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Study Title and Description

The effect of energy drinks on cortisol levels, cognition and mood during a fire-fighting exercise.



Key Questions Addressed
1 For [population], is caffeine intake above [exposure dose], compared to intakes [exposure dose] or less, associated with adverse effects on behavior*?
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Primary Publication Information
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TitleData
Title The effect of energy drinks on cortisol levels, cognition and mood during a fire-fighting exercise.
Author SI Sünram-Lea,J Owen-Lynch,SJ Robinson,E Jones,H Hu,
Country
Year 2012
Numbers

Secondary Publication Information
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Extraction Form: Behavior - Design Details - INCLUDED Studies
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Design Details
Question... Follow Up Answer Follow-up Answer
Refid 21710168
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What outcome is being evaluated in this paper? Behavior
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What is the objective of the study (as reported by the authors)? The aim of this study was to assess the effect of the two substances in combination under stressful and physically demanding conditions (fire-fighting training) on cognition, mood and cortisol release.
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Provide a general description of the methods as reported by the authors. Information should be extracted based on relevance to the SR (i.e., caffeine related methods) Using a double-blind, mixed measures design, 81 participants were administered a 330-ml drink containing either (1) 50 g glucose and 40 mg caffeine, (2) 10.25 g of fructose/glucose and 80 mg caffeine or a placebo drink and tested across a range of cognitive tasks, mood and physiological measures. Upon entering the testing site, participants were randomly allocated to a drink treatment regime. The timing of cortisol/blood glucose samples and cognitive testing was held constant across subjects and drink conditions to control for diurnal effects. Baseline behavioural and biochemical measures on day 1 were taken at the same time as post stressor measures on day 2 (11.40 pm), which allowed direct comparison of changes in these parameters across study days and controlled for differences in diurnal cortisol release. Baseline measures on day 2 (pre-exercise/drink) were taken before transport to the search and rescue site to allow evaluation of level of change in these measures on the day of stress exposure. The basic 3-day fire-fighter course was used as a physically demanding stressor. Over a course of 3 days, participants were briefed in the classroom on search and rescue procedure during a fire emergency and the use of the self-contained breathing apparatus (SCBA kit). On the final day, participants then took part in a 1-h simulated search and rescue mission involving the wearing of full turn-out gear including SCBA kit, entering a mock-up of a ship’s gallery filled with smoke and at temperatures of 60–130°C and the search retrieval of three dummies. On the second test day, following transportation to the fire-fighting ground, participants were given either one of the active drinks or placebo drink. Following a 15- min delay, participants then undertook the simulated search and rescue mission as described above. The exercise lasted approximately 1 h. Upon completion of the rescue mission, participants removed their breathing apparatus and were instructed report to the onsite office. There evaluation of handgrip strength, mood assessment, completion of cognitive tests battery and assessment of fire-fighting knowledge was carried out. Participants filled out a questionnaire comprising two separate self-rating scales, one measuring state anxiety and the other trait anxiety, each scale containing 20 items. This test consists of 25 adjectives that describe feelings and moods to measure levels of stress and arousal. Participants were instructed to indicate on a four-point scale how accurately each adjective matched their current state. The range of scores is 0–14 for stress and 0–11 for arousal.
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How many outcome-specific endpoints are evaluated? 2
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What is the (or one of the) endpoint(s) evaluated? (Each endpoint listed separately) Anxiety
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List additional health endpoints (separately).
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List additional health endpoints (separately)
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Notes
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Clinical
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Physiological
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Other Other
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What is the study design? Controlled Trial
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Randomized or Non-Randomized? RCT
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What were the diagnostics or methods used to measure the outcome? Subjective
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Optional: Name of Method or short description State-Trait Anxiety Inventory and Stress Arousal Checklist
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Caffeine (general)
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Coffee
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Chocolate
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Energy drinks
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Gum
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Medicine/Supplement
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Soda
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Tea
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Measured Measured
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Self-report
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Children
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Adolescents
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Adults Adults
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Pregnant Women
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What was the reference, comparison, or control group(s)? (e.g. high vs low consumption, number of cups, etc.) placebo drink vs high caffeine/low glucose drink
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What were the listed confounders or modifying factors as stated by the authors? (e.g. multi-variable components of models.  Copy from methods) None stated
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Provide a general description of results (as reported by the authors). There was no significant difference in trait anxiety levels [F(2, 78)=1.253; p=0.291] among the three drink groups. Mean trait anxiety levels were 37.48 (±7.673) for the high glucose/low caffeine group, 37.42 (±9.66) for the high caffeine/low glucose group and 34.3 (±7.907) for the placebo group. For state anxiety, a significant effect of time was observed [F(2, 156)=16.149; p<0.0001], with participants reporting greater anxiety after the fire-fighting exercise compared to day 1 (p<0.0001) and pre-exercise levels on day 2 (p<0.0001). The time×drink interaction failed to reach significance [F(4, 156)=1.854; p=0.121] (Fig. 5a). Assessment of drink effects on day 2 showed that those in the high glucose/low caffeine drink group reported significantly smaller increase in anxiety compared to placebo group (p=0.038), whereas no such effect was observed for the high caffeine/low glucose group compared to placebo (see Table 3 and Fig. 5b). There was a significant effect of time on feelings of stress [F(2, 156)=15.58; p<0.0001], which was due to a significant increase in stress levels after search and rescue exercise compared to levels on day 1 (p<0.0001) and pre-exercise levels (p<0.001). Analysis of levels of change on the day of drink administration revealed that those in the high glucose condition reported only a minimal increase in stress levels after fire-fighting exercise compared to those who ingested placebo drink (p<0.05). No such differences were observed for those administered the high caffeine drink (see Table 3 and Fig. 5c, d).
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Did the authors perform a dose-response analysis (or trend/related analysis)? No
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What were the authors's observations re: trend analysis?
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What were the author's conclusions? In terms of mood effects, irrespective of drink, participants reported a significant increase in anxiety, stress and arousal and a decrease in calmness after the search and rescue exercise. When exploring the effect of drink administration, the high glucose/low caffeine drink led to a reduction in anxiety in both experimental groups and significantly reduced self-reported levels of stress following the search and rescue exercise. The anxiety reducing effect of the high glucose drink is in line with previous reports of sedating and tension relieving effects of carbohydrate administration compared to protein (Hartmann et al. 1977; Spring et al. 1989; Benton and Owens 1993). ... It is important to note, however, that clear interpretation of the results in terms of the effects evinced by caffeine or glucose is not possible because of the use of drink mixtures. As we did not administer glucose and caffeine in isolation, we cannot determine whether the observed effects are due to one substance or the other and whether there are interaction effects.
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What were the sources of funding? This work was supported by a grant from GlaxoSmithKline to S. I. Sünram-Lea, J. Owen-Lynch. Experimental design, data analysis and report writing were carried out by S. I. Sünram-Lea with no further input from GlaxoSmithKline.
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What conflicts of interest were reported? The author Henglong Hu works for GlaxoSmithKline. All other authors declare that they have no conflicts of interest.
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Does the exposure (dose) need to be standardized to the SR? No
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Provide calculations/conversions for the exposure based on the decision tree in the guide (for all endpoints/exposure levels of interest).
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List all the endpoint(s) followed by the dose (mg) which will be used in comparison to Nawrot.  Characterize value as LOAEL/NOAEL, etc. if possible.  Anxiety NOAEL = 80 mg Stress NOAEL = 80 mg
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Notes regarding selection/listing of endpoints and exposures/doses to be compared to Nawrot.
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What is the importance of the study with respect to the adverseness of the outcome? Low
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