Pink noise reduces REM sleep and may harm sleep quality | Hacker News Reader

Pink noise reduces REM sleep and may harm sleep quality

pennmedicine.org

110 pointsgnabgib75 comments

Researchers observed 25 healthy adults, ages 21 to 41, in a sleep laboratory during eight-hour sleep opportunities over seven consecutive nights.

Absurdly low n. Additionally, I've become very skeptical of anything coming out of sleep labs after my wife was sent to one (at a prestigious teaching hospital) by her doctor some years ago: the 'sleep opportunity' was lights out at 9pm for 8 hours, and the staff were wholly indifferent to the fact that she's a night owl and prefers to sleep after midnight. Additionally she reported that it was not particularly quiet or dark.

I am not a fan of noise machines but I have noticed that I sleep best on rainy nights, which has a similar average sound spectrum, and is about the same as the sound of your blood circulating near your eardrums. Testing pink noise along with aircraft noise (which is closer to red noise) is equivalent to just making the noise level higher with slightly more midrange energy. Some noise can be relaxing for light sleepers; too much is just annoying.

Sleep labs are like doctors are like mechanics are like restaurants - their only legal obligation is to not kill you,

not be of any particular quality.

Do your homework.

That is a low n, but I’m not sure what the alternative is. Surely random anecdotes (n=1) are even less powerful?

Random anecdotes might be less biased. For example, no pressure to publish nor sell a product.

The low n is not the only questionable thing about the study. What a big n gives you is diversity of samples and tighter confidence intervals, but it can not correct for methodological limitations. Specifically, they didn't invite any people with sleep issues or who are already sleeping under noise. Therefore the conclusion is a "duh" - if you don't require pink noise to sleep, then don't add it.

I'm not inviting you to draw conclusions from my semi-random (but informed by years of professional thought about why people like different sounds) anecdote.

Personally, I trust the results of a sleep study, or any study on anything, by people I don’t know with questionable incentives than I do anecdotes of commenters I’ve been following for 10 years on HN, especially when they align with my own experiences, and conversations I’ve had over beers with people in industry (whatever that might be).

A lot of “science” is junk, not insofar as it’s false, but like water is wet.

Good science: there are compounds in cruciferous vegetables that appear to exert some health benefits.

Junk science: bok choy is green.

If a sleep lab is ignoring the fact of chronotypes (it’s obvious our genetic history would require some people to be predisposed to keep an eye out for toothy clawed things, and dangerous ‘others’) while most of their tribe / community are sleeping), the people who work there do so because it pays the bills, not because they’re passionate about working in the medicine / health industry at all.

I encourage people to get up and walk out if you find yourself at a service provider that doesn’t care about you. Find someone who gives a frak.

Once again, I am not suggesting you generalize from my anecdote. I like the sound of rain and sleep better with it. I have absolutely no idea how widespread this is in the population.

The alternative is higher n. The study makes a claim, it does not present the evidence necessary to back up that claim. Until someone does a larger study, no conclusion should be drawn.

Common sense and experience inform my theory of good sleep: Pitch black, stone quiet, with noise limited to pre-sleep audial approximations of the dream-like mental noise that precipitates sleep.

Glad that works for you! To me, silence sounds a lot like insomnia.

> -sleep audial approximations of the dream-like mental noise that precipitates sleep.

What does this mean for you?

My hypnagogia, or mental-noise that precipitates sleep as you put it, is entirely visual hallucinations.

I’m not aware of ever having been able to recall any auditory hallucinations.

I’ll match your anecdote. I slept with white noise in my former home which was in a noisier town and felt it improved my sleep. Now that we’ve moved to a nice historic neighborhood I find I sleep best with nothing on at all. The silence there is so wonderful. Maybe silence is the ultimate luxury.

The thing that stood out more to me than the n being low is "the participants reported not previously using noise to help them sleep or having any sleep disorders." Sleeping with pink noise seems like something that you'd end up getting acclimated to.

My n=1 is that I often sleep with a fan on and live in NYC -- whenever I stay in a place where there is no noise I tend to have trouble sleeping, so I end up turning on some nature sounds on my phone from myNoise.

Yeah that seems silly. I was a quiet-room sleeper until I met my wife, who needs some kind of white noise to sleep. I eventually adapted and now sleep much better with noise than without (at least subjectively), but that change took a while, at least several months. I found it quite difficult to sleep with for a while.

