Increased disease severity in non-Western immigrants with multiple sclerosis in Oslo, Norway

Background and purpose Non-Western immigrants to Norway acquire an increased risk of multiple sclerosis (MS) after migration. Ethnicity and the presence of oligoclonal bands (OCBs) in the cerebrospinal fluid (CSF) might influence the disease course. The aim of this study was to investigate differences in disease severity and in the presence of OCBs in ethnic Norwegian and immigrant MS patients. Methods Clinical data and CSF findings from 47 non-Western immigrants with MS were compared with those from 447 Norwegian and 48 immigrant patients from Western countries. Results The non-Western immigrants had a higher mean Multiple Sclerosis Severity Score (MSSS) than the Norwegian patients (5.68 vs. 4.13, P = 0.001). Age at onset was 4 years lower amongst the non-Western immigrants (P = 0.001). After adjusting for year of birth, age at onset, gender and disease course, the mean difference in MSSS between the groups was 2.17 (P < 0.001). Amongst the non-Western immigrants, 70% received disease-modifying drugs, compared with 48% of the Norwegian patients (P = 0.005). In both groups, 88% were OCB-positive. Conclusions Non-Western immigrants with MS had an increased disease severity compared with native Norwegians and immigrants from Western countries. The presence of OCBs in the CSF was not different between the groups.