Image: Austin Public Library
More In This Article
-
Overview
The Science of Happiness
Caffeine will get you going during the day but could leave you tossing and turning at night – unless you're a "night owl" to begin with, a new study suggests.
In the study, "morning people" who consumed caffeine during the day appeared more likely than late risers to awaken in the middle of their nighttime sleep.
The researchers said this is the first study to link caffeine intake with "chronotype," the categorizing of people by the time of day they are most alert and active. The findings are preliminary and more research is needed to confirm them, the researchers added.
Fifty college students were asked to record their caffeine consumption and their sleeping and waking times for a week. The students wore wrist devices that monitored their movements, to assess whether they had periods of wakefulness after they had fallen asleep. The researchers also measured caffeine levels in the students' saliva over the week.
As college students, they tended to be so sleep-deprived that, for most, "it didn't matter how much caffeine they had" – they slept well whenever they finally hit the sack, said study researcher Jamie Zeitzer, an assistant professor of psychiatry and behavioral sciences at Stanford University.
However, for the early risers, the more caffeine in their bodies, the more time they spent awake during the night after initially falling asleep. This was not seen in the night owls.
The next step is to see whether this effect applies to people other than college students, Zeitzer said.
The amount of caffeine in a person at bedtime can vary widely, Zeitzer said. Some people's bodies clear caffeine within a few hours, but lunchtime coffee may still be in the system of other people even late at night. Therefore it's hard to say whether any particular person could avoid the effects of caffeine on sleep by simply steering clear of coffee (or tea) in the afternoon or evening, Zeitzer said.
The study was published online Feb. 13 in the journal Sleep Medicine.
- 7 Tips to Sleep Soundly Tonight
- 5 Experts Answer: Is Caffeine Bad for Kids?
- Top 10 Spooky Sleep Disorders
Copyright 2012 MyHealthNewsDaily, a TechMediaNetwork company. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.
See what we're tweeting about
10 Comments
Add CommentWell I'm the opposite, I'm an early riser and get most of my creative and mundane jobs done in the morning. I tend to drink double shot black strong Italian coffee during the day and night and sometimes as late as 11:30pm before going to bed - I sleep like a child not waking till 5:30am when I get up feeling refreshed. I'm 74.
Reply | Report Abuse | Link to thisI am also just the opposite, but I'm a night owl that is exquisitely sensitive to caffeine. I don't go near the stuff, though I can have a cup of green or white tea in the morning and not regret it. Black tea destroys my sleep, as does coffee. I get a headache if I drink a caffeinated beverage after noon. But, no problem, because I've never needed the stimulant. I'm wired as it is.
Reply | Report Abuse | Link to thisOH my Gawd!!!
Reply | Report Abuse | Link to thisIs someone STILL repeating this bit of research? Or was this just an exercise for the students?
This same research was being done when I was at college - yes, it got the same results - and I'm 70!!
Will we next do "research" into whether or not the sun rises in the east or the world is flat?
But then this was done in America where students graduate high school with a Grade IV education.......
I formatted this into three sections in descending order of likely reading/caring/et.c.:
Reply | Report Abuse | Link to this1) tl;dr:
I believe that these articles are missing the point of the study and that the author is jumping to conclusions. The most important thing missing is determining the quality of sleep by observing its architecture under these conditions. Just because you do not 'wake up' does not mean you are not equally affected by CNS stimulants interfering with sleep architecture. If you don't get enough REM sleep, you can still not consolidate information. If you don't get enough SWS, your muscles may not fully repair. If you've ever woken up with a hangover feeling like you didn't sleep a wink, then there's a good example.
2) Why:
The data do not support the assertion that caffeine interferes with sleep architecture exclusively in one chronotype or another. That would be reducing the pharmacodynamics of a CNS stimulant on a complex series of interconnected feedback loops in your body to a black-and-white binary choice. Reductio ad absurdum, anyone?
However, a prior study indicated chronotype as being related to how the body handles increased concentrations of epinephrine & norepinephrine while asleep. Some are directly awoken, and others stay asleep but have other sorts of sleep architecture disturbances, notably in REM and deep/slow-wave sleep. This study in combination with the above could be used to plan further experimental methods to determine how these changes are mediated and how we can improve those conditions.
To those with seemingly paradoxical effects to caffeine, keep in mind that at this point you are likely physically acclimated to the presence of caffeine and not having it causes fatigue, anxiety, et.c. -- the same effects normally associated with too much coffee. At this point of usage, the 'first-time' effects are typically gone. Studies have shown that with caffeine's rebound symptoms on withdrawal, initial performance enhancements subside significantly over time, replaced by a return to normal function with your morning coffee. Some people respond with paradoxical reactions to CNS stimulants, such as those who respond to ADHD medication. This effect also can occur with depressants as well. Typically, this case points to an upstream or downstream limitation of the metabolism of one of the neurotransmitters involved. Or, maybe it's just a result of becoming acclimated to those stimulant effects and receiving no stimulation as a result of homeostatic regulation over time.
