Dr. Tabea Thies: Why speech needs more attention in Parkinson’s disease

Dr. Thies, to begin with, could you tell us a little about your professional path? How did you come to specialize specifically in speech-motor disorders in Parkinson’s?

Of course. It all started with a degree in linguistics and educational science. At the time, I really would not have expected to end up in neurological research. But one area of linguistics is phonetics — and that is what truly captured my interest. Phonetics is about very concrete, measurable features of speech production: for example, how the tongue and lips move during speech, how speech sounds are produced, and how different sounds can be distinguished from one another. I found that fascinating.

The real spark came when, by chance, I heard a lecture by Prof. Dr. Doris Mücke and Prof. Dr. Michael T. Barbe. They work at the interdisciplinary intersection of phonetics and neurology. I immediately thought: This sounds exciting — I want to write my bachelor’s thesis about it. At the time, my topic was still essential tremor. But from then on, I was hooked, as people say. My master’s thesis focused on people with Parkinson’s, my doctoral dissertation did as well — and a few years later, I am still here.

What fascinated you so much about working with people with Parkinson’s that you stayed in the field?

It’s the mixture. On the one hand, I have the part at my desk, working on data and analyses. But I also have direct contact with patients, see their reality, understand what concerns them – and learn how important speaking up is for their participation in life. It’s not just “research”, it’s about making a real difference. And that’s what makes my work so meaningful.

From your perspective, what are the biggest challenges in your research?

One thing is clear: speech is often underestimated in medicine! Everyone knows that Parkinson’s will eventually lead to speech disorders, but little is done about it in practice. Speech therapy is rarely prescribed, there is a lack of specialized therapists, and even in research, speech problems have long been classified as a late symptom. However, we now know that changes in speech often occur very early on – sometimes even before other symptoms are noticed.

Another factor is that people affected often do not perceive their own speech changes. This is due to an impaired feedback system. When they speak more softly, it sounds completely normal to them. And when they try to speak louder, it immediately feels like “shouting.” This gap between self-perception and how others perceive them makes things much more complicated.

You received the German Parkinson’s Foundation’s Innovation Award for your project. What exactly is the study about?

We want to find out whether speech changes can be used as speech-motor biomarkers — measurable indicators that point to the disease long before other symptoms appear. To do this, we analyze acoustic speech signals from people at different stages of Parkinson’s disease, as well as from people with REM sleep behavior disorder. This group is particularly interesting because many of them will develop Parkinson’s or a related disorder in the coming years.

We look very specifically at subsystems of speech, such as breathing, articulation, and phonation, and use AI to investigate whether and when changes occur. The hope is that one day we will be able to say: From this point onward, there are clear signs of a speech problem related to Parkinson’s. And then therapy could begin very early — perhaps even before more significant limitations develop.

What speech-motor deficits are typical in Parkinson’s, and how do they affect daily life?

The best-known symptom is probably a very soft voice, often combined with unclear articulation and a change in voice quality that may sound hoarse or breathy. What many people do not know is that prosody also changes — meaning the ability to use volume and pitch to emphasize what is being said. Many patients then speak in a more monotone, almost robotic way, which often leads to misunderstandings — both in terms of content and emotion.

That can be enormously distressing. Some people withdraw from conversations because they feel they are not being heard or understood anyway. There are even reports of people being perceived as “emotionless” simply because their voice no longer conveys emotion. Communication is a basic human need — and when it is impaired, it affects not only social life, but also very practical aspects of everyday living.

Why is it so important to detect speech changes early?

Because we know that later in the course of the disease, speech therapy can often only maintain speech function rather than improve it. Once function falls below a certain level, it cannot necessarily be regained. That is why early intervention is so crucial — at the very moment when the first changes appear, even if they are not yet perceived as problematic.

The challenge is reaching people early enough and helping them understand the significance of these early changes — even if they do not yet feel limited themselves. That is a communication challenge, but it is worth it.

Could your research findings change clinical practice in the future?

That is the goal, yes. We hope our findings can be integrated into digital tools — for example, simple screening apps or software that supports physicians in everyday clinical practice. An ideal scenario would be a tool into which patients briefly speak, after which an algorithm provides feedback: speech disorder, yes or no — and if yes, how severe?

