders and regulatory authorities. This decision-making process comes with significant challenges, particularly when considering the complexities of the available scientific data, making the formulation of clear science-based regulatory guidance more difficult. To allow for discussions of a number of key issues, the North American Branch of the International Life Sciences Institute (ILSI) convened a panel of subject matter experts for a caffeine-focused session entitled "Caffeine: Friend or Foe?," which was held during the 2015 ILSI Annual Meeting. The panelists' expertise covered topics ranging from the natural occurrence of caffeine in plants and interindividual metabolism of caffeine in humans to specific behavioral, reproductive, and cardiovascular effects related to caffeine consumption. Each presentation highlighted the potential risks, benefits, and challenges that inform whether caffeine exposure warrants concern. This paper aims to summarize the key topics discussed during the session.

An Investigation of the Acute Effects of Oligofructose-Enriched Inulin on Subjective Wellbeing, Mood and Cognitive Performance

Inulin is a natural food component found in many plants that are part of the human diet (e.g., leeks, onions, wheat, garlic, chicory and artichokes). It is added to many foods and is used to increase dietary fibre, replace fats or carbohydrates, and as a prebiotic (a stimulant of beneficial bacteria in the colon). Oligofructose, which is also present in these foods, produces similar effects and most research has used a combination of these products. A previous study (Smith, 2005) investigated the effects of regular consumption of oligofructose-enriched inulin on wellbeing, mood, and cognitive performance in humans. The results showed that oligofructose-enriched inulin had no negative effects but that it did not improve wellbeing, mood, or performance. The aim of the present study was to examine the acute effects of oligofructose-enriched inulin (5 g) over a 4 h period during which the participants remained in the laboratory. A double blind placebo (maltodextrin) controlled study (N = 47) was carried out with the order of conditions being counterbalanced and the two sessions a week apart. On each test day mood and cognitive performance were assessed at baseline (at 8:00) and then following inulin or placebo (at 11:00). Prior to the second test session (at 10:30) participants completed a questionnaire assessing their physical symptoms and mental health during the test morning. The inulin and placebo were provided in powder form in 5 g sachets. Volunteers consumed one sachet in decaffeinated tea or decaffeinated coffee with breakfast (9:00). Questionnaire results showed that on the day that the inulin was consumed, participants felt happier, had less indigestion and were less hungry than when they consumed the placebo. As for performance and mood tasks, the most consistent effects were on the episodic memory tasks where consumption of inulin was associated with greater accuracy on a recognition memory task, and improved recall performance (immediate and delayed). Further research is required to identify the mechanisms that underlie this effect with glucose metabolism being one candidate.

Polyphasic Temporal Behavior of Finger-Tapping Performance: A Measure of Motor Skills and Fatigue

Successive voluntary motor movement involves a number of physiological mechanisms and may reflect motor skill development and neuromuscular fatigue. In this study, the temporal behavior of finger tapping was investigated in relation to motor skills and fatigue by using a long-term computer-based test. The finger-tapping performances of 29 healthy male volunteers were analyzed using linear and nonlinear regression models established for inter-tapping interval. The results suggest that finger-tapping performance exhibits a polyphasic nature, and has several characteristic time points, which may be directly related to muscle dynamics and energy consumption. In conclusion, we believe that future studies evaluating the polyphasic nature of the maximal voluntary movement will lead to the definition of objective scales that can be used in the follow up of some neuromuscular diseases, as well as, the determination of motor skills, individual ability, and peripheral fatigue through the use of a low cost, easy-to-use computer-based finger-tapping test.

Acute effects of dietary constituents on motor skill and cognitive performance in athletes

Performance in many sports is at least partially dependent on motor control, coordination, decision-making, and other cognitive tasks. This review summarizes available evidence about the ingestion of selected nutrients or isolated compounds (dietary constituents) and potential acute effects on motor skill and/or cognitive performance in athletes. Dietary constituents discussed include branched-chain amino acids, caffeine, carbohydrate, cocoa flavanols, Gingko biloba, ginseng, guarana, Rhodiola rosea, sage, L-theanine, theobromine, and tyrosine. Although this is not an exhaustive list, these are perhaps the most researched dietary constituents. Caffeine and carbohydrate have the greatest number of published reports supporting their ability to enhance acute motor skill and cognitive performance in athletes. At this time, there is insufficient published evidence to substantiate the use of any other dietary constituents to benefit sports-related motor skill or cognitive performance. The optimal dose and timing of caffeine and carbohydrate intake promoting enhanced motor skill and cognitive performance remain to be identified. Valid, reliable, and sensitive batteries of motor skills and cognitive tests should be developed for use in future efficacy studies.

