Residency Training: The King-Devick test and sleep deprivation

OBJECTIVE: The current study investigates the effect of sleep deprivation on the speed and accuracy of eye movements as measured by the King-Devick (K-D) test, a <1-minute test that involves rapid number naming. METHODS: In this cohort study, neurology residents and staff from the University of Pennsylvania Health System underwent baseline followed by postcall K-D testing (n = 25); those not taking call (n = 10) also completed baseline and follow-up K-D testing. Differences in the times and errors between baseline and follow-up K-D scores were compared between the 2 groups. RESULTS: Residents taking call had less improvement from baseline K-D times when compared to participants not taking call (p < 0.0001, Wilcoxon rank sum test). For both groups, the change in K-D time from baseline was correlated to amount of sleep obtained (r(s) = -0.50, p = 0.002) and subjective evaluation of level of alertness (r(s) = 0.33, p = 0.05) but had no correlation to time since last caffeine consumption (r(s) = -0.13, p = 0.52). For those residents on their actual call night, the duration of sleep obtained did not correlate with change in K-D scores from baseline (r(s) = 0.13, p = 0.54). CONCLUSIONS: The K-D test is sensitive to the effects of sleep deprivation on cognitive functioning, including rapid eye movements, concentration, and language function. As with other measures of sleep deprivation, K-D performance demonstrated significant interindividual variability in vulnerability to sleep deprivation. Severe fatigue appears to reduce the degree of improvement typically observed in K-D testing.