Study Title and Description
The effects of caffeine abstinence on sleep: a pilot study.
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||The effects of caffeine abstinence on sleep: a pilot study.|
|Author||SC Ho,JW Chung,|
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 this study was to examine whether caffeine abstinence in the evening could improve the sleep quality of those who habitually consume coffee.|
|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)||2.1. Design This was a pilot study employing a double-blind control group design. The subjects were recruited in a university using convenience sampling. They were assigned alternately to the experimental (caffeine-free) and control (caffeine) groups, beginning with the caffeine-free group and followed by the caffeine group. The subjects were required to complete the Pittsburgh Sleep Quality Index (PSQI) before the commencement of the experiment, so that their quality of sleep and usual bedtime could be identified. Their caffeine consumption habits of the past 6 months were also recorded. The subjects then took part in a 14-day experiment. The outcome measurements of quality of sleep included sleep–wake parameters, self-reported sleep quality, and level of refreshedness. 2.2. Sample Full-time university students were recruited during the semester. All eligible subjects had to be in good health with normal blood pressure. However, students were excluded if they were (i) habitual smokers; (ii) habitual alcohol drinkers; (iii) regular consumers of decaffeinated coffee, tea and cola; (iv) pregnant; (v) taking prescribed medication regularly; (vi) oral contraceptive users; or (vii) taking drugs that would affect their sleep. For female students, the study was commenced when they were not menstruating. 2.3. Procedures During the 14 days, all subjects were told not to consume caffeinated products other than those provided by the research team. A list of examples of caffeinated products was provided to the subjects. They were instructed to consume coffee as usual, and to drink a cup of coffee with their dinner, within 6 hours of their bedtime. Both the caffeine and caffeine-free groups consumed 100% pure coffee (100% pure Nescafe Gold Blend powdered instant coffee, 60 mg caffeine per serving) for the first 7 days. For the following 8th to 14th days, the caffeine group continued the intake of pure coffee while the caffeine-free group consumed decaffeinated coffee (Nescafe Gold Blend powdered instant coffee from which 97% of the caffeine had been removed, i.e. 1.8 mg of caffeine was consumed per serving). Subjects were instructed to drink the prepared coffee as usual, with one of the daily servings being within the 6 hours preceding their bedtime. It was assumed that the 7-day caffeinated coffee consumption within the 6 hours prior to bedtime was analogous to habitual consumption in the evening (James, 1998). The 7-day decaffeinated coffee consumption was analogous to being caffeine-free. Proceeding from habitual consumption to being caffeine- free was analogous to abstaining from caffeine following a period of habitual coffee consumption. To monitor their sleep quality during the experimental period, subjects were told to complete the 14-day sleep log before breakfast and wear a wrist actigraph to bed. Data collected on the 7th and 14th days were used for analysis. 2.4. Measures 2.4.1. Pittsburgh Sleep Quality Index (PSQI) 2.4.2. Sleep log A sleep log was used to reveal the current sleep status of the subjects in more defined terms. It could display any modifications in their sleep–wake patterns, including sleep–wake parameters and sleep-related factors. In this study, a five-point Likert scale was also included in the sleep log for the measurement of self-reported sleep quality. The scale ranged from 1 to 5, with 1 as very good, 2 good, 3 acceptable, 4 bad, and 5 very bad. The level of refreshedness of the subjects was also measured, with 1 as refreshed, 2 acceptable, 3 unrefreshed, and 4 sleepy. Both self-reported sleep quality and the level of refreshedness were regarded as measures of the participants' subjective sleep quality. 2.4.3. Wrist actigraph To obtain relatively accurate measurement of sleep–wake parameters, a wrist actigraph was used. Polysomnography (PSG) is considered the gold standard. Its application in the field setting may not be as convenient as that of the actigraph, particularly since measurement is done in subjects' homes. In view of the highly significant correlation between polysomnographic and actigraphic data in several studies (Blackwell et al., 2008; Kemlink, Pretl, Sonka, & Nevsimalova, 2008), the wrist actigraph was employed instead of PSG. The wrist actigraph is a watch-like device. The Mini Motionlogger actigraph (the basic model of actigraph, BMA-32, manufactured by Ambulatory Monitoring Incorporation) was used in this study. Actigraphic sleep–wake parameters were used to evaluate the objective sleep quality of the subjects. 2.5. Analysis The data collected in this study include PSQI scores, actigraphic sleep–wake parameters, self-reported sleep quality and level of refreshedness. Descriptive statistics such as frequency, mean, mode and standard deviation were conducted. The Mann–Whitney U and Fisher's Exact tests were used to compare the caffeine and caffeine free groups. For intragroup comparison, the Wilcoxon test was done to compare the pre- (7th day) and post- (14th day)|
|How many outcome-specific endpoints are evaluated?||1|
|What is the (or one of the) endpoint(s) evaluated? (Each endpoint listed separately)||sleep|
|List additional health endpoints (separately).|
|List additional health endpoints (separately)|
|Notes||sleep quality, latency, efficiency|
|What is the study design?||Controlled Trial|
|Randomized or Non-Randomized?||RCT|
|What were the diagnostics or methods used to measure the outcome?||Both|
|Optional: Name of Method or short description||actigraph and sleep log|
|What was the reference, comparison, or control group(s)? (e.g. high vs low consumption, number of cups, etc.)||caffeinated coffee vs decaffeinated coffee|
|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).||To investigate the effects of caffeine abstinence on quality of sleep, we compared changes in the quality of sleep from habitual consumption (day 7) to being caffeine-free (day 14). In view of the small sample size, the Wilcoxon test was employed to examine the changes. As shown in Table 2, there were no significant changes in quality of sleep throughout the study in either group. When the data from both groups on day 14 were compared using the Mann–Whitney U test, no significant differences were revealed between them in the parameters related to sleep quality. Table 3 presents the results of the comparison.|
|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?||This study could not demonstrate significant differences between the caffeine and caffeine-free groups. However, the findings confirm that caffeine abstinence in the evening might not be helpful in sleep promotion in those who habitually consume low or moderate amounts of caffeinated products and who sleep well.|
|What were the sources of funding?||This research was supported by a Departmental General Research Grant (G-U360) of The Hong Kong Polytechnic University.|
|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).||1 cup of coffee = 60 mg caffeine per serving (as reported by authors)|
|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.||Sleep - NOAEL = 60-120 mg/day (no significant effect on sleep latency, efficiency, quality or refreshedness)|
|Notes regarding selection/listing of endpoints and exposures/doses to be compared to Nawrot.||no effects seen at levels below 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.