0047 The Moderating Effect of Shift Work on Circadian Rhythm Disruption and Heart Rate Variability During Sleep

Abstract Introduction It has been suggested that circadian rhythm disruption is closely associated with alterations in the autonomic nervous system, posing risks to both physical and mental health. Shift workers are particularly susceptible to circadian rhythm disruption. This study aimed to investigate the moderating effects of shift work on the association between circadian rhythm disruption and cardiac autonomic regulation during sleep. Methods Nocturnal polysomnography (PSG) and actigraphy data of 41 shift workers(mean age 34.0±8.6 years, 35 females) and 39 controls(mean age 35.9±9.5 years, 34 females) were analyzed. Time-domain, frequency-domain, and nonlinear heart rate variability (HRV) parameters were derived from 5-minute electrocardiogram (ECG) segments during sleep, and their averages were calculated for each sleep stage (W, N1, N2, N3, R). Cosinor analyses of actigraphy data were conducted to compute both parametric (e.g., amplitude, acrophase, F-statistics) and non-parametric parameters (e.g.,Interdaily Stability(IS), Intradaily Variability(IV)). Independent t-tests were conducted to compare group differences in HRV and cosinor analyses parameters. Moderation analyses were conducted to test the moderating effects of shift work on the relationship between circadian rhythm and autonomic regulation. Results Shift workers had higher Midline Estimating Statistic of Rhythm (MESOR) and Least active 5-hour period (L5) and lower IS, IV, Most active 10-hour period (M10) and Relative Amplitude (RA) (all Ps< 0.05). However, shift workers did not show significant differences in HRV parameters during sleep compared to controls. Shift work moderated the association between the mean HR during the N1 stage and F-statistics (F-statistics x shift work: b=0.002, SE=0.001, P=0.032), and between the mean HR during the N3 stage and RA (RA x shift work: b=20.064, SE=9.939, P=0.048). These associations were stronger in shift workers than controls. Conclusion Current study showed that circadian rhythm disruption was more pronounced in shift workers than controls. Even though shift workers showed no significant differences in HRV parameters compared to controls, the moderation results suggest that the influence of circadian rhythm disruption on cardiac autonomic regulation may be an important issue for shift workers. Support (if any) This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) (no. NRF-2022R1A2C1008209).