Chronic sleep restriction induces oculomotor impairment with inadequate compensation

Study Objectives: Chronic sleep loss is widespread and can cause deficits in vigilant attention. There are few practical biomarkers that can be used to assess the impact of chronic sleep loss on alertness and performance. Those that are available, such as tests of vigilant attention, cannot discriminate chronic sleep loss from other impairments, like alcohol intoxication, limiting the use of such tools. We aimed to test whether a suite of behavioral oculometrics would be sensitive, and perhaps specific, to chronic sleep restriction (CSR). Methods: We conducted a randomized, counterbalanced, cross-over study to compare behavioral oculometrics following a week of 5 h of time in bed versus 9 h of time in bed. Each experimental week was preceded by a washout week of 9 h nightly time in bed. Participants completed a visual tracking task every 2 h that allowed us to evaluate behavioral oculometrics associated with visual motion processing, pursuit, and saccade behavior. We used mixed-effects models to compare outcomes. Results: Twelve participants completed the 4-week study (6 female). We observed modest decrements in pursuit and tracking smoothness, and maladaptive saccadic behavior, where the rate of saccades increased during CSR, with an apparently compensatory decrease in catch-up saccade amplitude. Visual motion processing of direction, but not speed, was altered. Conclusions: Eye movements are a sensitive measure that can detect sensory and motor impairments from 1 week of 5 h of CSR, potentially distinguishable from those due to other causes, and thus may be a useful biomarker for identifying the source of impairment.