Comparing epidemiology and baseline characteristic of multiple sclerosis and neuromyelitis optica: A case-control study

Background: Autoimmune syndromes such as Multiple Sclerosis (MS) and Neuromyelitis Optica (NMO) are chronic, demyelinating diseases of the central nervous system which usually affect young adults. Both environmental risk factors and genetic susceptibility have been proposed to explain the etiology of these diseases. The aim of this study was to compare epidemiology and possible risk factors in MS and NMO in Tehran, Iran.

Method: A population-based incident case-control study was performed in Tehran based on a study conducted on1513 MS patients from Iranian MS Society registry center of Tehran, from 2014 to 2015, and 83 NMO patients diagnosed with NMO in 2015 at Sina hospital, a tertiary care referral center in Tehran. The random digit dialing (RDD) methods were established to select 400 population-based controls. A checklist was designed to cover the epidemiological variables to estimate the possible risk factors for MS and NMO based on a questionnaire designed for multinational case-control studies of environmental risk factors in multiple sclerosis. Structured face to face interviews with cases, and telephone interviews with controls were conducted by trained interviewers to collect data. The multiple logistic regression analysis was done via SPSS package.

Results: The adjusted odds ratio (OR) estimate of MS for females compared to males was (OR =1.47; 95% CI: 1.12, 1.95), and it was (OR=1.54; 95% CI: 1.17, 2.02) for people aged 18-27 years compared to younger ones aged 28-37 years. The adjusted OR estimate of NMO for people aged over 48 years compared to those aged 28-37 years was (OR=3.49; 95% CI: 1.59, 7.64). The point estimates were greater than eight-fold increased risk associated with MS among patients with a positive familial history 8.80 (95% CI: 4.10, 18.90).

Conclusion: The results of this study reveal that the risk of MS is significantly higher in female and younger people in comparison to NMO. Having positive family history of MS can increase the risk of MS substantially. The findings of the study indicated that factors that predict susceptibility to MS, including a positive history of MS in relatives, do not appear to have any association with NMO.