For a long time, the assessment of our cognitive health relied primarily on interviews and paper-and-pencil tests. Imagine a mechanic trying to diagnose an engine problem solely by listening to its noise. It's a useful method, but limited. Today, just as that mechanic can plug in a computer to read precise data about each component of the engine, medicine is beginning to use "biomarkers" to obtain a much more detailed and objective picture of our brain health. These new tools are no longer reserved for research laboratories; they are gradually entering our daily lives and transforming the way we understand, monitor, and protect our cognitive abilities.This article invites you to dive into the heart of this advancement, to understand what these famous biomarkers are and how they shape the future of brain health for each of us.To address this topic, it is essential to start with a clear definition. Far from being a complex concept reserved for scientists, the idea of a biomarker is actually quite intuitive.
A simple and accessible definition
A biomarker is a biological characteristic that can be measured objectively and acts as an indicator. Think of a thermometer: your body temperature is a biomarker. If it is 39°C, it is an objective sign of fever, indicating a possible infection. Similarly, a biomarker of cognitive health is an objective measure that informs us about the state of our brain and its functions (memory, attention, reasoning, etc.). It can be a protein in the blood, the thickness of a brain area visible on a scan, or even the speed at which you type on your phone's keyboard. The key is that this measure is reliable, reproducible, and linked to a specific cognitive state.Why are they so important?
The major interest of biomarkers is that they shift us from subjective assessment to objective measurement. A memory test can be influenced by your level of fatigue, stress, or even anxiety on the day of the exam. A biomarker, on the other hand, provides raw data, less subject to these variations.Their importance lies in three key areas:- Early diagnosis: Many neurodegenerative diseases, such as Alzheimer's disease, begin to damage the brain years, even decades, before the first visible symptoms appear. Biomarkers can act as early warning signals, allowing us to detect these silent changes much sooner. It's like spotting rust on a car's chassis before the bodywork is affected.
- Personalized monitoring: Every brain is unique. Biomarkers allow for the personalized tracking of an individual's cognitive health. They can help determine whether an intervention (a lifestyle change, medication, or cognitive training) is effective for a given individual.
- Assistance in research: For scientists, biomarkers are invaluable tools for understanding disease mechanisms, testing new drugs, and identifying individuals at highest risk.
The different categories of biomarkers
Biomarkers can be classified into several major families, each offering a different window into the health of our brain. There are imaging biomarkers, which show us the structure and activity of the brain; fluid biomarkers, which detect molecules in the blood or cerebrospinal fluid; and, more recently, digital biomarkers, which extract information from our daily interactions with technology.Classic biomarkers: the pillars of research
Before the advent of digital technology, research focused on very powerful biological analysis and imaging methods, which remain essential references in the clinical and scientific fields.Brain imaging: seeing the brain in action
Medical imaging has provided us with the first direct images of the inside of a living brain. MRI (Magnetic Resonance Imaging) allows us to measure the volume of certain brain structures. For example, a reduction in the volume of the hippocampus, a key region for memory, is a well-known biomarker associated with Alzheimer's disease.PET (Positron Emission Tomography) goes even further. By injecting a radioactive tracer that binds to specific proteins, doctors can visualize the accumulation of amyloid plaques and tau protein tangles, the two characteristic lesions of Alzheimer's disease. Seeing these plaques directly in a patient's brain is extremely powerful diagnostic information.Fluid biomarkers: clues in the blood
The brain is bathed in cerebrospinal fluid (CSF), a fluid that can be collected through a lumbar puncture. Analyzing this fluid allows for precise measurement of the levels of beta-amyloid and tau proteins. An abnormal concentration of these proteins is a very reliable indicator of ongoing pathological processes in the brain.More recently, a major advancement has been the development of blood tests capable of detecting specific forms of these same proteins. This is a true revolution, as a simple blood draw is much less invasive, less expensive, and more accessible than a lumbar puncture or PET scan. These blood tests are on the verge of becoming first-line screening tools.The limitations of these traditional approaches
Despite their power, these classic biomarkers have notable drawbacks. Brain imaging is very expensive and not available everywhere. A lumbar puncture can be perceived as an invasive and uncomfortable procedure. Moreover, these examinations only provide a "snapshot" of brain health at a specific moment. They do not allow for easy, regular, and at-home monitoring. This is where a new category of biomarkers comes into play.The revolution of digital biomarkers: your daily life as a source of information
What is a digital biomarker?
