May 13, 2023 – 8:57 PM
Limited vision is not the driving force behind fatigue and sleeping problems
|It has always been thought that sleep and fatigue problems in patients with Usher syndrome result from increased effort to compensate for their double sensory impairment: limited vision combined with hearing loss. Researchers at Radboud university medical center show in Ophthalmology Science that this idea is incorrect. In addition to serious problems with hearing and vision, sleeping problems also seem to be an essential characteristic of the disease.
|Patients with Usher syndrome often have major problems with vision and hearing. They are born deaf or hard of hearing and then slowly lose their sight from a young age. The large individual differences in the severity of the disease are closely related to the nature of the genetic mutation and the type of Usher syndrome, of which four are now known. No matter how great the differences in severity of the disease are, it is always about problems with vision and hearing. Those are the central features of the disease. “We regularly hear other complaints from patients, including balance disorders, but these have been classified as part of the disease,” says researcher Erwin van Wijk. “In addition, sleep problems and excessive fatigue are regularly reported in the consulting room. The fatigue is invariably dismissed as a result of the dual sensory impairment that patients experience. And it is believed that the sleep problems patients often report are due to limited light perception. Because those who see poorly or no longer at all lose their visual day and night rhythm, with consequences for sleep.”
|Researchers at Radboudumc have a lot of contact with patients, also through the Usher Syndrome Foundation. “At a certain point it was noticed that a lot of patients suffered from sleep problems and fatigue,” says Van Wijk. “That intrigued us. Was there perhaps something different going on than we always thought? Under the supervision of Erik de Vrieze, Juriaan Metz, Rob Collin and myself, PhD candidate Jessie Hendricks set out to find out. With no less than five different validated questionnaires, she mapped out the problems of 56 Usher syndrome type 2A (USH2A) patients and compared them with 120 healthy controls.”
This showed that USH2A patients did indeed sleep poorly more often than people in the control group. They more often had a strongly reduced sleep quality and were more often sleepy and more tired during the day. But the most striking thing was that the sleep problems were not related to the severity of the visual impairment. Van Wijk: “That corresponds with what patients often say, but which no one had ever really looked at in this way.”
Essential characteristic of Usher
|At first glance, it may only seem like a gradual difference, but the finding is much more important. Van Wijk: “Actually, this means that the ubiquitous sleep problems in USH2A are not primarily due to limited vision, but that they already exist in patients who still see well. So it seems that we should see the sleep problems as an essential additional feature of Usher syndrome, and not as a result of the poor or deteriorating vision.”
This indication, based on questionnaires, must of course be further substantiated. This can be done, for example, through research in an existing zebrafish model for Usher syndrome. Zebrafish also have a clear sleeping pattern. Is that also disturbing for them? And is there evidence in the brain that Usher genes are somehow involved in regulating sleep processes? Such follow-up research is now underway.
Better quality of life
Van Wijk also points to another aspect of the study. If sleep problems indeed appear to be part of the disease, a way to address those problems can be sought. “At the moment, sleep problems are not included in the care pathway for Usher syndrome patients, because it is not an official characteristic of the condition. The result is that the required examination in a sleep clinic is often not reimbursed by the health insurer. This may change as a result of the research published in Ophthalmology Science and follow-up research that is in the pipeline. Treatment of sleep problems can definitely improve the quality of life of patients with Usher syndrome.”
Publication in Ophthalmology Science: Evaluation of sleep quality and fatigue in patients with Usher syndrome type 2a – Jessie M. Hendricks, MSc, Juriaan R. Metz, Hedwig M. Velde, Jack Weeda, Franca Hartgers, Suzanne Yzer, Carel B. Hoyng, Ronald JE Pennings, Rob WJ Collin, H. Myrthe Boss, Erik de Vrieze, Erwin from neighbourhood