[Special Feature: Dementia and Society] Yasue Mitsukura: Detecting Dementia Risk Through EEG Measurement

The elderly population in Japan is expected to reach approximately 40 million by 2040, and Japan will face a super-aging society unlike any other in the world. Looking at the near future, the population with dementia is said to reach approximately 7 million by 2025—remarkably, one in five people aged 65 and over. Such an era is coming in just three years. Most cases of dementia are Alzheimer's-type dementia, which is caused by a decrease in brain cells and brain atrophy. It often begins with forgetfulness and progresses slowly and gradually. While Alzheimer's drugs are effective in improving symptoms, they do not have a fundamental curative effect, so even if cognitive functions such as memory improve with medication, the disease gradually progresses. In other words, early detection at the initial stage is crucial for the treatment of Alzheimer's disease.

In this context, the government's Comprehensive Strategy for the Promotion of Dementia Measures (commonly known as the New Orange Plan) sets out seven pillars, including (1) promotion of dissemination and awareness to deepen understanding of dementia, and (2) provision of timely and appropriate medical and nursing care according to the condition of dementia. Among these, the strengthening of measures for early-onset dementia is mentioned, stating that early detection should be used to "delay the onset of dementia" and "slow the progression even if dementia occurs." We resonate with this initiative and have developed a system that can easily measure Mild Cognitive Impairment (MCI). Our group has clarified the following two points:

・ By measuring the EEGs of people with dementia and Mild Cognitive Impairment (MCI), we suggested that each has characteristics compared to healthy individuals.

・ Furthermore, this is possible with simple EEG measurement.

In other words, it becomes possible to identify healthy individuals, MCI patients, and dementia patients just through simple EEG measurement!

Using an electroencephalograph (EEG) that can be measured easily anytime and anywhere, we measured the EEGs of 120 subjects divided into three groups: healthy, MCI, and dementia. We were able to clarify the characteristics of the EEG frequencies for each measured group (Figure 1).

To begin with, what you often hear about EEGs might be things like "high alpha waves = concentrating," "high theta waves = sleepy," or "listening to a certain song produces alpha waves." The terms "alpha" and "theta" used here are the names of the bands that appear when the signals obtained from the EEG sensors on the head are converted into frequencies.

Normally, our EEGs are simply waves in microvolts obtained as signals on the scalp. When these waves are converted into frequencies, human EEGs generally fall within values up to about 45 Hz. Within this range, up to 4 Hz is called delta waves, 4–6 Hz is theta waves, 7 to 13 Hz is alpha waves, around 14 to 23 Hz is beta waves, and anything above that is called gamma waves (definitions of frequency bands may vary depending on the researcher).

These alpha and beta waves are called bands. Naturally, EEGs contain a significant amount of noise when acquired (sometimes more than 60% becomes noise). These bands must be calculated after removing this noise in real-time. As long as noise removal is performed, EEGs can be captured clearly using any device. However, if noise is not accurately removed, the data will naturally be completely different.

We have obtained a patent for an algorithm that removes noise from EEG data in real-time. Using this, it has become possible to easily measure EEGs in any situation. In the past, measuring EEGs meant entering a special room called a shielded room to prevent noise and measuring while at rest. Now, however, it can be acquired in a normal state, allowing EEGs to be measured in a natural state and enabling the acquisition of more accurate EEGs suited to the situation (it's not normal to have to go into a shielded room just to take an EEG!).

Also, older electroencephalographs were multi-electrode, for example, attaching as many as 64 channels of electrodes to the brain to capture various information. Of course, many electrodes are still attached to the head in some cases today, but it's difficult to be told not to feel stress in that state, isn't it? Between the feeling of being constricted and the fact that it takes nearly an hour just to put on the EEG, it might be a stressful state. we choose the locations to attach electrodes based on the purpose. Moreover, if we're being ambitious, we aim to use as few electrodes as possible. By reducing the number of electrodes according to the purpose in this way, we reduce the burden. Figure 2 shows an EEG measurement system that has reduced the number of electrodes and can perform noise removal in real-time.

Based on the information obtained from this EEG, and using the characteristics of the EEG bands for dementia, MCI, and healthy individuals introduced earlier, anyone can determine whether they are in a healthy state or a state of dementia or MCI just by acquiring an EEG. The EEG used is a non-burdensome headband type, taking about 15 seconds to attach and 15 seconds for calibration before starting measurement, allowing for measurement in a total of about 30 seconds. Even if the head moves, noise is instantly removed and stable measurement is possible, making easy measurement possible anywhere.

By using these on a daily basis, it is expected that people will be able to easily measure the possibility of MCI or dementia while staying at home without going to a hospital. Until now, people had to make an effort to find time to go out, get MRI or PET scans at a hospital, and then go back to hear the results. However, without such trouble, it will be possible to know the possibility of being a healthy individual, an MCI patient, or a dementia patient with a simple device. If discovered at the MCI stage, it is possible to delay the progression.

Above all, it is necessary to be aware of one's own condition. Previously, this could only be done at a hospital, but since determination is possible with simple measurement, you can know your condition at home or elsewhere. In the future, we believe that even a hairband-type EEG will not be necessary, and the determination will be possible with, for example, a ring sensor or a wristband-type sensor. We won't let people say that one in five will have dementia in the upcoming year 2025. Through early detection, its progression can be slowed. Currently, drug discovery is also progressing by leaps and bounds. There is even a possibility that a "drug to cure" dementia, which did not exist until yesterday, will be created tomorrow. That is why, even if MCI is found, we delay its progression. By doing so, drugs to cure dementia will emerge.

Our efforts are not limited to dementia. We are also developing devices that can easily measure mental illnesses such as depression and sleep states. We are building a system that allows people to grasp their condition easily anytime, anywhere, even at home. Using the power of a comprehensive university, which is the greatest feature of Keio University, we are prepared to confront dementia through medicine-engineering-pharmacy collaboration. Until dementia becomes a curable disease. And so that we can welcome a bright 2040.