Brief bursts of ‘pink noise’ played while people with early-stage Alzheimer’s disease sleep might give them a slight memory boost, a small study suggests.
Pink noise is best described as a low-pitched hiss. There is some evidence that exposure to pink noise during sleep may help clear waste products from the brain. As such, researchers are beginning to assess whether pink-noise therapy has benefits for the treatment of Alzheimer’s disease.
An international team of researchers has explored this possibility. They worked with 37 people, each with diagnosed with Alzheimer’s and experiencing mild cognitive impairment affecting memory. On two occasions, 14 days apart, the 37 participants were invited into the lab in the evening and asked to memorise 30 word pairs. They then slept in the lab while the researchers monitored their brain activity.
Javier Mínguez at Elevvo Therapeutics in Spain, and a member of the research team, says slow brainwaves and brief bursts of neural activity known as sleep spindles help the brain consolidate memories, a process Alzheimer’s can disrupt. The researchers used a system developed by Spanish neurotechnology company Bitbrain that can identify when slow brainwaves are approaching their peak. Throughout the first night in the lab, the researchers played a 50-millisecond-long pulse of pink noise to the sleeping participants each time these peaks occurred.
“Timing is critical, because the useful window is only about 200 milliseconds wide,” says Mínguez.
On the second night in the lab, the study participants were not exposed to pink noise as they slept.
After both nights, the participants were asked to recall the word pairs they had learned the evening before. They remembered slightly more word pairs after exposure to pink noise than after the night without pink noise: 0.88 word pairs more, on average, after the pink-noise exposure. This is equivalent to about a 19 per cent improvement in memory, the researchers say. The clinical significance of this result remains uncertain.
“These results are meaningful theoretically and fit with an increasingly strong set of findings linking memory storage with overnight brain activity,” says Ken Paller at Northwestern University in Illinois, who wasn’t involved in the study.
The study hasn’t yet been peer-reviewed. Several authors have commercial connections to Bitbrain or its spin-off Elevvo Therapeutics, and three are inventors on a pending patent covering the method, says Mínguez.
Mínguez sees the study as a proof of concept. To find out whether the benefits can last, the researchers are now expanding their experiments. They have given study participants equipment to use at home that offers pink noise stimulation during sleep, and they will assess the effects of continued exposure over a 6-month period.