Abstract P203: Association of Sleep Characteristics with Heart Rate Variability: Chicago Area Sleep Study

Abstract

Introduction: Autonomic nervous system (ANS) dysfunction may contribute to the elevated incidence of hypertension, diabetes and coronary heart disease (CHD) among persons with shortened sleep duration. However, prior studies were conducted in adults who had obstructive sleep apnea (OSA), a correlate of short sleep, or using experimental designs that restricted sleep. To explore whether sleep duration is associated with ANS function in adults free from OSA, we tested whether sleep duration was associated with heart rate variability (HRV) indices that represent autonomic modulation of heart rate. Methods: The Chicago Area Sleep Study (CASS) identified men and women ages 35-64 via commercially available telephone listings. Data from 406 participants who had an apnea/hypopnea index<15 based on 1 night of in-home apnea detection (ApneaLink TM ) were studied. Participants wore wrist actigraphs for 7 days (Actiwatch TM ) to determine average sleep duration, sleep percentage (% of time during overnight sleep interval spent sleeping) and minutes of wake after sleep onset (WASO). A validated questionnaire, the Epworth Sleepiness Scale (ESS), was used to determine daytime sleepiness. Electrocardiograms were continuously recorded from participants for 10 minutes s from supine participants; time and frequency domain HRV indices were calculated from the RR interval to estimate overall autonomic modulation of heart rate (standard deviation of normal RR intervals [SDNN]) and parasympathetic modulation heart rate (high frequency power [HF], square root of the mean squared difference of successive R-R intervals [rMSSD]). Height and weight were measured and hypertension and diabetes were determined according to JNC-VII and American Diabetes Association 2010 criteria, respectively. Results: Participants’ mean age was 47.5 years, and 56% were female. Average sleep duration was 7.03 hours (SD=1.15), sleep percentage was 83% (SD=20.1), WASO was 41.4 min (SD=21) and the ESS score was 6.75 (SD=4.1). Following adjustment for age, race, sex, BMI, hypertension, diabetes, physical activity and smoking, sleep duration (per 1 hr) was significantly (p<0.01) inversely associated with SDNN (β=−2.5, SE=1.12), rMSSD (β=−2.6, SE=1.1) and log-transformed HF (β=−0.11, SE=0.05). Findings were similar in the subset of 285 participants with AHI<5. Conclusions: In contrast to prior studies, shorter sleep duration was associated with more favorable parasympathetic modulation of HR. These unexpected findings may suggest that ANS dysfunction associated with OSA may be attributed to hypoxemia rather than the direct effects of shortened sleep duration.