Abstract
The pupillary light reflex (PLR) has been used as a biomarker to detect and monitor sleep and circadian disruption (McGlashan et al., 2018) and altered neural status (Hall & Chilcott, 2018). Previous studies have found changes in PLR dynamics from alcohol, but only at high blood alcohol concentrations (e.g., BAC = ~0.1%; Reichelt et al., 2003). Sleep loss was also found to perturb PLR dynamics (Goldich et al., 2010). We investigated and compared the effects of low-dose alcohol (< 0.08% BAC) and of acute sleep deprivation (24 hours) in a separate constant routine (CR) protocol. Twelve participants completed a CR acute sleep deprivation study, which included 2–5 daytime (baseline) and 7–9 nighttime pupil measurements up to 25 hours after awakening. Sixteen participants received a single low-dose alcohol (producing < 0.08% peak BAC) preceded by 3 baseline and followed by at least 5–9 post-dosing pupil measurements. Five performance metrics of the PLR dynamics were computed: latency and time constant for both constriction and dilation, and mean pupil size (MPS). Sleep study. The dilation time constant and MPS showed significant (p < 0.01) linear decreases as a function of time awake (mean slope +/− SEM: −0.50 +/− 0.15%Δ/hr and −0.47 +/− 0.14%Δ/hr, respectively). In addition, the constriction time constant and MPS showed significant sinusoidal modulation as a function of circadian phase (mean r2 = 0.59, p < 0.05). Alcohol study. None of the PLR metrics showed a significant linear trend as a function of BAC up to 0.08%. Conclusion. Although 24-hours of sleep loss and 0.08% BAC have been shown to produce similar impairment in psychomotor performance (Dawson & Reid, 1997), the PLR appears well-able to distinguish between these two scenarios, given that PLR dynamics exhibit significant changes associated with sleep loss and/or circadian misalignment, yet appears unperturbed at BACs below 0.08%.
Acknowledgement: Supported by the Force Health Protection Program of the Office of Naval Research (SAA 402925)