People’s willingness, preferences and public health

What is it that makes people decide not to vaccinate their children or take part in a screening programme? And what would make them consider doing it? With the help of Discrete Choice Experiments, Jorien Veldwijk is trying to find out what people prefer and how willing they are to participate in public health interventions.

Jorien VeldwijkThere is always an element of risk involved in public health. But risk is difficult to understand and to communicate, especially the very small probabilities research in public health has to deal with, for example when 1 in 1,000,000 risk experiencing side effects after vaccination. According to Jorien Veldwijk, risk information is interpreted differently depending on how it is framed. People attach significantly higher values on a positive risk term such as survival than they do on a negative risk term like mortality. They also focus more on positive than negative risks. In order to ‘handle’ risks, people tend to interpret risk in categories, for example low, middle and high, without evaluating the numerical value of the risk.

This means that when we ask people to weigh risks, they will probably not tell you if they think 1 in 10 is a low risk. What you find out is that they consider it the lowest risk compared to the other risks it is weighted against. This means that, in numerical terms, a low risk can range from miniscule (1 in 1.000.000) to low (1 in 1.000). People perceive the difference between 1 in 1.000.000 or 100.000 essentially the same as the difference between 1 in 100.000 or 10.000, although the absolute difference is very different. Research shows that also for very high risk, people don’t really interpret the differences statistically correct. And people react differently if the risk is listed as 1 in 20 or 5 %.

Jorien Veldwijk’s PhD thesis had a method focus and used Discrete Choice Experiments, or DCE’s as they are also called, to determine people’s preference and explain their willingness to participate in in public health interventions. It is a way of capturing how people make trade-offs and weigh risks against benefits by using different attributes. With traditional questionnaires, researchers end up with a rating or ranking. A DCE adds value because it allows researchers to quantify the importance people place in different attributes relative to others.

During her PhD, Jorien Veldwijk worked at the Dutch National Institute for Public Health and the Environment (RIVM). This meant she was able to test DCE’s on three Dutch public health interventions: a lifestyle intervention for diabetes patients, one rotavirus vaccination and genetic screening for colorectal cancer. So why is it that people decide not to participate? According Jorien Veldwijk, they have different reasons. When it comes to rotavirus vaccination, parents severely over-estimated the side effects of the vaccine. For example, the risk for a sore arm or bowel issues is one in one million, but even so, these risks influenced parental decision making enormously, in a negative way.

We need a better understanding of how we make sure people understand the information that we communicate when they have to make health-related decisions, especially when it comes to risks. During her PhD, Jorien Veldwijk started reading the guidelines for conducting state-of-the-art DCEs and noticed that there was no mention of how to best communicate and present risk information. She believes communication is key. We have to be careful with how we present risk information. Using graphics for example might help some people to understand better, and quickly, if the risk is high or low. But it is a double-edged sword and might contribute to grouping risks as low, middle or high.

“Understanding risk is difficult for a lot of people. The real question is how people could ever really understand if we as researchers have problems explaining risk or if we don’t make an effort to improve our communication of risks. Especially if we are dealing with disease-related risks or if people’s children are involved”, says Jorien Veldwijk.

Jorien Veldwijk

Jorien Veldwijk was recruited to CRB to work on a project dealing with genetic risk information, Mind the Risk, where she is a much sought after DCE expert. More and more of CRB’s research concerns empirical ethics and Jorien Veldwijk is involved in several PhD projects using the same methods.

Jorien Veldwijk is organizing DCE training for CRB staff and Mind the Risk partners. This method combines qualitative and quantitative research and was originally developed in mathematical psychology. It is often used in marketing and transportation research and works very well for estimating willingness to pay. But instead of weighing time against cost, health related research use DCE’s to, weigh outcome or effectiveness of treatment against harms.

Jorien Veldwijk is involved in empirical research, but in the last couple of years it seems theoretical researchers also want to know how people weigh risks and benefits against each other. Jorien Veldwijk is happy to see research developing in this direction. She believes that instead of sitting in our ivory towers and deciding what is good for people, researchers should engage the people they want to target in designing and refining treatments and interventions:

“Luckily, researchers are starting to ask what it is their target population wants, using methods like DCE’s to elicit their preferences, and incorporating them in the design of treatments and interventions. This way, people might actually want, like and use the treatments and interventions that we as researchers develop. That is my main driving force” says Jorien Veldwijk.

About Jorien Veldwijk

Jorien Veldwijk has a master in Public Health and a master in Clinical Epidemiology. She obtained her PhD in public health/health economics in May 2015 and was appointed assistant professor at the University Medical Center Utrecht where her research continued to be focused on eliciting stated preferences. She is still working in the same field, using DCEs and dividing her time between CRB and the Erasmus Medical Centre in Rotterdam, the Netherlands.

Josepine Fernow, 17 May 2016