Comorbid MS Increases General Hospitalization Rates, But Not-MS Specific Rates


New retrospective data suggest that patients with MS who have comorbid conditions have increased all-cause hospital admission rates, especially early in the disease.

Dr Ruth Ann Marrie

Ruth Ann Marrie, MD, PhD, of the College of Medicine at the University of Saskatchewan

Ruth Ann Marrie, MD, PhD

Patients with multiple sclerosis (MS) who have comorbid conditions are more like to have all-cause, but not MS-specific, hospital admissions, particularly early in the disease course, new data suggest.

Compared to their counterparts without comorbidity, those with additional conditions had an adjusted risk ratio of 1.72 (95% CI, 1.48—1.99) for all-cause hospitalizations. Notably, having comorbidity did not increase the risk of having an MS-specific hospitalization (adjusted odds ratio [aOR], 0.76; 95% CI, 0.59–0.99). The data were compiled by Ruth Ann Marrie, MD, PhD, of the College of Medicine at the University of Saskatchewan, and colleagues.

“It has been suggested that comorbidity in subjects with MS increases the risk of hospitalizations, although few studies have examined this, and rarely in an incident population,” they wrote. “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.”

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The individual comorbidities assessed—including diabetes, ischemic heart disease, chronic lung disease, epilepsy, and mood disorders, among others—increased the rate of all-cause hospitalizations, save for hyperlipidemia (aRR 0.85; 95% CI, 0.72—1.02), but overall, they had little impact on MS-related hospitalizations. Hypertension, however, was linked to a 33% lower risk of MS-related hospitalization (aOR 0.67; 95% CI, 0.51–0.88).

Marrie and colleagues retrospectively analyzed 2275 individuals with incident MS from Saskatchewan, Canada, of which 54% had ≥1 comorbidity at the time of diagnosis. Having a hospitalization prior to the index date was significantly associated with an increased rate of all-cause hospitalizations, but not MS-specific hospitalizations.

Overall, the data revealed a decreasing trend for MS-related hospitalizations (−0.050; 95% CI, −0.096 to −0.003; P =0.04), with the rate of 7.2 per 100 persons (95% CI, 3.66—10.73) in 2001 lowering to 3.0 per 100 persons (95% CI, 2.2 – 3.7) in 2017.

“The rate of all-cause hospitalizations increased with age, whereas the odds of an MS-specific hospitalization decreased with age,” they wrote. “Both all-cause and MS-specific hospitalizations decreased with a longer MS disease duration.”

In those over the age of 60 years, all-cause hospitalizations increased compared to those under the age of 40 years (aRR, 2.51; 95% CI, 2.07—3.04). For those who were younger, the risk of MS-related hospitalization was higher, though it decreased over time with age.

Longer disease duration was also associated with lower hospitalization rates, both for all-cause (aRR, 0.93; 95% CI, 0.91—0.94) and MS-specific (aRR, 0.85; 95% CI, 0.83–0.88) hospitalization. Marrie et al. also remarked that a protective effect of disease duration was observed, even in models which they stratified by age.

“It is not clear why comorbidity did not increase the risk of MS-related hospitalizations given that comorbidities are associated with an increase in relapse rates and disability progression,” the authors noted. Although, they detailed that literature has suggested that increased health care contact for the management of comorbidities might aid in improved MS care as well.

“Another possibility is the potential pleiotropic effects of certain medications commonly used to treat comorbid conditions, such as statins and metformin, which have been suggested to have beneficial effects in MS,” they wrote. They concluded that further research into the possible impact of concurrent medications for comorbidities in MS is warranted.


Al-Skaran L, Marrie RA, Blackburn D, Knox K, Evans C. Impact of comorbidity on hospitalizations in individuals newly diagnosed with multiple sclerosis: A longitudinal population-based study. Mult Scler Rel Dis. 2020;40:101955. doi: 10.1016/j.msard.2020.101955.

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