I slept without noise for years until I needed it for a while for (reason) and now it feels difficult to sleep without noise. Acclimation’s a real effect

Confounding variable: the presence of your wife may be aiding your sleep more than the noise.

Perhaps too meta or off topic but I thought it was funny that you thought their n was low and then cited a story about one person.

The way I’m understanding it is that it’s more that if there’s a real population of people like his wife, that is only 5 percent of the actual population or even higher, for example, it may not be caught by such a small sample size.

But that is true of all sample sizes

My options are "fairly loud, low rumbly, mostly full spectrum noise" or "continual, nonstop barking." Only one of these options makes sleep possible. :) I'd prefer quiet, but it's so rare to actually have it.

It's a within-subject design and they literally did a power analysis in the paper. This is not absurdly low n.

Sleep studies often have low numbers of participants because conducting tests in a controlled environment of a sleep lab is expensive and time consuming, as they have only so many beds.

>Absurdly low n

Please divulge the statistical calculus showing this is an absurdly low n. Please explain how to determine the appropriate sample size.

No, "number _seems_ small" is not adequate statistical reasoning.

I wonder if gentle noise might be relaxing in the same way that watching trees swaying in the wind is relaxing.

My ex-partner has tinnitus and saw a psychologist who specialised in tinnitus. The psychologist suggested she buy a machine that generates a sound slightly quieter than her tinnitus which retrains the brain not to hear the tinnitus. So she bought a machine that generated about 15 different sounds and settled on a pink-ish sound and played while she slept. It took a couple of years but it effectively "cured" her tinnitus. It drove me mad for a while but after a while I didn't notice it.

The machine had different sounds because the sound of tinnitus is different for different people: hers sounded like cicadas, a sound I quite like but she hates!

I have misophonia and used to live in a house where a coffee van would start a generator at 0530 so I used a fan to help drown out the sound. I could still hear the generator but I could sleep through. It fundamentally changed the quality of my life.

Misophonia, interesting, I hadn’t heard (snort!) of that before. There are certain sounds I will inappropriately respond to, I’ll I read up on misophonia, thanks.

Anyways, you might be interested in a recent episode of DOAC (Diary of a CEO):

Sleep Expert Dr. Michael Breus breaks down the 4 chronotypes to master your sleep, how to fix insomnia, the truth about sleep apnea, and why the 8-hour myth is wrong!

Dr. Michael Breus is a clinical psychologist and a Diplomate of the American Board of Sleep Medicine. He has appeared on The Oprah Winfrey Show, served as a WebMD sleep expert, and is also the bestselling author of books such as, ‘Sleep Drink Breathe’.

Apple Podcast link or conjure your own from preferred provider:

https://podcasts.apple.com/au/podcast/the-diary-of-a-ceo-wit...

> Misophonia, interesting, I hadn’t heard (snort!) of that before. There are certain sounds I will inappropriately respond to, I’ll I read up on misophonia, thanks.

The misophonia isn't a bad place to start: https://www.reddit.com/r/misophonia/

I've watched a few episodes of DOAC so I'll watch that. I know my chronotype but that's about all so it'll be interesting so what they say!

If your in to sleep hygiene there might not be much new to you.

I use the Background Sounds feature (in Accessibility settings) on iOS with a Bluetooth speaker every night while I sleep. It's quite battery-friendly and has several sound options alongside dedicated volume control with which you can set background sound volume independently of the main volume. It's also possible to add a shortcut button to this feature in the Control Center (the screen that's shown when you pull down from the top of the screen).

This makes occasional outside/neighbour noises much less noticeable, although I do keep earplugs near my bed just in case (not great for my tinnitus, but still usually better than without them if they're needed).

A lot of comments here dismiss the study for having a small N.

Exploratory research uses small N at the start. This kind of research can have value even if it is not conclusive.

Imagine the expense (and dominance of Big Research) if every study needed 100,000 participants to run.

If you don’t want to read exploratory studies, ignore them when they hit the headline news.

Other criticisms of this study (e.g., participants didn’t previously sleep with noise) seem more on the mark. I’m not an uncritical fan.

Bashing studies for having now N is common because it’s the easiest thing for non-scientists to criticize when they don’t like a study’s findings.

Scientists, on the other hand, know that low N does not necessarily reduce the validity or the value of a study.

Only tangentially related.

I occasionally fall asleep to either a movie / TV episode on repeat in a media player on the PC in my bedroom, or a YouTube short which repeats.

The audio almost always gets integrated in to my dreams, and almost always in a highly entertaining and humours way.

