Listening to a low-frequency sound may help the brain flush out toxic proteins linked to Alzheimer’s disease, according to new research on monkeys.
In the experiment, a steady hum at 40 hertz (Hz) increased levels of an Alzheimer’s-associated waste protein (β-amyloid) in the animals’ cerebrospinal fluid – a sign that the brain was clearing the toxin more effectively.
The findings, published in Proceedings of the National Academy of Sciences, suggest sound stimulation could one day form part of a non-invasive treatment for the disease.
Sound stimulation
As we get older, our brain’s neurons become coated in a ‘plaque’ made of a waste protein called β-amyloid. This plaque interferes with communication between brain cells and causes cognitive decline.
Usually, our brain operates smoothly thanks to synchronised electrical rhythms, which also help to regulate its waste clearing processes.
But “in Alzheimer’s, this rhythm weakens and becomes chaotic,” Prof Giuseppe Battaglia of the Institute for Bioengineering of Catalonia told BBC Science Focus. Battaglia was not involved in the new study.
“Hypothetically, sound stimulation might resynchronise brain activity, […] restoring timing signals that instruct cleaning systems when and where to act.”
Previous research on rodents indicated that neural cleanup systems clear this plaque better at a frequency of 40Hz. But this new research, according to Battaglia, “bridges the gap between mice and humans” by showing a similar effect in primates.
A team of researchers from the Kunming Institute of Zoology (KIZ) at the Chinese Academy of Sciences tested the approach on nine elderly monkeys.
The animals were played the sound for one hour every day for one week. After the trial, the researchers found that the levels of β-amyloid in the cerebrospinal fluid were 200 per cent higher than before, suggesting a significant quantity of plaque had been cleared.
And the effect appeared to last – the elevated levels of β-amyloid persisted for five weeks afterwards, according to the study.
Yet Battaglia cautioned against reading too much into the results of the study, which was short with a small sample size and focused on biomarkers rather than memory and behaviour.
“It is best seen as a strong clue, not a breakthrough treatment,” he said. While the results are “encouraging”, only carefully conducted human trials, he added, will show whether this could “translate into lasting protection of memory.”
Human impact
If such trials were successful, sound treatment could be an effective and non-invasive treatment for Alzheimer’s. Currently, there is no cure for the disease, despite 55 million people living with Alzheimer’s (the most common form of dementia) worldwide.
So should you listen to 40Hz tracks at home? Though “listening at moderate volume is unlikely to be harmful for most people,” there’s also no evidence that this will help, according to Battaglia. The track played during the study had specific conditions, such as tone structure and volume.
In other words, the research offers early, experimental results that are as much preliminary as they are promising.
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