Study Title and Description
Effects of dietary caffeine on mood when rested and sleep restricted.
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 dietary caffeine on mood when rested and sleep restricted.|
|Author||JE James,ME Gregg,|
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)?||Thus, the main aims of the present study were twofold. First, accepting that caffeine has the potential to restore mood levels degraded by short-term caffeine withdrawal, the study aimed to determine whether sustained (i.e. dietary) use of caffeine has any net effects on mood compared with sustained abstinence. Secondly, the study aimed to determine whether dietary caffeine has the potential to restore mood levels degraded by non-caffeine influences, in this instance, loss of positive mood due to sleep restriction.|
|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)||Participants Prospective participants were recruited from amongst the University student community. The project proposal was evaluated and assessed to be in strict adherence to institutional guidelines on human experimentation. Prospective participants were provided with printed details of the study, and the consent form stated that participants were free to withdraw consent at any stage. Using the symptom substance questionnaire (James et al., 1989), 48 healthy volunteers were selected, comprising 30 females and 18 males. All participants reported being habitual caffeine consumers, with intakes ranging from 180 to 680 mg caffeine per day (mean 355 mg), the approximate equivalent of 2–7 cups of coffee per day. Participants were normotensive (blood pressure less than 140/ 90mmHg), were not taking any prescription medication, and were not consulting a physician for any medical condition at the time of the study. Cigarette smokers and users of oral contraceptive steroids were excluded, because the elimination half-life of caffeine is significantly decreased by smoking (Parsons and Neims, 1978) and significantly increased by oral contraceptives (Abernethy and Todd, 1985). Participants ranged in age from 17–52 years (mean = 19 years), with body mass index (kg/m2) of 18–28 for females and 20–28 for males. Experimental design Throughout the study, caffeine and placebo (maize starch) were administered in gelatin capsules. At the start of each of 4 consecutive weeks, participants were supplied with the requisite number of capsules to be taken over the ensuing days. All capsules were visually identical and contained either starch alone or caffeine (B. P. anhydrous) plus starch filler. Participants were required to abstain from all caffeine beverages throughout the 4 weeks of the study, and were provided with supplies of decaffeinated coffee and tea to facilitate adherence to this requirement. Capsules were assigned double-blind to ensure alternating weeks of caffeine and placebo ingestion, with counterbalancing between participants. On day 7 of each week, participants visited the laboratory. On the evening preceding two of the laboratory visits (one in a placebo week and the other in a caffeine week), participants had their usual sleep. On the remaining two evenings preceding laboratory visits, participants received substantially less sleep than was their habit (procedure described below). Dietary caffeine For purposes of the study, dietary use was operationally defined as the ingestion of caffeine 1.75 mg/kg of body weight (the approximate equivalent of 1.0 to 1.5 cups of coffee) taken three times daily at 09.00, 11.00 and 15.00 for 7 consecutive days. This level and rate of intake approximates the ‘average’ pattern of caffeine consumption for the United States, the United Kingdom, Canada and Australia (James, 1991), and produces steady state levels of plasma caffeine concentration within 24 h of the commencement of regular intake (Pfeifer and Notari, 1988). In addition, because previous research has generally shown that caffeine tolerance plateaus (Denaro et al., 1991; Robertson et al., 1981) and withdrawal effects abate (Griffiths et al., 1986; Hughes et al, 1993) within 3– 5 days of continuous use, the present study employed 7 consecutive days of placebo/caffeine intake to achieve stability of responding by the end of each alternating period. Salivary caffeine To check compliance with the prescribed caffeine regimen, participants provided a 5 ml sample of saliva at 17.00 everyday for each of the 4 weeks. Previous research has shown that caffeine concentrations measured in saliva correlate highly with levels measured in blood (Alkaysi et al., 1988). Moreover, because plasma caffeine levels typically increase progressively during the day (due to intermittent consumption of caffeine beverages) and plateau by late afternoon or early evening, the best single-sample bioassay of daily caffeine intake is provided by samples obtained in the late afternoon (Lelo et al., 1986). The four laboratory visits were scheduled for 30 min after participants ingested their first caffeine/placebo capsule of the day. A saliva sample was taken 10 min after arriving at the laboratory (40 min after capsule ingestion) for the purpose of checking adherence to the caffeine/ placebo regimen at the time of each laboratory visit. Samples were stored at _x0001_20_x0002_C prior to being assayed using a method of enzyme immunoassay (EIA) developed in our laboratories. A competitive microtitre plate EIA was established, and a reproducible standard curve was obtained over the range 5–500 mg/ml caffeine. Cross-reactivities for paraxanthine, theobromine and theophylline (the main caffeine metabolites in humans) were considered satisfactory at 6.3, 0.7 and 2.3, respectively. The assay showed a good linear response when different volume