mild cognitive impairment

Pink Noise Improves Memory, Deepens Sleep

Slow-wave sleep may be a key therapeutic target in individuals with mild cognitive impairment, new research shows. According to a new study, playing gentle sound stimulation during deep sleep can enhance slow-wave sleep among those at risk for Alzheimer disease.

To analyze the effect of pink noise during sleep on memory, the researchers analyzed data on 9 participants with mild cognitive impairment.


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The participants slept 2 nights in a sleep laboratory, with the second night being approximately 1 week apart from the first night. Each participant received sounds during 1 of their sleep visits and no sounds during the other; the order of which night had sounds and which did not was random. 

During the slow-wave stage of sleep, the participants received short pulses of pink noise, which is deeper than white noise.

The researchers conducted memory testing each night and morning of the 2 days and compared the change in memory across both nights. The difference in slow-wave sleep with sound stimulation and without sounds that the system monitored was also analyzed.

The participants were tested on their recall of 44 word pairs. Participants whose slow-wave activity increased by 20% or more after the sound stimulation were able to remember approximately 2 more words in the morning memory test. One of the participants—who had a 40% increase in slow-wave activity—was able to recall 9 more words.

In turn, the researchers determined that the relationship between the enhancement of deep sleep by sound and memory was significant. However, because of the study size and variance in response, the memory improvement was considered not statistically significant. 

“These results suggest that improving sleep is a promising novel approach to stave off dementia," said study co-author Roneil Malkani, MD, from Northwestern University Feinberg School of Medicine, in a press release.

—Colleen Murphy


Pink noise boosts deep sleep in mild cognitive impairment patients [press release]. Chicago, IL: Northwestern University; June 28, 2019. Accessed June 28, 2019.