What’s the science behind someone being a “light sleeper”?



What’s the science behind someone being a “light sleeper”?

In: Biology




Everything I’ve heard so far has very little science behind it.

what allows a ‘deep sleeper’ the ability to wake up when someone walks into the front door… but ignore the tv that includes a front door sound?



Here’s my question: what’s the science behind me sleeping so long? 10-12 hours is typical for me.

I researched this once and I believe a contributing factor is how active an individual’s thalamus is. The thalamus is the part of the brain responsible for relaying sensory signals and regulating sleep/consciousness/alertness. Individuals with a highly active thalamus may allow sensory input during sleep to get “lost in the noise” so that they are less likely to be disrupted. Those with a less active thalamus may therefore be able to pay more attention to the same stimuli and thus have a greater chance of disrupting sleep.
Edit: spelling

Used to sleep like a log. Became a light sleeper once I had my first child. One day I will sleep again. Maybe not today, maybe not tomorrow, but one day *she whispered wistfully to herself*

So as far as I’m aware, we actually still don’t have a like, comprehensive, in depth understanding of sleep. We’ve gotten some good ideas and all! Like we’re pretty sure that deep sleep phases are about energy saving and physical maintenance down time; and that the lighter and dream sleep phases have to do with memory. (I saw a fascinating study recently implying it’s about correctly associating emotional reactions and circumstances. They showed that when people had a “fearful” experience and slept poorly over the next week or so, they became more generally anxious; but if they slept well, they “correctly” associated the fear with its specific cause, such as a car crash or tiger chasing them, etc; and their general stress levels were unchanged.)

Anyways, sleep is *especially* complex and whole-brain, but here’s *a* hypothesis from someone that doesn’t really know neuroscience but would like to: there’s part of your “hindbrain” (the reptile brain, in that slightly outdated model) that continues to do some processing of senses while you’re asleep. I almost said that it “is still awake” while you’re asleep, but that’d be very incorrect, since being awake and conscious involves all kinds of other activity in the brain that you’re just not doing. The same part of the brain gets input from the ears (and other senses!) before it goes on to your full auditory cortex, and it handles startle reflexes, the way you’ll jump at a loud noise before you’ve fully put together what the noise is, where it’s coming from, etc. So this part of the brain “decides” (in a crude, simpler animal, or even mechanistic kind of way) if some input is worth startling you awake.

And so of course different hindbrains can be more or less “jumpy”, and can also care more or less about different things. I know mine sure fixates on the sounds of people talking or moving around; it just doesn’t feel safe if there are people around and it doesn’t know what they’re up to, so I’ve gotta wake up and listen. Hurricane though? Eh, we’ll sort that in the morning, if we’re still alive.

**ETA: TL;DR**: We aren’t sure, but it’s probably something like our hindbrain’s automatic startle/danger reflex activating.

Obstructive Sleep Apnea causes you to wake up several times an hour, which is pretty much by definition sleeping lightly.

For me its trauma. When you don’t feel safe in an environment I don’t think you ever fully go to sleep or fully relax

You’re like a cat who sleeps through all the regular noises but you’re super sensitive to something you didn’t expect and you find out the cat was never fully resting in the first place

I think it has to do with what your brain reacts to in your sleep, partially learned/trained from habit. Personally I can sleep through all my alarms, but I take care of a relative alone, so if they call out I’ll wake up immediately. Your ears are always listening anyways.


I dunno the science but i wake up on a pindrop, while my husband could sleep through a cataclysmic earthquake, no prob. Drives me absolutely insane! I feel absolutely no remorse when i push him off the bed when his snoring gets too loud.

I sleep all the way through the night without waking up, *maybe* five times a year. I typically wake up a minimum of two times, but I would say 3 is typical. And that’s with earplugs and a cold dark room. I don’t drink caffeine in the afternoon, I don’t drink alcohol at all. I’ve just always been like this since I was a kid. Fucking sucks man.

Being a light sleeper w a husband who snores. I know I can’t be the only one around here.

Anxiety, or rather overwhelming thoughts specifically, can keep me awake for hours sometimes. Exercise definitely helps. And therapy, definitely therapy. Therapy makes it worse before it gets better though.

I read that all humans have internal clock, but it run on different speeds for everybody.
There’s an “internal second” – it’s interval that out body think have a 1 second length, but in reality it could be anywhere from 0.7 to 1.2 seconds.

People with shorter values need less sleep, because their brain process things faster than for people with longer intervals.

There is a test that allow you to measure it – it will ask you to measure time intervals without help of clock and then show you your value. I was passing it ~20 years ago in university.

Imagine a gate. On one side of the gate is a bunch of sheep (baa!). On the other side of the gate is a field of grass (yum). In this example, If a sheep gets to the grassy field, you begin to wake up.

The sheep are always trying to bump into the gate to get it open. When you’re awake, the gate’s just open. When most people are asleep, there’s someone pushing back on the gate each time the sheep bump into it, keeping it closed. For ‘light sleepers’ there’s still someone pushing back on the gate but they’re a bit weaker and so it’s easier for a sheep to bump open the gate and get into the field. Why are some gate-keepers weaker? For the same reasons people are just different. We’re born differently and we have different experiences and there’s nothing wrong with different.


Taking this out of ELI5 territory, the sheep is the bombardment of sensory information to the brain, the field of grass is your body’s systems that begin to wake you up (e.g. the ascending reticular activating system, ARAS), the gate is a part of your brain called the thalamus (and generally the thalamocortical circuit of the brain), and the person at the gate are special brain waves called sleep spindles.

It is thought that the presence of sleep spindles affects the amount of sensory information from the body’s sense organs that go through the thalamacortical circuit and hence to the ARAS. It is thought that when sleep spindles are produced more frequently, sleep is less likely to be disturbed. As such, ‘light sleepers’ are would produce fewer sleep spindles during their sleep, hence, causing them to arouse more easily. There is also experimental evidence to support this hypothesis, as cited and referenced below. In the study, they found that the people who were more likely to wake up from a quieter noise (lighter sleepers) had less frequent sleep spindles than people who required a louder noise to wake them (heavier sleepers).

As another commenter points out, there are many factors that could affect these sleep spindle frequencies and to list them all would be too effortful for me. But sleep-wake disorders, genetics, various substances, and previous nights’ sleeps are just some of the things that can and do affect sleep spindle frequency

Answer based on this Cell journal article ([Dang-Vu, McKinney, Buxton, Solet, and Ellenbogen, 2010](https://www.cell.com/action/showPdf?pii=S0960-9822%2810%2900778-5)) and my 2019, undergraduate-level knowledge on sleep, which I found consistent to what is proposed in the article.


Dang-Vu, T.T., McKinney, S.M., Buxton, O.M., Solet, J.M., and Ellenbogen, J.M. (2010). Spontaneous brain rhythms predict sleep stability in the face of noise. *Cell*, 20(15), R626-R627. DOI: https://doi.org/10.1016/j.cub.2010.06.032

Edit: To anyone curious as to why this post was removed, this was a mod’s response. “It was removed because we don’t have the time and manpower to keep it clean to the level that is appropriate and it was inviting personal stories and medical advice.

I hope you appreciate the broad category removal reason, the “medical advice” one might technically be more accurate but doesn’t really make sense the way those removal reasons are phrased, does that make sense?”

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