0320 Racial/Ethnic Disparities in Circadian Misalignment and Cardiac Autonomic Modulation in Adolescents

Abstract Introduction Prior studies have shown that circadian misalignment is associated with heart rate variability (HRV), an indicator of cardiac autonomic modulation (CAM), in adolescents. However, whether this association differs by race/ethnicity remains unclear. We hypothesize that, in addition to experiencing greater circadian misalignment and more blunted HRV, adolescents from racial/ethnic minority groups will exhibit a stronger association between circadian misalignment and blunted HRV compared to non-Hispanic White adolescents. Methods We analyzed 360 adolescents from the Penn State Child Cohort (median 16 years; 46% female; 21% racial/ethnic minority) with at least 3 nights of at-home actigraphy (ACT), in-lab 9-h polysomnography (PSG) and 24-h Holter-monitoring heart rate variability (HRV) data. Sleep midpoint (SM) was the intra-individual mean middle point of the sleep period. Sleep irregularity (SI) was the intra-individual standard deviation of SM. Social jetlag (SJL) was the absolute difference in SM between weekdays and weekends. Sleep duration (SD) was the intra-individual mean total sleep time. Sleep variability (SV) was the intra-individual standard deviation of SD. Primary HRV outcomes included frequency- and time-domain indices such as high-frequency oscillations (HF), standard deviation of normal-to-normal intervals (SDNN), and root mean square of successive differences (RMSSD). Race/ethnicity was self-reported and categorized as non-Hispanic White or racial/ethnic minority. Linear regression models stratified by race/ethnicity tested SM, SI, and SJL as predictors of HRV, adjusting for demographics, body mass index, SD, SV, AHI, and schooling. Results Minoritized adolescents showed significantly later SM (p=0.011), greater SI (p=0.009), and shorter SD (p=0.048), as well as lower Log-LF (p=0.003), SDNN (p=0.012) and higher HR (p=0.027) compared to non-Hispanic Whites. Among non-Hispanic White adolescents, those with a later SM had higher 24-h LF/HF (p< 0.008), lower 24-h Log-HF and RMSSD (p< 0.045), and lower nighttime Log-LF and SDNN (p< 0.005). Conclusion Minoritized adolescents sleep less, later, and more irregularly, and exhibit blunted HRV, indicating impaired CAM and increased vulnerability to cardiovascular disease. Circadian misalignment in non-Hispanic white adolescents is also associated with a similar degree of impaired CAM as minoritized adolescents. Future research should examine whether circadian interventions that reduce sleep health disparities can improve CAM. Support (if any) R01HL136587, UL1TR002014