Tehran University of Medical Sciences Acta Medica Iranica 0044-6025 55 8 2017 10 07 502 506 EN Golshan Fahimi Department of Neurology, Yale School of Medicine, New Haven, Connecticut, USA. Seyed Mahmoud Tabatabaei Department of Physiology, Tabriz Branch, Islamic Azad University, Tabriz, Iran. Elnaz Fahimi Department of Physiology, Tabriz Branch, Islamic Azad University, Tabriz, Iran. Hamid Rajebi Department of Radiology, University of Texas, Health Sciences Center at San Antonio, San Antonio, Texas, USA. 2016 09 11 2017 04 15 Alzheimer's disease (AD) is a devastating neurodegenerative disorder in human beings associated with cognitive, behavioral and motor impairments. The main symptom of AD is dementia, which causes difficulties in carrying out daily practices. Brain waves are altered in people with AD. Relative indices of brain waves can be beneficial in the diagnosis of AD. In this case-control study, 50 patients with AD and 50 matched healthy individuals were enrolled in case and control groups respectively. With recording and analyzing of brain waves with the utilization of quantitative electroencephalogram (QEEG), index of theta/alpha ratio was assessed in both groups. The index of theta/alpha ratio was significantly higher in patients with AD in comparison to healthy individuals (P<0.05). Index of theta/alpha ratio obtained by QEEG provides a non-invasive diagnostic marker of AD, which may be helpful in identification of non-advanced disease in susceptible individuals. https://acta.tums.ac.ir/index.php/acta/article/view/5875 https://acta.tums.ac.ir/index.php/acta/article/download/5875/4973