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Study Title and Description

Effects of repeated doses of caffeine on performance and alertness: new data and secondary analyses.



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 Effects of repeated doses of caffeine on performance and alertness: new data and secondary analyses.
Author P Hewlett,A Smith,
Country
Year 2007
Numbers

Secondary Publication Information
There are currently no secondary publications defined for this study.


Extraction Form: Behavior - Design Details - INCLUDED Studies
Arms
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Design Details
Question... Follow Up Answer Follow-up Answer
Refid 17514640
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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)? he present study aimed to determine whether caffeine withdrawal influenced mood and performance by comparing regular consumers who had been withdrawn from caffeine overnight with non-consumers. Following this repeated caffeine doses were administered to test the claim that repeated dosing has no extra effect on mood or performance.
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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) One hundred and twenty volunteers participated in the study. Regular caffeine consumption was assessed by questionnaire and this showed that 36 of the volunteers did not regularly consume caffeinated beverages. Volunteers were instructed to abstain from caffeine overnight and then completed a baseline session measuring mood and a range of cognitive functions at 08.00 the next day. Following this volunteers were given 0, or 1 mg/kg caffeine in a milkshake, glucose solution or water (at 09:00), followed by a second 0 or 1 mg/kg caffeine dose (at 09:40) and the test battery repeated at 10:00. MOOD AND PERFORMANCE TESTS The mood and performance test battery (described in detail in Smith et al., 1999) was run on IBM compatible computers. A response box attached to the computers contained a microchip, which controlled timing of the presentation of stimuli and timed the responses to the nearest millisecond. The following tasks were chosen as they had previously been used to examine the effects of caffeine. Predictions could therefore be made about the effect of caffeine on these tasks. Mood Mood was assessed before and after each battery of tasks using visual analogue rating scales (after Herbert et al., 1976; described in detail in Smith et al., 1999). These scales have been analysed to produce three factors: alertness, hedonic tone and anxiety.
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How many outcome-specific endpoints are evaluated? 1
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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 alertness and hedonic tone were also measured as part of the mood scales. the focus of the paper was not on anxiety per se
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Clinical
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Physiological
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Other
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What is the study design? Controlled Trial
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Randomized or Non-Randomized? NCT
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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 visual analogue scale
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Caffeine (general) 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.) 0, 1mg/kg, 2mg/kg caffeine
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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) N/A
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Provide a general description of results (as reported by the authors). [authors do not directly report on results of the anxiety outcome] From Table 4. Pre-session anxiety levels 0 mg/kg = 88.3, SE = 2.3; 1 mg/kg = 85.1, SE = 1.6; 2 mg/kg = 87.6 (SE = 2.3) Post-session anxiety levels 0 mg/kg = 90.0, SE = 2.1; 1 mg/kg = 87.4, SE = 1.5; 2 mg/kg = 86.9 (SE = 2.1)
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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? [authors do not directly report on results of the anxiety outcome]
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What were the sources of funding? Some of Professor Smith’s caffeine research has been supported by the Institute for the Scientific Investigation of Coffee
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What conflicts of interest were reported? N/A
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Does the exposure (dose) need to be standardized to the SR? Multiple metrics
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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). 2 mg/kg caffeine (administered as a split dose, 1mg/kg followed by another 1 mg/kg) 2 mg/kg caffeine x 80 kg (average standardized adult weight) = 160 mg/day
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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 = 160 mg/day
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Notes regarding selection/listing of endpoints and exposures/doses to be compared to Nawrot. no effects seen at levels below Nawrot. Authors do not explicitly make any conclusion based on this data though.
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What is the importance of the study with respect to the adverseness of the outcome? Important
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