The Disease Modifying Drugs (DMDs) has radically improved the success of Multiple Sclerosis (MS) treatment by preventing relapses and delaying disease progression.

Multiple Sclerosis patients monitored at the Adult Neuroimmunology clinic of Hacettepe University Faculty of Medicine between 2010-2021 have been retrospectively screened.

658 patients were included in the study. The median age of the patients was 42 (min:19-max:77), and 416 (63.2%) patients were women. 114 patients were using Dimethyl-Fumarate, 236 were on Fingolimod, 263 were on Ocrelizumab, and 47 were using Natalizumab. Among female patients using Dimethyl Fumarate, no increase in liver function tests with age was observed (p<0.05). For patients using Fingolimod, male gender is a risk factor for lymphopenia (especially < 50). The first low lymphocyte counts of women had a trend to be lower than men at all ages. The degree of lymphopenia was corralted with the risk of clinical infections and female gender was a risk factor for infections for Fingolimod group. Pulse rates were similar in all age groups after the initial use of Fingolimod. In patients using Ocrelizumab, the risk of neutropenia was corralted to infection risk, and it was higher among younger patients. Ocrelizumab induced lymphopenia was observed more in men aged 30-39. No differences were found according to age and gender in patients using Natalizumab. 

Contrary to expectations, the use of DMDs in older patients was not always associated with a worse side effect profile. The changing characteristics of the immune system with age might be responsible for this.