Study Title and Description
Psychostimulant and other effects of caffeine in 9- to 11-year-old children.
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||Psychostimulant and other effects of caffeine in 9- to 11-year-old children.|
|Author||SV Heatherley,KM Hancock,PJ Rogers,|
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 withdrawal reversal hypothesis predicts that before they are given caffeine, caffeine consumers will have poorer mood, including lower alertness, and will display poorer cognitive performance than non-consumers because they will be experiencing the negative effects of caffeine withdrawal (Prediction 1). It also predicts that mood, including alertness, and performance will be improved by caffeine (relative to placebo) in caffeine consumers, but not in non-consumers (Prediction 2). Such results would suggest an overall adverse impact of caffeine consumption at a young age. On the other hand, if caffeine was found to have reliable psychostimulant effects in children who never or rarely consume caffeine this would show that caffeine can provide a net benefit for mood and performance.|
|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)||This was a double-blind, placebo-controlled study, cross-over study. Following overnight caffeine abstinence, 9- to 11-year-old children drank a fruit juice drink on two test days two weeks apart. The 125 ml drink contained either 50 mg of caffeine or no caffeine (placebo). All participants received each type of treatment, half receiving caffeine and half receiving placebo on the first test day, and vice versa on the second test day. Participants completed a number search task and selfratings of mood and physical symptoms both shortly before (pre-treatment baseline) and starting 30 minutes after these treatments. In order to assess the impact of habitual exposure to caffeine, the children were divided into two groups based on their reported usual level of caffeine consumption, namely non/low-consumers (£27 mg/d) and consumers (‡37 mg/d). This division of groups was based on a discontinuity in the distribution of average daily caffeine intakes in these children, which occurred at about 30 mg (which is also the amount of caffeine contained in a 330 ml can of cola). Participants Thirty-five children, 17 female, in year 5 and year 6 at a primary school in Wales, UK participated with the informed consent of their parents/guardians. Therefore the final data analyses were based on 26 participants: 17 non/low consumers (9 female), and 9 consumers (4 female). The children were not paid for their participation, but were rewarded with confectionery on completion of the study. Prior to testing, questionnaires were distributed to the parents/guardians of the children requesting information on caffeine consumption of their children on recent typical weekdays and weekend days. The responses showed that average daily caffeine consumption (according to the estimated caffeine-content of various beverages in James, 1997) of the participants ranged from 0 mg to 221 mg. This information was used to split the participants into two groups, namely non/low-consumers (£27 mg/d, mean ± SD, 12 ± 9 mg/d) and consumers (‡37 mg/d, 109 ± 70 mg/d). Age, gender ratio and body weight did not differ significantly between these groups. The relevant data (means ± SD) for the non/low-consumers and consumers are, respectively: 9.84 ± .64 and 10.11 ± .60 years; 9 girls, 8 boys and 4 girls, 5 boys; 39.9 ± 7.5 and 38.6 ± 3.2 kg. Mood and physical symptoms questionnaire The questionnaire described by Goldstein and Wallace (1997) was used. There were 20 items describing feelings of mood, including alertness, and various physical sensations, which participants rated on a 1- to 5-point scale (1 ¼ strongly disagree and 5 ¼ strongly agree, with points 2, 3 and 4 of the scale unlabelled). These 20 items were reduced to a smaller number of variables for analysis, as follows: ‘alertness’ (I feel energetic, I feel extra tired, I can think clearly, I don’t feel like doing much, I feel wide awake, I am having trouble thinking clearly, I feel like doing something active, I feel sleepy), ‘happy/friendly’ (I feel cheerful, I feel friendly, I feel sad, I feel angry, I feel happy), ‘headache’ (I have a headache), and ‘other negative physical symptoms’ (My muscles ache, I feel strong, My stomach hurts, My fingers tingle, I feel healthy, I feel good). Negative items were reversed scored except for ‘other physical symptoms’ for which positive items were reversed scored. Drinks Caffeine was administered in 125 ml apple or orange juice, containing 13 g sugar (Tesco Stores Ltd, UK). Fruit juice, rather than cola, was used in order to eliminate expectancy effects. For the caffeinated drink, food grade caffeine hydrochloride was dissolved in the drink at a concentration of 50 mg per 125 ml serving. The 125 ml placebo drink contained no caffeine. Individual children received the same juice (once with and once without caffeine) on each of the two test days, according to their preference stated on the first test day. Procedure As indicated above, each participant was tested twice. Testing took place in the same classroom between 9.30 and 10.30 a.m. on two Tuesday mornings two weeks apart. Participants completed the mood questionnaire and the number search task finishing shortly before (pre-treatment baseline) and again starting 30 minutes after administration of the drink. On both occasions participants had been instructed to abstain from all caffeine-containing drinks and foods from 8 p.m. the previous evening. Order of treatment (caffeine and placebo) was balanced across test days. Participants were instructed to fill out the mood questionnaire by thinking about how they were feeling at that particular time. No time constraints were put on this task. Following the completion of the questionnaire, the cognitive task was explained and administered. Within 5 minutes of finishing these ‘baseline’ measures, participants consumed their drink, which was served in a plastic cup. They were informed that the juice might or might not contain caffeine. During the next 30 minutes the experimenter occupied the participants with quiet exercises including a general knowledge quiz, and on the first test day each child was weighed during this time as well. After they had completed the post-treatment mood ratings and cognitive task the children were asked to record their answers to the following questions:  What did you have for breakfast?  