Anyways, I feel I sleep better when there is background sound, even if it’s other people (quietly) partying in the house.

I'm with you. The way I deal with insomnia is to pretend I'm sleeping in a noisy environment. For example an apartment under a elevator highway or a cot behind a bunch of refrigerators. Or even in a tent on a lively beach.

Don't know why but it works great.

This study had no controls at all, and can safely be ignored.

>The participants reported not previously using noise to help them sleep or having any sleep disorders.

All this study said was that people who didn't need noise to sleep had their sleep disrupted when noise was introduced. It has absolutely no implication for people who use noise to help them sleep.

Meaningless trash.

"Pink noise sounds like a waterfall." https://en.wikipedia.org/wiki/Pink_noise

Helps me quite a bit to focus when Im in noisy spaces.

This reminds me of an old Wired interview with Danny Hillis when he developed a system called Babble that used unintelligible vocal bits as background sound to help concentration, too bad it never really went anywhere. https://www.wired.com/2005/06/applied-minds-think-remarkably...

A number of noise generators have that sort of nonsensical babble as a component of the sound. For instance

https://mynoise.net/NoiseMachines/cafeRestaurantNoiseGenerat...

Nothing that your mind has enough edges on to try to interpret, but vaguely human-like.

mynoise's Cafe Restaurant generator got me through years of working in a noisy open office. Can't recommend it enough. I put the cutlery noises on mute though.

For me that would be the worst kind of distraction: always triggered by sounds of communication, never able to recognize what is said.

I suspect not all such statistical results apply uniformly to all people.

Yes I have the opposite. I can focus better when I'm working from a coffee shop and I don't understand what people are saying.

With some friends we usually go camping near a waterfall and we always try to camp a little further so we don't hear the noise. At least not too much. We always assumed it was related to the fact that you can't hear anything approaching, some kind of primal instinct

Sounds like my tinnitus.

I grew up in South East Asia with air con running all night, when I moved away I found it hard to sleep in 'quieter' countries

This. In summer I get ‘addicted’ to fan noise and cant sleep without. I moved to Asia and the AC is such a blessing.

I'm also addicted to the fan but not only for the noise I like feeling the wind in my face, I think that as it also helps lower your body temperature you sleep better

Wind in my face literally makes me catch a cold within the night, feet/legs is where it is at for me haha

Same for me, one night with a fan on my face / neck and I’ll wake up with an URTI (Upper Respiratory Tract Infection).

Definitely sleep better if I’m not feeling hot.

The study may well be flawed—small n, selection bias, lack of proper controls, sure. But can we please stop using personal anecdotes to dismiss scientific inquiry?

Arguments like 'well, it works for me,' or 'I took this med and recovered immediately,' or 'I saw X happen right after a vaccine' are not valid refutations. Science is frequently counter-intuitive and often contradicts our personal experience and gut instincts. That is precisely why we rely on the scientific method and statistical rigor—rather than individual perception—to establish evidence.

This study is tiny and of negligible value. They didn't even try to pretend it's of real value, and instead just dropped the classic "our study clearly demonstrates that people should probably study this stuff". Conditioned norms are by far the most relevant condition for sleep for most people, and sleep studies of tiny durations with tiny sets are basically just noise makers (har har). Even worse, they seem to have specifically excluded people who already use noise machines, ensuring that their participants were conditioned for the silent norm.

Scientific method, statistical rigour...eh, this looks like a headline chasing study.

Sure, you are absolutely right. Even a sloppy study like this still had something useful than any anecdotes.

On the other hand, my life isn’t a double-blind randomised controlled study.

I can’t bifurcate n times and give half of the me’s one treatment and the other half of me’s no treatment, and I especially can’t do that without revealing to myself which group of me’s received the treatment, and which received no treatment or a placebo. Who even know motivates us.

Additionally, what works for some version of me, for example there was a me who was younger and fitter and more appealing to the ladies, may not work for the older version of me who is less young, relies on testosterone supplementation to not be a writhing crying mess on the floor, and hasn’t had a root in 18 months.

That’s why the practice of medicine has always been considered an art and a science.

There’s art in learning to apply the practice of medicine in an effective way.

Also, populations change over time. Older doctors will notice that decades ago every second person came in with problem x, but now the patients of a similar age and similar live experience now seem to be experiencing more y and less x.

The human condition, while at least somewhat consistent insofar as we’re still puzzled by some age old questions, is also a moving target.

