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By: Brendan Duffy on May 18th, 2020

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Caffeine and Sleep: A Virtual Coffee Break With Sleep Experts


I recently spoke with several sleep experts about caffeine and sleep. These wonderful sleep professionals were very giving of their time and knowledge, and I thank them immensely. It is because of their willingness to share their time, thoughts and friendship that I can share this information with you. 

Below is a summary of the questions I posed — and some of their responses. So, pour yourself a “Double Ristretto Venti Half-Soy Nonfat Decaf Organic Chocolate Brownie Iced Vanilla Double-Shot Gingerbread Frappuccino Extra Hot with Foam Whipped Cream Upside Down Double Blended, One Sweet’N Low and One NutraSweet” — or perhaps just a refreshing glass of ice water — and enjoy this coffee break with sleep experts.

In what ways does caffeine affect sleep, and are there benefits to using caffeine as a way to increase alertness and/or reaction time?

Dr. Jaques Reifman, Ph.D., senior research scientist, U.S. Army:https://www.sciencedaily.com/releases/2018/06/180604093116.htm

Caffeine binds to brain receptors (adenosine receptors, which, when activated by adenosine, promote sleepiness and suppress arousal). Hence, when caffeine, instead of adenosine, binds to these receptors, it inhibits the slowdown of neural activity and reduces your feeling of sleepiness. Therefore, caffeine acts as a stimulant to the central nervous system, promoting alertness and reducing reaction time. 

Dr. Ian Dunican, Ph.D., MineEng, MBA, GCASSc, BA, sleep and performance expert: Twitter: @sleep4perform

Caffeine affects sleep mainly by delaying sleep onset. As we know from the pharmacokinetics, it takes an hour to peak, has anywhere from a four- to six-hour half-life, and takes up to eight hours or more to leave the body. So, we know when people have caffeine when going to bed, that actually delays sleep onset. We also see it can cause disruptions in sleep after sleep onset, which means more awakenings throughout the night.

As for the second part of the question about reaction time, this is interesting because the data in athletes is a little bit contradictory in some ways; in some studies, it does increase alertness and, in some, it does not. It depends how you want to quantify alertness and/or reaction time. What is interesting is if we look at military studies where people are taking caffeine after sleep deprivation to negate the effects of sleep deprivation. In a military study where reaction time was being tested, they found that reaction time improved but accuracy diminished. We have also seen with athletes as well that excessive use of caffeine may increase alertness and reaction time, but it may lead to cramping. Although, again, the literature is divided, and there is no direct correlation on that, but we have seen anecdotally in athletes that they do cramp within 60-70 minutes after consuming excessive caffeine levels.

Dr. Marta Maczaj, AASM Board certified sleep physician; co-director, St. Charles Sleep Disorders Center, Port Jefferson: https://stcharleshospital.chsli.org/sleep-disorders-center 

Although a cup of coffee (or other caffeinated beverage) in the morning should not interfere with your ability to sleep at night, some individuals are sensitive to caffeine. Others may metabolize caffeine more slowly, and these individuals could have difficulty falling asleep due to the caffeine. Caffeine is found in many substances, not just coffee. It is present in black tea, green tea, soda, chocolate and energy drinks.

Although it is usually ok to have a caffeinated drink up until noon, if you are having trouble falling asleep or staying asleep, then you should consider either restricting or eliminating caffeine intake. 

Dr. Daniel Erichsen, sleep physician: https://www.youtube.com/channel/UC_tdQDMQon0CfD0xAbZPNDg/videos  

You may be surprised to hear this, but caffeine is virtually never the cause of insomnia. The occasional difficulties falling asleep if you have more coffee at a later time than you normally would, absolutely. Caffeine could be the culprit. Constant or intermittent insomnia for weeks or months, very unlikely. This is important to know because giving up coffee, or anything else you enjoy, increases the influence insomnia has over your life. And for no reason.

Dr. Amy Bender, senior research scientist, Calgary Counselling Centre; sleep performance expert
Twitter: @sleep4sport 

Caffeine causes more arousals, longer sleep latency, and potentially an effect on slow wave activity, so not just the sleep parameters but more the brain wave activity. Per some research studies, if you are sleep restricted, caffeine can benefit you for a short period of time, but after the third day it seems to impair your performance. One of my quotes for World Sleep Day was “Use caffeine strategically; not automatically.” I think if people are addicted, that they have to have their coffee every morning, that can become problematic.


What are your thoughts on “caffeine naps” where a person drinks coffee prior to a short nap? Sometimes referred to as a “nappuccino.” 

Dr. Jacques Reifman:

I understand that this “old” idea came back last year with Daniel Pinks’ publishing of “WHEN.” I have not seen studies that support this idea, which does not mean they do not exist. With that said, “sleep is sleep,” meaning the sleep community currently believes that sleep is always beneficial, even if it is a short nap. Separately, caffeine promotes alertness. Hence the idea of short naps (20 minutes) seems to make sense, because it takes about 45 minutes for the full effect of caffeine to take place.

Dr. Ian Dunican:

I think it is good. What we have seen is it’s recommended a lot here in Australia where people have to drive long distances, and there are lots of problems with people experiencing micro-sleeps, or driving long distances such as 30 hours or more. This gets back to the pharmacokinetics where the caffeine kicks in after the nap of 20 to 30 minutes, and it will help to negate the sleep inertia.

