Multiple sclerosis (MS) is associated with increased incidence and prevalence of some comorbidities including vascular disease and mood disorders. Although immigrants have lower incidence of MS than long-term residents in Ontario, Canada, comorbidity burden was associated with increased MS risk in immigrants.
To compare prevalence of individual comorbidities in immigrants and long-term residents at MS diagnosis, and in matched control populations without MS.
We identified incident cases of MS aged 20-65 years using a validated case definition applied to health administrative data in Ontario, Canada from 1994-2017. Incident MS cases were categorized as immigrants or long-term residents. We identified two control populations of immigrants and long-term residents without MS matched 3:1 on sex, age and rurality status to MS cases. We identified comorbidities at MS diagnosis using validated administrative case definitions applied to the three years before MS diagnosis. We calculated prevalence ratios (PRs) of individual comorbidities for immigrants compared to long-term residents with MS and for both MS groups compared with their respective controls.
There were 1,534 immigrants and 23,731 long-term residents with MS, as well as 4,585 immigrant and 71,193 long-term resident controls without MS. Common comorbidities in immigrants at MS diagnosis included mood or anxiety disorders (27.4%), hypertension (9.1%), and migraines (4.7%). Chronic obstructive pulmonary disease (COPD) (PR 1.68; 95%CI 1.17-2.40), diabetes (PR 2.57; 95%CI 1.86-3.55), ischemic heart disease (IHD) (PR 1.41; 95%CI 1.05-1.90), migraine (PR 2.12; 95%CI 1.73-2.60), epilepsy (PR 2.20; 95%CI 1.32-3.68), and mood/anxiety disorders (PR 1.97; 95%CI 1.78-2.17) were more common in immigrants with MS compared to immigrant controls. These comorbidities were also more common in long-term residents with MS than in long-term resident controls (p<0.05). Immigrants with MS had relatively higher prevalence of diabetes, migraine, and mood/anxiety disorders compared to long-term residents with MS.
Immigrants who develop MS have a high comorbidity burden and are more likely to be affected by comorbidities such as mood/anxiety disorders, migraine, diabetes, COPD, and IHD than other immigrants. Since comorbidities worsen long-term outcomes in MS, clinicians should pay close attention to identification and management of comorbidity in immigrants with MS.