Cognitive decline and anxiety in Parkinson's disease are often only recognised at a late stage, in spite of their great impact. Research by Marit Ruitenberg focuses on new tests and methods to show up these symptoms earlier and make them more specific.
With Parkinson's, the first thing many people think of is the problem with motor skills, such as tremors or slowness in moving. Anxiety and cognitive problems often go unrecognised, even in clinical practice. And that, while 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 is therefore researching 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 unimportant. However, research on Alzheimer's shows that these improvements can contain important information: how much a person improves in 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. By no means everyone with Parkinson's experiences these cognitive problems. In the study, both people with Parkinson's and a healthy control group twice performed a series of neuropsychological tests, 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 what are the most suitable tests 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
As well as cognitive decline, anxiety symptoms are also an important, but often neglected element of Parkinson's. Some 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 in people with Parkinson's manifests itself. A distinction is made here in three dimensions of anxiety: general anxiety, episodic anxiety in particular situations and anxiety that leads to avoidance behaviour. 'We hope in the future to develop a more targeted treatment for anxiety in Parkinson's sufferers, depending on the effects exhibited.'
Making a real difference
Although the implementation may still take years, Ruitenberg is optimistic. 'Ultimately, we hope this research will mean that patients receive the right support at an earlier stage, not 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.'
