Earables – unlocking the future of wearable health monitoring

31 Aug 2024 13min read

Headphones, earphones, earbuds: people wear them while they run, when they are on the bus and just whenever and wherever. These ear-worn devices have become an everyday part of life, but they also hold the potential for a new approach to wearable health monitoring. Much like wristwatches have evolved to detect vital signals, other technologies such as contact lenses and ear-worn devices have as well. The question is, are “earables” the next wearables?

The following are some of the latest advancements in ear-worn devices in the healthcare sector, from innovations in biosignal monitoring to non-invasive mental health therapeutics and more.

What are earables?

The term earable can be defined as an ear-worn device with sensors located in the vicinity of the ear, with functionality that extends beyond just audio input or output. A subset of earable technology is ‘hearables’, which are devices used for audio purposes, such as earphones for music and hearing aids. Earables can, however, be used for other functions, including a number of health applications.

Biosignals monitoring via the ear

Much like measuring via the wrist, multiple vital signals can also be tested via the ear non-invasively. This includes temperature, heart rate, blood oxygen saturation (SpO2) and respiration rate. In fact, the ears might be a better place to record these signals compared to the wrist, since they are closer to vital organs like the heart and brain.

Taking temperatures via the ear using infrared technology is already common practice (one example being the handheld ear thermometer). The eardrum shares the same blood supply – the carotid artery – as the hypothalamus, which is a structure in the brain that functions as the body’s thermostat. As a result, the body’s temperature can be determined by measuring the infrared energy emitted from the eardrum.

Labeled diagram of the ear’s auricular blood supply

Diagram depicting the external carotid artery (arteria carotis externa) and its branches

Another area with great potential for wearable health monitoring via the ear is heart rate monitoring. Many modern smartwatches and wearables employ photoplethysmography (PPG) to achieve this, a technology that uses light to detect blood volume through the skin. Using a light source and a detector, PPG technology measures changes in light intensity that correspond to changes in blood volume in a cardiac cycle. The ear is a good location for this as it contains a large blood supply and is also less susceptible to motion artifacts compared to the wrist, for example.

Earable devices for biosignal monitoring

Ear biosignal monitoring is already being actively explored by several companies. Cosinuss has developed a CE Class II behind-the-ear device that can measure temperature, heart rate and blood oxygen saturation (SpO2). They achieved this by combining a thermometer and pulse oximeter into a single sensor. The data obtained are then transmitted via Bluetooth to a smart device, processed in real-time and can be viewed on an app. Healthcare providers or researchers can also access and visualize the data, allowing a patient’s vital signs to be monitored continuously throughout the patient’s journey, from the point of injury to the healthcare facility.

The company demonstrated the functionality of the device during Covid-19, where it allowed healthcare workers to remotely monitor the vital signs of patients. Cosinuss has also demonstrated their earable technology in mountain and alpine rescues, resulting in rescuers needing to carry fewer pieces of heavy monitoring equipment. In the future, they would like to use the product in emergency rooms as well.

Another company, EarSwitch, is developing a medical-grade sensor, EarMetrics, to be integrated into existing hearing aids. This sensor can measure several biosignals, including respiration rate and blood pressure, offering the potential to transform an existing technology into a wearable health monitoring tool.

MindMics is taking an alternative approach, using ultrasound to measure biosignals at the ear using an earbud device. Unlike the light-based technology mentioned above, acoustic signals are unaffected by the physical characteristics of the user, such as skin tone, skin thickness and body mass. By analyzing the low-frequency sounds produced by bodily mechanisms and functions, the company’s earbud device provides insights into the user’s cardiovascular health, which can be accessed on an associated app.

Established tech giants are also starting to take an interest in the earable space. Just last year, Apple filed a patent for their ear pods to have biosignal sensing capabilities. Although the status of the patent is still pending, the fact that a company like Apple, famous for its Apple Watch with health monitoring functions, is looking into this shows the potential for earables to become viable health monitoring devices.

Mental health therapeutics via the ear

Another promising application for ear-worn devices in healthcare is mental health therapeutics. A particular area of interest in this space has been in finding non-invasive methods to stimulate the vagus nerve as a treatment for both epilepsy and depression.

The vagus nerve is the main nerve of the autonomic nervous system, which regulates functions that cannot consciously be controlled, such as heart rate, breathing and temperature. Vagus nerve stimulation was first approved by the FDA in 1997 for the treatment of drug-resistant epilepsy for patients above the age of 12, and in 2005 for treatment-resistant depression. However, these treatment procedures were and are still invasive, requiring surgery to implant the required electrodes.

As part of a search for a non-invasive method, research into how the vagus nerve operates has since revealed that it extends to some parts of the skin in the ear. As shown in the diagram below, the nerve innervations marked in green display the auricular branch of the vagus nerve. This allows easy external access to apply a stimulus non-invasively. One way of stimulating the vagus nerve is by using electrical pulses. This alters the brain activity, but the exact mechanism of how this works is still unclear. One line of thought is that electrical stimulation alters the electrical pattern and the level of neurotransmitters in the brain.

Image depicting the aricular branch of the vagus nerve

Diagram depicting the location of the vagus nerve’s auricular branch

Earable devices for mental health therapeutics

There are already several companies actively applying non-invasive vagus nerve stimulation via ear-worn devices. Parasym has developed the Neurosym, an earable that the user clips to the tragus, the middle fleshy part of the ear where the vagus nerve innervates. The wearable works alongside an accompanying handheld device that allows the user to vary the energy intensity of the electrical impulse. Through a proprietary waveform, the device analyzes the heart rate variability waveform and sends targeted electrical impulses to the brain, activating specific self-repair mechanisms of the body and mind. This device is a certified medical device (CE) in Europe and has received FDA Non-Significant Risk Designation in multiple studies in the USA.

