I. J. A. B. M. S. JULY 2013 (5) HEART RATE VARIABILITY IN DELAYED SLEEP PHASE SYNDROM E Names of All Authors/ Contributors: 1. Md Dilshad Manzar , PhD student, Sleep Research Unit, Centre for Physiotherapy and Rehabilitation Sciences, Jamia Millia Islamia 2. Unaise Abdul Hameed, PhD student, Centre for Physiotherapy and Rehabilitation Sciences, Jamia Millia Islamia 3. Dr. Mani Sethi, Project Fellow, UGC Research Project, Centre for Physiotherapy and Rehabilitation Sciences, Jamia Millia Islamia 4. Dr. M Ejaz Hussain, PhD, Professor and Director, Centre for Physiotherapy and Rehabilitation Sciences, Jamia Millia Islamia * Corresponding Author : Dr. M Ejaz Hussain Professor and Director Centre for Physiotherapy and Rehabilitation Sciences Jamia Millia Islamia Email: ehusain@jmi.ac.in Abstract The study investigated the heart rate variability (HRV) measures and electrocardiogram (ECG) features during sleep after 24 h total sleep deprivation (TSD) in a mild chronic adult male patient of delayed sleep phase syndrome (DSPS). The findings of mean Heart Rate (HR), mean RR (RRI time series), time domain and frequency domain measures are presented. Bradycardias, sinus pauses and ectopic beats were observed during specific parts of sleep. HRVs suggest a sustained sympathetic and decreased parasympathetic activity in the sleep deprived DSPS patient. Keywords Delayed sleep phase syndrome, heart rate variability, autonomic nervous system, sleep Introduction HRV is an effective non-invasive method providing quantitative evaluation of the autonomic neural activity modulating the cardiac function. It has been widely used to study the sleep associated changes in sympathovagal balance. 1 We present findings of HRV and ECG manual