Comorbidity and modifiable risk factors in multiple sclerosis.

Multi-system comorbidities are common in patients with multiple sclerosis (PwMS) and significantly influence the disease's presentation and progression. A comorbidity is defined as an illness other than the specific disease of interest (in this case, MS). Generally, chronic or recurrent conditions are included, while transient conditions such as infection or concussion are excluded. Certain modifiable metabolic diseases in PwMS, such as hypertension, diabetes, dyslipidemia, and modifiable health factors such as smoking, alcohol, and obesity, are also considered part of MS comorbidity in this review, since these are risk factors not only for poor outcomes in MS but also for other vascular comorbidities in PwMS. Cohort studies and clinical trials have reported that comorbidity could have multiple adverse effects on MS. The purpose of this review is to summarize studies investigating modifiable risk factors of comorbidity of MS, as well as multiple body system comorbidities in MS, focusing on the influence these comorbidities have on MS outcomes. We aim to emphasize that the management of MS involves not only disease-modifying therapy, but also requires controlling and preventing modifiable risk factors for comorbidities and appropriate treatment of comorbidities, as these interventions may be equally crucial in improving the prognosis of MS.