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The Promise of Pink Noise

Sound Stimulation May Improve Memory

This article was originally published in Northwestern Medicine Feinberg School of Medicine News Center. It has been modified for Northwestern Medicine’s content hub, HealthBeat.

The hum of white noise soothes many to sleep by masking disruptive sounds. But, can noise go beyond helping you get a good night’s rest?

That’s what researchers at Northwestern Medicine Feinberg School of Medicine set out to determine in a small pilot study analyzing the benefits of pink noise for people with mild cognitive impairment who are at risk for Alzheimer’s disease. Pink noise is deeper and has slower waves than white noise.

“Our findings suggest slow-wave or deep sleep is a viable and potentially important therapeutic target in people with mild cognitive impairment,” says Roneil Malkani, MD, assistant professor of Neurology in the Division of Sleep Medicine, and a Northwestern Medicine sleep medicine physician. “The results deepen our understanding of the importance of sleep in memory, even when there is memory loss.”

Uncovering the Results

Nine people with mild cognitive impairment participated in this study by spending two nights in the sleep laboratory, a week apart. They slept with pink noise during one of the nights and no sound during the other at random. Before bed and the following morning, participants did memory testing so that researchers could analyze change in memory across both nights. The slow wave activity of their brains was also monitored so that scientists could compare the difference in the quality and duration of slow brainwave, deep sleep, with and without sound.

Participants were tested on their recall of pairs of words. Participants whose slow-wave brain activity responded the most to the sound stimulation showed an improved memory response the following day. Northwestern Medicine scientists had previously shown that sound stimulation improved memory in older adults in a 2017 study. Because the new study was small and some individuals responded more robustly than others, further research must be conducted to deem the improvement in memory statistically significant.

Digging Into Deep Sleep for Alzheimer’s and Dementia

Deep sleep is also critical for consolidating memories. Some studies have even shown a link between deep sleep disturbances and mild cognitive impairment.

“There is a great need to identify new targets for treatment of mild cognitive impairment and Alzheimer’s disease,” Malkani says. “These results suggest that improving sleep is a promising novel approach to stave off dementia.”

There is a promising relationship between the enhancement of deep sleep with sound and memory. From this small study, it seems that the greater the deep sleep enhancement, the better the memory response.

“As a potential treatment, this would be something people could do every night,” Malkani said.

Other Northwestern University authors include first author Nelly Papalambros; Phyllis Zee, MD, PhD, chief of Sleep Medicine in the Department of Neurology; Sandra Weintraub, PhD, professor of Psychiatry and Behavioral Sciences; Daniela Grimaldi, MD, PhD, research assistant professor of Neurology in the Division of Sleep Medicine; Ken Paller, PhD, professor of Psychology in the Weinberg College of Arts and Sciences; Tammy Chen; and Giovanni Santostasi, PhD.

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Roneil G. Malkani, MD
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