“Pink Noise” May Improve Sleep and Memory in Older Adults

A new study has found that sound stimulation at night can lull people into a deep sleep

No word on cats, though. iStock/1001slide

Research has shown that deep sleep plays a crucial role in memory formation. As humans age, sleep becomes lighter and more fragmentary, however, which in turn means that older adults get less deep sleep than younger ones. So it isn’t entirely surprising that deprivation has been linked to memory loss among the elderly.

Fortunately, there might be a rather easy fix to this problem. As Amanda MacMillan reports in TIME, a new study suggests that “pink noise” can lull adults into deeper slumbers and help them form stronger memories.

Pink noise is similar to white noise, but while white noise is one continuous sound, pink noise includes high and low frequencies. “[I]t kind of resembles a rush of water,” Phyllis Zee, professor of neurology at Northwestern University and lead author of the study, tells MacMillan. “It’s just noticeable enough that the brain realizes it’s there, but not enough to disturb sleep.”

Zee and a team of researchers at the Northwestern gathered 13 adults who were 60 or older and monitored their sleep in a lab for two nights. On both nights, the participants took a memory test, went to bed while wearing headphones and an electrode cap, and took another memory test in the morning. But unbeknownst to the sleepy subjects, researchers only played pink noise into the headphones on one night.

More specifically, they timed the sounds to match the participants’ slow-wave oscillations. During deep sleep, brain waves slow to about one oscillation per second, compared to about ten oscillations per second during wakefulness, the researchers write in a press release. The algorithm they employed in the study allowed the team to deliver a low burst of pink noise at the “precise moment” that the participants’ slow waves rose—a pattern that is unique to each person. 

The results of the study, published in the journal Frontiers in Human Neuroscience, found that participants’ slow waves increased after the night of sound stimulation, suggesting that they were getting more deep sleep. And on the morning after hearing pink noise, they performed three times better on memory tests than they did after sleeping without any sound stimulation.

The study was a relatively small one, so further research is needed to confirm its findings, and study how longer-term use of pink noise effects sleep. But as MacMillan reports in TIME, Northwestern has taken steps to patent the researchers’ technology, which seems to have hit upon a way to stimulate slow waves at the right moment. The team hopes to develop an affordable device that people can use at home, from the comfort of their beds.

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