In recent years, researchers have begun using eye movements as one of the clues that someone might develop Alzheimer’s. Now, one group of scientists is saying the ears might be an even better way to detect early signs of the disease.
One way to measure Alzheimer’s risk is through an eye exam that looks for certain changes in a person’s retina, the part of the eye that detects light and converts it into signals for your brain to interpret.
Doctors also look for changes in something called saccades, which are fast and jerky shifts used when looking around quickly.
People with Alzheimer’s tend to have a harder time completing this type of eye movement, taking longer to move from looking at one object to the next, or sometimes looking in the wrong direction entirely.
While doctors aren’t sure why these changes occur, it likely has to do with the loss of brain tissue during dementia.
Typically, to detect the changes in eye pattern, doctors must use expensive eye tracking equipment – but these machines aren’t widespread and not all patients can afford this type of testing.
To get around this, researchers from Dartmouth University and the École de Technologie Supérieure, a Canadian university in Quebec, developed a device that can ‘hear’ Alzheimer’s instead.
The movement during saccades produces tiny vibrations in the eardrums, and the scientists are hoping that their device, called a hearable, will be able to track a persons eye movements through these vibrations.
The hearable contains tiny, hyper sensitive microphones that can detect vibrations within the body
By using this device at the same time researchers test patients with traditional eye-tracking devices, the scientists can identify unique sound patterns to look out for that may help them diagnose Alzheimer’s early, and for cheap.
Approximately 6.7million Americans are currently living with Alzheimer’s, and the Alzheimer’s Association predicts that number will only continue to climb – reaching an estimated 13million by 2050.
The dementia affects memory, judgement, mood, sense of direction, decision making and task completion, amongst other things.
Because the symptoms for the disease are so widespread, and are often subtle in early stages, people can go undiagnosed for a long time – missing out on crucial treatments.
Though there are no cures that reverse the disease, there are some early treatments that seem to help people delay some of the worst symptoms of the disease, which makes early diagnosis crucial.
The researchers, who presented their findings at a meeting of the Acoustical Society of America, are hoping the hearable can be another – more accessible – tool that addresses the need for early diagnosis.
One of the early symptoms scientists have started to look at for Alzheimer’s risk and diagnosis is eye movement.
Moving the eye is a complex process, which involves both reflexes and control from the brain.
As someone’s brain begins deteriorating when they have dementia, this has the potential to change the way the eyes function, a 2017 report from neurologists at Vanderbilt said.
This is particularly evident when looking at saccades. People with Alzheimer’s often struggle to move their eyes in quick, distinct directions to look at objects in the periphery when directed to do so in the lab.
The Dartmouth team created a device that takes advantage of the physics of sound to translate eye movements into a message that can be picked up by a tiny microphone in their hearable device.
When the eye moves around in the socket, it creates subtle vibrations within the skull that can vibrate the eardrum. Vibrations travel from the external ear, through the eardrum, where they activate a set of tiny bones called the ossicles, which send the vibrations through fluid, jostling tiny fluids that translate the vibration into sound in the nerves
When you hear sounds, they travel through the inner ear, vibrating tiny hairs and bones.
These sound waves then get turned into electrical signals and processed through the auditory nervous system to the brain, where the organ attaches meaning to them.
Though it’s imperceptible to us, even the movement of our eyes sends little bouncing vibrations into our ear canal.
The researchers thought if they identified the rhythm of a saccade, they could forego expensive eye-tracking equipment for their hearable device, though it is not known how much their device would cost.
This may essentially allow them to ‘hear’ the early signs of Alzheimer’s.
Though research has linked difficulties with saccades to the early signs of dementia, it’s still not a test used everywhere, and was only developed relatively recently.
A 2022 study from Loughborough University that tested saccades on people with both mild cognitive impairment and Alzheimer’s found using eye tracking reliably predicted which patients had dementia.
The researchers note, if someone has saccades, they may be more likely to also develop dementia. Still, it’s not conclusive that every person who has these eye movements also has the disease.
Arian Shamei, a PhD Candidate in Linguistics at the University of British Columbia who also authored the study, said though their work is early days, they think it may have the potential to help identify other diseases in the future.
Shamei said: ‘While the current project is focused on long-term monitoring of Alzheimer’s disease, eventually, we would like to tackle other diseases and be able to differentiate between them based on symptoms that can be tracked through in-ear signals.’
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