CHICAGO, June 29 (Xinhua) -- Gentle sound stimulation played during specific times in deep sleep enhanced deep or slow-wave sleep for people with mild cognitive impairment, who are at risk for Alzheimer's disease.
And the individuals whose brains responded the most robustly to the sound stimulation showed an improved memory response the following day, according to a study posted on the website of Northwestern University (NU) on Friday.
For the study, NU researchers conducted a trial of sound stimulation overnight in people with mild cognitive impairment. Participants spent one night in the sleep laboratory and another night there about one week later. Each participant received sounds on one of the nights and no sounds on the other. The order of which night had sounds or no sounds was randomly assigned. Participants did memory testing the night before and again in the morning.
The sound stimulation consisted of short pulses of pink noise, similar to white noise but deeper, during the slow waves. The system monitored the participant's brain activity. When the person was asleep and slow brain waves were seen, the system delivered the sounds. If the patient woke up, the sounds stopped playing.
The researchers then compared the difference in slow-wave sleep with sound stimulation and without sounds, and the change in memory across both nights for each participant.
The participants were tested on their recall of 44 word pairs. The individuals who had 20 percent or more increase in their slow wave activity after the sound stimulation recalled about two more words in the memory test the next morning. One person with a 40 percent increase in slow wave activity remembered nine more words.
"Our findings suggest slow-wave or deep sleep is a viable and potentially important therapeutic target in people with mild cognitive impairment," said Roneil Malkani, assistant professor of neurology at NU Feinberg School of Medicine. "The results deepen our understanding of the importance of sleep in memory, even when there is memory loss."
"These results suggest that improving sleep is a promising novel approach to stave off dementia," Malkani added.
As the new study was small, having only nine participants, and some individuals responded more robustly than others, the improvement in memory was not considered statistically significant.
In the next step, the researchers plan to evaluate pink noise stimulation in a larger sample of people with mild cognitive impairment over multiple nights to confirm memory enhancement and see how long the effect lasts.
The study was published on Friday in the Annals of Clinical and Translational Neurology.
