Comorbidity in multiple sclerosis patients from Nordland County, Norway - validated data from the Norwegian Patient Registry

Background: Knowledge of comorbid disorders is important to optimize therapy for multiple sclerosis (MS), but data are limited. The aim of this study was to assess comorbidity in persons with MS living in Nordland County on January 1, 2017. Methods: Data were retrieved from the Norwegian Patient Registry (2008-2017) and validated through review of electronic hospital charts (1970-2017). Comorbidity was defined as any distinct disorder, classified in the International Classification of Diseases (ICD-10), that had existed or occurred after the diagnosis of MS was established. Results: Data from 637 subjects were reviewed, and 97.5% were registered with at least one comorbid condition. Malignant melanoma was found in 0.5%, and non-melanoma skin cancers in 1.9%. In female subjects, breast cancer was found in 3.3%. Hypothyroidism was confirmed in 3.1%, type-1 diabetes in 0.3%, type-2 diabetes in 3.9%, psychosis in 0.6%, epilepsy in 2.8%, myocardial infarction in 1.7%, subarachnoid hemorrhage in 0.2%, cerebral infarction in 0.6%, pulmonary embolism in 0.9%, inflammatory bowel disease in 1.3%, and rheumatoid arthritis in 0.6%. Conclusion: Compared to reports from other Norwegian epidemiological studies, a higher proportion of inflammatory bowel disease and epilepsy was found. This is in accordance with findings from other studies. The prevalence of non-melanoma skin cancers was significantly higher than in the general Norwegian population as they were reported by The Cancer Registry of Norway