High prevalence of comorbidities at diagnosis in immigrants with multiple sclerosis.

BACKGROUND: Multiple sclerosis (MS) has been associated with certain comorbidities in general population studies, but it is unknown how comorbidity may affect immigrants with MS.

OBJECTIVE: To compare prevalence of comorbidities in immigrants and long-term residents at MS diagnosis, and in matched control populations without MS.

METHODS: We identified incident MS cases using a validated definition applied to health administrative data in Ontario, Canada, from 1994 to 2017, and categorized them as immigrants or long-term residents. Immigrants and long-term residents without MS (controls) were matched to MS cases 3:1 on sex, age, and geography.

RESULTS: There were 1534 immigrants and 23,731 long-term residents with MS matched with 4585 and 71,193 controls, respectively. Chronic obstructive pulmonary disease (COPD), diabetes, hypertension, ischemic heart disease, migraine, epilepsy, mood/anxiety disorders, schizophrenia, inflammatory bowel disease (IBD), and rheumatoid arthritis were significantly more prevalent among immigrants with MS compared to their controls. Prevalence of these conditions was generally similar comparing immigrants to long-term residents with MS, although COPD, epilepsy, IBD, and mood/anxiety disorders were less prevalent in immigrants.

CONCLUSION: Immigrants have a high prevalence of multiple comorbidities at MS diagnosis despite the "healthy immigrant effect." Clinicians should pay close attention to identification and management of comorbidity in immigrants with MS.