01dragonslayer
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Sleep is a critical component of physical and emotional wellbeing, and current guidelines suggest healthy adults should achieve 7-9 hrs of sleep per night. 1
Yet, despite the recognised health benefits of sleep, it’s estimated that between 20-45% of adults are sleep deprived, which isn’t a good thing considering chronic sleep deprivation is linked to various undesirable health outcomes such as impaired cognitive function, diminished mood, and an increased risk of injury. 23 4
Additionally, chronic sleep loss is associated with an increased probability of cardiometabolic disease and mental health disorders and may reduce productivity. 5 6
Given the potential negative effects of a lack of a good night’s sleep, it’s prudent to consider strategies that can help with sleep hygiene.
One such strategy is reducing caffeine intake, particularly close to bedtime, to help improve total sleep time and the quality of sleep.
Caffeine is a psychostimulant/drug that is common in foods, beverages, and medications. Caffeine is consumed by 80% of the world’s population, which basically makes it the world’s most socially accepted form of drug use! 7
Caffeine works as an adenosine antagonist, meaning that it blocks the molecule ‘adenosine’ from binding its receptor on cells. 8
Adenosine and its ability to bind to its receptor are implicated in the regulation of the sleep-wake cycle and the induction of sleep. Therefore, caffeine functions as a counter to the processes that induce sleepiness and drowsiness, and this is why it’s commonly used by most of the world as a supplement to increase alertness and wakefulness during the day. 9
In addition to countering drowsiness and promoting wakefulness, caffeine also improves our exercise performance, which may be another reason folks supplement with caffeine. 10
However, there isn’t much point in using caffeine before a training session if it impairs our sleep that night. In this scenario, we might be trading a very small benefit on exercise performance for a potentially large, negative impact on our recovery from poor sleep.
This then raises the question: When should we take our caffeine to minimise any potential adverse effect on our sleep?
A recent study aimed to quantify the effects of caffeine intake (including timing) on subsequent sleep. Let’s see what they did! 11
If you sleep ~6-8 hours per night, that’s roughly a 10% reduction in sleep duration, which is a decent decrease in total sleep time due to a nutritional supplement alone!
Caffeine consumption was also associated with increased time to fall asleep (~10 mins) and time spent awake during the night after having initially fallen asleep (~12 mins).
Overall, caffeine consumption does seem to impair sleep quantity and quality, but these effects were moderated by the dose of caffeine and the time of ingestion before sleep.
Caffeine timing may also need to be considered when consuming different sources of caffeine (likely due to the dose of caffeine).
For example, if your bedtime is 10pm, the results from this study suggest a cup of black tea can be consumed at any time prior to bed without reducing sleep time. On the other hand, a cup of coffee would need to be consumed before 1pm to avoid an effect on sleep time and a pre-workout supplement would need to be consumed before 9am to avoid any negative effect on sleep time.
It should be noted these effects happen in a time-dependent manner. In other words, having a pre-workout at 10am would have a relatively small effect on sleep time compared to having the pre-workout at 5pm before a training session (assuming a bedtime of 10pm).
In sum, the results of this study suggest caffeine sources containing higher doses should be taken as early in the day as possible to reduce any negative effect on total sleep.
Yet, despite the recognised health benefits of sleep, it’s estimated that between 20-45% of adults are sleep deprived, which isn’t a good thing considering chronic sleep deprivation is linked to various undesirable health outcomes such as impaired cognitive function, diminished mood, and an increased risk of injury. 23 4
Additionally, chronic sleep loss is associated with an increased probability of cardiometabolic disease and mental health disorders and may reduce productivity. 5 6
Given the potential negative effects of a lack of a good night’s sleep, it’s prudent to consider strategies that can help with sleep hygiene.
One such strategy is reducing caffeine intake, particularly close to bedtime, to help improve total sleep time and the quality of sleep.
Caffeine is a psychostimulant/drug that is common in foods, beverages, and medications. Caffeine is consumed by 80% of the world’s population, which basically makes it the world’s most socially accepted form of drug use! 7
Caffeine works as an adenosine antagonist, meaning that it blocks the molecule ‘adenosine’ from binding its receptor on cells. 8
Adenosine and its ability to bind to its receptor are implicated in the regulation of the sleep-wake cycle and the induction of sleep. Therefore, caffeine functions as a counter to the processes that induce sleepiness and drowsiness, and this is why it’s commonly used by most of the world as a supplement to increase alertness and wakefulness during the day. 9
In addition to countering drowsiness and promoting wakefulness, caffeine also improves our exercise performance, which may be another reason folks supplement with caffeine. 10
However, there isn’t much point in using caffeine before a training session if it impairs our sleep that night. In this scenario, we might be trading a very small benefit on exercise performance for a potentially large, negative impact on our recovery from poor sleep.
