Oculomotor impairment during chronic partial sleep deprivation

Objective: The effects of chronic partial sleep (sleep deprivation) and extended sleep (sleep augmentation) followed by recovery sleep on oculomotor function were evaluated in normal subjects to explore the usefulness of oculomotor assessment for alertness monitoring in fitness-for-duty testing. Methods: Sixty-six commercial drivers (24–62 years, 50m/16f) participated in a 15 day study composed of 3 training days with 8 h time in bed per night, 7 experimental days with subjects randomly assigned to either 3, 5, 7, or 9 h time in bed, and 3 recovery nights with 8 h time in bed. Data from 57 subjects were used. Saccadic velocity (SV), initial pupil diameter (IPD), latency to pupil constriction (CL), and amplitude of pupil constriction (CA) were assessed and correlated with the sleep latency test (SLT), the Stanford sleepiness scale (SSS), and simulated driving performance. Results: Regression analyses showed that SV slowed significantly in the 3 and 5 h groups, IPD decreased significantly in the 9 h group, and CL increased significantly in the 3 h group. SLT and SSS significantly correlated with SV, IPD, CL, and driving accidents for the 3 h group, and with CL for the 5 h group. Analyses also showed a significant negative correlation between decreasing SV and increasing driving accidents in the 3 h group and a significant negative correlation between IPD and driving accidents for the 7 h group. Conclusions: The results demonstrate a sensitivity primarily of SV to sleepiness, and a correlation of SV and IPD to impaired simulated driving performance, providing evidence for the potential utility of oculomotor indicators in the detection of excessive sleepiness and deterioration of complex motor performance with chronic partial sleep restriction. Significance: This paper shows a relationship between sleep deprivation and oculomotor measures, and suggests a potential utility for oculometrics in assessing operational performance readiness under sleep restricted conditions.