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

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

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

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.

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).

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.