This then raises the question: When should we take our caffeine to minimise any potential adverse effect on our sleep?
A recent study aimed to quantify the effects of caffeine intake (including timing) on subsequent sleep. Let’s see what they did! 11
What did the researchers do?
- This study was a systematic review (qualitative/descriptive analysis of the included studies) with meta-analysis (quantitative/statistical analysis of specific outcomes within the studies included in the review).
- The researchers searched several academic databases for experimental trials that administered caffeine and a control/placebo condition to participants and then measured sleep that same evening through to the morning.
- The caffeine condition was administered to participants in a variety of ways, including black tea, coffee, pre-workout formulas, and caffeine mixed with water.
- Meanwhile, the control/placebo condition was generally water only or artificially sweetened water.
- The researchers extracted the data from each individual study and performed a meta-analysis for several outcomes, including:
- Total sleep time.
- How long it took to fall asleep (sleep onset latency).
- How long it took to reach the rapid eye movement (REM) stage of sleep (REM onset latency).
- Total wake time after having fallen asleep (wake after sleep onset), and sleep efficiency (time spent asleep divided by time spent in bed).
What did the researchers find?
- Twenty-four studies were included in the analysis.
- Caffeine consumption was associated with 45.3 minutes less total sleep time, and this was moderated by the timing of caffeine intake and the final dose of caffeine (i.e., the closer caffeine was taken to sleep and the larger the dose of caffeine, the longer the participant took to fall asleep).
- Participants took 9.1 mins longer to fall asleep with caffeine when compared to the control condition.
- The time to reach the REM stage of sleep was not different between caffeine and no caffeine.
- The time spent awake during the night was significantly greater with caffeine consumption, by 11.8 mins, compared to the control condition.
- To have no effect on total sleep time, the model identified a cut-off time of 13.2 h prior to bedtime for a standard serving of pre-workout supplement, a cut-off time of 8.8 h prior to bedtime for a cup of coffee, and no cut-off time for a cup of black tea.
What do these results mean for you?
The results from this study suggest caffeine consumption is associated with a reduction in the total time spent sleeping during the night by ~45 minutes.If you sleep ~6-8 hours per night, that’s roughly a 10% reduction in sleep duration, which is a decent decrease in total sleep time due to a nutritional supplement alone!
Caffeine consumption was also associated with increased time to fall asleep (~10 mins) and time spent awake during the night after having initially fallen asleep (~12 mins).
Overall, caffeine consumption does seem to impair sleep quantity and quality, but these effects were moderated by the dose of caffeine and the time of ingestion before sleep.
Caffeine timing may also need to be considered when consuming different sources of caffeine (likely due to the dose of caffeine).
For example, if your bedtime is 10pm, the results from this study suggest a cup of black tea can be consumed at any time prior to bed without reducing sleep time. On the other hand, a cup of coffee would need to be consumed before 1pm to avoid an effect on sleep time and a pre-workout supplement would need to be consumed before 9am to avoid any negative effect on sleep time.
It should be noted these effects happen in a time-dependent manner. In other words, having a pre-workout at 10am would have a relatively small effect on sleep time compared to having the pre-workout at 5pm before a training session (assuming a bedtime of 10pm).
In sum, the results of this study suggest caffeine sources containing higher doses should be taken as early in the day as possible to reduce any negative effect on total sleep.
TL;DR
- Consuming caffeine prior to sleep reduces total sleep time and sleep efficiency and increases the time required to fall asleep and the time spent awake during the night.
- Reductions in total sleep time are observed when larger doses of caffeine are consumed closer to bedtime.
- Consuming caffeine sources that have smaller doses (~50 mg of caffeine, such as black tea or 600ml of Coke) seem to be fine in the hours before bed.
- However, larger doses, such as a cup of coffee (~110 mg of caffeine per 250 ml) or a pre-workout formula (~220 mg caffeine per dose), need to be consumed approximately 9 and 13 hours before sleep, respectively.