Late-onset multiple sclerosis in Isfahan, Iran.

BACKGROUND Multiple sclerosis (MS) typically affects young adults; however, the first symptoms can occur after age 50 and is classified as late-onset MS (LOMS).  METHODS In this retrospective study, we extracted the records of 3522 MS patients (2716 females and 806 males) registered in the Isfahan MS Society (IMSS) from 2003 to 2010. Next, we searched for LOMS cases. We aimed to compare these cases with 1698 non-LOMS subjects also extracted from the IMSS database. RESULTS We found 48 LOMS patients (28 females and 20 males), which gave a crude frequency of 1.36%. The frequency by sex of LOMS in males (2.4%) was significantly greater than in females (1.0%, P = 0.002). The mean age at onset was 55.1 ± 4.3 years. The female to male ratio of 1.4:1 in these patients was significantly lower than in non-LOMS subjects (3.37:1, P = 0.003). The leading pattern of MS was relapsing-remitting (RR) in 62.5%, followed by primary progressive (PP) in 27.1%, and secondary progressive (SP) in 10.4%. Predominant presenting symptoms and signs were motor disturbances (35.4%), followed by brainstem (25%), optic neuritis (22.9%), and sensory related deficits (18.7%). The mean progression index (PI) in LOMS patients (0.88 ± 0.48) was significantly higher than in non-LOMS cases, 0.37 ± 0.17 (P < 0.0001). DISCUSSION In comparing LOMS patients with the non-LOMS cohort, there was a higher frequency of the PP pattern and a higher PI in the LOMS group. In comparing other high-risk populations with the Isfahan cohort, LOMS formed a lower percentage of the total Isfahan MS population.