Uncorrected Proof Ann Mil Health Sci Res. 2022 June; 20(2):e130616. Published online 2022 August 27. doi: 10.5812/amh-130616. Research Article Alteration of Serum Acetylcholinesterase Activity in Patients with Gastroesophageal Reflux Mohammad-Reza Mirzaii-Dizgah 1 , Iraj Mirzaii-Dizgah 2, * and Marjan Mokhtare 3 1 Student Research Committee, School of Medicine, Iran University of Medical Sciences, Tehran, Iran 2 Department of Physiology, School of Medicine, AJA University of Medical Sciences, Tehran, Iran 3 Department of Internal Medicine, Colorectal Research Center, Hazrat-e Rasool General Hospital, School of Medicine, Iran University of Medical Sciences, Tehran, Iran * Corresponding author: Department of Physiology, School of Medicine, AJA University of Medical Sciences, Tehran, Iran. Email: emirzaii@alumnus.tums.ac.ir Received 2022 August 08; Revised 2022 August 15; Accepted 2022 August 15. Abstract Background: Gastroesophageal reflux disease (GERD) is one of the most common gastrointestinal diseases. One of the factors that are known to play a role in reducing inflammation is acetylcholine (Ach), which decreases cholinesterase to increase Ach. The present study investigated cholinesterase activity in the serum of patients with GERD. Methods: In this cross-sectional study, 30 patients with GERD were referred to Imam Reza Hospital, and 30 healthy individuals were included in the study. Serum was collected in the morning and the fasting state. Cholinesterase activity was measured photometri- cally and analyzed by unpaired student t-test and receiver operating characteristic (ROC) curve analysis. Results: The mean serum cholinesterase activity was significantly lower in the GERD group (5,445 ± 411 IU/L) than in healthy indi- viduals (6,728 ± 305 IU/L). The cut-off for the detection of patients suffering from GERD by the serum activity of cholinesterase was 5,637 IU/L. Conclusions: It seems that the cholinesterase activity reduces in the serum of patients with GERD. Keywords: Cholinesterase, GERD, Serum 1. Background Gastroesophageal reflux disease (GERD) is one of the most common diseases of the digestive system, which is caused by the dysfunction of the lower esophageal sphinc- ter and also by causing a disturbance in the clearing of stomach acid (1, 2). This disease is especially common in de- veloped countries. Its prevalence is 18 - 27% in North Amer- ica, 8 - 25% in Europe, 23% in South America, 11% in Australia, and 7 - 2% in East Asia (3). Compared to other Asian countries, it seems that GERD is more common in Iran, and its prevalence is similar to Western countries. The prevalence of 21.2% in a study in Tehran is the best estimate for reflux in Iran (1). The es- timate of 21.5% in one study, and 25.5% in one study in Shahrekord, can indicate the high prevalence of the dis- ease in Iran. The annual prevalence rate in one of the stud- ies is estimated to be more than 85% (4). This high preva- lence affects not only the quality of life but also the econ- omy. The financial burden of GERD in the United States of America may directly reach 9 - 10 billion dollars annually. This amount is apart from the indirect costs that are im- posed on society due to the reduction of productivity in daily work (3). Gastroesophageal reflux disease is a disorder in which the reflex passage of stomach contents into the esophagus leads to signs such as stomachache, chest pain, hoarseness, asthma, painful throat, globular feeling, and tooth decay (5). The frequent presence of gastric contents with pH < 1 in the mouth may create a persistent acidic situation that can harm the mouth’s solid and soft tissues. A sufficient amount and quality of salivary secretions are necessary to protect the teeth and mucous membranes of the mouth, pharynx, and esophagus (5). In the pathophysiology of GERD, dysfunction of vari- ous mechanisms known as the "anti-reflux barrier" occurs, one of the most obvious of which is the dysfunction of the autonomic nervous system, especially the parasym- pathetic nerves, so that parasympathetic activity is im- paired in all patients with GERD (6, 7). Inflammation mo- tivates releasing of acetylcholine (Ach) from the parasym- pathetic end. Ach can suppress inflammation in both the central nervous system (CNS) and peripheral tissues. Cholinesterases include a group of enzymes that hydrolyze acetylcholine and other choline esters. Cholinesterase ac- Copyright © 2022, Annals of Military and Health Sciences Research. This is an open-access article distributed under the terms of the Creative Commons Attribution-NonCommercial 4.0 International License (http://creativecommons.org/licenses/by-nc/4.0/) which permits copy and redistribute the material just in noncommercial usages, provided the original work is properly cited.