Caffeine and cognitive performance: persistent methodological challenges in caffeine research

Human cognitive performance is widely perceived to be enhanced by caffeine at usual dietary doses. However, the evidence for and against this belief continues to be vigorously contested. Controversy has centred on caffeine withdrawal and withdrawal reversal as potential sources of experimental confounding. In response, some researchers have enlisted "caffeine-naïve" experimental participants (persons alleged to consume little or no caffeine) assuming that they are not subject to withdrawal. This mini-review examines relevant research to illustrate general methodological challenges that have been the cause of enduring confusion in caffeine research. At issue are the processes of caffeine withdrawal and withdrawal reversal, the definition of caffeine-naïve, the population representativeness of participants deemed to be caffeine-naïve, and confounding due to caffeine tolerance. Attention to these processes is necessary if premature conclusions are to be avoided, and if caffeine's complex effects and the mechanisms responsible for those effects are to be illuminated. Strategies are described for future caffeine research aimed at minimising confounding from withdrawal and withdrawal reversal.

Effects of upper respiratory tract illnesses, ibuprofen and caffeine on reaction time and alertness

RATIONALE

Compared with healthy individuals, those with upper respiratory tract illnesses (URTIs) report reduced alertness and have slower reaction times. It is important to evaluate medication that can remove this behavioural malaise.

OBJECTIVES

The aim of this study was to compare the effects of a combination of ibuprofen plus caffeine with ibuprofen and caffeine alone, and placebo on malaise associated with URTIs, as measured by psychomotor performance and mood testing.

METHODS

Volunteers were randomly assigned to one of four medication conditions as follows: 200 mg ibuprofen and 100 mg caffeine; 200 mg ibuprofen; 100 mg caffeine; placebo. A single oral dose was given and testing followed for 3 h. Efficacy variables were based on the volunteers' performance, measured by psychomotor performance and mood.

RESULTS

The pre-drug results confirmed that those with an URTI had a more negative mood and impaired performance. Results from the simple reaction time task, at both 55- and 110-min post-dosing, showed that a single-dose of caffeinated products (I200/C100 and CAF100) led to significantly faster reaction times than IBU200 and placebo. These effects were generally confirmed with the other performance tasks. Subjective measures showed that the combination of ibuprofen and caffeine was superior to the other conditions. There were no serious adverse events reported, and study medication was well tolerated.

CONCLUSIONS

The results from the post-drug assessments suggest that a combination of ibuprofen and caffeine was the optimum treatment for malaise associated with URTIs in that it had significant effects on objective performance and subjective measures.

Effects of caffeine and alcohol on mood and performance changes following consumption of lager

RATIONALE

The present study examined whether caffeine would modify the behavioural effects of alcohol.

OBJECTIVES

The aim of the study was to determine whether caffeine modifies the effects of alcohol on mood and psychomotor performance and to identify possible dose-response and temporal relationships.

METHODS

A double-blind study examined the effects of three successive lager drinks (330 ml each) in the early afternoon on mood and psychomotor performance assessed at 30-min intervals over a 2-h period. Participants carried out a baseline session and were then randomly assigned to one of six conditions formed by combining three different doses of caffeine (0, 62.5 and 125 mg per drink) with either no alcohol or 4.3 % alcohol. One hundred and forty-six young adults (65 male, 81 female; age range 18-30 years) participated in the study. Mood (alertness, hedonic tone and anxiety) was assessed before and after performing simple reaction time and choice reaction time tasks.

RESULTS

Alcohol was associated with higher hedonic tone (p < 0.005), reduced anxiety (p < 0.05) and reduced alertness (p < 0.005). Caffeine had no modifying effect on hedonic tone or anxiety. However, the highest dose of caffeine did remove the effect of alcohol on alertness (p < 0.05). Effects of alcohol and caffeine were found on the performance tasks (all p values < 0.05) but these were independent effects.

CONCLUSIONS

The results from the present study confirm that caffeine does not remove the negative effects of alcohol on performance although high doses counteract the drop in subjective alertness produced by alcohol.