Early comorbidities and diagnostic challenges in people with multiple sclerosis with possible impact on disease...

Comorbidities in people with multiple sclerosis (PwMS) can affect disease course and quality of life.

To investigate comorbidities in the five years after diagnosis, timing of comorbidity occurrence, age and sex effects, and differences between multiple sclerosis (MS) and other chronic autoimmune diseases (AIDs).

In this retrospective cohort study, we systematically assessed differences in diagnosis frequencies in newly diagnosed PwMS (n = 9,880) compared to matched controls (noAID, n = 29,640) and individuals with other AIDs (psoriasis, n = 29,640; Crohn's disease, n = 9,880).

Some comorbidities of PwMS are similarly frequent in other AIDs, while others, such as depression, are more prevalent in PwMS (odds ratio (OR) vs noAID = 2.03(1.94-2.13)). We found that personality disorders are more frequently recorded in PwMS before (OR  = 1.34(1.21-1.49)) and after MS diagnosis (OR  = 1.32(1.16-1.5)), especially in women (OR  = 1.39(1.2-1.6)). PwMS are more frequently diagnosed with Lyme disease (OR  = 1.98(1.69-2.33)), which was predominantly recorded by general practitioners after presentation with neurological symptoms. We observed lower acute tonsillitis frequencies in PwMS (OR  = 0.8(0.75-0.85)).

Our results suggest that PwMS might have a generally increased risk for specific personality disorders. More frequent Lyme disease recordings for PwMS suggest misdiagnoses of MS symptoms. Lower tonsillitis frequencies suggest a link between MS and protection from specific infections.