Dr. Marta Maczaj:

Caffeine naps can be very useful to get through the second half of your work day if you are severely sleep or jet lagged. Schedule a 20-minute nap around 2-3 p.m. and have a cup of coffee or tea/caffeine. When you are waking up after your nap, the caffeine is kicking in and making it easier for you to awaken.

Dr. Amy Bender:

In general, I am not a fan of the caffeine nap because the caffeine can stay in your system at night, therefore impacting your nighttime sleep. So, if I take caffeine at 3 p.m., it’s going to impact my nighttime sleep and, therefore, I think just having a nap — a short power nap — is more beneficial than the nap with caffeine.


What would you like people to know about caffeine metabolism? 

Dr. Jacques Reifman:

In our mathematical model, we account for the pharmacokinetics of caffeine (PK; the caffeine concentration time course in the body) and the pharmacodynamics of caffeine (PD; the response of the body to caffeine concentration in the blood). The effect and concentration of caffeine peaks about 45 minutes after consumption and decays exponentially with a half-life of 1.5 hours. Hence, four hours after caffeine consumption, for example, the effect and concentration of caffeine are about 25% of their peak values.

Dr. Ian Dunican:

I would like people to know that everybody is different. We are not all like machines. This is the problem. People kind of think like engineers, like inputs and outputs, but we are all different. I am sure we all know people who can drink coffee and go to bed and be knocked out straight away without a problem. For me, I’d be bouncing around like a frog for two or three hours after consuming caffeine at 7-8 p.m. at night. So, everybody is different as to how they metabolize caffeine, and people like Dr. Amy Bender and Dr. Nanci Guest have done some work on this so they can offer more on this than I can.

Dr. Marta Maczaj: 

The half-life of coffee is around 4.5 hours. It usually takes three half-lives before caffeine is totally eliminated from your system, and this should be taken into consideration when having your last cup of coffee. Some people metabolize caffeine more slowly (or more rapidly), and the caffeine can last a longer time in their system and can interfere with nighttime sleep. Some individuals are very sensitive to caffeine, and the caffeine can also cause a sense of nervousness, an increase in heart rate and also contribute to insomnia.

Dr. Daniel Erichsen: 

Having a cup of coffee can help you stave off the fatigue and inability to focus that often comes with trouble sleeping. Use common sense. If you are sensitive to caffeine, then having a Red Bull in the evening is probably not a good idea. But, most importantly, know that what is often considered part of the problem can become an important part of the solution.

Dr. Amy Bender:

Everybody has a different metabolism for caffeine. The go-to study that I refer to a lot is from Dr. Nanci Guest (https://www.ncbi.nlm.nih.gov/pubmed/29509641). She found that in cyclists, when given caffeine, their performance was based on genotype, so those who were slow metabolizers of caffeine actually performed worse than those who were fast metabolizers. And for the fast metabolizers, it was really beneficial for them. So, I think you really have to be careful about making the assumption that caffeine is beneficial for everyone all the time.


How does caffeine detox affect a person? Do you recommend cold turkey or gradual withdrawal?

Dr. Ian Dunican: 

This would be a personal thing. All I ever do is drink caffeine. I don’t drink or smoke. So, when I have been off caffeine, it’s been tough. So, I’m not sure on that one. It depends on the person.

Dr. Marta Maczaj:

Death before decaf! Just kidding! I would not recommend rapid detox. The individual will develop headaches. Caffeine is a vasoconstrictor, and removing caffeine causes vasodilation and can lead to headaches due to the vasodilation. The person can also feel much drowsier during the day and may have drowsy driving. I suggest a gradual withdrawal. Consider half caffeine and half decaf for all your cups of coffee for a few days, then decrease to one-third caffeine and two-thirds decaf for a few days, then one-quarter caffeine and three-quarters decaf for a few days, and then all decaf.

Dr. Amy Bender:

I recommend gradual. I didn’t really drink caffeine until college and grad school — about two cups a day every single day for years. For me, the gradual method worked really well when I went off caffeine. I eliminated coffee, but then I would replace it with black tea, and it took me two weeks to be to the point where I wasn’t tired and exhausted from not having that much caffeine. I would be really tired in the morning and have a black tea. I may then be tired in the afternoon so I would have a green tea and then I just gradually started reducing that to only needing the green tea.


Can you give me an example of how caffeine negatively impacted performance of one of your patients or athletes?

Dr. Ian Dunican:

The best example of this would be the caffeine usage in a paper we published about caffeine use in a super rugby team (https://www.ncbi.nlm.nih.gov/pubmed/29431593). Basically, all the guys had various levels of caffeine consumption before the game and during the game. Afterward, the caffeine level was very high in some players. What was really interesting that didn’t make it into our paper was that some of those athletes who had the highest amount of caffeine really had issues with performance during the last quarter of the game — the last 20 minutes. Going forward, for the following season we advised the team dietitian/nutritionist to devise a caffeine strategy: the timing of caffeine, dosage of caffeine, in relation to player body weight.

Dr. Marta Maczaj:

One of my insomnia patients drank Red Bulls in the evening after dinner. His insomnia improved after he stopped drinking the Red Bulls! 


Originally published in the  A2Zzz Q3 2019 Issue