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Sleep deprivation does not cause eye movements that mimic alcohol intoxication

1 May 2006


INTRODUCTION. Previous research shows that sleep deprivation (SD) produces cognitive an some motor impairment similar to that caused by alcohol intoxication. Consequently, SD often has been used as an excuse in place of dnving while intoxicated. We wanted to determine if SD would cause changes in performance on field sobriety tests (FSTs) - walk-and-turn (WAT), one leg stand (OLS), Romberg balance, horizontal gaze nystagmus (HGN), vertical gaze nystagmus (VGN), and lack of convergence (LOC) - in a manner that could be confused with intoxication.

METHODS. Twenty-nine healthy adult Caucasian subjects participated in 2 alcohol workshops each, one after wakefulness of at least 24 hrs, the other after a full night's rest. Subjects consumed prescribed amounts of alcohol over a 2-hr period during each workshop; some subjects were maintained as placebo drinkers. Subjects received a $20 gift card after their participation. At each workshop, trained police officers assessed FSTs similar to the manner in which an impaired driver would be assessed at roadside. We also measured attentional field of view (AFOV), convergence nearpoint (NPC), and presence of endpoint nystagmus (EN). We monitored blood pressure (BP), pulse rate, and pupil size throughout the study. Measures were assessed at Baseline, after 1 hour of drinking, after 2 hours of drinking, and at least 1 hour after the end of drinking (Final). To avoid practice effects, WAT, OLS, and Romberg balance were assessed only at Baseline and Final. A calibrated breath analysis instrument was used to measure blood alcohol concentration (BAC). Subjects and evaluators were masked to the BAC readings during the workshops. Evaluators did not confer regarding their findings during the workshops.

RESULTS. Subjects' BACs ranged up to 0.115 gldl. Regardless of subject restedness, the presence and number of impairment clues increased with increasing BAC for HGN, VGN, LOC, AFOV, NPC, EN, and the other FSTs, most at statistically significantly levels (p < 0.05). However, there were no significant differences for any of these tests when comparing baseline measures for the SD and well-rested conditions, prior to the consumption of any alcohol. Blood pressure and pulse rates did not vary significantly, regardless of condition. Pupil sizes in room light were about 1 mrn larger following SD, but there was no variation with intoxication.

DISCUSSION. While SD may affect cognitive ability and certain motor skills, we found no evidence that it affects eye movements, FOV, or motor skills assessed with FSTs or standard clinical tests, unless the subject is also intoxicated.


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