Sleep Disordered Breathing is Adversely Associated With Cardiac Autonomic Modulation in Adolescents

Introduction: Sleep disordered breathing (SDB), as measured by the apnea/hypopnea index (AHI), is a known risk factor for cardiovascular disease (CVD) in adults. Although SDB is prevalent in pediatric populations, there has been less focus on SDB as a primary risk factor for CVD in youth. The recent AHA scientific statement on SDB and CVD in children and adolescents suggests that, in order to better understand the long-term CVD-related risk associated with SDB in youth, additional longitudinal studies incorporating noninvasive markers of CVD are needed. The current study aimed to fill this important gap. Hypothesis: We hypothesized that SDB is associated with decreased HRV in adolescents. Methods: We studied 421 subjects from the Penn State Child Cohort who were 8.7 (1.7) years old at baseline and were followed-up as adolescents 16.5 (2.3) years old. We estimated the AHI from 9-hour, in-lab polysomnography (PSG), and frequency and time-domain heart rate variability (HRV) indices from 24-h Holter EKG monitoring immediately following PSG. We stratified 24-h HRV data into daytime and nighttime periods. Linear regression analyses examined the association between AHI with 24-h HRV indices, while adjusting for age, sex, race/ethnicity, BMI percentile, and metabolic syndrome (MetS) score in adolescence as well as AHI and nighttime HRV indices in childhood. Results: While there were no significant associations between AHI and daytime (p=0.233) or nighttime (p=0.147) HR, there were significant associations with frequency and time-domain HRV indices. A higher AHI was associated with lower Log-HF, Log-LF, SDNN and RMSSD, yet higher LF/HF, for both daytime and nighttime periods (all p<0.05). For example, for each additional apnea or hypopnea per hour of sleep there was a decrease of -1.74ms (0.73) and -1.65ms (0.77) in SDNN during the daytime (p=0.018) and nighttime (p=0.033), respectively, even after adjusting for all covariates including MetS, childhood AHI and SDNN. More specifically, the 24-h SDNN of adolescents with an AHI≥5, indicative of moderate-to-severe SDB, was 10.9ms (4.4) lower than that of adolescents with an AHI=0 (p=0.014). Conclusions: SDB is associated with impaired cardiac autonomic balance in adolescence independently of MetS, prior SDB and prior HRV status. These data further support the role of SDB as an independent risk factor for CVD early in life.