Pink noise can improve sleep and memory in seniors, study shows

Sound may be an important part of helping all of us finally get a good night's rest, and not only that, improve our memories, according to a new Northwestern University study.

Pink noise pulses coincide with brainwaves and increase effectiveness of deep sleep

Researchers found that seniors exposed to pink noise in their study were three times better at a word association test than those who were not exposed to pink noise. (Unsplash / Benjamin Combs)

The rushing sounds of a waterfall, the pitter patter of rain or the rhythmic beating of a heart — all these sounds are usually found in white noise machines designed to help babies sleep. 

Sound may be an important part of helping all of us finally get a good night's rest, and not only that, improve our memories, according to a new Northwestern University study.

Science columnist Torah Kachur has the details.

What does this research say about what's going to help me sleep better?

A simple, non-invasive, non-medicinal, safe and cheap way to get a better night's sleep is to play some pink noise, according to a study published on Wednesday in the journal Frontiers in Human Neuroscience.

Pink noise has more lower octaves than typical white noise and is hardly soothing. For example, it can be one-second pulses of the sound of a rushing waterfall. The short pieces of quick, quiet sounds would be really annoying if you were trying to fall asleep.

But the pink noise isn't trying to get you to fall asleep; it's trying to keep you in a very deep sleep where you have slow brainwaves. This is one of our deepest forms of sleep and, in particular, seems to decline in aging adults.

"When you play the pulses at particular times during deep sleep, it actually leads to an enhancement of the electrical signal. So it leads to essentially more of a synchronization of the neurons," said Nelly Papalambros, a PhD student at Northwestern University and the first author on the work.

The pulses are timed to coincide with your entry into slow wave sleep. They sound to the same beat as your brainwaves, and they seem to increase the effectiveness of your very valuable and very elusive deep sleep. 

That slow wave sleep is critical for memory consolidation or, basically, your ability to incorporate new material learned that day with old material and memories.

To be clear, this sound therapy didn't mean participants actually slept deeply for longer — it's really about quality over quantity. You may not be more rested, but you will remember more. 

How did the researchers determine that it works?

The group looked exclusively at older adults in the 60-plus category and had 13 participants who did a memory test at night. The technique was pretty simple — try to memorize loosely associated words like oil and energy, or marriage and altar. 

The researchers then tested the participants to see how much they remembered before they went to sleep. The following day the participants were tested again to see how well they remembered their training from the night before. 

The word association recall test scores were three times better if participants had the pulses during sleep than if they had a sham treatment. 

The group that received the sham treatment had the same sleep routine, it just didn't get the faint pulses of sound when they entered the slow wave sleep phase.

Why look at older adults?

For two main reasons: one, as you age your sleep becomes more fragmented. You don't have as much slow wave sleep and that can lead to memory decline. And two, memory decreases as you age for lots of other reasons that are tied to the aging body and the cellular stuff going on.

So, perhaps if you can boost the effectiveness of deep sleep on memory consolidation, you won't see as rapid a decline in cognition that is seen in older adults.

Can we implement this strategy at home?

Not yet. It does require a precise timing of the sounds with brainwaves, but researchers are looking at trying to make it more widely available. You won't be hooked up to some crazy brain-scanner or anything.

The researchers just had a single electrode on the forehead and a computer reading the participants' sleep patterns to synchronize with the sounds.

So, we have a ways to wait for this kind of intervention to help improve our sleep and mostly our memory but it's coming.


Torah Kachur

Science Columnist

Torah Kachur has been the syndicated science columnist for CBC Radio One since 2013. Torah received her PhD in molecular genetics from the University of Alberta and studied how worm gonads develop. She now teaches at the University of Alberta as a contract lecturer in cell biology and genetics.