Advanced Search

Study Preview



Study Title and Description

Effects of expectation and caffeine on arousal, well-being, and reaction time.



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?
  • Comments Comments (
    0
    ) |

Primary Publication Information
  • Comments Comments (
    0
    ) |
TitleData
Title Effects of expectation and caffeine on arousal, well-being, and reaction time.
Author R Schneider,M Grüner,A Heiland,M Keller,Z Kujanová,M Peper,M Riegl,S Schmidt,P Volz,H Walach,
Country
Year 2006
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
  • Comments Comments (
    0
    ) |
What is the objective of the study (as reported by the authors)? The objective of this study is to determine the impact of expectation associated with placebo and caffeine ingestion.
  • Comments Comments (
    0
    ) |
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) [NOTE: This paper includes Experiment I and Experiment II. The majority of methods are described under Experiment I; however, that experiment was limited to decaffeinated coffee and is thus not applicable to this systematic review.] Participants Experiment 2 consisted of N = 45 German adults (25 women and 20 men) recruited from responses to a local newspaper advertisement addressing a general interest in the investigation of caffeine effects. Participants were included in the study if they met none of the following criteria: pregnancy, breast feeding, consumption of medicine or drugs, heart or circulation disease, continuing psychological or psychiatric treatment, and nonage. The mean age of the sample was 26.6 years (SD = 8.4 years; range, 20 to 62 years). Measures Blood pressure (systolic and diastolic) and heart rate were measured with a calibrated digital oscillometric sphygmomanometer, the boso-carat (boso Inc., Germany), which automatically inflates the arm cuff and shows the values on a Liquid Cristal display. Participants were asked to rest for 10 min before having their blood pressure taken. Caffeine, serving as the independent variable, was triturated (1g of quinine, 8 g of caffeine, ad 200 g lactose) and administered at a dose of 2 mg caffeine per kg body weight. Because caffeine has a neutral taste, the slightly bitter tasting quinine was added to reinforce the impression that the orange juice actually contained an active pharmacologic agent. Procedure All participants were asked to fast for a period of 4 hr prior to the experiment. They were asked to refrain from consumption of substances containing stimulants or caffeine (e.g., chocolate, cola) 24 hr prior to participation. They were greeted by a female experimenter in the experimental room of the Department of Psychology, University of Freiburg, and introduced to the study. The experimenter was blind in the sense that she had no knowledge of the substance administered in the experimental condition where participants were falsely informed. Participants were weighed to assess the amount of caffeine per body weight to be administered. During the whole session of about 1 hr, participants were asked to remain seated in order to reduce artifactual impact of movement on the measurement of blood pressure and heart rate. All dependent measures were taken at two time points, before and after administration of the beverage. Following the baseline measurements, the experimenter opened an opaque and numbered envelope containing the assignment to the experimental group that had been randomly generated by the first author before the experiment. Group allocation was according to a random sequence generated by the statistical software SPSS using a pseudo-random algorithm. Participants of the true information group (n = 15) were told that they were to consume a glass of caffeinated orange juice that was mixed by the experimenter before the eyes of the participants. They were told the dose and its approximate equivalent of one cup of coffee. The beverage was to be consumed within 1 min. Participants of the false information group (n = 15) were told that they had been assigned to the control group that was to consume orange juice, yet they ingested caffeine. In order to both avoid suspicion and enhance credibility on behalf of the experimenter, the experimenter was told that the substance she blindly mixed with the orange juice was a placebo bitter substance. In so doing, standardization of treatments was ensured. After awaiting period of 30 min necessary for caffeine to show its effect, posttreatment measures were taken. Participants of the control group (n = 15) were informed to belong to the group drinking no beverage and receiving no instructions. Statistical Analysis Preplanned analyses were repeated analyses of covariance (ANCOVAs) conducted on physiological, psychological, and reaction measures. In all analyses, baseline values served as the covariate. Effects for group differences were calculated according to the measure d by Cohen (1988).
  • Comments Comments (
    0
    ) |
How many outcome-specific endpoints are evaluated? 2
  • Comments Comments (
    0
    ) |
What is the (or one of the) endpoint(s) evaluated? (Each endpoint listed separately) Blood pressure (SBP and DBP)
  • Comments Comments (
    0
    ) |
List additional health endpoints (separately). 2 Heart rate
  • Comments Comments (
    0
    ) |
List additional health endpoints (separately).3
  • Comments Comments (
    0
    ) |
List additional health endpoints (separately).4
  • Comments Comments (
    0
    ) |
List additional health endpoints (separately).5
  • Comments Comments (
    0
    ) |
List additional health endpoints (separately).6
  • Comments Comments (
    0
    ) |
Clinical, physiological, other Physiological
  • Comments Comments (
    0
    ) |
What is the study design? Controlled Trial
  • Comments Comments (
    0
    ) |
Randomized or Non-Randomized? RCT
  • Comments Comments (
    0
    ) |
What were the diagnostics or methods used to measure the outcome? Objective
  • Comments Comments (
    0
    ) |
Optional: Name of Method or short description Blood pressure (systolic and diastolic) and heart rate were measured with a calibrated digital oscillometric sphygmomanometer, the boso-carat (boso Inc., Germany.
  • Comments Comments (
    0
    ) |
Caffeine (general) Caffeine (general)
  • Comments Comments (
    0
    ) |
Coffee, Chocolate, energy drink, gum, medicine/supplement, soda, tea, other?
  • Comments Comments (
    0
    ) |
Measured or self reported? Measured
  • Comments Comments (
    0
    ) |
Children, adolescents, adults, or pregnant included? Adults
  • Comments Comments (
    0
    ) |
What was the reference, comparison, or control group(s)? (e.g. high vs low consumption, number of cups, etc.) Placebo controls
  • Comments Comments (
    0
    ) |
What were the listed confounders or modifying factors as stated by the authors? (e.g. multi-variable components of models.  Copy from methods) Instructions to participants (one treatment group told beverage contained caffeine whereas other treatment group told it did not contain caffeine when it actually did)
  • Comments Comments (
    0
    ) |
What conflicts of interest were reported? No information provided
  • Comments Comments (
    0
    ) |
Refid 17228991
  • Comments Comments (
    0
    ) |
What were the sources of funding? This study was funded by the Samueli Institute, Alexandria, Virginia.
  • Comments Comments (
    0
    ) |




Results & Comparisons

No Results found.