Study Title and Description
Effects of caffeine are more marked on daytime recovery sleep than on nocturnal sleep.
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 are more marked on daytime recovery sleep than on nocturnal sleep.|
|Author||J Carrier,M Fernandez-Bolanos,R Robillard,M Dumont,J Paquet,B Selmaoui,D Filipini,|
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 compare the effects of caffeine on nocturnal sleep initiated at habitual circadian time as well as on daytime recovery sleep. Since caffeine decreases SWS, we predicted that the effects of caffeine on the sleep consolidation parameters would be stronger when administrated before daytime recovery sleep than before habitual nocturnal sleep.|
|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)||Subjects Thirty-four moderate caffeine consumers (equivalent to one to three cups of coffee per day) participated in these studies. All subjects were in good health according to their medical history. They were all non-smokers, and were not consuming any drug or medication that affect the sleep–wake cycle. None of the subjects reported any sleep problems. Subjects were instructed to abstain from alcohol and medication during the laboratory component of the experiment. Subjects were divided into two groups (matched for age and gender): (1) Night group (n=17; 10 women, 7 men; mean age=37.2 years, SEM=3.5) and (2) DayRec group (n=17; 10 women, 7 men, mean age=39.9 years, SEM=3.8). BMI did not differ between the two groups (Night group: mean=23.02, SEM=0.7; DayRec group: mean=23.6, SEM=0.7; NS). Procedures were similar for the two groups. Exceptions were the time of day of caffeine/placebo administration, and the timing of the sleep episode. Subjects in the Night group followed their habitual sleep–wake cycle and slept in the laboratory during the night, while subjects in the DayRec group were sleep deprived for one night (25 h of wakefulness) and recovery sleep started in the morning, 1 h after their habitual wake time. All subjects participated in both the caffeine (200 mg) and placebo (lactose in identical capsules) conditions, with a double-blind crossover design. This dose of caffeine is considered to be moderate, and is known to produce significant effects on sleep (Landolt et al, 1995). Subjects received one capsule containing either caffeine (100 mg) or placebo 3 h prior to their bedtime, and the remaining dose of caffeine (100 mg) or placebo was administered 1 h before bedtime. One week prior to each laboratory condition, subjects were instructed to keep a regular sleep–wake pattern within 30 min of their habitual sleep–wake schedule, and to maintain their habitual caffeine intake. Subjects kept the same sleep–wake schedule for each condition. During this time, they were asked to complete the French version of the ‘Pittsburgh Sleep Diary’ (Monk et al, 1994), and to report the amount as well as the different caffeinated products they had consumed (ie coffee, tea, chocolate, etc.). The mean number of milligrams of caffeine consumed per day was approximated for each subject according to the following criteria: 250 ml of coffee=100 mg caffeine; 250 ml of tea=50 mg of caffeine; 250 ml of cola=35 mg of caffeine; 10 g of chocolate=5mg of caffeine. Subjects also reported alcohol intakes on the sleep diaries. Mean daily alcohol intake for the week prior to each laboratory session was low and did not differ between the groups (Night group: mean=0.6 drinks, SEM=0.1; DayRec group: mean=0.7, SEM=0.2; NS). On experimental days, subjects were required to abstain from alcohol, medication, and naps, and were permitted to maintain their habitual caffeine consumption in the morning, in order to prevent potential effects of caffeine withdrawal. Starting at noon, subjects stopped consuming caffeinated beverages and foods. Subjects in the Night group came to the chronobiology laboratory for two sessions. Each session (caffeine, placebo) was separated by 6–9 days. Subjects arrived in the laboratory at the end of the afternoon. Bed and wake times in the laboratory were based on the subject’s habitual sleep– wake cycle, averaged from their sleep diary. For each session (caffeine, placebo), subjects came to the laboratory for one baseline night. Following their departure from the laboratory in the morning, subjects performed their regular activities until the end of afternoon, at which point they came back to the chronobiology laboratory. Subjects then remained awake in bed until the next morning. A research assistant was present at all times to make sure subjects were not falling asleep. A morning recuperative sleep episode was initiated 1 h after their habitual wake time (following 25 h of wakefulness). Subjects were asked to stay in bed for their habitual sleep duration. In both groups, subjects