THIEME 1 Original Article Effect of Caffeine on Otoacoustic Emissions Drepath Sanish Kumar 1 Athira Rajan 1 Srikanth Nayak 1,2 Arya Vijay 1 Sathish Kumar 3 1 Department of Audiology and Speech-Language Pathology, Nitte Institute of Speech and Hearing, Mangalore, Karnataka, India 2 Department of Audiology and Speech-Language Pathology, Yenepoya University, Mangalore, Karnataka, India 3 Department of Audiology and Speech-Language Pathology, Madras ENT Research Foundation (P) Ltd, Chennai, Tamil Nadu, India Address for correspondence Sathish Sanish Kumar, MSc, Department of Audiology and Speech-Language Pathology, Madras ENT Research Foundation (P) Ltd, Chennai, 600028, India (e-mail: sathish.sreeni58@gmail.com). Introduction Caffeine is consumed everyday in a variety of ways by a large popula- tion around the world, including coffee, tea, and soft drinks. Therefore, there is a sig- nificant need to explore the effects of caffeine on human auditory system. The present study aimed to investigate the effect of caffeine on cochlea using distortion product otoacoustic emission (DPOAE). Materials and Methods Thirty-three young adults were recruited for the study. The effect of caffeine on cochlea was assessed using DPOAE at frequencies between 1 to 10 kHz before and after caffeine consumption. Results The signal to noise ratio of DPOAE was compared before and after coffee intake, which revealed no significant differences. Conclusion The current study results suggest that caffeine has no effect on cochlear functioning. Abstract DOI https://doi.org/ 10.1055/s-0041-1735385 ISSN 2581-9607 © 2021. Indian Society of Otology. This is an open access article published by Thieme under the terms of the Creative Commons Attribution-NonDerivative-NonCommercial-License, permitting copying and reproduction so long as the original work is given appropriate credit. Contents may not be used for commercial purposes, or adapted, remixed, transformed or built upon. (https://creativecommons.org/licenses/by-nc-nd/4.0/). Thieme Medical and Scientific Publishers Pvt. Ltd. A-12, 2nd Floor, Sector 2, Noida-201301 UP, India Introduction Coffee is a nonalcoholic beverage which is used most widely in industrialized countries. Coffee is a mixture of many com- ponents in which caffeine is the active constituent. 1 There is approximately 60 ± 120 mg of caffeine in 150 mL of cof- fee. 2 Caffeine reduces the cerebral blood flow inducing rela- tive brain hypoperfusion, but at the same time, it increases energy metabolism throughout the brain. 3 It has been shown that a 250-mg dose of caffeine reduces resting cerebral blood flow by 22% and middle cerebral artery blood velocity by 13%. 4 Coffee contains many bioactive substances which result in physiological effects with functions including anti-inflammatory, antioxidant, antifibrotic, and anticancer effects. 5 Regular coffee intake leads to the risks of cancer, diabetes, cardiovascular disease, Parkinson’s disease, liver disease, dementia, and depression and can even increase the heart rate and ambulatory blood pressure. 6 According to the Global Burden of Disease, hearing loss is a major health issue and over 5% of the world population experience hearing loss, leading to communication diffi- culties and social withdrawal. 7 Few studies investigated the long-term effects of caffeine consumption using pure tone audiometry 8 and speech in noise test 9 and found a low incidence of hearing loss. On the other hand, caffeine’s short-term effect on the auditory system in humans was less researched. Thus, the present study investigates the short-term effect of coffee on the cochlea’s outer hair cell (OHC) functioning using the distortion product otoacoustic emissions (DPOAEs) test. Ann Otol Neurotol Keywords ► caffeine ► coffee ► cochlea ► otoacoustic emissions Published online: 2021-09-10