Prevalence of comorbidities in Multiple Sclerosis and impact on physical disability according to disease phenotypes.

BACKGROUND: Comorbidities are prevalent among Multiple Sclerosis (MS) patients. Few studies have characterized their prevalence and impact in Latin American populations. OBJECTIVE: We aim to assess the prevalence of comorbidities and their impact on the risk of physical disability across different MS phenotypes. METHODS: Cross-sectional multicenter study of patients under regular clinical care at the Programa de Esclerosis Múltiple UC and Hospital Dr. Sótero del Río in Chile. Prevalence of comorbidities was estimated from the retrospective assessment of electronic medical charts. Disease phenotypes were categorized into two groups: clinically isolated syndrome/relapsing-remitting (inflammatory group) and primary/secondary progressive MS patients (progressive group). A multivariable analysis using binary logistic regression for assessing the risk of EDSS ≥ 6.0 in each group was performed. RESULTS: A total of 453 patients was included, 71% female, mean age at onset 31 years, mean disease duration 10 years, and median EDSS 2.0 (range 0-10). In the whole sample, most prevalent comorbidities were ever-smoking (42.2%), depression/anxiety (34.9%), thyroid disease (15.7%), hypertension (11.3%) and insulin resistance/type 2 diabetes mellitus (11.0%). When assessing the risk of EDSS ≥ 6, in the inflammatory group (N = 366), age at onset (OR 1.06, 95%CI(1.02-1.11), p = 0.008), disease duration (OR 1.06, 95%CI(1.00-1.12), p = 0.039) and epilepsy comorbidity (OR 5.36, 95%CI(1.33-21.5), p = 0.018) were associated with a higher risk of disability. In the progressive group (N = 87), disease duration was a risk factor (OR 1.08 95%CI(1.02-1.16), p = 0.014), while shorter diagnostic delay (OR 0.91 95%CI(0.85-0.99), p = 0.025) and insulin resistance/type 2 diabetes mellitus comorbidity were protective factors (OR 0.18 95%CI(0.04-0.83), p = 0.028), 72% of these patients were receiving metformin. CONCLUSIONS: Comorbidities are common across different MS disease phenotypes. Epilepsy seems particularly related with a higher risk of physical disability in relapsing-remitting patients, while the role of insulin resistance/type 2 diabetes mellitus or the impact of metformin use as a protective factor should be further studied. Prospective and larger studies are still needed in order to assess the real impact of comorbidities and their management in MS outcomes.