3) How:
Caffeine competitively blocks adenosine receptor sites so the adenosine will activate the receptors less and also tend towards increased extracellular concentration. Adenosine is an inhibitory neurotransmitter with a number of direct effects on cardiovascular tone, e.g., vasodilation and increased oxygen transfer throughout the body, et.c.. Without adenosine activation to inhibit increased firing, synaptic glutamate release -- typically mediated by adenosine going into and activating adenosine receptors instead of being plugged up by caffeine doing nothing -- goes up. Glutamate increases firing in the cellular wiring. Then, epinephrine, norepinephrine, and dopamine are increased, similar to any other stimulant. Caffeine itself is then metabolized into a number of other compounds with other effects, such as theobromine (a vasodilator, the opposite of caffeine's multiple mechanisms for mediating indirect vasoconstrictive effects) and theophylline (a smooth muscle relaxant active in the bronchial region). Interestingly, glutamate is a precursor to GABA, an inhibitory neurotransmitter involved in the actions of most sleeping medications such as benzodiazepenes and z-drugs. This could be related to paradoxical vasodilation and decrease in sympathetic nervous system activity reported by regular users. By 'regular users' I'm referring to a couple of other people who replied, many people in studies on journals that you can look up on PubMed, and myself during my 2 pots of nearly-espresso-strong coffee a day phase (IT consulting). Another mechanism likely involved could be adenosine receptor expression up-regulation reducing antagonism of adenosine by allowing normal levels of adenosine to bind at their respective sites at the same time as structurally-similar caffeine.
I'd link journals but scholar.google.com and nlm's pubmed will find you everything. Cheers all you crackbucks junkies!
Just my non-scientific anecdotal perspective:
Reply | Report Abuse | Link to thisA cup of coffee in the afternoon puts me to sleep. Coffee in the evening has no effect either way. Ilike a cup of coffee in the morning but don't need it as a 'boost'.
Do we really need a study for something each individual can figure out for themselves? I drink 4 to 5 cups a day and fall asleep every night at about the same time and sleep like a log.
Reply | Report Abuse | Link to thisYes, because you could say the same thing for ephedra and its derivative compounds and their analogs in individuals with tolerance. However, there's a reason caffeine is our society's drug of choice, and it's not just hundreds or thousands of years of use. It directly produces short-term stimulant effects as well as indirectly producing the dopaminergic effects associated with other stimulants. However, this indirect mechanism allows for a lot of mediating factors, essentially creating more possible mechanisms for tolerance. Couple this with the intrinsic differences in individuals' neurochemical makeup and balance and many outcomes are possible as a result of treatment. The real question to ask here is: HOW MUCH caffeine it takes to alter sleeping patterns in individuals with different circadian patterns, and HOW MUCH do their respective sleep architectures suffer as a result. Since we don't have conclusive baseline numbers to compare with, this is all a moot point. This time could have been spent much better researching that rather than re-hashing the last hundred years in experiments done in basic physiology classes.
Reply | Report Abuse | Link to thisI agree with you that this is a waste of resources. These findings provide nothing new to us.
Reply | Report Abuse | Link to thisHowever, I don't know so much about your assertion about the level of education of high school graduates. If you want to look at a "lowest common denominator" and include places that lack funding and have a large number of children from third-world backgrounds that are told they need to catch up in the three years since they came to the USA in their sophomore year of high school, sure. There will not be a way around that statistics-skewing bottom outlier group until the education system is recognized as flawed and is reformed. The issue is that since the people who have the money don't really have any issues as a result of the public school system since they can throw money at the problem and buy the best of private education nothing will ever change. Regardless of what people may think about freedom and whatnot, it's a very class-based society. However, when I graduated high school, I was doing polymerase chain reactions in my bio class and learning calculus in my math class. It is what you make of it, and it takes a lot of time. I never had the money for tutors or any of that princeton review nonsense, I just studied hard and was motivated by my own interest. Not very many people are. Maybe if the link between knowledge, money, and the class-based nature of society were impressed on students, this might change. Food for thought.
Like Monki, I am alert in the morning, which I drink the equivalent of four cups of French style coffee. Sometimes, I drink a cup in the late afternoon. I always sleep fully until 5:00 or 5:30, when I get up. I am 70.
Reply | Report Abuse | Link to thisPeople (others or yourself) are referred to as WHO, while inanimate objects, entities or animals, are referred to as THAT.
Reply | Report Abuse | Link to this