Restorative Effect of Nighttime Naps on Brain Functional Organisation and Memory in Night Shift Nurses

Shift work-related sleep deprivation (SD) among nurses is associated with cognitive decline, which may be partially mitigated by nighttime nap (NNAP). This study aimed to investigate the restorative effects of NNAP on brain functional organisation and memory in nurses with night shift-related SD. Resting-state functional magnetic resonance imaging data were collected from 24 nurses at three time points: during rested wakefulness (RW), after 24 h of SD and following a period of SD when a NNAP was taken. Memory function assessments were conducted using the Complex Figure Test (CFT) and the California Verbal Learning Test (CVLT) following SD and NNAP sessions. Functional connectivity density (FCD), which quantifies the sum of functional connections for a given voxel within the entire brain network, was calculated. Voxel-wise post hoc paired t tests, following one-way repeated-measures analysis of variance, were employed to evaluate FCD differences. Improved performance in the CFT and CVLT-II tests was observed following NNAP, compared with SD. Compared with RW, a disturbed FCD within the whole-brain network was noted in SD, particularly involving cognition-related regions, somatosensory and motor areas, the visual cortex, the auditory cortex and the thalamus. Following NNAP, FCD restoration was identified in cognition-related regions, somatosensory and motor areas and the thalamus. Improved memory performance correlated with the FCD changes noted between SD and NNAP sessions. Our findings propose that NNAP may facilitate restoration of brain functional organisation and memory disrupted by SD in nurses working night shifts.