Mindspire is also stimulating the vagus nerve using electrodes in its earable development, although with a focus on decoding and releasing stress. The first clinical application is tinnitus treatment to relieve the stress a person with tinnitus might experience. Tinnitus is a ringing or buzzing sound experienced by sufferers that is not caused by a real external sound and currently has no cure.

Similar to biosignal monitoring, ultrasound is also another candidate for vagus nerve stimulation and is being used by Zenbud in their device. It is said that using ultrasound can stimulate structures that are more difficult to reach, as it can penetrate deeper compared to electrical stimulation.

Control and communication via the ear

Hands-free control has come a long way in recent years thanks to advancements in technologies such as voice recognition. But there are times when we would like to communicate discreetly or we need to talk and use our hands at the same time. This is where earables come into play, with a number of devices in development that enable hands-free and voice-free control.

Earable devices for control and communication

Wisear has developed an ear-worn device that allows the user to control a device through jaw clenching and eye activity. The technology works by using tiny electrodes in the device that acquire biosignals in the ear region. While the exact signals that are acquired have not been disclosed by the company, it is suggested to be EEG, EMG and EOG, which are signals from the brain, muscles and eyes, respectively. After amplifying the signal, an AI algorithm interprets the neural activity in real-time and executes the action intended by the user. The company has already collaborated with developers of AR and VR headsets to allow a more immersive experience for users. In the future, they aim to translate the product into medical applications as well, such as for the detection of neurological conditions.

EarSwitch, mentioned earlier, is also working on a technology called EarControl, which aims to provide hands-free control of devices for various applications, including gaming and assisting people with neurological conditions. Focusing on the latter potential use case, people with conditions like motor neuron disease (MND) have a lack of muscle control that worsens over time. For example, MND patients lose muscle control at their extremities first, which slowly progresses to the rest of the body. This means they will soon lose the ability to use their fingers once diagnosed with the disease. EarSwitch believes that the tensor tympani muscle, a muscle in the ear that can be trained to voluntarily squeeze, is retained in late-stage neurological conditions. How the device acquires and interprets ear muscle activity is not made public, but the company intends to market the device as a Class I medical device.

Hearing aids

The hearing aids market has progressed in many aspects in recent years, including aesthetics, functionality and regulations. While there might still be a stigma around wearing hearing aids as it is often associated with age, the design of hearing aids has become sleeker and slimmer to provide a better experience for users. Some companies are even developing hearing aid glasses to help with the stigma.

In terms of functionality, machine learning techniques have also begun to be integrated into these devices to allow the audio settings to be automatically tuned to the environment the user is in. In these approaches, the algorithms decide which sounds to dim and which sounds to amplify.

As previously mentioned, some companies are also now integrating more features into hearing aids, such as built-in fitness trackers, brain trackers to detect signs of dementia and fall-detection sensors. These hearing aids typically have apps associated with them to give patients greater control over how they use the device and provide knowledge about their health.

In addition to new applications and approaches, the ease of accessibility to hearing aids has also been increasing in recent years. In 2022, the FDA approved the sale of over-the-counter (OTC) hearing aids for people with mild to moderate hearing loss. These devices are cheaper compared to prescription hearing aids, costing in the range of hundreds of dollars instead of thousands. They are also usually designed to allow users to tune their own hearing aids without making a trip to the audiologist.

Despite their potential, audiologists have concerns about the safety and audiological care a user receives from OTC hearing aids. Without an in-person counseling session, there is a risk that a user would not be able to tune the hearing aid themselves to suit their needs, potentially damaging their hearing even more in the process. Or users might feel that their OTC hearing aid has not provided any assistance to them, causing them to lose trust in hearing aids overall.

Finally, individuals considering purchasing an OTC hearing aid might wonder how to determine whether they have hearing loss and the severity of it. This might mean a trip to the audiologist is still needed.

Nevertheless, these concerns do not negate the potential of OTC hearing aids to become more accessible and inclusive. The shifting access to hearing aids from the clinic to the community would likely also result in community pharmacists building the required knowledge in OTC hearing aids to better support their customers, an area that is currently lacking. Such a development would coincide well with other ear health devices that are currently pushing the democratization of healthcare, such as the Tympa System, an all-in-one ear clinic that is increasingly being used in pharmacies across the UK to provide access to a hearing health assessment.

What is clear is that education will likely be needed for the various stakeholders involved, so that there is a greater understanding of the benefits and risks of OTC hearing aids. Since the FDA regulation is still relatively new, constant engagement with and feedback from stakeholders might help refine and improve this regulation in the future as well.

Image depicting Earables by showing a dark haired person’s ear and hearing aid

The future of earables

The ear device market is huge, with the earphones and headphones market valued at US$71.5 billion in 2023 and the hearing aids market at US$7.96 billion in 2023. As companies continue to strive for more aesthetic looks for earables with medical purposes, this will likely help earables become more acceptable and inclusive, increasing their market size.

What is clear is that the ear is able to provide vital health information, potentially more so than our wrists. As more companies look to innovate in this space and more ear-worn devices incorporate enabling technologies that increase device functionalities, earables could easily be the next big thing in the world of wearables.

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