Study Title and Description
Sex differences in reinforcing value of caffeinated beverages in adolescents.
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||Sex differences in reinforcing value of caffeinated beverages in adolescents.|
|Author||JL Temple,AM Bulkley,L Briatico,AM Dewey,|
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 purpose of this study was to test the hypothesis that adolescents find caffeinated soda more reinforcing than noncaffeinated soda and that this would be related to the level of usual caffeine consumption and to sex.|
|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)||Adolescents, aged 12–17 years were recruited through a direct mailing targeted at households with at least one child who was 12–17 years of age. Eligible participants and their parents were asked to visit the laboratory on three occasions, each separated by 1 week, between 12.00–17.00 h. During the first session, a parent accompanied their child to the laboratory. They had the opportunity to ask questions and, if they decided they wanted to complete the study, they signed the forms. The child completed the behavioral checklist (Hughes et al., 1991) while the parents then completed a demographic questionnaire. Participants then sampled five different flavors of soda (green apple, black cherry, grape, cream soda, and citrus flavor) and rated each one for novelty and liking on 100mm Visual Analog Scales. All participants rated at least one of the beverages greater than 70 on the novelty scale. .... At the end of the testing session, the participant was given four, 64-oz bottles of the soda that was selected for them based on their taste–test ratings (the beverage rated closest to 100mm for liking that was also greater than 70mm on the novelty scale). These bottles had the labels removed and were relabeled with an A or a B. They were either caffeinated (33 mg/8 oz) or noncaffeinated. This concentration of caffeine was chosen because it is similar to that found in soda that is commonly consumed among adolescents. In addition, we decided to standardize the amount consumed by each participant. The participant was not explicitly made aware of the fact that caffeine was being manipulated. Instead, caffeine was listed as one of several things that could have been manipulated between the two sodas, including artificial sweetener, carbonation, and artificial coloring. This deception was an alteration in the usual Institutional Review Board procedure, but was acceptable because it involved no greater than minimal risk, and it did not adversely affect the welfare of the participants because they were told at the beginning that they would be debriefed as to the exact nature of the experiment at the end. This level of deception was necessary to prevent potential preconceptions of caffeine from altering experimental results. Participants were instructed that the beverage provided should be consumed in place of any other soda, coffee, energy drink, or tea. They were told to consume 32 oz per day and that the beverage was to be consumed in 8 oz portions. They were provided with an 8 oz measuring cup and were told to pour the 8 oz into a glass and drink it within 15 min. They were also instructed to record times and amounts of beverages and food consumed in a provided habit book. One week later, all empty bottles were returned to the laboratory. During this visit, the participant completed the behavioral checklist, a previous day dietary recall, and a beverage-liking questionnaire. Participants were given a new habit book and a second set of four, 64-oz bottles with the opposite caffeine condition (if they received A during week 1, they would get B during week 2) and the procedures were repeated. The following week, 8 days after the second laboratory visit, participants returned to the laboratory for a third visit. Before this visit, participants were instructed not to eat or drink anything containing caffeine and to terminate consumption of the test beverages for 24 h prior to the visit. Data from any participant who had caffeine levels indicative of recent usage were excluded. The participant then completed the same behavioral checklist and liking questionnaires from the previous week as well as a 24-h dietary recall. The debriefing was conducted in an interview-style using the following open-ended questions. (i) What do you think the purpose of this experiment was? (ii) Did you think that the drinks you drank at home had caffeine in them? If Yes, which one(s). (iii) Did you think any of the drinks you drank at home had sugar in them? If Yes, which one(s). After the participant answered the questions, they rejoined their parent and both parent and child were told the purpose of the study. To prepare the beverages, caffeine was suspended in flattened Sprite using a heated stir plate at a concentration of 16.5 mg/ml. Sprite was chosen so that the sweetness would help to mask the bitterness of the caffeine. When 2-l bottles were prepared, 16ml of soda were removed from each and 16 ml of either the ‘A’ solution (flat Sprite only) or the ‘B’ solution (flat Sprite plus caffeine) were added back into each bottle. All solutions were prepared by a research assistant who was not involved in the data collection for this study so that the experimenters could remain blind to the caffeine content of the beverages. This [behavioral] questionnaire consisted of a list of 31 physical or psychological adjectives that the child rated using a Likert scale from 1 to 9 with 1 being ‘Not at all’ and 9 being ‘Extremely’ (Hughes et al., 1991). The items on the list were made up