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Study Title and Description

Cerebral blood flow and behavioural effects of caffeine in habitual and non-habitual consumers of caffeine: a near infrared spectroscopy study.



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 Cerebral blood flow and behavioural effects of caffeine in habitual and non-habitual consumers of caffeine: a near infrared spectroscopy study.
Author DO Kennedy,CF Haskell,
Country
Year 2011
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 current placebo-controlled double-blind, balanced-crossover study employed near infrared spectroscopy to monitor pre-frontal cerebral-haemodynamics at rest and during completion of tasks that activate the pre-frontal cortex.
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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) Treatment: Each participant in each group received each of the treatments on separate days, not less than 48 h apart, in an order dictated by random allocation to a counterbalancing schedule. Depending on the condition to which the participant was allocated on each day they received either: inert placebo; or 75 mg caffeine hydrochloride BP (Fisher Scientific UK, Leicestershire). In order to maintain the double-blind procedure the treatments were prepared and coded by a third party who had no further involvement in any aspect of the study and each treatment was administered in size 1 gelatine capsules. Heart and blood pressure were monitored using the Boso medicus prestige (Bosch and Sohn, Jungingen, Germany). This is a fully automatic upper arm monitor that measures heart rate (bpm) and systolic and diastolic blood pressure (mmHg). Measurements were taken before the completion of the pre-dose baseline cognitive tasks and before the start of the pose-dose cognitive task period (i.e. ∼27 min post-dose). Cerebral blood flow—near infrared spectroscopy (NIRS): NIRS is a non-invasive brain imaging technique in which two nominal wavelengths of light (in this case using the manufacturer’s settings of ∼765 and 855 nm) which are differentially absorbed by oxygenated and deoxygenated haemoglobin respectively are introduced through the skull via a laser emitter and measured, following transit through the upper surface of the cortex, by an optode placed at a pre-set distance from the light source (4cm in this case). Relative changes in the absorption of near infrared light were measured at a time resolution of 10 Hz using a 12 channel Oxymon system (Artinis Medical Systems B.V.).
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How many outcome-specific endpoints are evaluated? 3
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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
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List additional health endpoints (separately).3 Cerebral blood flow
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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 and blood pressure were monitored using the Boso medicus prestige (Bosch and Sohn, Jungingen, Germany). This is a fully automatic upper arm monitor that measures heart rate (bpm) and systolic and diastolic blood pressure (mmHg). Cerebral blood flow—near infrared spectroscopy (NIRS): NIRS is a non-invasive brain imaging technique in which two nominal wavelengths of light (in this case using the manufacturer’s settings of ∼765 and 855 nm) which are differentially absorbed by oxygenated and deoxygenated haemoglobin respectively are introduced through the skull via a laser emitter and measured, following transit through the upper surface of the cortex, by an optode placed at a pre-set distance from the light source (4cm in this case). Relative changes in the absorption of near infrared light were measured at a time resolution of 10 Hz using a 12 channel Oxymon system (Artinis Medical Systems B.V.).
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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.) Placebo treatment; balanced, crossover study.
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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) Exclusion criteria included: lack of proficiency in English to the level of a native speaker; pregnancy or seeking to become pregnant; currently taking food supplements, illicit drugs or medication (including the contraceptive pill); food allergies or intolerances; a body mass index >40; tobacco consumption (even occasionally); a history of, or current, drug or alcohol abuse; head injury; neurological disorder or neuro-developmental disorder. The primary analyses of cognitive performance, ‘mental fatigue’ and ‘difficulty’ measures were conducted by MANOVA of ‘change from baseline data’ from individual tasks with treatment and repetition as within-subjects terms and consumer status as a between-subjects term. The primary analysis of the NIRS total-Hb data was conducted by repeated measures ANOVA with treatment and epoch as within-subjects terms and consumer status as a between-subjects term. Two sets of a priori planned comparisons were made to address the specific experimental questions. In order to assess the overall effects of caffeine on CBF (as indexed by total-Hb) comparisons were made between mean data from each epoch for the caffeine and placebo conditions irrespective of habitual/non-habitual consumption group. Additionally, in order to investigate any differential effects between the two consumption groups, comparisons were made separately for the habitual and non-habitual consumption groups on mean data from each epoch for the caffeine and placebo conditions. The planned comparisons were carried out using Bonferroni corrected t tests calculated with mean squares error from the ANOVA and evaluated with the degrees of freedom associated with this error term (Keppel, 1991) with the significance level adjusted for the number of comparisons (epoch x treatment interaction = 13 comparisons−adjusted alpha p < 0.0038; caffeine x treatment x consumption group interaction = 26 comparisons− adjusted alpha p < 0.0019 [p < 0.01, adjusted alpha p < 0.00038]). Heart rate, blood pressure and mood visual analogue scale outcomes were analyzed with mixed-design ANOVA, with assessment (pre/post treatment) and treatment as within-subjects terms and consumer status group as a between subjects terms.
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What conflicts of interest were reported? Authors stated, "The authors declare no conflicts of interest."
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Refid 21262317
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What were the sources of funding? Not mentioned.
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Results & Comparisons

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