Eye-tracking test adapted to better measure hunger behaviors in PWS
Study highlights how caregiver input improved eye-tracking tool for research
Working closely with caregivers and clinical experts, an international team of scientists has adapted an eye-tracking test to more objectively measure the intense, constant hunger — called hyperphagia — that affects people with Prader-Willi syndrome (PWS).
“By integrating stakeholder insights, we enhanced feasibility, accessibility and data quality,” demonstrating “the value of codesign in tailoring neurocognitive protocols for individuals with complex needs,” the researchers wrote.
“The adapted eye-tracking protocol shows promise as a scalable, objective method to assess hyperphagia-related cognitive responses and may inform future clinical trials in PWS and related conditions,” they wrote.
The study, “Codesigning a Neurocognitive Assessment Protocol for Hyperphagia: Perspectives From Stakeholders in Prader–Willi Syndrome,” was published in the Journal of Intellectual Disability Research.
Understanding hyperphagia and why it’s hard to measure
One of the hallmark symptoms of PWS is hyperphagia, a persistent, intense feeling of hunger that doesn’t go away after eating. This constant drive to eat can lead to food-seeking behaviors, weight gain, and health complications.
“Despite progress in therapeutic development, hyperphagia remains difficult to measure objectively,” the researchers wrote.
Common tools for measuring hunger, such as caregiver-reported rating scales, are indirect and rely on memory, making them less sensitive to real-time changes in food-related behavior. People with PWS may also have difficulty describing their hunger accurately, which adds to the challenge.
Because of this, “there is an urgent need for valid, objective tools to assess hyperphagia and support clinical trials for emerging therapies,” the researchers wrote.
Scientists in Canada and Ireland previously developed the Food Attentional Bias (FAB) Task, an eye-tracking test that measures how strongly a person’s attention is drawn to food. During the task, a person sees images of food and non-food items while cameras track how long they look at each.
People who are hungry tend to spend more time looking at food images, so the test can provide an objective, numerical readout of hunger levels.
In a previous study, the team shared proof-of-concept results using this approach in typically developing, healthy-weight volunteers. They found a significant reduction in the time spent looking at food after the participants had eaten a standardized meal.
Adapting the FAB Task to meet the needs of people with PWS
Now, the researchers set out to adapt the FAB Task so it could objectively assess hyperphagia in people with PWS, while ensuring the test would fit the unique routines, sensitivities, and support needs of this community.
To guide the changes, the team held focus groups with nine parents/caregivers of people with PWS across different age groups and five PWS experts, including clinicians and leaders from PWS advocacy organizations.
“To our knowledge, this is the first time stakeholders were involved in codesigning a neurocognitive protocol for individuals with PWS,” the team wrote.
The focus group discussions raised several important issues. For example, caregivers said the test’s required period of fasting wasn’t a major concern, but “they emphasized the importance of flexibility in scheduling the study to align with participants’ typical meal routines, which would enhance their compliance with the fasting condition,” the team wrote.
There is an urgent need for valid, objective tools to assess hyperphagia and support clinical trials for emerging therapies.
People with PWS often have rigid thinking and resistance to change, and disruptions in their routines may cause stress and anxiety. Likewise, while some individuals may tolerate a standardized meal, others may find unfamiliar foods or changes in portion size very stressful.
These findings highlighted the need to work closely with caregivers to create a personalized plan for each participant, including the timing and type of meal provided, so the study could run smoothly and minimize stress.
The original FAB Task included a hunger rating scale, but researchers determined this was not appropriate for people with PWS, who may not reliably describe hunger cues. As a result, the hunger rating was removed, and the modified protocol used a simplified three-point food-stimuli rating scale, with caregivers completing a parallel version to help identify foods that might cause stress.
In addition, parents/caregivers offered recommendations “such as creating a good rapport with the participant before the study, accommodating anxiety and repetitive questioning, structuring the research visit and providing a personalized thank-you gift,” the team wrote.
Study tests the updated protocol in people with PWS
The researchers then recruited 27 individuals with PWS (mean age 16.6 years) and 27 age- and sex-matched healthy participants to complete the modified FAB Task.
Results showed that people with PWS were able to complete the modified test at high rates, nearly as well as the comparison group. All participants finished the pre-meal task, and all but two completed the post-meal task. Those two individuals had sensory sensitivities related to screen brightness.
A few participants had mobility issues that affected how consistently the camera could track their eye movements. Still, the researchers reported solid data quality, with median gaze samples of 77% pre-meal and 73% post-meal.
In addition, 92.6% of caregivers completed the study questionnaires.
The researchers wrote that further work is needed to validate this approach as a tool for assessing hyperphagia, but these results show that the protocol can be used in people with PWS when appropriate accommodations are built in.
More broadly, the researchers wrote that this study underscores how essential it is to involve people living with a condition, and those who support them, in shaping research.
“This study highlights the transformative potential of participatory approaches in tailoring research protocols for PWS and other complex neurodevelopmental conditions.”
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