stayed awake in bed in a semirecumbent position in dim light (o15 lux) from the time they arrived at the laboratory until bedtime. Measures Salivary caffeine concentration. Saliva was collected using the Salivette devices (Sarstedt, Inc.), and was then centrifuged and frozen immediately. Each subject provided a saliva sample 2.5 h before the first caffeine/placebo capsule, 5 min before bedtime, and 5 min after wake times. Sleep stage variables and the number of minutes of wakefulness were computed from sleep onset to the last epoch of sleep. Sleep efficiency was defined as (the number of minutes spent asleep/total number of minutes from sleep latency to lights on)_x0002_100. Number of minutes of wakefulness, REM sleep, and SWS sleep per third of the bedtime period (from sleep onset to lights on) were calculated. Statistical Analyses To evaluate group differences in salivary caffeine concentration, a three-way ANOVA with one independent factor (Group: Night and DayRec) and two repeated measures (Condition: placebo and caffeine; and Time: baseline, bedtime and wake time) were performed. Since the morning measure was missing for one subject in each group, this analysis was performed with the 32 remaining subjects. Two-way ANOVAs with one independent factor (Group: Night and DayRec) and one repeated measure (Condition: placebo and caffeine) were performed to evaluate differences on habitual caffeine consumption (log transformed) and PSG sleep variables. To evaluate differences in sleep per third of the bedtime period, three-way ANOVAs with one independent factor (Group: Night and DayRec) and two repeated measures (Condition: placebo and caffeine; and Part of the bedtime period: 1/3, 2/3, 3/3) were performed. Due to an abnormal distribution total wake time, some sleep variables were log transformed (sleep latency, REM latency, % and min stage 1 sleep, % and min SWS, % stage 2 sleep). Minutes of wakefulness, REM sleep and SWS per third of the bedtime period were squared-root transformed. Simple effects analyses were performed when significant interactions were found. p-values for repeated measures with more than two levels were adjusted for sphericity with Huynh–Feldt correction.|
|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||includes measures of latency, efficiency, and information on stages of sleep|
|What is the study design?||Controlled Trial|
|Randomized or Non-Randomized?||NCT|
|What were the diagnostics or methods used to measure the outcome?||Objective|
|Optional: Name of Method or short description||polysomnograph|
|Caffeine (general)||Caffeine (general)|
|What was the reference, comparison, or control group(s)? (e.g. high vs low consumption, number of cups, etc.)||placebo (no caffeine) vs 200 mg (split dose, 100 mg each)|
|What were the listed confounders or modifying factors as stated by the authors? (e.g. multi-variable components of models. Copy from methods)||none listed|
|Provide a general description of results (as reported by the authors).||Compared to placebo, caffeine administration lengthened sleep latency, increased stage 1 (%), and reduced stage 2 and SWS (min) both in the Night and DayRec groups. Significant interactions between conditions (caffeine, placebo) and groups (Night, DayRec) were found for total sleep time, number of minutes of wakefulness, sleep efficiency, and REM sleep (min and %). Contrast analyses showed that caffeine reduced sleep efficiency more strongly in the DayRec group (F(1,32)=59.5; p<0.0001) than in the Night group (F(1,32)=4.6; p=0.04). Compared to placebo, caffeine increased the number of minutes of wakefulness (F(1,32)=29.7; po0.001), decreased total sleep time (F(1,32)=41.8; p40.001), and reduced the percentage (F(1,32)=3.7; p=0.06) as well as the number of minutes of REM sleep (F(1,32)=12.9; p¼0.001) only in the DayRec group (see Figure 3).|
|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 lengthened sleep latency, increased the percentage of stage 1 sleep, and decreased the number of minutes of stage 2 sleep and of SWS similarly during daytime recovery sleep and nocturnal sleep.|
|What were the sources of funding?||This research was supported by scholarships and grants from the Canadian Institutes of Health Research (CIHR), the Fonds de Recherche en Sante´ du Que´bec (FRSQ), and the Natural Sciences and Engineering Research Council of Canada (NSERC).|
|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.||sleep - LOAEL = 200 mg/day increased sleep latency|
|Notes regarding selection/listing of endpoints and exposures/doses to be compared to Nawrot.||single dose dose was split into 100 mg 3 hours before bedtime and 1 hour before bedtime|
|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|
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No quality rating data was found.