Development and validation of a brain fog scale for coeliac disease

Summary Background Brain fog is a subjective cognitive impairment commonly reported in coeliac disease. A standardised tool to define and assess it is an important unmet need. Aims To develop a patient‐informed tool to assess brain fog in coeliac disease to support clinical care, research and drug development. Methods A pilot online study defined patient descriptors of brain fog. A second study evaluated the factor structure and performance of the scale across two‐time points (‘Now’ and in the ‘Past week’). One month later, participants were invited to repeat the study with two online cognitive processing tests, the Stroop task and the trail making test. Results Among adults with treated coeliac disease, 37 (91.9% F) participated in the pilot study and 510 (88.8% F) in the second study of whom 99 repeated the study 1 month later with 51 completing cognitive testing. The most common brain fog descriptors were ‘difficulty focusing’, ‘difficulty thinking’ and ‘difficulty finding the right words and communicating’. The 12‐item scale reflects ‘cognitive impairment’ and ‘somatic and affective experience’ and demonstrates strong psychometric properties. It tracked with patients report of brain fog being present or absent across two‐time points. It did not significantly correlate with the cognitive tests. Conclusion The brain fog assessment and severity scale is the first patient‐informed clinical outcomes assessment tool measuring brain fog in coeliac disease. It is brief and validated for two time‐based formats. Further research coupling it with biomarker discovery is needed to confirm its validity as a predictor of cognitive performance.