108 Copyright © 2020 The Korean Society of Sleep Medicine pISSN 2093-9175 / eISSN 2233-8853 ORIGINAL ARTICLE Background and ObjectiveaaIn recent years, sleep problems have been increasing globally, there exists an urgent need to develop a therapeutic program promoting sleep quality. Tis study investigated the efect of three types of deep breathing cycles programs on heart rate (HR) and sleep parameters in healthy young adults. MethodsaaTirty healthy participants were recruited. HR and sleep parameters were measured via a smartwatch in all participants for two consecutive days. Participants were randomized into the forced deep breathing cycles (FDBC), non-forced deep breathing cycles (N-FDBC) and breath- ing control (BC) groups, with each participant performing the breathing cycle programs before sleep latency for 30 minutes. ResultsaaN-FDBC showed a signifcant increase in sleep quality (p < 0.001), time in bed (p < 0.05), and total sleep time (p < 0.001), as well as a signifcant decrease in sleep latency and %awake during sleep (p < 0.001). During sleep, maximum HR, minimum HR, average awake HR during sleep, average light sleep HR, and average deep sleep HR were signifcantly lower (p < 0.01). For the FDBC group, signifcant increases in sleep latency (p < 0.05) and decreases in %awake during sleep (p < 0.05) were observed. HR before sleep was higher (p < 0.01). Average HR while awake dur- ing sleep and light sleep stages signifcantly decreased (p < 0.001). Such changes in all parameters were not observed afer the BC group. ConclusionsaaOur study demonstrates that N-FDBC yields clinical benefts by improving sleep quality and HR response during sleep in healthy adults. Sleep Med Res 2020;11(2):108-115 Key WordsaaBreathing, Sleep, Heart rate. INTRODUCTION Tose that live an average lifespan will spend approximately one-third sleeping [1], of which approximately 30–35% may be deemed inadequate. In recent years, sleep problems have in- creased globally [2]. Over 50 epidemiological studies of sleep problems have been conducted worldwide. One previous study categorized sleep problems into two groups, namely, abnormal sleep quantity and abnormal sleep quality [3]. Many factors induce abnormal quantity and qual- ity of sleep such as stress, age, physical illness, mental disorder, and abnormal circadian rhythm [4]. Sleep quantity and sleep quality are infuenced by both the sympathetic and parasympa- thetic nervous systems concurrently [5]. One previous study reported on the relationship be- tween sleep quantity and quality with autonomic activity balance. In brief, it was found that parasympathetic activity promoted sleep drive but sympathetic activity delayed time to sleep [6]. Consequently, sleep problems impact upon work, safety, psychology, and other aspects [3]. Furthermore, sleep problems are also recognised as factors that increase the risk of depression, mental health problem, cardiovascular diseases, cardiometabolic diseases, and dementia [4]. Terefore, the adverse efects of sleep problems cannot be underestimated, and it is an high pri- https://doi.org/10.17241/smr.2020.00668 Te Efect o f Breathing Cycles Program on Heart Rate and Sleep Parameters in Healthy Young Adults Jirawat Wattanapanyawech, PhD, Premtip Thaveeratitham, PT, PhD Department of Physical Therapy, Faculty of Allied Health Sciences, Chulalongkorn University, Thailand Received: August 3, 2020 Revised: October 6, 2020 Accepted: October 24, 2020 Correspondence Premtip Taveeratitham, PT, PhD Department of Physical Terapy, Faculty of Allied Health Sciences, Chulalongkorn University, Tailand Tel +6622181591 E-mail Premtip.T@chula.ac.th ORCID Jirawat Wattanapanyawech https://orcid.org/0000-0003-4358-4897 Premtip Taveeratitham https://orcid.org/0000-0002-6768-2363 cc Tis is an Open Access article distributed un- der the terms of the Creative Commons Attribu- tion Non-Commercial License (https://creative- commons.org/licenses/by-nc/4.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.