Longitudinal BMI trajectories in multiple sclerosis: Sex differences in association with disease severity

Abstract

Background: Adolescent obesity is a risk factor for multiple sclerosis (MS), but little is known about changes in body mass index (BMI) after MS onset.

Objective: To assess the relationship between MS and longitudinal changes in BMI.

Methods: We analyzed prospectively collected BMIs in a cohort of patients with adult-onset MS and matched adult healthy controls (HC) gathered from the same hospital network central clinical data registry.

Results: We made three main observations. First, at baseline MS patients had a significantly higher BMI than HC (age- and sex- adjusted mean difference=0.57; 95% CI: 0.15, 0.99; p=0.008). Second, a significant age by MS status interaction was observed (p<0.0001), such that in MS, BMIs did not increase significantly higher in older individuals, whereas BMIs in HCs were higher with increasing age. Third, we observed sex-specific associations with disease severity: higher BMI was associated with higher cross-sectional EDSS in women, but with lower EDSS in men (p=0.003, N=758). There were no longitudinal associations between BMI and EDSS in either sex or in the entire cohort (p=0.65, N=772).

Conclusion: After MS onset, patients may not experience age-expected increases in BMI. BMI may have sex-specific associations with MS disability scores. More refined measures of body composition are warranted in future studies to distinguish adiposity from muscle mass.

Keywords: Body mass index; Multiple sclerosis; Obesity; Sex differences.