equivalents of saliva were tested, and also gave good recovery of standard added to saliva samples (94– 123%). A good correlation was obtained when the same samples were assayed using standard HPLC method (r2=0.77, n=80). Mood scales Mood was assessed using a computerized version of the profile of mood states (POMS), consisting of 65 items designed to sample current mood (McNair et al., 1981). Although various mood scales have been used in previous caffeine research, the POMS has been the most widely used. Even then, comparing studies is limited by the fact that researchers have sometimes devised modified versions (e.g. Azcona et al., 1995). The standard form of the POMS yields a total score and sub-scale scores for each of six mood dimensions: anger–hostility; confusion–bewilderment; depression–dejection; fatigue–inertia; tension–anxiety; vigour–activity. Level of agreement to each of the 65 items is indicated by response to a five-point scale (‘not at all’ through ‘extremely’). An alternative form of the scale has been devised by the original authors, consisting of six mood dimensions characterized as bipolar states (confident–unsure, energetic–tired, etc.) (McNair et al., 1988). However, in the absence of empirical evidence indicating greater sensitivity of one or other form, we chose to use the standard form as doing so would facilitate direct comparisons with a larger number of previous studies. In the present study, the POMS was administered twice during the laboratory visit, at the beginning of the session and again, 35min later, at the end of the session. Statistical analysis The principal data-analytic procedure was three-way mixed-model analysis of variance (ANOVA), incorporating a between-groups factor for gender, and repeated-measures factors for caffeine (caffeine_x0003_ placebo) and sleep (restricted_x0003_rested).|
|How many outcome-specific endpoints are evaluated?||5|
|What is the (or one of the) endpoint(s) evaluated? (Each endpoint listed separately)||Anger-hostility|
|List additional health endpoints (separately).||Tension-anxiety|
|List additional health endpoints (separately)|
|Notes||POMS also measured vigour-activity|
|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||Profile of Mood States (POMS)|
|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 (no caffeine) vs 1.75 mg/kg-bw, 3x/day|
|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).||Total score and scores for the six dimensions of the POMS, expressed as averages of the first and second administration of the test, are summarized in Table 1. Table 2 summarizes the results of the three-way mixed-model ANOVA for total POMS score and each of the six POMS dimensions. Tables 1 and 2 also show that there were significant main effects for caffeine, indicative of detrimental influences in relation to total POMS score, and the dimensions of confusion–bewilderment [F=5.30, p<0.05] and vigour–activity.|
|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?||Caffeine had a detrimental effect on total POMS score, and on two of the six underlying dimensions of the POMS, confusion–bewilderment and vigour– activity. Previous research has shown that abrupt caffeine withdrawal leads to decrements in self-reported mood that are restored by caffeine re-ingestion (Griffiths et al., 1990; Hughes et al., 1993; Lieberman et al., 1987; Smit and Rogers, 2000; Evans and Griffiths, 1991; James, 1998; Lane and Phillips-Bute, 1998; Phillips-Bute and Lane, 1998; Richardson et al., 1995; Silverman and Griffiths, 1992). As explained above, these restorative effects have frequently been mistaken to be net benefits of caffeine consumption. By controlling for withdrawal effects induced by brief periods of caffeine abstinence, the present study was able to provide relatively unconfounded measures of net effects. The findings indicate that dietary caffeine had net detrimental effects on mood quality. Similarly, caffeine has been suspected of contributing to the development of anxiety disorders (DSM-IV-TR, American Psychiatric Association, 2000), which might suggest an exacerbating potential on the tension–anxiety dimension. Again, however, dietary caffeine was found to have no net effects on this dimension of mood. However, the apparent negative mood bias of the original POMS form may be more apparent than real. Within the range of moods typically assessed in caffeine studies (where more pronounced states of positive mood, for example, elation, have not been a focus of attention), absence of negative mood may provide a reasonably good representation of positive state of wellbeing. Thus, although seemingly representing mostly ‘negative’ states, the standard POMS subscales possibly provide a good indication of moderate levels of both positive and negative states. Caffeine had no significant net enhancing effects on mood when participants were rested... On the contrary, decrements in some aspects of mood were observed when participants were rested|
|What were the sources of funding?||This work was supported by the European Commission Fifth Framework Programme, Grant No. QLK1-CT-2000-00069.|
|What conflicts of interest were reported?||N/A|
|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).||Dosing = 1.75 mg/kg-bw, 3x/day (1.75 mg x 80 kg) x 3 = 420 mg/day|
|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.||Anger-hostility - NOAEL = 420 mg/day Confusion-bewilderment - LOAEL = 420 mg/day Depression-dejection - NOAEL = 420 mg/day Fatigue-inertia - NOAEL = 420 mg/day Tension-anxiety -NOAEL = 420 mg/day|
|Notes regarding selection/listing of endpoints and exposures/doses to be compared to Nawrot.||single dose Effects at dose higher than Nawrot.|
|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.