of the following words: anxious, alert, content, depressed, dizzy, drowsy, fatigued, frequent urination, headache, insomnia, irregular heartbeat, diarrhea, impatient, hungry, irritable, motivated to work, well-being, mood swings, muscle twitches, talkative, nausea, palpitation, restlessness, ringing in ears, energetic, stomachache, vigorous, perspiration, tremor, sleepy, and tired. Participants were asked to indicate the extent to which each word described how they felt during the past week. Participant characteristics, including age, BMI, and self-reported caffeine consumption and measured variables, including scores on the triangle test and food intake data from the Block Food Frequency Questionnaire, were compared using a one-way analysis of variance with sex and caffeine consumption group (high vs. low) as between-subjects factors. Caffeine consumption group was determined using a median split of the data with participants consuming less than 50 mg/day considered as ‘low’ users and those consuming greater than or equal to 50 mg/day considered as ‘high’ users. Other characteristics, such as race and parental education and income, were compared across the sex and caffeine consumption group using X^2 analyses. The pattern of operant responding for portions of soda and responses on the behavioral checklist were compared using mixed effects regression models (MRM) with sex, usual caffeine consumption (continuous variable) and soda type (placebo or caffeine) as time-invariant predictors, and phase (baseline or posttest) and schedule of reinforcement (operant responding only) as time-variant predictors. In addition, order of placebo or caffeine presentation (for weekly beverage consumption), kilocalories consumed on the day of the experiment, preexperimental thirst, and score on the triangle test were included as covariates in the analysis. Ratings of thirst were compared using the same MRM, but pre/post was added as an additional time variant predictor for these analyses. Post-hoc analyses were conducted using linear contrasts.|
|How many outcome-specific endpoints are evaluated?||3|
|What is the (or one of the) endpoint(s) evaluated? (Each endpoint listed separately)||Irritability|
|List additional health endpoints (separately).|
|List additional health endpoints (separately)|
|What is the study design?||Controlled Trial|
|Randomized or Non-Randomized?||NCT|
|What were the diagnostics or methods used to measure the outcome?||Subjective|
|Optional: Name of Method or short description||Unspecified questionnaire|
|Caffeine (general)||Caffeine (general)|
|What was the reference, comparison, or control group(s)? (e.g. high vs low consumption, number of cups, etc.)||Individuals served as their own controls. They were given noncaffeinated or caffeinated soda for 1 week, followed by a week of the beverage not consumed in the week prior.|
|What were the listed confounders or modifying factors as stated by the authors? (e.g. multi-variable components of models. Copy from methods)||None reported|
|Provide a general description of results (as reported by the authors).||There was a significant main effect of sex on ratings of irritability (P<0.05), with females reporting higher irritability than males (3.0±0.6 vs. 2.5±0.5). There was a significant main effect of phase on hunger (P<0.02) with higher reports of hunger during the week of placebo (4.65±0.5) than the week of caffeine (4.09±0.4). There was a significant main effect of caffeine use group on ratings of headache (P<0.05), stomachache (P<0.01), dizziness (P<0.05), muscle twitch (P<0.05), and tremor (P<0.05) with all measures reported to be greater by high-caffeine users compared with low-caffeine users.|
|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?||We found some differences in results from the behavioral checklist as a function of typical caffeine use, with high caffeine users reporting more headache, stomachache, dizziness, muscle twitching, and tremor than low-caffeine users. Finally, we found no sex or caffeine-use differences in any of the measures from the Food Frequency Questionnaire. When taken together, these data suggest that, after exposure to a caffeinated and noncaffeinated version of the same soda, males find the caffeinated version more reinforcing than females. Future studies will focus on determining the mechanism for this sex difference.|
|What were the sources of funding?||This study was supported by a grant to J.L.T. from the National Institute of Drug Abuse (KO1-DA021759).|
|What conflicts of interest were reported?||None Reported|
|Does the exposure (dose) need to be standardized to the SR?||Yes|
|Provide calculations/conversions for the exposure based on the decision tree in the guide (for all endpoints/exposure levels of interest).||Adolescents had an average age of 14.3 (males) and 13.9 (females), thus 56.8 kg was used for conversion. 132 mg/56.8 kg = 2.32 mg/kg/d|
|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.||Irritability NOAEL = 2.32 mg/kg/d Headache NOAEL = 2.32 mg/kg/d Hunger LOAEL = 2.32 mg/kg/d|
|Notes regarding selection/listing of endpoints and exposures/doses to be compared to Nawrot.||The study authors do not explicitly state that irritability and headache were nonsignificant. However, wording of the results and review of the provided data (Table 3) lead me to believe these should be NOAELs when comparing caffeine to placebo. This study only administered caffeine at one exposure level (2.32 mg/kg/d)|
|What is the importance of the study with respect to the adverseness of the outcome?||Low|
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.