Original Article Association between respiratory events and nocturnal gastroesophageal reflux events in patients with coexisting obstructive sleep apnea and gastroesophageal reflux disease Nattapong Jaimchariyatam a,b, *, Warangkana Tantipornsinchai a , Tayard Desudchit b,c , Sutep Gonlachanvit d a Division of Pulmonary and Critical Care Medicine, Department of Medicine, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand b Excellence Center for Sleep Disorders, King Chulalongkorn Memorial Hospital, Thai Red Cross Society, Bangkok, Thailand c Division of Neurology, Department of Pediatrics, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand d Division of Gastroenterology, Department of Medicine, Chulalongkorn University, Bangkok, Thailand ARTICLE INFO Article history: Received 27 January 2016 Received in revised form 16 April 2016 Accepted 19 April 2016 Available online 8 June 2016 Keywords: Obstructive sleep apnea Gastroesophageal reflux disease Arousal Esophageal pH monitoring Esophageal impedance monitoring A B ST R AC T Background: Literature has addressed the increased prevalence of gastroesophageal reflux disease (GERD) in obstructive sleep apnea (OSA). Significant improvement of GERD has been found after OSA treat- ment. However, precise mechanisms underlying this correlation remain unclear. We examined the association between nocturnal gastroesophageal reflux (GER) and sleep events in patients with coexist- ing OSA and GERD. Methods: A case-crossover study among 12 patients with coexisting moderate–severe OSA and GERD was conducted. Participants underwent simultaneous polysomnography and esophageal impedance and pH monitoring. GER subtypes (ie, acid reflux, non-acid reflux) were defined as outcomes. Respective control time points were selected in all eligible control periods. Each sleep event was assessed individually. Es- timated odds ratios (ORs) and 95% confidence intervals (CIs) were analyzed. A p-value of < 0.05 was considered significant. Results: Patients were determined as moderate to severe OSA (respiratory disturbance index of 42.66 [±22.09]). There were a total of 50 GER episodes, 22 acid reflux and 28 non-acid reflux. Arousals and awak- enings were significantly associated with subsequent GER events. The OR for GER following an arousal was 2.31 (95% CI 1.39–3.68; p < 0.001) and following an awakening was 3.71 (95% CI 1.81–7.63; p < 0.001). GER events were significantly less likely to occur after other respiratory events (OR 0.38 [95% CI 0.18– 0.82]; p = 0.01). No sleep events followed GER events (p > 0.05). Conclusions: Both awakening and arousal appear to precipitate any subtype of GER events in patients with coexisting GERD and moderate to severe OSA. However, GER events were significantly less likely to occur after other respiratory events and did not appear to cause sleep-related events. © 2016 Elsevier B.V. All rights reserved. 1. Introduction Gastroesophageal reflux disease (GERD) is a common chronic dis- order presenting with a broad spectrum of symptoms, including esophageal and extraesophageal symptoms. Normal sleep physi- ology results in many changes of gastroesophageal function that contribute to the pathogenesis of GERD. Sleep may alter physio- logical mechanisms responsible for normal esophageal clearance, resulting in impairment of esophageal acid clearance. The rate of swallowing is reduced during sleep, leading to a decrease in primary peristalsis, a pivotal defense mechanism that is responsible for volume clearance of refluxate from the esophagus. Diminished sal- ivary production during sleep, as well as reduced delivery of saliva to the distal esophagus due to decreased primary peristalsis delay alkalization and thus, normalization of esophageal pH after acid reflux occurs. The upper-esophageal sphincter basal pressure is sig- nificantly reduced, resulting in an increased risk of aspiration. In addition, gastric acid secretion is increased and gastric emptying is delayed during nighttime [1]. Obstructive sleep apnea (OSA) is a sleep-related breathing disorder characterized by repeated epi- sodes of upper-airway occlusion that result in brief periods (at least 10 s) of breathing cessation (apnea) or a marked reduction in tidal * Corresponding author. Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand; Excellence Center for Sleep Disorders, King Chulalongkorn Memorial Hospital, Thai Red Cross Society, 1873 Rama IV Road, Phathumwan, Bangkok 10330, Thailand. Tel.: +66 2256 4252; fax: +66 2256 4252. E-mail address: drboy48@yahoo.com (N. Jaimchariyatam). http://dx.doi.org/10.1016/j.sleep.2016.04.013 1389-9457/© 2016 Elsevier B.V. All rights reserved. Sleep Medicine 22 (2016) 33–38 Contents lists available at ScienceDirect Sleep Medicine journal homepage: www.elsevier.com/locate/sleep