Somatically Unexplained Physical Complaints — physical complaints that cannot be adequately explained by a diagnosed organic disease — represent a significant issue within healthcare. These complaints can vary widely (including headaches, digestive issues, fatigue, muscle pain, breathlessness, etc.) and can lead to severe functional limitations. SOLK can manifest as transient singular complaints, occur within the context of stress-related disorders such as overstress and burnout, or take on a chronic form, as seen in functional syndromes (e.g., chronic fatigue syndrome, fibromyalgia, chronic whiplash syndrome). The known high prevalence of SOLK is associated with substantial societal costs.

A narrow biomedical disease model fails to acknowledge that self-reported health complaints are always the result of a complex integration in the brain of afferent signals from the body (bottom-up) and perceptual-cognitive and affective processes (top-down). Integrating findings from interoception and symptom perception research with stress physiology and neurobiological data allows us to transcend dualistic thinking (either psychological or physical). Our research group aims to contribute to the further identification of the underlying mechanisms of SOLK and translate this knowledge into concrete treatment components.

Project 1:

Identification of (Psycho)physiologically Based Subgroups in Chronic Fatigue Syndrome and Their Relevance for Rehabilitation (R-11754)
Promoters: Katleen Bogaerts (UHasselt) and Lukas Van Oudenhove (KULeuven)
FWO Junior Research Grant: G057921N

Approximately 20,000 people in Belgium suffer from chronic fatigue syndrome (CFS), a condition characterized by persistent fatigue that cannot be adequately explained by medical or psychiatric disorders. Research has demonstrated dysfunctions in various (psycho)physiological systems in CFS, including the stress response system, immune system, and central nervous system (e.g., neuroinflammation and changes in functional connectivity in the brain). Conversely, health psychology research has shown disruptions in symptom perception among CFS patients. However, these two lines of research are insufficiently integrated, which is necessary to overcome dualistic debates that have hindered progress in understanding and treating CFS. Specifically, it remains unclear how the aforementioned dysfunctions relate to symptom perception among CFS patients, particularly regarding the perception of physical and mental fatigue. The goal of this FWO project is to investigate the complex relationships between fatigue perception and various psychophysiological dysfunctions in CFS patients, identify subgroups based on these dysfunctions, and link them to rehabilitation success. This is urgently needed to develop a refined integrative pathophysiological model of this serious but poorly understood condition, for which treatment options are currently limited.

Project 2:

Detection of Underlying Mechanisms of Somatically Unexplained Physical Complaints (SOLK) and Translation into Treatment Components (R-11736)

The hypothesis is that dysregulated stress physiology and inadequate interoceptive processes play a crucial role in the development and persistence of Somatically Unexplained Physical Complaints (SOLK). In our studies, we aim to examine the autonomic stress physiology (breathing, heart rate, muscle tension, peripheral skin temperature, and skin conductance) and interoceptive skills (accuracy, sensitivity, and awareness) of individuals with stress-related and/or functional physical complaints [overstress, burnout, and functional somatic syndromes (FSS)]. The effect of a brief interoceptive training on interoceptive accuracy in an FSS population will also be investigated. Furthermore, a new, broader definition of interoception includes all afferent information originating from the body, including proprioception. Therefore, we seek to translate the interoceptive theoretical framework into a proprioceptive framework. This will involve developing a new measure for proprioceptive accuracy and validating a proprioceptive sensitivity questionnaire. In a follow-up study, we will map both interoceptive and proprioceptive skills in FSS patients. Lastly, we will further explore personal characteristics such as "need for control" as potentially influential factors, with the ultimate goal of validating the "Need for Controllability and Predictability Questionnaire" (NCP-q) within a SOLK population.

Project 3:

Symptom Perception as a Transdiagnostic Underlying Mechanism for Functional Syndromes
ESR 1 Tara Petske: (Co-)Promoters: Michael Witthöft, Johannes Gutenberg-University, Mainz, Germany; Katleen Bogaerts, Hasselt University, University of Leuven, Tumi Therapeutics, Belgium; Ferenc Köteles, Eötvös Lorànd University, Budapest, Hungary; Nadine Lehnen, Technische Universität München, Germany (including a 4-month work visit at Tumi Therapeutics, MOU L-654 – acquiring knowledge about translation from scientific results to clinical services).

