Reversal of caffeine withdrawal by ingestion of a soft beverage

Variability of physiological brain perfusion in healthy subjects - A systematic review of modifiers. Considerations for multi-center ASL studies

Quantitative measurements of brain perfusion are influenced by perfusion-modifiers. Standardization of measurement conditions and correction for important modifiers is essential to improve accuracy and to facilitate the interpretation of perfusion-derived parameters. An extensive literature search was carried out for factors influencing quantitative measurements of perfusion in the human brain unrelated to medication use. A total of 58 perfusion modifiers were categorized into four groups. Several factors (e.g., caffeine, aging, and blood gases) were found to induce a considerable effect on brain perfusion that was consistent across different studies; for other factors, the modifying effect was found to be debatable, due to contradictory results or lack of evidence. Using the results of this review, we propose a standard operating procedure, based on practices already implemented in several research centers. Also, a theory of 'deep MRI physiotyping' is inferred from the combined knowledge of factors influencing brain perfusion as a strategy to reduce variance by taking both personal information and the presence or absence of perfusion modifiers into account. We hypothesize that this will allow to personalize the concept of normality, as well as to reach more rigorous and earlier diagnoses of brain disorders.

Physiological and glycemic responses following acute ingestion of a popular functional drink in patients with type 1 diabetes

OBJECTIVE

To determine the physiologic and glycemic responses to energy drinks by people with type 1 diabetes.

METHODS

In a double-blind randomized comparison of Red Bull, Red Bull Light and a control drink, 16 adults (11 females; average age 31.5 years) with type 1 diabetes and an average glycated hemoglobin (A1C) of 68 mmol/mol were given 750 mL of Red Bull, Red Bull Light and Suso Orange in a random order. During 3 hours, comparisons were made of blood pressure and blood glucose and caffeine levels; 4-choice reaction time (4CRT) and a digit symbol substitution test were used to assess cognitive performance. Mood was measured using the University of Wales Institute of Science and Technology mood adjective checklist.

RESULTS

Consumption of Red Bull and Suso Orange were associated with an early sustained rise in blood glucose, which was augmented by Red Bull (p=0.02). A transient rise in systolic blood pressure (115.9 mm Hg to 124.5 mm Hg and 115.8 mm Hg to 125.9 mm Hg, respectively, both p<0.01) followed consumption of Red Bull and Red Bull Light. There were less consistent changes in diastolic blood pressure and heart rate. Consumption of both energy drinks resulted in modest improvement in performance on the digit substitution test but had no effect on 4CRT. Energy arousal and hedonic tone were influenced transiently only, following the consumption of Suso Orange.

CONCLUSIONS

Consumption of energy drinks can result in a significant carbohydrate load for people with diabetes, and patients must consider the need to adjust their insulin regimens appropriately. Caffeine-containing energy drinks can cause a rise in blood pressure, which may be an important consideration for individuals at risk for diabetes-related complications.

Differential responsiveness to caffeine and perceived effects of caffeine in moderate and high regular caffeine consumers

RATIONALE

Individual differences in responsiveness to caffeine occur even within a caffeine-consuming population, but the factors that mediate differential responsiveness remain unclear.

OBJECTIVES

To compare caffeine's effects on performance and mood in a group of high vs moderate consumers of caffeine and to examine the potential role of subjective awareness of the effects of caffeine in mediating any differential responsiveness.

MATERIALS AND METHODS

Two groups of regular caffeine consumers (<200 mg/day and >200 mg/day) attended two sessions at which mood and cognitive functions were measured before and 30 min after consumption of 400-mg caffeine or placebo in a capsule. Cognitive tests included visual information processing, match-to-sample visual search (MTS) and simple and choice reaction times. Post-session questionnaires asked participants to describe any perceived effect of capsule consumption.

RESULTS

High consumers, but not moderate consumers, demonstrated significantly faster simple and choice reaction times after caffeine relative to placebo. These effects were not attributable to obvious group differences in withdrawal or tolerance because there were no group differences in baseline mood or in reports of negative affect after caffeine. Instead, the high consumers were more likely to report experiencing positive effects of caffeine, whereas the moderate consumers were more likely to report no effect.

CONCLUSIONS

The sensitivity of caffeine consumers to the mood- and performance-enhancing effects of caffeine is related to their levels of habitual intake. High caffeine consumers are more likely than moderate consumers to perceive broadly positive effects of caffeine, and this may contribute to their levels of use.

Effects of caffeine on performance and mood: withdrawal reversal is the most plausible explanation

RATIONALE

Although it is widely believed that caffeine can enhance human performance and mood, the validity of this belief has been questioned, giving rise to debate. The central question is whether superior performance and mood after caffeine represent net benefits, or whether differences between caffeine and control conditions are due to reversal of adverse withdrawal effects.

OBJECTIVES

To provide a focussed review of relevant experimental studies with the aim of clarifying current understanding regarding the effects of caffeine on human performance and mood.

METHODS

To avoid the shortcomings of standard placebo-controlled studies, which are ambiguous due to failure to control for the confounding influence of withdrawal reversal, three main experimental approaches have been employed: studies that compare consumers and low/non-consumers, pre-treatment and ad lib consumption studies, and long-term withdrawal studies.

RESULTS

Of the three approaches, only long-term withdrawal studies are capable of unambiguously revealing the net effects of caffeine. Overall, there is little evidence of caffeine having beneficial effects on performance or mood under conditions of long-term caffeine use vs abstinence. Although modest acute effects may occur following initial use, tolerance to these effects appears to develop in the context of habitual use of the drug.

CONCLUSIONS

Appropriately controlled studies show that the effects of caffeine on performance and mood, widely perceived to be net beneficial psychostimulant effects, are almost wholly attributable to reversal of adverse withdrawal effects associated with short periods of abstinence from the drug.

A critical review of caffeine withdrawal: empirical validation of symptoms and signs, incidence, severity, and associated features

RATIONALE

Although reports of caffeine withdrawal in the medical literature date back more than 170 years, the most rigorous experimental investigations of the phenomenon have been conducted only recently.

OBJECTIVES

The purpose of this paper is to provide a comprehensive review and analysis of the literature regarding human caffeine withdrawal to empirically validate specific symptoms and signs, and to appraise important features of the syndrome.

METHODS

A literature search identified 57 experimental and 9 survey studies on caffeine withdrawal that met inclusion criteria. The methodological features of each study were examined to assess the validity of the effects.

RESULTS

Of 49 symptom categories identified, the following 10 fulfilled validity criteria: headache, fatigue, decreased energy/activeness, decreased alertness, drowsiness, decreased contentedness, depressed mood, difficulty concentrating, irritability, and foggy/not clearheaded. In addition, flu-like symptoms, nausea/vomiting, and muscle pain/stiffness were judged likely to represent valid symptom categories. In experimental studies, the incidence of headache was 50% and the incidence of clinically significant distress or functional impairment was 13%. Typically, onset of symptoms occurred 12-24 h after abstinence, with peak intensity at 20-51 h, and for a duration of 2-9 days. In general, the incidence or severity of symptoms increased with increases in daily dose; abstinence from doses as low as 100 mg/day produced symptoms. Research is reviewed indicating that expectancies are not a prime determinant of caffeine withdrawal and that avoidance of withdrawal symptoms plays a central role in habitual caffeine consumption.

CONCLUSIONS

The caffeine-withdrawal syndrome has been well characterized and there is sufficient empirical evidence to warrant inclusion of caffeine withdrawal as a disorder in the DSM and revision of diagnostic criteria in the ICD.