Study Title and Description
Effects of caffeine on mood and performance: a study of realistic consumption.
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*?|
Primary Publication Information
|Title||Effects of caffeine on mood and performance: a study of realistic consumption.|
|Author||CF Brice,AP Smith,|
Secondary Publication Information
There are currently no secondary publications defined for this study.
Extraction Form: Behavior - Design Details - INCLUDED Studies
No arms have been defined in this extraction form.
|Question... Follow Up||Answer||Follow-up Answer|
|What outcome is being evaluated in this paper?||Behavior|
|What is the objective of the study (as reported by the authors)?||The aim of the present study was to determine whether these effects would be observed with both administration of multiple small doses and a single large dose of caffeine.|
|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)||Design A within-subjects design was employed with each participant attending four test sessions on separate days. On 2 days, the participant received a single dose of either 200 mg caffeine or placebo, and on the remaining 2 days participants received four smaller doses of 65 mg caffeine or placebo. The order of caffeine condition presentation was counterbalanced with 50% of participants performing first under the caffeine condition and 50% under the placebo condition. Order of single/ multiple dose was also counterbalanced, as was the order in which the tests were performed. Administration of the caffeine was double blind. Participants Twenty-four male participants were recruited from the student population of the University of Bristol. The mean age of the sample was 20.96 years (range 19–23 years); the mean weight was 71.91 kg (range 60–86 kg); and the mean daily caffeine consumption, assessed by self-report, 210 mg (range 100–375 mg). In order to directly compare the two methods of administering the caffeine conditions, it was essential to control for factors known to influence caffeine metabolism (Brice and Smith 2001b). Participants were not eligible for the study if they were female, taking medication or if they smoked. Upon arrival at 0920 hours, participants provided a baseline saliva sample. At 0930 hours, participants performed a 30-min battery of the computer tasks. Between 1000 hours and 1300 hours, the testing schedule varied for the multiple-/single-dose conditions. In the multiple-dose condition, participants consumed their first cup of coffee immediately after completing the performance tasks at 1000 hours. When they had consumed all of the drink, participants were allowed to go about their normal everyday activities. Participants were reminded not to consume any caffeinated products. They were then required to return to the lab at 1100, 1200 and 1300 hours for a cup of coffee. For the single-dose condition, participants were allowed to go about their normal everyday activities at 1000 hours, and then returned at 1300 hours for a cup of coffee. From 1300 hours onwards, the testing schedule for both dose conditions resumed the same format. After drinking coffee at 1300 hours, participants were allowed to go for lunch as normal and then returned to the lab at 1455 hours, when a second saliva sample was taken. Details of what they had eaten and drunk during the morning and at lunch were recorded at this time. At 1500 hours, participants began the second test session. On completion of the second test session, participants were required to answer a second questionnaire to ascertain their perceptions of whether they believed that they had previously received caffeinated or de-caffeinated coffee. Matching of the caffeine doses. A pharmacokinetic analysis to ascertain equivalent dosage for the two conditions was conducted [utilising a linear two-compartment model (parametric population PK–PD model) employing the computer programme NONMEM version IV, level 1.0 (Shi et al.1993)]. The amount of caffeine assigned to the two dose conditions was calculated to ensure that the same levels of caffeine were present in the body at the final test session. From this analysis, it was ascertained that over a 5-h consumption period the caffeine dosage for each condition would be: a single dose of 200 mg (consumed at 1300 hours) and four doses of 65 mg (consumed at 1000, 1100, 1200 and 1300 hours). Nature of the drinks For both conditions all drinks were made with one rounded teaspoon of decaffeinated coffee in a 150-ml mug of boiling water. Milk and sugar were added in accordance with the participants’ usual preferences and this was recorded. Saliva samples Throughout this study caffeine levels were monitored via saliva samples collected through salivettes (Newton et al. 1981). An Emit caffeine assay (a homogenous enzyme immunoassay) was used to determine caffeine levels. Mood and performance All of the tasks are described in detail in Brice and Smith (2001b). Mood was assessed both pre- and post-performance using 18 computerised visual analogue mood rating scales. Three main factors were derived from these scales; alertness, hedonic tone and anxiety.|
|How many outcome-specific endpoints are evaluated?||1|
|What is the (or one of the) endpoint(s) evaluated? (Each endpoint listed separately)||anxiety|
|List additional health endpoints (separately).|
|List additional health endpoints (separately)|
|Notes||also assessed alertness and hedonic tone|
|What is the study design?||Controlled Trial|
|Randomized or Non-Randomized?||RCT|
|What were the diagnostics or methods used to measure the outcome?||Subjective|
|Optional: Name of Method or short description||visual analogue scale|
|Caffeine (general)||Caffeine (general)|
|What was the reference, comparison, or control group(s)? (e.g. high vs low consumption, number of cups, etc.)||comparison groups included placebos (0 mg caffeine), caffeine divided into 4x65 mg servings (260 mg); caffeine at 200 mg single dose|
|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|
|Provide a general description of results (as reported by the authors).||Analyses of co-variance with the baseline measure as a covariate were carried out. The within-subject variables were caffeine condition and multiple versus single dose. The between-subject factors were order of caffeine administration, order of dose and order of tasks. The method of analysis controls for any unwanted differences at baseline and removes order effects from the error term. Significant main effects of caffeine were found for anxiety. Anxiety (low scores = greater anxiety;maximum scores = 150). Caffeine single dose = 79+/- 13.3; Caffeine Multiple dose = 79+/- 17.8; De-caffeinated single dose = 85.8 +/- 10.2; Decaffeinated multiple doses = 84.2 +/- 28.76|
|Did the authors perform a dose-response analysis (or trend/related analysis)?||No|
|What were the authors's observations re: trend analysis?|
|What were the author's conclusions?||From the analysis, several effects of caffeine were found irrespective of dose regime. Furthermore, all the significant effects of caffeine supported previous findings in the literature (an increase in alertness – Roache and Griffiths 1987; Smith et al. 1990; an increase in anxiety – Loke 1988; faster simple reaction time – Smith et al. 1993; improvement in accuracy on the choice reaction time task – Smith et al. 1977; improved accuracy on a measure of vigilance – Smith et al. 1990; faster self-paced responding – Smith et al. 1993; increased speed with which new information was encoded – Brice and Smith 2001a; Smith AP et al. 1999; improved tracking accuracy – Kerr et al. 1991).|
|What were the sources of funding?||Carolyn Brice was supported by an Economic and Social Research Council post-graduate studentship. Professor Smith’s research on caffeine is supported by the Institute for Scientific Information on Coffee. The pharmacokinetic model used to determine the caffeine doses was supplied by Procter and Gamble Ltd. The caffeine assays were conducted by Unilever.|
|What conflicts of interest were reported?||N/A|
|Does the exposure (dose) need to be standardized to the SR?||No|
|Provide calculations/conversions for the exposure based on the decision tree in the guide (for all endpoints/exposure levels of interest).|
|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 - LOAEL = 200 mg/day|
|Notes regarding selection/listing of endpoints and exposures/doses to be compared to Nawrot.||Average weight of adult population was 71.92 kg. Anxiety also increased in the 4x65mg dosing schedule.|
|What is the importance of the study with respect to the adverseness of the outcome?||Important|
No baseline characteristics have been defined for this extraction form.
Results & Comparisons
No Results found.
|Arm or Total||Title||Description||Comments|
No quality dimensions were specified.
No quality rating data was found.