Do you think you got caffeine in your drink? At the end of the session on the second test day participants were told when (first or second test day) they had received caffeine in their drink. Data analysis The cognitive performance and questionnaire data were analysed to test the two predictions of the withdrawal reversal hypothesis concerning: pre-treatment differences between caffeine consumers and non/low-consumers (Prediction 1 – caffeine consumers will have poorer mood, including lower alertness, and will display poorer cognitive performance than non-consumers), and differences in their subsequent response to caffeine administration (Prediction 2 – mood, including alertness, and performance will be improved by caffeine relative to placebo in caffeine consumers, but not in non-consumers, resulting in habit by treatment interaction effects). Pre-treatment scores on the first and second test days were averaged and the data were analysed using one-way ANOVA with caffeine habit as the factor. The effects of caffeine administration were analysed by calculating difference scores (post-treatment minus pre-treatment) and subjecting these to ANOVA with caffeine habit, treatment (caffeine vs. placebo) and treatment order (caffeine first/placebo second vs. placebo first/caffeine second) as factors. In the above analyses caffeine habit and treatment order were between-subjects factors, and treatment was a within subjects factor. Appropriate post hoc comparisons were carried out using the Newman–Keuls test (Winer, 1971), for which P values are reported (in brackets) in the results section. Paired samples t-tests were conducted to compare caffeine consumption on weekdays and weekend days, for both non/low-consumers and consumers. Pearson’s correlation was used to explore interrelationships among measures and within measures over time. An alpha level of .05 (two-tailed) was used for all statistical tests. The statistical analyses were carried out using SPSS version 9.0.|
|How many outcome-specific endpoints are evaluated?||1|
|What is the (or one of the) endpoint(s) evaluated? (Each endpoint listed separately)||headache|
|List additional health endpoints (separately).|
|List additional health endpoints (separately)|
|Notes||focus on the effects of withdrawal; other aspects of mood were studied, though only "alertness" and "happiness" were specified.|
|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||Questionnaire described by Goldstein and Wallace (1997) was used. There were 20 items describing feelings of mood, including alertness, and various physical sensations|
|Caffeine (general)||Caffeine (general)|
|What was the reference, comparison, or control group(s)? (e.g. high vs low consumption, number of cups, etc.)||placebo controlled in subjects just receiving juice (0 mg caffeine) vs 50 mg caffeine|
|What were the listed confounders or modifying factors as stated by the authors? (e.g. multi-variable components of models. Copy from methods)||subject's IQ was mentioned as a confounder, but this may not be relevant to the headache outcome|
|Provide a general description of results (as reported by the authors).||Directly in line with Prediction 2, there was a significant interaction effect for headache. (The maineffect of treatment on headache was also significant.) Following placebo treatment the consumers showed an increase in self-rated headache from the pretreatment level, whereas this did not occur when they received caffeine (P < .05). In contrast, the non/low-consumers’ level of headache changed little from pre- to post-treatment and it was not significantly by caffeine (P > .1).|
|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?||In some respects the present findings are even more striking, as the level of caffeine intake of the consumer group was in fact fairly modest. Despite this, these children differed from the non/low-consumers in their performance at ‘baseline’ (Prediction 1) and in their responses to caffeine (Prediction 2) in ways that suggest a negative impact of overnight caffeine withdrawal. For example, they performed less well than the non/low-consumers on the cognitive task before receiving caffeine, and if they did not receive caffeine their level of headache increased substantially (by over 1.5 points on a 5-point scale). Their performance was subsequently improved by caffeine, but not to above that of the non/low-consumers. This suggests an overall adverse impact of caffeine consumption: overnight caffeine withdrawal caused negative effects, which were reversed by subsequent caffeine consumption|
|What were the sources of funding?||This research was supported by a grant from the European Union Fifth Framework Programme (grant no. QLK1-2000-00069).|
|What conflicts of interest were reported?||None listed|
|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.||headache - NOAEL = 50 mg (1.3 mg/kg using 38.6 kg/child average as reported by authors)|
|Notes regarding selection/listing of endpoints and exposures/doses to be compared to Nawrot.||single dose headache scores were lessened (improved) in subjects who normally consume caffeine following the treatment compared to placebo; however, caffeine had no effect on headache in naive subjects.|
|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.