Risk factors affecting the age at onset in adult patients with multiple sclerosis.

Several factors can predispose patients to experience a sooner onset of multiple sclerosis (MS). In this study, we aimed to investigate the possible effect of environmental factors on the age at onset of adult-onset MS.Methods In this cross-sectional study, 6802 MS patients with age at onset after 18 years old and below 50 years old were included. Descriptive and regression analysis was applied to assess the correlation between age at onset and environmental factors.Results Chronic diseases and reproductive history were associated with a later onset, while smoking showed a complex relationship with onset timing.Conclusion Environmental factors can possibly alter the age at MS onset in adults.