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Study Title and Description

Timing of caffeine's impact on autonomic and central nervous system measures: clarification of arousal effects.



Key Questions Addressed
1 For [population], is caffeine intake above [exposure dose], compared to intakes [exposure dose] or less, associated with adverse effects on cardiovascular outcomes?
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Primary Publication Information
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TitleData
Title Timing of caffeine's impact on autonomic and central nervous system measures: clarification of arousal effects.
Author RJ Barry,AR Clarke,SJ Johnstone,JA Rushby,
Country
Year 2008
Numbers

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


Extraction Form: Cardiovascular Design
Design Details
Question... Follow Up Answer Follow-up Answer
What outcome is being evaluated in this paper? Cardiovascular
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What is the objective of the study (as reported by the authors)? The timing of caffeine effects on arousal levels was examined. From previous work in the authors’ laboratory, an increase in skin conductance level (SCL) was used as the marker of arousal increase, and they sought to identify the timing of this and related effects following caffeine ingestion. A single oral dose of caffeine (250 mg) was used in a randomized double-blind placebo-controlled repeated-measures cross-over study. Eyes-closed resting electroencephalogram (EEG) and autonomic data (SCL, heart rate, respiration rate, and systolic and diastolic blood pressure) during 2 min epochs that commenced every 4 min after ingestion, were analyzed.
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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) Subjects: Participants were 24 university students (17 females) recruited from the undergraduate psychology pool at a university. Testing sessions were scheduled in the afternoon, and subjects were instructed to abstain from caffeine for at least 4 h before the first session, and to follow the same consumption pattern before their second session. Subjects were screened for neurological disease, head injury, learning disability and psychiatric conditions. Participation was restricted to non-smokers, as nicotine is known to have strong effects on caffeine metabolism Heart Rate Recording: Heart rate was recorded via an electrocardiogram using a pair of pre-jelled disposable Ag/AgCl electrodes, placed at mid sternum and over the third rib on the left mid-axillary line. Blood pressure was recorded continuously using a Finapres Ohmeda 2300, with a finger cuff over the proximal phalange of digit IV on the non-dominant hand. Procedure: Prior to testing, subjects received one of two identical gelatin capsules containing either 250 mg caffeine or placebo in a pre-determined randomized order. The experiment was conducted in a double-blind manner. Then they began a testing session of approximately 1 h consisting of (a) 2 min eyes closed followed by 2 min eyes open, with each change signalled by a brief (20 ms duration with 15 ms rise- and fall-times) 1000 Hz 80 dB tone, for a total of 32 min; (b) an active auditory oddball task or Continuous Performance Task lasting approximately 12 min; (c) alternating 2 min eyes closed followed by 2 min eyes open, as in part (a), for a total of 16 min; these segments were separated by brief rest periods. They were asked to remain still, to fixate on a point on a screen in front of them during eyes-open conditions, and to try to avoid excessive blinking. All 2 min segments from the eyes-closed resting condition in parts (a) and (c) were examined in this study. Subjects returned for a second test at the same time 1 week later, when the same procedure was followed and the alternate capsule was administered.
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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) Heart rate
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List additional health endpoints (separately). 2 Blood pressure (systolic and diastolic)
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List additional health endpoints (separately).3
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List additional health endpoints (separately).4
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List additional health endpoints (separately).5
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List additional health endpoints (separately).6
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Clinical, physiological, other Physiological
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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? Objective
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Optional: Name of Method or short description Heart rate was recorded via an electrocardiogram using a pair of pre-jelled disposable Ag/AgCl electrodes, placed at mid sternum and over the third rib on the left mid-axillary line. Blood pressure was recorded continuously using a Finapres Ohmeda 2300, with a finger cuff over the proximal phalange of digit IV on the non-dominant hand.
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Caffeine (general) Caffeine (general)
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Coffee, Chocolate, energy drink, gum, medicine/supplement, soda, tea, other?
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Measured or self reported? Measured
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Children, adolescents, adults, or pregnant included? Adults
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What was the reference, comparison, or control group(s)? (e.g. high vs low consumption, number of cups, etc.) Subjects were their own control. They received either a gelatin capsule containing either 250 mg caffeine or placebo in a pre-determined randomized order.
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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) Subjects were screened for neurological disease, head injury, learning disability and psychiatric conditions. Participation was restricted to non-smokers.
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What conflicts of interest were reported? The authors did not mentions whether there were conflicts or not.
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Refid 18093716
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What were the sources of funding? Australian Research Council Discovery funding scheme.
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Results & Comparisons

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