Multiple Sclerosis in Tehran: Rising Prevalence alongside Stabilizing Incidence – True Increase or Enhanced Diagnosis?

Background: Multiple sclerosis (MS) is a chronic and potentially progressive demyelinating disease of the central nervous system. The incidence and prevalence rate of the disease has been increasing globally, especially in females. Methods: In this cross-sectional population-based study based on Iranian MS Society data (1989-2016), we aimed to present most recent age-standardized incidence and prevalence rate of MS, female to male ratio, mean onset age, and prevalence of positive family history of MS alongside with their time trend via Joinpoint regression analysis in 27 years. Additionally, a linear regression model was used for evaluating the association of onset age with sex and family history in patients. Results: In 18,061 registered cases: female to male ratio was generally 3.06:1, showing a general decreasing trend. The mean onset age of the disease was 28.50 ± 8.61 with a general increasing trend. 12.52% of the cases had at least a positive any-degree family history of MS, exhibiting a weak increasing trend. The age-standardized incidence and prevalence rate was 1.8 (95% CI: 1.3, 7.2) and 116 (95% CI: 96, 139) per 100 000 populations, respectively, both presenting a significant increasing trend, however, incidence rate ended in plateaued and finally decreasing trend. Finally, onset age was predicted to be lower in females and subjects with positive family history of MS. Conclusion: Tehran is among MS high-risk areas with increasing trends in prevalence and increasing followed by plateaued incidence rates indicating necessity of extra investigations of the underlying reasons and health system preparedness for further health care requirements of MS patients.