Preliminary results of a study in Danish patients with multiple sclerosis (MS) suggest that inverse comorbidity may exist in the MS population, lowering patients’ risk for other types of diseases. The results were given in an oral presentation, “Inverse comorbidity in multiple sclerosis. Findings in a complete nationwide cohort,” at the 32nd Congress of the European Committee for Treatment and Research in Multiple Sclerosis (ECTRIMS), held in London (Sept. 14-17).
Inverse comorbidity is a concept that defines a lower-than-expected probability of disease (in comparison to the general population) in individuals who have been diagnosed with other medical conditions.
Researchers, in a study financed by the Danish Multiple Sclerosis Society, performed a combined case-control and cohort study using a total nationwide cohort of Danish MS patients, whose clinical disease onset was registered between 1980 and 2005. Each MS case was randomly matched to five healthy individuals (the control group) by gender, year of birth, and municipality on Jan. 1 in the year of MS onset (index date). Following the study population from January 1977 until the index date, and from the index date until December 2012, the team assessed the occurrence of comorbidities (at the individual level) before and after disease onset.
The study included, in total, 8,947 eligible MS cases and 44,735 control cases.
Researchers found a decreased risk for cerebrovascular comorbidity in MS patients when compared to controls before the index date — or date of disease onset — although the findings here didn’t reach the level of statistical significance. After the index date, researchers observed a decrease in the occurrence of chronic lung disease (asthma and chronic obstructive pulmonary disease [COPD]), as well as overall cancer among MS patients. Once again, however, the results did not reach a statistical significance.
Still, findings suggest that MS patients may carry lower risks for cerebrovascular disease before the onset of MS, and a decreased risk for cancers and pulmonary diseases after MS onset, hinting at a trend toward inverse comorbidity in MS patients for certain medical conditions. But the authors state that future studies should confirm this hypothesis.
“Identification of inverse comorbidity and of its underlying mechanisms may provide new important entry points into the understanding of MS,” the team concluded.