The main objective of this project is to investigate whether changes in the perception of bodily signals (i.e., interoception) and dysregulated emotion regulation are causally related to the experience of complaints in functional syndromes. ESR1 will explore interoception (i.e., interoceptive accuracy measured through heartbeat mental tracking tasks and signal detection tasks) and emotion regulation (i.e., reappraisal, expressive suppression, regulatory choice) among individuals at risk of developing functional syndromes (versus a healthy control group). Identified changes in interoception and emotion regulation will be actively manipulated using training protocols to investigate their causal role in triggering and influencing physical complaints.
This project is part of the H2020 project Marie Sklodowska-Curie Research Training Group “INT ETUDE” (01/01/2021 – 31/12/2024; dossier number: 956673). Within "Encompassing Training in Functional Disorders across Europe" (ETUDE), 30 European expert groups collaborate on (1) scientific research and clinical translation regarding diagnostics, treatment, and communication in functional disorders (FD), as well as (2) training the next generation of multidisciplinary experts within an international PhD training program. The ETUDE program will contribute to identifying underlying mechanisms, optimizing diagnostics and treatment, and reducing stigma among FD patients.

Balance problems during standing and walking are crucial issues in children with cerebral palsy (CP). Although balance problems have been increasingly recognized in recent decades, the underlying causes for poorer balance performance remain unclear. This consequently leads to mixed results regarding the effects of various balance training programs.

At the peripheral level, prolonged physical activity can increase balance problems due to muscle fatigue. Since muscle fatigue is a frequent complaint in CP, balance problems may also occur as a result of physical exertion. Therefore, the main goal of this project is to gain insight into this underexplored, but likely very relevant, peripheral determinant for the balance problems in children with CP.

Abstract research project degenerative hip disorders

Osteoarthritis (OA) is one of the leading causes of pain and disability worldwide, and the hip joint is clinically one of the most affected locations of OA. The global prevalence and incidence of hip OA are expected to increase considerably in the upcoming decades, as a result of the aging population and an increasing prevalence of risk factors such as obesity and sedentary lifestyle. This raise will be accompanied with an increase in personal, financial, healthcare, and societal burden, as hip OA accounts for a large number of years lived with disability.

Large heterogeneity exists in the structural and clinical manifestation of hip OA, and persons with hip
OA exhibit different biopsychosocial characteristics. In order to unravel the complex and heterogeneous nature of hip OA, this research project aims to identify clinical phenotypes in persons with hip osteoarthritis, based on a set of biopsychosocial characteristics. The identification of distinct subgroups within the hip OA population might offer a foundation for individualized care pathways, with potential improvement of clinical outcomes.

Correspondingly with the increasing prevalence and incidence of hip OA, the mean utilization rate of hip arthroplasties is expected to increase considerably in the upcoming decades. Total hip arthroplasty (THA) is a cost-effective procedure in persons with hip OA. However, previous studies have reported that 8% of patients is dissatisfied with the outcome, and up to 23% of patients report long-term pain after THA. Furthermore, about 25% of patients report activity limitations and participation restrictions after THA. An important step towards understanding and improving outcomes after THA is prognostic factor research.

Knowledge of prognostic factors enables healthcare providers to identify persons at risk of poor outcome, and consequently increases options for shared decision making, expectation management and stratified care. Research suggests that the difference in outcome after THA cannot be entirely explained by structural factors or the surgery itself. Our research aims to unravel the prognostic role of biopsychosocial factors, including childhood trauma, mental disorders, and somatosensory function, on outcomes related to pain and disability after THA in persons with hip OA.

Tinnitus is the perception of sound in the absence of an external source for the sound. It is a common symptom that affects 10 to 15% of the adult population, causing mood changes, anxiety, depression, sleep disorders, concentration problems and other psychological/emotional issues leading to severe disruptions of the quality of life. Tinnitus does not represent a disease itself but instead is a symptom of a variety of possible underlying diseases or malfunctions making the tinnitus population very heterogeneous.

Apart from well-known causes of tinnitus such as hearing loss and noise trauma, in 25% of patients, tinnitus is influenced by neck or jaw dysfunctions. These patients with so called somatic or somatosensory tinnitus are our main research population.

Studies in this population comprise clinical trials investigating the effectiveness and cost-effectiveness of musculoskeletal treatment and technology-based treatment options. An example is the FWO-funded study: The CATT trial.

In addition, research on somatic tinnitus diagnostics is being performed and more fundamental studies are being set up on brain changes in this population. For the latter we collaborate with colleagues from the neurological rehabilitation research domain.

Apart from specific somatic tinnitus research we also investigate the effect of movement and physical training on tinnitus complaints in general. For this study we collaborate with the colleagues from the cardiac rehabilitation research domain.