The Trail Making Test in healthy controls and Huntington's disease: Demographic effects and normative tables based on...

The Trail Making Test (TMT) is a common component of neuropsychological assessment and research in neurocognitive disorders, including Huntington's disease (HD). Using an unprecedented data set from Enroll-HD, the world's largest study of HD, we aimed to (a) characterize TMT performance in healthy controls, describe demographic effects, and establish new normative data using a large demographically diverse sample; (b) describe TMT performance in people with HD, with accompanying HD-specific TMT norms; and (c) characterize the extent of "floor effects" on the TMT, a common phenomenon observed in neurocognitive disorders. We analyzed data from 2,215 healthy controls and 13,484 HD gene expansion carriers from Enroll-HD. Age and education emerged as the strongest predictors of TMT performance in both healthy controls and HD, and the sex effect was negligible across both groups. Age-related differences in performance were not evident until older adulthood in healthy controls but were detectable from early adulthood in HD. We provide age- and education- adjusted normative data for both healthy controls (ages 19-79) and HD (ages 18-92), which serves as an updated resource for the clinical interpretation of the TMT. In HD, TMT completion times tracked disease severity with effect sizes increasing with disease stage, demonstrating utility in monitoring disease status across a broad range of the HD severity spectrum. A pronounced "floor effect" was, however, observed on TMT Part B, with over a quarter of later stage HD participants unable to complete the task within the allotted time, for which we provide practical considerations for TMT use and interpretation. (PsycInfo Database Record (c) 2026 APA, all rights reserved).