A comparative analysis of partial sleep restriction versus split sleep regimen on cognitive processing, declarative memory, and affective behaviour in nursing students
Authors: Anand Nirmala Subhash , Anantha Sunaina , Altayib Lina S. 
Published: November 2024

Objectives:
Sleep plays a regulatory role in functions such as abstraction, fluid intelligence, and declarative memory. This research seeks to assess the influence of two sleep restriction schedules—partial nocturnal sleep restriction and a split sleep (SS) regimen—on fluid intelligence and various memory functions (including encoding, consolidation, and retrieval) in shift-working nurses.

Materials and Methods:
The research involved 46 4th-year nursing students (23 males and 23 females) assigned to night duties, categorised into two groups: Partial sleep restriction (5 h of night sleep with 4 h of daytime recovery sleep) and SS (5 h of night sleep with 1.5 h of an afternoon nap and recovery sleep of 2.5 h following the tests). Instruments such as the Pittsburgh sleep quality index (PSQI), Karolinska sleepiness scale (KSS), and Raven’s Progressive Matrices were utilised to evaluate sleep quality, sleepiness levels, overall mood, benefits of daytime naps, and fluid intelligence. Memory-related activities comprised a picture-encoding task and a factual knowledge task, evaluated through subjective assessments and two alternative choice questions.

Results:
The PSQI global scores highlighted notable differences, with female nursing students in the partial sleep group scoring lower (9 ± 2.311) than their counterparts in the SS group (5 ± 1.09). Sleepiness, gauged by the KSSKSS score, was higher in the partial sleep group (7 ± 3.2) compared to female nursing students in the SS regimen (5 ± 5.8). Results from Raven’s progressive matrices pointed to delayed abstraction in the partial sleep restriction group (9.31 ± 6.24) in contrast to the SS group (9.01 ± 5.59), indicating poorer performance in visual attentive tasks. Positive and negative affect schedule scores unveiled heightened negativity in mood due to sleep restriction in the partial sleep group, with less hostility observed in those with an afternoon nap, albeit not reaching statistical significance. Positive moods exhibited fluctuation, with attentiveness declining in the partial sleep group. The study affirmed the advantages of a daytime nap on long-term memory. Female nurses in the SS regimen displayed statistically significant picture encoding accuracy (78 ± 3.65) with faster reaction times (2 ± 6.37) compared to the partial sleep group. Males in the SS regimen recorded a higher percentage of hits (88 ± 5.16). Learning sessions at 3 pm, coinciding with the circadian dip, affected the partial sleep groups, whereas the nap mitigated such effects for the SS group. Allowing a 1.5-h afternoon nap synchronised with the circadian dip enhanced memory in the SS group.

Conclusion:
By comparing partial nocturnal sleep restriction and a SS regimen, this study unveils their distinct effects on fluid intelligence and memory processes among shift-working nurses. The results provide valuable insights into the degree of dependence of basic cortical functions on sleep for healthcare professionals navigating demanding schedules, underscoring the significance of accounting for both nocturnal sleep duration and daytime naps to optimise cognitive performance.