In 2012, I made a Web-based tone generator with the goal of helping tinnitus patients determine the frequency of their tinnitus to better target therapy. Since then, I have heard from people using my generator to teach physics, practice violin, drive away carpenter bees, tune DIY speakers, analyze room acoustics, calibrate vintage synthesizers, cause mischief in class with frequencies the teacher can’t hear, and even open a portal to Sedona, AZ. Far be it from me to take away from all these worthwhile applications, but last week, I got a message from Dennis Tuffin (of Devon, England), describing a new use for my generator which may very well trump everything else:For the past 7 weeks I have been using your tone-generator for a purpose I wouldn’t think you had envisaged but about which I am sure you will be interested.
I have been following up on some research which my daughters had done about the treatment of Alzheimers by using a 40Hz flickering light source or alternatively a 40Hz sound source. There is sparse info on the net about these experiments though there is a recent piece about it. [here Dennis is referring to this paywalled article]
So I have been trying the sound therapy on my wife who is in the advanced stages of Alzheimer’s and to my surprise after 8 days she started to show small signs of being more mentally alert than before. So I have continued to use your tone generator using a 40Hz sine wave for about an hour each day. (I’ve recently started to do it twice a day for slightly shorter sessions). I found it necessary to connect external speakers to my laptop in order to pick up such a low note and to run it at a level of between 46-54 decibels so that she hears it wherever she is in the room. (Dementia sufferers get very fidgety!). So now 7 weeks on the improvement in her awareness has continued to the point where she is starting to be able to put a few words together and to respond to questions neither of which she has been able to do for nearly a year. Her odd physical habits have not been changed so far but she is definitely walking better and not shuffling her feet as she used to. Surprisingly, she is also sleeping better and not suffering as much with the sleep apnoea problem that she’s always had.
Of course I expect there to be a limit to this progress as in the 8 years since my wife was first diagnosed her brain will have shrunk considerably so I do not expect her memory to return but on the other hand my wife’s quality of life has been improved.
To date I have not gone public on this and only close family have known but by the end of another week when it will be 8 weeks since we started I think I would like to spread the word and hopefully prompt a few professionals to do more proper research.
THE SCIENCE SO FAR
- It has been known since at least the 1980s that cognitive activity triggers brainwaves (wave-like patterns of activation) at a frequency of 40 Hz in humans and other mammals.
- In 1991, researchers from the NYU Medical Center discovered that Alzheimer’s patients have reduced 40 Hz brainwaves compared with healthy people. (paywalled paper)
- In 2016, MIT’s Alzheimer’s group did experiments on transgenic micewith early Alzheimer’s disease and found that exposing them to a light flickering at a frequency of 40 Hz (40 times a second) for 1 hour a day for 7 days causes an almost 60% reduction in β-amyloid plaques, which are a molecular hallmark of Alzheimer’s. 20 Hz and 80 Hz tones did not have the same effect. An important qualification here is that the effect was limited to the visual cortex, which is not significantly affected in human Alzheimer’s patients. Here’s an accessibly written report in The Atlantic and here’s the original paper (published in Nature) if you’re strong in science-speak. MIT also made a video about the findings.
- According to the New Scientist (paywalled article), the same MIT team achieved even better results by playing mice a 40 Hz sound. β-amyloid plaques shrank by about 50% in the auditory cortex and – crucially – in the hippocampus, perhaps because the two areas are close to each other. This is a very important discovery, because the hippocampus is the region of the brain which is involved in forming memories. It is the hippocampus that suffers the most damage in human Alzheimer’s patients. As of 15 Jan 2019, these results have not been published, but were presented at the Society for Neuroscience conference in Washington in November 2017.
- In March 2016, scientists at the University of Toronto published the results of a small, placebo-controlled pilot study (paywalled paper), in which they exposed 20 Alzheimer’s patients to a 40 Hz sound. After six 30-minute sessions (done twice a week), the patients’ average score on the 30-point SLUMS scale improved by 4 points, while the placebo group did not improve. It should be noted that the “dosage” of the treatment was rather low, which may explain the modest results.
- In July 2018, the International Journal of Alzheimer’s Disease published the results of a pilot study in which 6 human patients were exposed to a 40-hertz flickering light bulb for 2 hours a day for 10 days. The therapy was administered in a home setting by the patients’ caregivers. No difference in β-amyloid plaque was found after therapy. If there was an effect, it must have been smaller than 20%, which is not comparable to the 50% reduction seen in mice.
- Some of the members of the MIT team have started a company, Cognito Therapeutics, which will market some sort of device for audio-visual stimulation. They are now conducting three clinical trials, the first of which is expected to complete by October 2019.
- Good overview from Nature magazine (March 2018)
- Podcast on gamma brainwaves from Radiolab (this one’s from late 2016 and doesn’t include the latest research)
If you want to try playing a 40 Hz tone to someone with Alzheimer’s, here’s some technical advice:
Getting a 40 Hz tone is easy – you can use my frequency generator. (Please note I do not take responsibility for the purity of the produced tone, as it is generated by your Web browser – though I think it should be fine. By the way, I am also not a doctor and I am not giving medical advice or offering any medical product here.)
You will need decent speakers. 40 Hz is a very deep bass tone – the kind of rumbling tone that you feel in your body as much as you hear it. Small speakers, such as laptop speakers or small computer speakers, don’t go that low. If you try anyway, you will either hear nothing, or you will hear mostly – or only – distortion. What is distortion? It’s a higher-pitched, buzzing noise that speakers make when you push them too hard.
Bookshelf speakers will do 40 Hz, but their output at that frequency will be significantly reduced, so you will need to turn up the volume significantly, and they will produce easily audible distortion. Because the ear is more sensitive to high frequencies, the distortion may be subjectively louder than the fundamental 40 Hz tone, and may make the sound harder to tolerate, thus limiting the volume (and possibly the therapeutic effect).
The best solution is a high-quality subwoofer. It won’t be distortion-free, but you can expect the distortion to be 2–3 times quieter than with bookshelf speakers. This will give you as pure a tone as you can get. If you don’t care about playing music, you can get just a subwoofer (without any other speakers) and connect it to your computer or mobile device.
A neat trick to amplify the bass output of any speaker is to place it against as many walls as possible. For the maximum boost, put the speaker(s) on the floor, in a 3-way corner between two walls and the floor – that way, it will be adjacent to three surfaces.
How important is sound quality? It’s hard to say. Dennis seems to have had great results with cheap computer speakers. It is not known to what extent the therapeutic effect depends on volume or the presence of distortion. On the other hand, if you use small speakers, it won’t be obvious whether they’re actually playing 40 Hz or just distortion – so it’s worth getting something bigger just to be on the safe side.
Can you use headphones instead? It’s hard to say with certainty, as a 40 Hz tone played through your speakers will not just be heard with your ears – it will also be felt in your whole body. With headphones, the effect is strictly auditory. However, so far I haven’t seen any specific scientific reasons to suggest that this difference is important. If you decide to use headphones, make sure they can do 40 Hz. The earbuds that came with your smartphone are probably not the way to go here. HeadRoom has a database of frequency response graphs for high-quality headphones, so you can check how loud a given model is at 40 Hz. Want a specific recommendation? Get the Koss Porta Pros (Amazon.com, Amazon.co.uk). They’ll do the job, they’re the most comfortable headphones I’ve used, and – at $40 – they’re tremendous value.