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Study Title and Description

Expectations and placebo responses to caffeine-associated stimuli.



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 Expectations and placebo responses to caffeine-associated stimuli.
Author MA Flaten,O Aasli,TD Blumenthal,
Country
Year 2003
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 contribution of the present study was to investigate the relationship between expectation, induced through repeated use of caffeine in the natural environment, and the placebo response to caffeine-associated stimuli.
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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 A total of 20 subjects (ten females and ten males, mean age 26.8 years, range 19–45 years) participated in the experiment. Subjects with a history of serious disease or injury were not included. All subjects drank at least one cup of coffee per day (mean 2.5 cups, range one to six cups per day), and had been drinking coffee for at least 6 months (mean 7.2 years, range 6 months to 25 years). Four subjects were removed from the blood pressure and two subjects were removed from the heart rate data due to experimenter error. Design The design for the blood pressure and heart rate was a three solution (caffeine in orange juice, orange juice without caffeine, decaffeinated coffee) x two cups within-subjects design. The order of presentation of the solutions across the three sessions was rotated according to a Latin-square design. The data were analysed by analysis of covariance (ANCOVA). A 0.05 a-level was chosen unless otherwise stated. Significant main effects and interactions were followed-up with the Tukey HSD test. The Statistica (Statsoft) software was used. The caffeine solution comprised 100% anhydrous caffeine (Pharmacy at the University Hospital of North Norway) dissolved in distilled water at a concentration of 8 mg/ml. Flat tonic water was used as placebo. Caffeine solution 25 ml (i.e. 200 mg caffeine), stored in a bottle marked "A", was mixed with about 175 ml sour tasting orange juice (Rora) that masked the taste of caffeine, in the caffeine condition. Tonic water 25 ml, stored in bottles marked "B" or "C", was added to about 175 ml orange juice or about 175 ml unsweetened, black decaffeinated coffee (Coop) in the orange juice and decaffeinated coffee conditions, respectively. The experimenter was blind regarding which bottle contained caffeine and which bottles contained tonic water. Blood pressure and heart rate were measured by an Omron HEM-405C digital monitor. Measurements were made three times with a 2-min pause between each measurement, and blood pressure and heart rate were computed as the mean of the last two measurements. Procedure All subjects were run on 3 separate days, and received different solutions on each day. The subjects were asked to refrain from ingesting caffeine and the use of nicotine or other drugs for at least 12 h prior to each session. To control for time of day effects, each subject was run at the same time each day. All subjects were run between 8 a.m. and 12 a.m. All administration of caffeine or tonic water was double-blind. The procedure for the experimental sessions was as follows: After arrival at the laboratory blood pressure and heart rate were recorded and several pre-tests (startle reflexes, noise stimuli, skin conductance) were conducted. The experimenter then measured up 25 ml caffeine solution (containing 200 mg caffeine) or 25 ml flat tonic water. The caffeine was always mixed with about 175 ml orange juice. The tonic water was mixed with either about 175 ml decaffeinated filter coffee, or with about 175 ml orange juice. Thus, each cup always contained about 200 ml of one of the solutions. Immediately after the end of the pretest the solution was administrated to the subject, who drank it as quickly as possible. Thirty minutes after ingestion of the solution, the first post-test was in effect. In this post-test, the effect of one cup of one of the solutions was tested. The post-test (startle reflexes, noise stimuli, skin conductance) lasted for about 10 min. Afterwards, blood pressure and pulse rate were again recorded. Immediately after the first post-test, a second cup with the same contents as the first cup was administrated. Thus, if 200 mg caffeine in orange juice was administrated in the first cup, 200 mg caffeine in orange juice was also administrated in the second cup. In the second post-test, performed 30 min after the second cup, the effect of two cups of one of the solutions was tested. The same recordings were made in the second post-test as in the first post-test. The subjects were debriefed after the third day. The duration of each experimental session was about 95 min.
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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) Blood pressure (SBP and DBP)
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List additional health endpoints (separately). 2 Heart rate
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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 Blood pressure and heart rate were measured by an Omron HEM-405C digital monitor.
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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 served as their own controls
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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
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What conflicts of interest were reported? No information provided
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Refid 12759808
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What were the sources of funding? This research was funded by a grant from the Norwegian Science Council (project no. 142540/320) to Dr. Flaten.
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Results & Comparisons

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