Exposure to gentle sounds during sleep may improve memory in older adults, a new study has found.

Researchers at Northwestern University’s Feinberg School of Medicine in Chicago found that sounds played to the rhythm of brain waves significantly enhanced deep sleep in study participants and improved their memory test scores.

Although the study was small, researchers say it could help with treatment of dementia, Alzheimer’s disease and other cognitive disorders.

The study, published in Frontiers in Human Neuroscience, involved 13 participants over the age of 60. For one night, they slept in a lab where gentle sounds, such as the rush of a waterfall, were synchronized with their brain waves.  On a different night, they slept in the lab with no sounds. Researchers tested the participants’ memories before and after sleep.

Those who listened to the “acoustic pulses” during sleep recalled three times as many words the next morning, compared to people who received no sound at all, study co-author Nelly Papalambros told CTV News Channel on Wednesday.

“So it kind of suggests to us that the degree of sleep enhancement is related to the degree of memory improvement,” she said.

Papalambros said scientists have been studying the links between sleep and memory “forever.”

“We know that deep sleep, also known as slow-wave sleep, is critical for memory consolidation,” she said.

The so-called “slow waves”, which are large brain waves that occur about once per second, “are thought to be important as a restorative process,” she added.

Papalambros said previous studies have looked at how sounds during sleep can improve the memories of young people, but there hasn’t been a lot of similar research involving older adults. 

“We know that deep sleep changes as we age. It decreases pretty substantially…and it’s thought to play a part in the memory decline we see with age,” she said.

Papalambros said a larger study with more participants over a longer period of time is needed to confirm the results and better understand the impact of sound waves on sleep and memory.