title: Comorbidity increases the risk of hospitalizations in multiple sclerosis.
abstract: OBJECTIVE
  We aimed to evaluate the association between comorbidity and rates of hospitalization in the multiple sclerosis (MS) population as compared to a matched cohort from the general population.
  
  
  METHODS
  Using population-based administrative data from the Canadian province of Manitoba, we identified 4,875 persons with MS and a matched general population cohort of 24,533 persons. We identified all acute care hospitalizations in the period 2007-2011. Using general linear models, we evaluated the association between comorbidity status and hospitalization rates (all-cause, non-MS-related, MS-related) in the 2 populations, adjusting for age, sex, and socioeconomic status.
  
  
  RESULTS
  Comorbidity was common in both cohorts. Over the 5-year study period, the MS population had a 1.5-fold higher hospitalization rate (adjusted rate ratio [aRR] 1.56; 95% confidence interval [CI] 1.44-1.68) than the matched population. Any comorbidity was associated with a 2-fold increased risk of non-MS-related hospitalization rates (aRR 2.21; 95% CI 1.73-2.82) in the MS population, but a nearly 4-fold increase in hospitalization rates in the matched population (aRR 3.85; 95% CI 3.40-4.35). Comorbidity was not associated with rates of hospitalization for MS-related reasons, regardless of how comorbidity status was defined.
  
  
  CONCLUSIONS
  In the MS population, comorbidity is associated with an increased risk of all-cause hospitalizations, suggesting that the prevention and management of comorbidity may reduce hospitalizations.
authors.affiliation: From the Departments of Internal Medicine (R.A.M., J.M., M.C., A.T., N.Y.) and Community Health Sciences (R.A.M., L.E.), University of Manitoba, Winnipeg, Canada. rmarrie@hsc.mb.ca.
authors.forename: Ruth Ann
authors.initials: RA
authors.lastname: Marrie
authors.affiliation: From the Departments of Internal Medicine (R.A.M., J.M., M.C., A.T., N.Y.) and Community Health Sciences (R.A.M., L.E.), University of Manitoba, Winnipeg, Canada.
authors.forename: Lawrence
authors.initials: L
authors.lastname: Elliott
authors.affiliation: From the Departments of Internal Medicine (R.A.M., J.M., M.C., A.T., N.Y.) and Community Health Sciences (R.A.M., L.E.), University of Manitoba, Winnipeg, Canada.
authors.forename: James
authors.initials: J
authors.lastname: Marriott
authors.affiliation: From the Departments of Internal Medicine (R.A.M., J.M., M.C., A.T., N.Y.) and Community Health Sciences (R.A.M., L.E.), University of Manitoba, Winnipeg, Canada.
authors.forename: Michael
authors.initials: M
authors.lastname: Cossoy
authors.affiliation: From the Departments of Internal Medicine (R.A.M., J.M., M.C., A.T., N.Y.) and Community Health Sciences (R.A.M., L.E.), University of Manitoba, Winnipeg, Canada.
authors.forename: Aruni
authors.initials: A
authors.lastname: Tennakoon
authors.affiliation: From the Departments of Internal Medicine (R.A.M., J.M., M.C., A.T., N.Y.) and Community Health Sciences (R.A.M., L.E.), University of Manitoba, Winnipeg, Canada.
authors.forename: Nancy
authors.initials: N
authors.lastname: Yu
mesh_terms: D000328:Adult; D015897:Comorbidity; D005260:Female; D006760:Hospitalization / Q000706:statistics & numerical data*; D006801:Humans; D008297:Male; D008350:Manitoba / Q000453:epidemiology; D008875:Middle Aged; D009103:Multiple Sclerosis / Q000453:epidemiology*; D012306:Risk