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The COS-DIP study: a Core Outcome Set for Dysphagia Interventions in Parkinson’s disease

Why has this study been done?

Swallowing difficulties (dysphagia) are common in people with Parkinson’s disease. Research studies of swallowing treatments need to be able to measure how well the treatment works, but also what side effects it may have and how they may affect patients. Researchers do this by measuring ‘outcomes’. Examples of outcomes include ‘quality of life’ and ‘severity of swallowing difficulty’.

So far researchers have been using different outcomes when conducting these studies. Some for example measure quality of life and others do not. Furthermore, people living with Parkinson’s disease and swallowing difficulties, family members and family caregivers have not been involved in deciding what to measure in these research studies. Thus, the results of the research might have little importance to them.

The aim of this study was to find out what the most important outcomes to measure are when assessing if a swallowing treatment for people with Parkinson’s disease works. We developed a minimum standard (a core outcome set) of what should be measured and how it should be measured in research studies on swallowing treatments for people with Parkinson’s disease.

The video below describes how the COS-DIP study reached agreement on the most important outcomes and presents the six core outcomes.

Who and what was involved in the study?

This was a larger study that comprised several different stages. These are outlined in Figure 1 and the text below. Overall, people living with Parkinson’s disease and swallowing difficulties, family members and caregivers, healthcare professionals and researchers were involved in the development of the COS-DIP.

Picture showing the 5 Cos stages

Figure 1: Stages of the COS-DIP development process

  • A systematic literature search (scoping review) to identify what outcomes have been used in research studies on swallowing interventions in Parkinson’s disease. The publication can be found here.
  • An online survey and group interviews (focus groups) with people living with Parkinson’s disease and swallowing difficulties, family members and caregivers to find out what outcomes matter to them most when deciding if a swallowing treatment works. Additionally, an online survey with dysphagia clinicians to find out what outcomes matter to them most when deciding if a swallowing treatment works.
  • Three consecutive, online surveys (so called Delphi surveys) with people living with Parkinson’s disease and swallowing difficulties, family members and caregivers, healthcare professionals and researchers to identify the most important outcomes.
  • Two online consensus meetings to agree on all core outcomes, definitions, methods and timepoints of measurement.

We have published the study protocol outlining all steps of this research project. The publication can be found here.

The three, consecutive online Delphi surveys were open from January to April 2024. In May 2024, we conducted the two online consensus meetings and agreed on six core outcomes, their definitions, methods and timepoints of measurement.

More information

If you would like any further information about the COS-DIP study, please do not hesitate to contact Julia Hirschwald via email at cosdip.tcd@gmail.com.