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Cracking the Caffeine Code: When and How It Affects Your Sleep


This week's topic is caffeine and its effects on our sleep - but in a more straightforward way. Most of us know that consuming caffeine too close to bedtime can disrupt our ability to fall and stay asleep. You've also likely heard the guideline to avoid caffeine intake around 6-8 hours before bedtime. However, there's more to this story, so let's take a closer look at a recent study that examined the relationship between caffeine consumption and sleep, particularly regarding the timing of caffeine intake.

Sleep Deprivation

Sleep is crucial for our overall well-being, and guidelines recommend that the average adult aim for 7-9 hours of sleep per night. Unfortunately, a nice chunk of the population, estimated at 20-45%, doesn't get enough sleep. This is concerning because chronic sleep deprivation is associated with various negative health outcomes, including impaired cognitive function, mood disturbances, an increased risk of accidents, potential links to chronic diseases, overeating (as mentioned in previous blogs), and mental health issues. So, it's important to consider strategies that can help improve our sleep hygiene.


A common strategy to improve your sleep is to reduce caffeine intake, especially in the hours leading up to bedtime.

Caffeine is a widespread stimulant in many foods, beverages, and medications. It's used by most people worldwide and is the most socially accepted form of drug use.

Caffeine works by blocking the effects of adenosine, a molecule that promotes sleepiness and helps regulate our sleep-wake cycle. Caffeine inhibits adenosine, keeping us alert and awake. No wonder it's a popular choice for staying alert during the day.

However, while caffeine can be a useful tool for increasing alertness, it may have negative consequences if consumed too late in the day. This raises an important question: when is the best time to consume caffeine to minimize its potential impact on sleep?

The Research

A recent study aimed to answer this question by investigating the effects of caffeine intake, including the timing of consumption, on subsequent sleep. Let's delve into the details of this study.

The study involved a systematic review, which analyzed the included studies qualitatively, and a meta-analysis, which quantitatively examined specific outcomes within those studies. Researchers scoured academic databases for experimental trials that administered caffeine to participants. They compared it to a control or placebo condition and then monitored the participants' sleep patterns from evening to morning.

Caffeine was administered in various forms, such as black tea, coffee, pre-workout formulas, and caffeine mixed with water. In contrast, the control or placebo condition typically involved artificially sweetened or plain water. The researchers collected data from each individual study, as well as a meta-analysis to examine several sleep-related outcomes, including total sleep time, sleep onset latency (how long it took to fall asleep), REM onset latency (the time it took to reach the REM stage of sleep), wake time after falling asleep, and sleep efficiency (the ratio of time spent asleep to time spent in bed).

Here are the key findings from the study:

  • The analysis included data from twenty-four studies.

  • Caffeine consumption was associated with a reduction of approximately 45 minutes in total sleep time.

  • Participants took about 10 minutes longer to fall asleep when they consumed caffeine than when they didn't.

  • The time it took to reach the REM stage of sleep was not significantly different between caffeine and no caffeine.

  • Participants spent about 12 minutes more awake while consuming caffeine at night.

  • The study suggested a cutoff time of approximately 13.2 hours before bedtime for a standard serving of pre-workout supplement, around 8.8 hours before bedtime for a cup of coffee, and no specific cutoff time for a cup of black tea to avoid sleep disruption.

So, in plain language, these findings tell us that if you sip on caffeine right before bedtime, you're likely to end up with less satisfying sleep that's shorter and not as restful. How much it messes with your sleep depends on how much caffeine you have and when you have it. It might be a good idea to rethink your caffeine routine based on these findings to keep your sleep in check.

Expand for Resources

National Sleep Foundation's sleep time duration recommendations: methodology and results summary, Hirshkowitz M et al. 2015 ​ Epidemiological Overview of sleep Disorders in the General Population, Ohayon MM. 2011 ​

Sleep Duration in the United States: A Cross-sectional Population-based Study, Krueger PM, Friedman EM. 2009 ​

Short-and long-term health consequences of sleep disruption, Medic G et al. 2017 ​

Depression in sleep disturbance: A review on a bidirectional relationship, mechanisms and treatment, Fang H et al. 2019 ​

Public health implications of sleep loss: the community burden, Hillman DR, Lack LC. 2013 ​ Caffeine (1, 3, 7-trimethylxanthine) in Foods: A Comprehensive Review on Consumption, Functionality, Safety, and Regulatory Matters, Heckman MA et al. 2010 ​ Adenosine, Adenosine Receptors and the Actions of Caffeine, Fredholm BB. 1995 ​ Adenosine, caffeine, and sleep-wake regulation: state of the science and perspectives, Reichert CF et al. 2022 ​ International society of sports nutrition position stand: caffeine and exercise performance, Guest NC et al. 2021 ​The effect of caffeine on subsequent sleep: A systematic review and meta-analysis, Gardiner C et al. 2023


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