0017 Interplay of Sleep Depth and Circadian Misalignment on Cardiac Autonomic Modulation in Adolescents

Abstract Introduction We previously showed that the odds ratio product (ORP), an EEG measure of sleep depth, is associated with lower heart rate variability (HRV), an EKG measure of cardiac autonomic modulation (CAM), in adolescents. Specifically, ORP was associated with decreased low-frequency HR oscillations (Log-LF) and decreased standard deviation between normal sinus rhythms (SDNN). In addition, circadian misalignment, as measured by a delayed sleep midpoint (SM), high sleep irregularity (SI) or high social jetlag (SJL), has also been shown to impact HRV. However, the interplay of sleep depth and circadian misalignment on CAM has not been previously evaluated. Methods We studied 344 adolescents from the Penn State Child Cohort (Md age=16y; 47% female, 23% racial/ethnic minority) who had at least 3 valid nights of actigraphy. We extracted ORP during NREM sleep from 9-hour, in-lab polysomnography (PSG). Log-LF and SDNN were extracted from Holter EKG monitoring during the 24-h after PSG. SM, the intra-individual mean middle point of the sleep period, SI, the intra-individual standard deviation of SM, and SJL, the intra-individual weekends vs. weekdays difference in SM, were extracted from actigraphy. Multivariable linear regression models examined the interactions between ORP and circadian indices with 24-h Log-LF and SDNN. Covariables included sex, age, race/ethnicity, obesity, metabolic syndrome, PSG-measured sleep apnea, insomnia symptoms, and actigraphy-measured mean sleep duration. Results The interaction terms between ORP and SI on 24-h Log-LF (p=0.002) and SDNN (p=0.046) were statistically significant. Specifically, higher ORP was associated with lower Log-LF [B=-0.161 (0.046), p< 0.001] and SDNN [B=-5.299 (1.941), p=0.007] amongst those with high SI (> 45 minutes; n=183), while ORP was not significantly associated with HRV indices among those with low SI (both p’s>0.591; n=161). No significant interactions were observed between ORP and either SM or SJL on HRV (all p’s>0.10). Conclusion A highly irregular timing of sleep impacts the association between sleep depth and CAM in adolescents. These data support the synergistic adverse effect between circadian misalignment and homeostatic dysregulation on heart health. Future studies should examine whether these associations are further impacted by entrainment to the academic school schedule. Support (if any) R01HL136587, R01MH118308