More than movement: study of cognitive and psychological symptoms of Parkinson’s
Parkinson's disease
Cognitive decline and anxiety in Parkinson’s disease are often only recognised at a late stage, yet they can greatly impact people's lives. Research by Marit Ruitenberg focuses on new tests and methods to improve early identification of these symptoms.
With Parkinson’s, the first thing many people think of is are the characteristic movement problems, such as tremors or slowness in moving. Anxiety and cognitive problems often go unrecognised, even in clinical practice, though they have a major influence on quality of life. ‘Some people with Parkinson’s even say that the cognitive complaints have a bigger impact on their quality of life than the motor symptoms,’ neuropsychologist Marit Ruitenberg explains. She therefore studies how these complaints can be made visible and treated at an earlier stage.
Practice effects as predictor
Practice effects are a known phenomenon in cognitive tests: ‘People get better results because they are familiar with the test, or because they know how it worked the time before.’ Most researchers write these improvements off as noise. However, research on Alzheimer’s shows that these improvements can contain important information: how much a person improves on a test says something about their cognitive functioning.
Ruitenberg and her colleagues are investigating whether these practice effects can also be valuable in predicting cognitive decline in people with Parkinson’s. Not everyone with Parkinson’s experiences these cognitive problems. In the study, both people with Parkinson’s and a healthy control group completed a series of neuropsychological tests twice, with an interval of one year. The healthy participants exhibited greater and clearer practice effects than the group with Parkinson’s. One surprising finding was that people with Parkinson’s who showed smaller practice effects later exhibited greater cognitive decline.
This was just an initial exploratory study, Ruitenberg stresses. ‘We wanted to see whether it was possible to translate this effect to Parkinson’s. We now have a first indication that practice effects do have some potential, but we’re not there yet. More research needs to be done on which tests are most suitable and whether shorter intervals (for example, a week rather than a year) can also be applied. If the practice effects are a useful predictor of cognitive decline, they can be used not only in clinical practice as a non-invasive method of monitoring decline but can also help in the selection of patients for new studies.
An interdisciplinary study on anxiety
Besides cognitive decline, anxiety symptoms are also an important, but often overlooked element of Parkinson’s. About 30 to 50% of patients with Parkinson’s develop anxiety complaints. These symptoms are difficult to recognise because there is an overlap in symptoms with the physical complaints of Parkinson’s, such as tremors and changes in blood pressure.
To gain a better picture of these anxiety symptoms, an extensive interdisciplinary collaboration involving psychologists, neurologists and movement scientists has been started between the LUMC and the Canadian University of Waterloo. From Leiden University, Isabelle van Hapert, Julie Hall and Hanneke Hulst are also taking part. Using large datasets, network analyses and VR studies, the researchers are investigating how anxiety manifests in people with Parkinson’s. A distinction is made here in three dimensions of anxiety: general anxiety, episodic anxiety in specific situations and anxiety that leads to avoidance behaviour. ‘We hope to develop a more targeted treatment for anxiety in Parkinson’s in the future, depending on the dimensions an individual shows.’
Making a real difference
Although the implementation may still take years, Ruitenberg is optimistic. ‘Ultimately, we hope this research will ensure that patients receive the right support at an earlier stage, not only once the complaints are already visible. It’s these invisible symptoms that warrant more attention.’ She emphasises that scientific research takes time and rigorous care: ‘If there is one thing I have learned, it is that in science you have to have a lot of patience. But my ambition is clear: I want the knowledge we acquire to really make a difference in the lives of people with Parkinson’s.’