Comorbidities Do Not Increase Odds of Multiple Sclerosis–Specific Hospitalizations

What relationship does the existence of comorbidities have on multiple sclerosis-related hospitalizations?

Recognizing and managing comorbidity in the multiple sclerosis (MS) patient population, especially in their early disease, likely will reduce hospital admissions for these patients, according to a paper published in Multiple Sclerosis and Related Disorders.

Investigators from Canada conducted a retrospective cohort study in Saskatchewan in order to examine the risk of comorbidity on hospitalizations in 2275 MS patients. They said that the idea had been suggested, but there are only few studies to verify this idea — especially not in an incident population. The investigators gathered incident MS cases between 1996 and 2017 and identified every hospitalization that occurred after the date for the first claim of MS or a demyelinating condition. They assessed the link between comorbidity and MS-related hospitalizations in the patients with at least 1 hospitalization within the follow-up period, which was about 8.7 years.

The investigators centered on 8 specific comorbidities in their analysis: hypertension, diabetes, hyperlipidemia, ischemic heart disease, chronic lung disease, migraine, epilepsy, and mood and anxiety disorders (depression, anxiety and bipolar disorder were grouped together). They based these 8 on their prevalence or relevance to MS, they said.

Comorbidities were identified a year prior to the index MS date, then reevaluated every year throughout the follow-up period. Once a comorbidity was identified, it was considered prevalent throughout the follow-up period.

During the study period, the investigators identified 3312 hospitalizations in about half of the MS patients. They also found that over half of the cohort had at least 1 existing comorbidity at their index date, most commonly: mood and anxiety disorders (26%), hypertension (16%), migraine (14%), and chronic lung disease (13%).

Having any comorbidity increased the rate of all-cause hospitalization, the study authors found. This remained true whether the MS patients had a comorbidity at MS index or it was acquired over the study period. The number of comorbidities also increased the rate of hospitalizations in a dose-response manner, the study authors added.

However, the presence of any comorbidity did not increase the odds of having an MS-specific hospitalization, the study authors learned. An increase in the number of comorbidities was associated with lower hospitalization rates, they added.

The only comorbidity to be associated with MS-specific hospitalization rates was hypertension, which was associated with 33% lower odds of an MS-related hospitalization, the study authors said.

All-cause hospitalization also increased with age, more than doubling in MS patients over the age of 60 years compared to those under 40, the study authors said. On the other hand, MS-related hospitalizations were more likely to occur in younger adults, they added, and rates decreased consistently with increasing age. Finally, a hospitalization prior to the index date was significantly associated with an increased rate of all-cause hospitalizations, they said, but not MS-specific hospitalizations.

“Comorbidity increases the rate of all-cause hospitalizations, but appears to have little impact on MS-related hospital admissions,” the study authors concluded. “We also observed increased hospitalization rates during the earlier stages of MS, when the disease is typically more active. These findings highlight the importance of recognizing and managing comorbidity in the MS population, especially early in the disease course, as this will likely have the biggest impact on reducing overall hospital admissions.”


Al-Sakran 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 Relat Disord. 2020; 5(40). doi: 10.1016/j.msard.2020.101955.