It's the dehumidifier for me. Which kills two birds with one stone.

I noticed I'd feel sleepy after more than half an hour in the server room. Likely the fan noise but the lower temperature might influence it as well.

Unfortunately too expensive and large to set this up in the bedroom to help me sleep nowadays.

used to run data centers. the hot aisle after lunch would always lull me to sleepiness. cold aisle sometimes too, assuming I was bundled up.

I grew up near train tracks. I’m totally of incapable of even hearing trains unless they’re directly in front of me.

I would recommend reading the paper rather than the article, or at least the abstract:

> Compared to a noise-free control night, EN reduced N3 deep sleep (p < .0001) while PN reduced REM sleep (p < .001). Adding PN to EN worsened sleep structure, despite minor dose-dependent improvements of EN-induced sleep fragmentation and N3 sleep increases. Earplugs mitigated nearly all EN effects on sleep but started failing at the highest EN level (65 dBA). Morning cognition, cardiovascular measures, and hearing were not affected by nighttime noise, but subjective assessments of sleep, alertness and mood were significantly worse after EN and PN exposure.

I feel unsafe wearing earplugs. You're so totally unaware. I'm worried I'd sleep through an alarm.

Since I own a house, I’m afraid of burglars (or rapt) and any crack seems like a sign the roof might fall… so yes, no earplugs…

Intentionally misspelling rape won’t make it go away.

Believing people won’t be triggered by seen the word rapt instead of raped isn’t doing anyone a service.

I have the best. Natural noise generator, which means microphones outside. With 3 layered windows the winter is just too silent, or rather: filled annoying multistory house noises. In summertime windows are open and that is about the suitable noise level.

Also there is the outdoorsman's reaction to silence. When birds go silent, there is something bad happening. Bears or wolf pack.

It's too bad that cities are so unlivable due to noise pollution (constant aircraft noise, road noise, loud rumbling that travels for miles, 24/7 emergency vehicle sirens, etc.)

Yes, after I've heard that, I used pink noise on purpose to induce more deep sleep. It's beneficial when you want your brain to flush more metabolites. I guess.

study aside, pink noise is awful imo - it's perfect if you're calibrating a PA system and need specific power spectral density properties, but bad for my brain. if sleeping somewhere without a fan or whatever i use brown noise, it's closer to a lower rumbling.

I really like brown noise at night.

My immediate thought about this article was that I'd love to see this study on brown noise (albeit, with more participants).

Second thought was that, I wonder if some A/B testing with my garmin watch would give signal on this. Life is probably too hectic to get real signal.

Dr Seth Horowitz did some interesting work in psychoacoustics and documented how low amplitude low pitch movement-based sound(s) promotes falling asleep mediated by the vestibular system. Explains why its so easy to fall asleep in the car

Thanks for sharing. I'll have to reconsider my nightly noise setup, but good to know.

If you're resting well with your current setup, I wouldn't change it. There are so many individual factors involved with good sleep.

> 25 healthy adults

Come on guys. Replication crisis has been fully documented

> Participants slept under different conditions, including being exposed to aircraft noise, pink noise, aircraft noise with pink noise and aircraft noise with earplugs

And yet the conclusion is about pink noise vs silence. We may have a new textbook example of HARKing right here!

The conclusion is:

> The results, the researchers said, suggest not only that earplugs—which are used by as many as 16% of Americans to sleep—are likely effective, but also that the overall health effects of pink noise and other types of broadband noise “sleep aids” need to be studied more thoroughly.

One of those least-worst choices?

What if the intensity was modulated as a function of the dB of externally sourced sounds?

7 nights is not nearly enough to get used to new environmental factor introduced in the study, possibly exacerbating disruption from sleeping in a new place (sleep clinic).

n=25? Seriously?

This is barely passable as an early hypothesis test before you perform an actual study.

I get how difficult a study like this is to carry out, but each participant was involved for just seven days, each night exposed to different conditions. The control environment was silence, and every other conditions did worse than controlled silence. In others they piped in fake environmental noises, pink noise, or made the participants wear earplugs with some other combination.

Eh. People condition to an environment, and someone conditioned to something like pink noise wouldn't have the acclimation issue (and they either specifically selected for people who don't use noise machines, or they just randomly got only people who don't), and it might drown out smaller environmental noises that otherwise would have disrupted their sleep. It would take a much longer study to determine this.

Or hey, maybe those insecure sleep masks tracking EEG and other things will give us some insights eventually. People just need to harvest the data from the other services.

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