Change in sex ratio, disease course and age at diagnosis in Oslo MS patients through seven decades

Objectives - To study changes in sex ratio, disease course, time from onset to diagnosis and age at diagnosis by year of birth in a well-defined population of multiple sclerosis (MS) patients. Materials and methods - Based on the Oslo MS Registry patients born from 1910 to 1980 with residence in Oslo at time of diagnosis were studied. Data were analyzed by 10-year intervals based on year of birth. Results - The female to male ratio increased significantly from 1.48 to 2.30 through seven decades. Also, the ratio of initial relapsing-remitting (RR-MS) to primary progressive (PP-MS) disease course increased significantly from 1.93 to 16.00. The time from onset to diagnosis and the mean age at diagnosis declined significantly during the same period. Conclusions - This study shows that there has been a change in MS sex ratio, disease course and age at diagnosis through a period of seven decades, suggesting an environmental factor mainly affecting women at a younger age and causing a RR-MS disease course.