O048 The sleep regularity index: a new way to evaluate shiftwork

Abstract Introduction Although rarely assessed during shiftwork, sleep regularity is an important dimension that can be used to inform schedule selection. We used the recently introduced Sleep Regularity Index (SRI) to evaluate maritime defence watchbills. Methods This is a retrospective analysis of pre-collected data from active-duty sailors on Navy ships during underway, i.e., 218 sailors in Study 1 (3hr-on/9hr-off [3/9], 6/18, 7/5/5/7, and 5/15 watchstanders, and dayworkers), and 24 sailors in Study 2 (sailors first stood watch on the 5/10, then the 3/9 ~ four months later). Wrist-worn actigraphy (~8 days) and the psychomotor vigilance task (PVT) were used to assess sleep and performance, respectively. Subjective sleepiness, sleep quality, and mood were assessed using the Epworth Sleepiness Scale (ESS), Pittsburgh Sleep Quality Index (PSQI) and Profile of Mood States (POMS), respectively. Partial correlation analysis was used to examine the relationship of SRI to ESS, PVT, POMS, and PSQI. Results (Study 1) SRI score was lower for the 5/15 (43.33, IQR = 10) compared to all other watchbills (all p<.001). (Study 2) Independent of watchbill, SRI was associated with PSQI (Spearmans rho [rs] = -0.326, p=.031) and POMS (rs = -0.361, p=.038), but not PVT or ESS (all p>.05). Discussion The SRI is a useful new tool for examining sleep regularity across different shiftwork schedules. Sleep duration and regularity are both important dimensions of sleep to be considered with shiftwork schedules, and those schedules that protect both should be preferred.