Impact of comorbidity on hospitalizations in individuals newly diagnosed with multiple sclerosis: A longitudinal...

It has been suggested that comorbidity in subjects with multiple sclerosis (MS) increases the risk of hospitalizations, although few studies have examined this, and rarely in an incident population.

Incident MS cases were identified retrospectively from administrative data in Saskatchewan, Canada (1996 - 2017) using a validated definition (≥3 hospital, physician or drug claims for MS); the date of the first claim for MS or a demyelinating condition was considered the index date. All hospitalizations occurring after the index were included in the analyses. Comorbidity was defined in 3 ways: any comorbidity (yes/no); a total count of comorbidity (0, 1, or ≥2); and by individual comorbidities. The impact of comorbidity on all-cause hospitalizations was examined with negative binomial regression models fitted with generalized estimating questions. In subjects with at least one hospitalization during the follow-up period, we examined associations between comorbidity and MS-related hospitalizations logistic using regression models fitted with GEE.

Subjects with comorbidity had a higher rate of all-cause hospitalizations compared to those without any comorbidity (aRR 1.72; 95% CI: 1.48-1.99); comorbidity did not increase the odds of having an MS-specific hospitalization (aOR 0.76; 95% CI: 0.59-0.99). Individual comorbidities including diabetes, ischemic heart disease, chronic lung disease, epilepsy, and mood disorders increased the rate of all-cause hospitalizations, but had little impact on MS-related hospitalizations. A longer disease duration was associated with decreased all-cause and MS-specific admissions.

Comorbidity increased the rate of all-cause, but not MS-specific, hospital admissions. Hospitalization rates were higher during the earlier stages of MS. Therefore, recognizing and managing comorbidity in the MS population, especially early in the disease course, will likely have the biggest impact on reducing overall hospital admissions.