Tehran University of Medical Sciences Current Journal of Neurology 2717-011X 18 3 2019 06 16 93 98 EN Sharareh Eskandarieh Multiple Sclerosis Research Center, Neuroscience Institute, Tehran University of Medical Sciences, Tehran, Iran Abdorreza Naser Moghadasi Multiple Sclerosis Research Center, Neuroscience Institute, Tehran University of Medical Sciences, Tehran, Iran Mohammad Ali Sahraian Multiple Sclerosis Research Center, Neuroscience Institute, Tehran University of Medical Sciences, Tehran, Iran Amir Reza Azimi Multiple Sclerosis Research Center, Neuroscience Institute, Tehran University of Medical Sciences, Tehran, Iran Negar Molazadeh Multiple Sclerosis Research Center, Neuroscience Institute, Tehran University of Medical Sciences, Tehran, Iran 2019 02 24 2019 06 12 Background: Neuromyelitis optica spectrum disorder (NMOSD) is a neuroinflammatory demyelinating disease caused by the presence of a highly specific serum autoantibody marker, NMO-immunoglobulin G (NMO-IgG), that reacts against the water channel aquaporin-4 (AQP4). The present study examined the association between NMO-IgG sero-positivity and environmental factors such as cigarette smoking. Methods: A cross-sectional study was conducted in Sina Hospital, a tertiary referral center in Tehran, Iran. All the patients with a definite diagnosis of NMOSD were involved in this study. The enzyme-linked immunosorbent assay (ELISA) was used to examine the AQP4-IgG status. To assess the association between NMO-IgG sero-positivity and cigarette smoking, a researcher-made questionnaire covering patients’ lifestyle information on smoking habits was designed and administered using the structured face-to-face interviews with the patients. Results: The positive and negative NMO-IgG results were found in 44 (46.8%) and 50 (53.2%) patients, respectively. The increased NMO-IgG sero-positivity odds were observed among the lifetime smokers [odds ratio (OR) = 3.24, 95% confidence interval (CI): 1.16-9.08], current smokers (OR = 6.08, 95% CI: 1.26-29.39), and passive smokers (OR = 2.22, 95% CI: 1.10-4.50). Conclusion: Lifetime and current smoking as well as passive smoking can be regarded as risk factors for NMO-IgG sero-positivity. Smoking with its immunological effects can lead to the production of autoantibodies such as NMO-IgG. https://ijnl.tums.ac.ir/index.php/ijnl/article/view/1757