Trait-like vulnerability to total and partial sleep loss

Abstract

Objective: To determine the extent to which individual differences in vulnerability to total sleep deprivation also reflect individual differences in vulnerability to multiple nights of sleep restriction.

Design: Two sleep loss conditions (order counterbalanced) separated by 2 to 4 weeks: (a) total sleep deprivation (TSD) of 2 nights (63 h continuous wakefulness); (b) sleep restriction (SR) of 7 nights of 3 h nightly time in bed (TIB). Both conditions were preceded by 7 in-laboratory nights with 10 h nightly TIB; and followed by 3 recovery nights with 8 h nightly TIB. Measures of cognitive performance (psychomotor vigilance, working memory [1-Back], and mathematical processing), objective alertness, subjective sleepiness, and mood were obtained at regular intervals under both conditions. Intra-class correlation coefficients (ICC) were computed using outcome metrics averaged over the last day (08:00-20:00) of TSD and SR.

Setting: Residential sleep/performance testing facility.

Participants: Nineteen healthy adults (ages 18-39; 11 males, 8 females).

Interventions: 2 nights of TSD and 7 nights SR (3 h nightly TIB).

Results: volunteers who displayed greater vulnerability to TSD displayed greater vulnerability to SR on cognitive performance tasks (ICC: PVT lapses = 0.89; PVT speed = 0.86; 1-Back = 0.88; mathematical processing = 0.68, Ps < 0.05). In addition, trait-like responsivity to TSD/SR was found for mood variables vigor (ICC = 0.91), fatigue (ICC = 0.73), and happiness (ICC = 0.85) (all Ps < 0.05).

Conclusion: Resilience to sleep loss is a trait-like characteristic that reflects an individual's ability to maintain performance during both types of sleep loss (SR and TSD). Whether the findings extend to sleep schedules other than those investigated here (63 h of TSD and 7 nights of 3 h nightly TIB) will be the focus of future studies.

Keywords: Sleep deprivation; cognitive performance; individual differences; mood; partial sleep deprivation; sleep restriction.

Figure 1

Study design, showing nightly time in bed for (A) Sleep Restriction, including Overnight and Full-time In-laboratory nights [Baseline, Sleep Restriction, Recovery] and (B) Total Sleep Deprivation, including Overnight and Full-time In-laboratory nights (Baseline, Total Sleep Deprivation, Recovery). Dashes indicate actigraphy recording and asterisks indicate waking neurobehavioral and alertness testing (psychomotor vigilance testing, automated neurological assessment metric, mood, Stanford Sleepiness Scale, and maintenance of wakefulness test). SR and TSD phases were administered in counterbalanced order. Shaded regions indicate sleep and white regions indicate wake. O, Overnight; B, Baseline; SR, Sleep Restriction; TSD, Total Sleep Deprivation; R, Recovery.

Figure 2

Responses to Total Sleep Deprivation (TSD; solid black squares) and Sleep Restriction (SR; open circles), calculated as the average of the last 12 h of sleep deprivation and the last 12 h of sleep restriction day 7 for (A) psychomotor vigilance task lapses, (B) psychomotor vigilance task speed, (C) ANAM MATH throughput, and (D) ANAM 1-Back throughput. Volunteers are indicated by randomly assigned numbers and rank order of volunteers on the x-axis was determined by ranking of the average of the responses to TSD and SR. ICC values are indicated in italics at the top of each figure.

Figure 3

Patterns of change over days for the group means with differentiation between the 2 orders of conditions for (A) psychomotor vigilance task lapses, (B) psychomotor vigilance task speed, (C) ANAM Mathematical Processing, (D) ANAM 1-Back, (E) Vigor, (F) Fatigue, (G) Happiness, (H) Stanford Sleepiness Scale, and (I) MWT sleep latency. Days of Total Sleep Deprivation (TSD) are indicated on the top x-axis, and days of Sleep Restriction (SR) are indicated on the bottom x-axis. Closed circles indicate SR condition with order of SR second; open circles indicate SR condition with SR first; closed squares indicate TSD condition with order of SD first; and open squares indicate TSD condition with TSD second.

Figure 4

Responses to Total Sleep Deprivation (TSD; solid black squares) and Sleep Restriction (SR; open circles), calculated as the average of the last 12 h of sleep deprivation and the last 12 h of sleep restriction Day 7 for mood variables (A) vigor, (B) fatigue, (C) happiness. Volunteers are indicated by randomly assigned numbers and rank order of volunteers on the x-axis was determined by ranking of the average of the responses to TSD and SR. ICC values are indicated in italics at the top of each graph.

Figure 5

Responses to Total Sleep Deprivation (TSD; solid black squares) and Sleep Restriction (SR; open circles), calculated as the average of the last 12 h of sleep deprivation and the last 12 h of sleep restriction day 7 for sleepiness measured as (A) Stanford Sleepiness Scale (SSS) and (B) modified maintenance of wakefulness test (MWT). Volunteers are indicated by randomly assigned numbers and rank order of volunteers on the x-axis was determined by ranking of the average of the responses to TSD and SR. ICC values are indicated in italics at the top of each figure.