Should you booze before you snooze?
One of the most noticeable aspects of our circadian rhythm is the fact that we feel tired at certain times of the day, usually in the evening, and we then spend the next 8 hours sleeping. This happens because a chemical called adenosine builds up in the brain when we are awake and is flushed out when we nod off, so it acts as a sleep signal that makes us feel tired. But sleep is not an on/off process. Throughout the night, our brains cycle every 90 minutes or so through phases of lighter and deeper sleep. The lighter sleep is referred to as REM or rapid eye movement sleep and it’s also when we appear to dream. Periods of REM sleep, and hence the richness and complexity of dreaming, also become longer as the night goes on. But why, we have no idea! What we do know is that sleep plays a critical role in health and well-being, and if you disturb the pattern of sleep, both suffer. One very common way that can happen is if you have one drink too many. Although booze can send you to sleep, paradoxically, it robs you of restful sleep, contributing to feeling rough the next day, as Montana State University’s Ian Greenlund explained to James Tytko…
Ian - What alcohol is, is it mimics a neurotransmitter in the brain called GABA aminobutyric acid. We're gonna call that GABA for short. And what GABA does is it turns on deep sleep and turns off REM sleep. So if we have a lot of alcohol in our system, in our bodies, while we are trying to initiate sleep, you can see why REM would be inhibited and/or pushed off until further in the night, maybe towards the second half or the last two hours before we wake up or something like that. So you can see when that is circulating, that's definitely going to be disruptive to REM and it's still going to be affected in the second half of sleep as well, because when we're sleeping, alcohol is being metabolized specifically within the liver and within the kidneys. And it's byproducts include two molecules that are called a acetaldehyde and acetate, which then accumulate and can further trigger sleep fragmentation. So one, REM sleep percentage is being decreased, and second REM sleep is also being fragmented. So you're waking up more during REM sleep, which you may or may not remember going into the next morning.
James - And you are interested specifically in binge drinking's effects on sleep and namely on the sympathetic nervous system. I wonder if before we get into what the effects of alcohol will be on the sympathetic nervous system, if we can first start by defining that just for our listener's benefit not, for mine at all, of course.
Ian - Of course. Yes. So the sympathetic nervous system is part of our autonomic nervous system or the part of this nervous system that we have no conscious control over. It's important for us to think about that without the sympathetic nervous system we wouldn't able to be doing simple things such as standing up or it's a very principle regulator of our blood pressure. So while, yes, we need the sympathetic nervous system, when it is overactive it is a large contributor towards heightened blood pressure or hypertension. And we know that alcohol can trigger a more robust activation of the sympathetic nervous system.
James - So that's what happens is it? If you've had a heavy drinking session before you go to sleep, this fight or flight branch of the nervous system is more activated during your sleep and more likely to disrupt that sleep cycle that was so important as we mentioned earlier.
Ian - Yes, that is correct. So during sleep, what you normally want to see is more of an activation of your parasympathetic nervous system to slow brain activity, to bring down blood pressure into a natural resting state for your body to be resting and repairing itself. But with alcohol in the system that is disrupted, you're in a more of a hyper-aroused state that is not conducive to overall restorative sleep.
James - And how do you go about showing this or proving it? How do you go about testing it?
Ian - We've actually dosed men and women with a four to five drink equivalent of alcohol. So this would be like drinking four to five shots of liquor glasses of wine or cans of beer.
James - Is it difficult to find participants for these studies or are there quite a lot of willing people who sign up for these sorts of things?
Ian - It's fairly easy. It's a good study I think to participate in and to be a part of on my side. So it's good for all involved. But what we see with that is then increased sympathetic nervous system activity lasting into the early morning hours, which coincides with, uh, when most cardiovascular events like heart attacks and strokes are most common. And then these mechanisms also help us explain why individuals who struggle with alcoholism and alcohol abuse also present with other cardiovascular diseases such as hypertension.
James - So what about drinking in moderation? How does this impact the sympathetic nervous system? Is it still a significant impact or something much more moderate?
Ian - So light drinking, or maybe drinking one to two drinks, or moderate drinking, three to four drinks, are still associated with some sleep deficits, but it may be fewer than binge drinking as one might expect. But there is some research out there to show light and moderate drinking may help us fall asleep faster and limit nocturnal awakenings, but we still see decreases in REM. So overall that's good news that a small glass of wine prior to bed is likely not impacting our overall sleep quality a great deal, but it speaks to that if we are drinking alcoholic beverages, give yourself some time to decrease blood alcohol content prior to sleep to minimize any potential detriments.
James - Despite what some people might think about maybe a drink, helping them get off a bit quicker and get to sleep sooner. It's not going to have any sort of actual benefit to the quality of sleep. And that's something of a myth.
Ian - That is correct. And majority of the time individuals who struggle with sleep issues and if they do reach for alcohol rather than reaching out to their medical provider first, it's that subjective feeling of falling asleep faster that many individuals associate with getting more quality restful sleep, but they still may be having those detriments to REM sleep. And if the alcohol dose begins to increase as a tolerance is built up to that, it will result in more sleep fragmentation and non-restorative.