Such a tool could help therapies be prescribed earlier or allow the course of the disease to be monitored more closely. It is also an exciting approach for personalized medicine. We are now working on this question in parallel in the research project “Digital Biomarkers for Speech Changes in Parkinson’s Disease,” which began in Cologne in early 2025.

How do patients themselves experience these changes? What kind of feedback do you receive?

When therapy works — for example after deep brain stimulation, or DBS — we often hear that speaking no longer feels as exhausting, that patients no longer have to repeat themselves constantly, and that they can take part in conversations more actively again. That is wonderful feedback, and it shows us how important speech is for quality of life.

On the other hand, it is of course frustrating when everything gets better – except the speech. We then try to change the DBS settings, for example, to achieve better results. It’s a constant balancing act – but if we find a solution together with the patient, it’s worth it.

You also work with artificial intelligence. What role does AI play in your research?

A major one. We have a collaboration with a start-up that specializes in AI-based speech biomarkers. We want to analyze large amounts of data automatically in order to identify patterns that the human ear cannot hear.

What is important to me is that AI should not simply make decisions blindly. We work closely with experts in phonetics and neurology to interpret the results in a meaningful way. Especially in Parkinson’s, the course of the disease is so individual that we need nuanced, intelligent models that do not think only in black and white.

I am convinced that in five to ten years, AI will be an important part of diagnostics and therapy support — not as a replacement, but as a useful tool.

What advice would you give to Parkinson’s patients who want to maintain their ability to speak?

Speak out loud! It sounds banal, but speaking out loud activates the respiratory muscles, improves articulation and acts like a full-body workout for speaking. Just five to ten minutes a day can make a big difference.

If you like, you can use a smartphone and a decibel app to check whether you are reaching 70 or 80 decibels, for example – this is often necessary to be understood well in everyday life. Holding a long vowel (“Aaaaaa…”) at as constant a volume as possible is also a good exercise.

And anyone who enjoys singing should look for a choir and join in. Singing combines social practice, breathing training, and communication support all in one. There are even special Parkinson’s choirs. It is not only therapeutically useful; it is also simply enjoyable.

What role do family members play in therapy for speech disorders?

A very important one. Patients often need external prompts to become aware that their voice is too soft. A simple “Could you please speak a little louder?” can already help. Feedback through technical tools such as decibel meters can also change perception.

I always say: Patients can speak loudly — they just have to intend to. Often, they even speak much louder in the clinic than they do at home. Then a family member will say, “But he doesn’t talk like that at home!” And most of the time, that is true. So the goal is to establish a new normal — both for the person’s own perception and for those around them.

How important is collaboration with other specialties in your work?

Extremely important! Parkinson’s affects so many levels – motor, cognitive, linguistic – you can’t cover everything on your own. We work closely with neurologists, speech therapists, computer scientists and other specialists to really get a comprehensive picture.

A great example is the kind of interdisciplinary network that exists in Osnabrück, Germany. There, neurologists, therapists, and others regularly come together to discuss cases. I found that incredibly inspiring. That is collaboration in action, for the benefit of patients. In Cologne, we are currently trying to build something similar with a focus on speech therapy.

What motivates you personally in your work — and what are you especially proud of?

What fulfills me is the connection between research and real-world impact. I am not just sitting alone in an office; I can see that my work can help people. And that motivates me tremendously.

I am especially proud of the Innovation Award from the Parkinson Foundation. For me, it was a sign that the topic of speech is being taken seriously — including in neurological research. And the fact that I was able to secure research funding in this context as a non-physician was a real highlight for me.

Was there a moment with a patient that you particularly remember?

Yes. Very early in my research, I had a patient who suddenly developed very strong dyskinesias during a recording — uncontrolled movements. She simply lay down on the floor and said very calmly, “I do this at home, too.” For me, as a young researcher, that was a shock at first — but she was completely relaxed. That taught me a lot about living with the disease: how individual it is, and how much calm some people bring to it.

And finally: How do you see the future of Parkinson’s research when it comes to speech and communication?

I believe that language and speech will become an increasingly important window into the disease process — both for diagnosis and for therapy. The speech systems are highly sensitive and finely tuned, which makes them very well suited to detecting even the smallest changes early on. And if we succeed in developing robust speech-motor biomarkers from this that can be recognized automatically, then we will have an incredibly powerful tool in our hands.

Thank you very much for speaking with us, and we wish you every success with your research.