Body mass index as a predictor of MS activity and progression among participants in BENEFIT.

Background: There is a lack of studies on the association between obesity and conversion from a clinically isolated syndrome (CIS) to multiple sclerosis (MS).
Objective: The aim of this study was to determine whether obesity predicts disease activity and prognosis in patients with CIS.
Methods: Body mass index (BMI) at baseline was available for 464 patients with CIS in BENEFIT. Obesity was defined as BMI ⩾ 30 kg/m ² and normal weight as 18.5 ⩽ BMI < 25. Patients were followed up for 5 years clinically and by magnetic resonance imaging. Hazard of conversion to clinically definite (CDMS) or to 2001 McDonald criteria (MDMS) MS, annual rate of relapse, sustained progression on Expanded Disability Status Scale (EDSS), change in brain and lesion volume, and development of new brain lesions were evaluated.
Results: Obese individuals were 39% more likely to convert to MDMS (95% CI: 1.02-1.91, p  = 0.04) and had a 59% (95% CI: 1.01-2.31, p  = 0.03) higher rate of relapse than individuals with normal weight. No associations were observed between obesity and conversion to CDMS, sustained progression on EDSS or magnetic resonance imaging (MRI) outcomes, except for a larger reduction of brain volume in obese smokers as compared to normal weight smokers (-0.82%; 95% CI: -1.51 to -0.12, p  = 0.02).
Conclusion: Obesity was associated with faster conversion to MS (MDMS) and a higher relapse rate.