A digital biomarker is data collected via a digital device (smartphone, tablet, smartwatch, computer) that provides information about our health status. The idea is to transform our daily interactions into objective measures. Instead of going to the hospital for a one-time examination, the assessment is done continuously, passively, and in the person's natural environment. It's the difference between taking a single photo of your garden and installing a camera that films its evolution day after day, season after season.Concrete examples of digital biomarkers
The possibilities are immense and continue to develop. Here are some concrete examples of what can be measured:- Keystroke analysis: The speed at which you type, the pressure on the keys, the rhythm, the number of typos, and how you correct them can reveal information about your fine motor skills and attention. Changes in these patterns can be early indicators of cognitive decline.
- Voice analysis: Your voice is a complex instrument. Algorithms can analyze the speed of your speech, pauses, richness of your vocabulary, complexity of your sentences, or variations in tone. Changes, such as more halting speech or a dwindling vocabulary, can be relevant signs.
- Movement analysis: The accelerometer present in all smartphones can track your movements. It's not just about counting your steps, but analyzing the fluidity of your walk, your balance, or the time spent outdoors. Changes in gait or a reduction in social and physical activity may be linked to cognitive changes.
- Social interactions: The frequency of calls and messages sent can reflect the level of social engagement, a factor known to be protective for the brain.
The advantage of discretion and continuity
The main strength of these biomarkers is their ability to collect data continuously and non-intrusively. You don't have to think about taking a test. Data is collected in the background while you live your life normally. This wealth of longitudinal data allows for the detection of very subtle changes over time that might go unnoticed during a one-time consultation.Cognitive training and monitoring: the role of apps like JOE
While passive digital biomarkers are promising, there is another, more active approach: the use of dedicated apps for cognitive stimulation. These tools, designed to train the brain, are also becoming powerful assessment platforms.Measuring to improve
When you use a brain training app, every game you play generates data: your reaction time, success rate, number of errors, decision-making speed, etc. These performance measures, when tracked over the long term, constitute a form of digital biomarker in themselves. A sudden and lasting drop in your usual scores could be a weak signal, an alert indicating that it may be time to pay increased attention to your health, get better sleep, or consult a professional.JOE, your brain coach: a practical example
Let's take the example of an app like JOE, your brain coach. Designed to train various cognitive functions through fun and personalized games, it does not just make you work. It also acts as a true dashboard of your abilities.Imagine that you regularly play a working memory game on JOE. The app records your score at each session. After a few months, it has an accurate curve of your average performance. If this curve, which was stable or slightly progressing, starts to decline significantly over several weeks, without apparent reason (lack of sleep, temporary stress), this information becomes valuable. It is not a diagnosis, but an objective indicator that may prompt you to take action.An app like JOE can thus play a dual fundamental role:- Active stimulation: By offering targeted exercises, it helps you maintain and strengthen your neural networks, much like a gym for your brain.
- Longitudinal monitoring: By recording your performances, it creates a personal baseline. Any deviation from this norm can be detected quickly.
- Awareness: It makes you an active participant in your brain health. By visualizing your own data, you are better able to understand the impact of your lifestyle (sleep, diet, stress) on your cognitive abilities.
The combination of training and assessment
The future likely lies in the fusion of these approaches. An app could combine games to actively assess your memory and attention while using (with your explicit consent) your phone's sensors to passively analyze your typing speed or sleep patterns. This combination of active and passive data would provide an even more complete and reliable picture of your cognitive health.◆ ◆ ◆
