Why Does the Subway Make Me So Damn Sleepy?
Photo: Stocksy
My commute to work is typically an hour by subway. I wished I used all that time to read long articles on Pocket and listen to podcasts, but nope: Shut-eye always gets the best of me, even when I’ve had an ample night’s rest, which is…almost always. Still, all it takes is five minutes for my lids to start feeling heavy. I know I’m not alone either. I’d guess 80 percent of my Queens-to-Manhattan comrades on the E line are typically knocked out, too. What is it about the train that lulls everyone to sleep?
For answers, I turned to Dr. Michael Breus, a clinical psychologist, diplomate of the American Board of Sleep Medicine, and a fellow of The American Academy of Sleep Medicine. He also owns the domain name thesleepdoctor.com and can accurately be referred to as The Sleep Doctor. The man knows everything.
I always fall asleep on the train, even when I slept enough the night before. What’s going on?
I think that people who have this situation fall into two different categories. One is people who could have Sopite syndrome, a neurological disorder that relates symptoms of fatigue, drowsiness, and mood changes after long periods of motion. The other is people who are sleep deprived, and when they get into this particular environmental situation where you’re relaxed enough and not having to pay attention to something-there’s motion, consistent sounds, and there’s no real safety threat-you become sleepy. I mean, I can’t count the number of patients that say, “I can’t go to a movie because I fall asleep,” or, “I get into a vehicle, and I’m asleep in five minutes” type of thing. A lot of the time I’m trying to discover, are they sleep deprived and that’s what’s causing this?
How do you determine that?
Well, there’s no real test that I can do for Sopite syndrome, so I just try to improve their overall level of sleep and see what happens. The more quickly it happens is usually a signal of sleep deprivation more so than actual Sopite syndrome. Sopite syndrome takes maybe eight to 10 minutes or so [for the patient to fall asleep when in motion].
What’s happening in my body that’s making me feel sleepy?
So what happens when you’re sleepy or sleep deprived is you have a buildup of nerve chains that are called adenosine. Adenosine is actually a byproduct of cellular metabolisms. As a cell eats, it produces a byproduct. So just like we eat, and then we have a byproduct from what we eat, cells are no different. So that’s what happens-adenosine comes from that. That then travels through the bloodstream, ends up in the brain, and we actually have adenosine receptor cells in the brain, and it latches on there. When you have enough of them, you start to feel sleepier and sleepier.
When you’re moving around, you may not notice how sleepy you are, but then once you’re stable, that overall level of sleepiness can hit you pretty hard. Interestingly enough, when you look at the molecular compound of adenosine, and you look at the molecular structure of caffeine, they’re almost identical. So the caffeine cell actually fits quite nicely into the adenosine receptor and blocks the adenosine. This is why caffeine makes you feel less sleepy. It doesn’t mean that you have any less sleep need or sleep drive, it’s just being blocked by the caffeine in the adenosine receptor.
I also read, or try to, on the train. Does that trigger sleepiness?
It has nothing to do with the act of reading. It has more to do with the fact that you’re in the environment, and you’re already probably pretty tired.
If I wanted to stay awake, what would you suggest I do?
It’s pretty hard to fall asleep standing up, so I would say instead of sitting down on the metro or subway, you could stand up. I would say that engaging in some level of conversation will, in fact, help you with that as well, so that’s another possibility. Any type of physical activity that you could do, like instead of taking the train, you could walk.
Say I am sleep deprived…what are the typical signs?
When you wake up in the morning, are you hitting the snooze button? Because if you are, you’re probably not getting the right amount of sleep. If you wake up within five minutes of your alarm naturally, guess what? You’re getting the right amount of sleep and you shouldn’t really experience [the urge to hit snooze]. Now, there is one time of the day that you will experience a small amount of sleepiness, and that’s between 1 and 3 P.M. The reason this occurs is because there’s actually a small dip in core body temperature, and when you have that dip in core body temperature, it’s a signal for the brain to release melatonin. By releasing melatonin, that can cause a small level of sleepiness as well.
Some people have told me that falling asleep on a moving vehicle is related to being rocked as a baby in infancy–does that have anything to do with it?
It does. There’s actually some data to suggest that, in fact, there is something to that rocking motion. They’re making cribs that have these automatic rockers and things like that, so there is some data that suggests that that could be true. But if you’ve gotten the right amount of sleep, then you shouldn’t be falling asleep on your ride home even if you’re rocking. It shouldn’t have that great of an effect. Otherwise, every time you got into a vehicle you’d fall asleep.
Do all these explanations apply to why I get sleepy right away on planes, too? Like, even before takeoff. It’s weird!
Yes. Although I would say a plane would have one small difference in that you have recirculated oxygen. I guess you could argue that it’s the same on the subway as well because I don’t know how good their ventilation system is. But yeah, I would say there’s a small oxygen component there. Or, it’s not really an oxygen component, it’s actually an increase in carbon dioxide component because of all the bodies in close quarters with each other. With an increase in carbon dioxide, you’re starving the brain for oxygen, so the brain is slowing down.
