Trait Interindividual Differences in the Magnitude of Subjective Sleepiness from Sleep Inertia

Abstract

In shift work settings and on-call operations, workers may be at risk of sleep inertia when called to action immediately after awakening from sleep. However, individuals may differ substantially in their susceptibility to sleep inertia. We investigated this using data from a laboratory study in which 20 healthy young adults were each exposed to 36 h of total sleep deprivation, preceded by a baseline sleep period and followed by a recovery sleep period, on three separate occasions. In the week prior to each laboratory session and on the corresponding baseline night in the laboratory, participants either extended their sleep period to 12 h/day or restricted it to 6 h/day. During periods of wakefulness in the laboratory, starting right after scheduled awakening, participants completed neurobehavioral tests every 2 h. Testing included the Karolinska Sleepiness Scale to measure subjective sleepiness, for which the data were analyzed with nonlinear mixed-effects regression to quantify sleep inertia. This revealed considerable interindividual differences in the magnitude of sleep inertia, which were highly stable within individuals after both baseline and recovery sleep periods, regardless of study condition. Our results demonstrate that interindividual differences in subjective sleepiness due to sleep inertia are substantial and constitute a trait.

Working around the Clock: Is a Person’s Endogenous Circadian Timing for Optimal Neurobehavioral Functioning Inherently Task-Dependent?

“…To account for any idiosyncratic differences between subjects in basal neurobehavioral functioning, outcome measures were expressed relative to the baseline average, calculated using the second through fourth test bouts on day two (at 08:15, 09:20, and 12:00), leaving enough time after the first in-laboratory sleep opportunity to dissipate sleep inertia [ 57 ] and preceding the daytime nap at the start of the simulated night shift condition. Difference scores for the DSST were inverted so that larger values corresponded to greater neurobehavioral impairment for all three assays.…”

Electrodermal Activity Is Sensitive to Sleep Deprivation but Does Not Moderate the Effect of Total Sleep Deprivation on Affect

“…Despite these strengths, our findings are limited by the fact that we included only data from two time points per day. Other studies of EDA during sleep deprivation generally collect measures of interest, such as EDA, affect, sleepiness, or PVT performance, across the circadian cycle (see Miró et al, 2002 ; Michael et al, 2012 ; Posada-Quintero et al, 2018 ), as do studies of interindividual differences (e.g., Van Dongen et al, 2004a , b ; Lundholm et al, 2021 ). Because this study retrospectively analyzed previously collected data, we were only able to gather SCL and NSSCR data during time periods immediately preceding when SCR recording had taken place, which were limited to periods intended to study task-specific performance at two designated time intervals during the daytime hours.…”

A preliminary framework for managing sleep inertia in occupational settings

“…For example, some personnel report feeling alert almost immediately after waking, while for others, optimum alertness is delayed for several minutes post-waking [ 33 ]. Other recent studies have also found significant interindividual differences in the subjective experience of sleep inertia [ 52 , 53 ]. Furthermore, subjective ratings of performance during sleep inertia do not always match objective performance indicating poor self-assessment of performance during the sleep inertia period [ 54 ].…”

“…Such measures could then be implemented as part of recruitment procedures to help inform scheduling based on susceptibility to sleep inertia. An important consideration here is that, to date, several studies have only demonstrated a subjective difference in sleep inertia severity between individuals, rather than an objective difference [ 52 , 53 ]. Furthermore, research suggests that there tends to be a misalignment between an individual’s subjective perception of their sleep inertia impairment compared to their objective performance [ 54 ].…”