BACKGROUND: ADHD is the most prevalent pediatric neurodevelopment disorder. In the United States, it is estimated that 5.4 million children 6 and 17 years of age (or 9.5% of U.S. children) have received an ADHD diagnosis. The King-Devick (K-D) test is a vision-based test of rapid number naming that requires saccades and visual processing. In sideline studies of youth and collegiate athletes with concussion, the K-D test consistently demonstrates higher (worse) time scores post-injury compared to pre-season baseline scores. There is growing evidence that, like concussion and mild traumatic brain injury, ADHD may be associated with visual pathway dysfunction.
PURPOSE: Using the King-Devick (K-D) test, a vision-based test of rapid number naming that requires saccades and visual processing. We investigated whether children with ADHD has worse scores compared to similar aged controls.
METHODS: Design: Prospective study of children with ADHD (diagnosed by Conners Scale and NYU pediatric neurologist) and age-matched controls. Participants: Patients diagnosed with ADHD (5-21 years of age) seeking care from the NYU Neurology Faculty Group Practice and Child Study Center. Analyses compared K-D scores of patients with ADHD to those of pre-season baseline scores for student-athletes controls category matched for age and gender. King-Devick Test: a vision-based measure of rapid number naming that varies the spacing between numbers on successive cards.
RESULTS: Among 134 participants in this study, ADHD vs. control status was significantly associated with higher K-D test time scores (p<0.001, logistic regression models, accounting for age). K-D showed a greater capacity to distinguish ADHD vs. control groups in youths older than 11 years of age (ROC curve areas from logistic regression models was, 0.55 for youths ≤11 years of age and 0.79 for youths ≥11 years of age). Patients with ADHD took an average of 14 seconds longer to complete the K-D test, compared to control youth (p<0.001, two-sample t-test). Use of stimulant medications was not associated with differences in K-D time scores within the cohort of patients with ADHD (p > 0.05, best KD trial of ADHD on Rx vs. best KD trial of ADHD off Rx).
CONCLUSIONS: Visual pathways may perform or be utilized differently in youths with ADHD compared to controls. This alteration in visual performance on the K-D test in youths with ADHD is likely due to the widespread distribution of brain pathways devoted to vision (approximately 50% of the brain’s circuits). The limited capacity of the K-D to distinguish ADHD in youths younger than 11 years of age may be due to variations in reading ability in this age group. Use of stimulant medication was not associated with altered K-D test performance.
Summary Points:
- Investigated if there was a difference in the King-Devick Test of rapid number naming in subjects (ages 5-21) with ADHD verses those without.
- Subjects with ADHD showed significantly worse K-D scores compared to the controls.
- The K-D Test demonstrated a greater capacity to distinguish ADHD vs. control groups in youths older than 11 years of age (ROC curve areas from logistic regression models was, 0.55 for youths ≤11 years of age and 0.79 for youths ≥11 years of age).
- Patients with ADHD took an average of 14 seconds longer to complete the K-D test, compared to control youth (p<0.001, two-sample t-test).
- ADHD medication was not associated with differences in K-D scores within the cohort.
- Since ADHD is a neuro-development disorder and more than 50% of the brain is devoted to vision, the K-D Test highlights aspects of vision which may be affected by ADHD.