Mediation Analysis Between Brain Age, Disease-Modifying Factors, and Disability and Cognitive Performance in Multiple Sclerosis

BACKGROUND AND OBJECTIVES: The brain-predicted age difference (brain-PAD) is considered a marker of neurodegeneration in people with multiple sclerosis (pwMS) and is associated with greater disability and cognitive impairment. However, the impact of disease-modifying factors (DMFs) on brain-PAD remains unknown, as does the extent to which their effect on disability and cognition is mediated through brain-PAD. The goal of this study was to investigate this in pwMS using a same-age cohort to eliminate calendar age as a confounding factor. METHODS: -scores. DMFs included lifetime smoking, alcohol consumption, physical activity, diet, leisure, and educational level, as well as body mass index (BMI) at 18 years. The effect of DMFs on brain-PAD was examined using linear regression, adjusting for sex. Mediation analyses were performed to investigate to what extent brain-PAD is a mediator of DMF effects on disability and cognition. RESULTS: = 0.034). DISCUSSION: DMFs unrelated to MS, particularly smoking, alcohol use, and BMI at 18 years, accelerate brain aging. Brain-PAD mediates these effects and contributes to worsening disability and cognition, underscoring the potential of lifestyle interventions to mitigate neurodegeneration and preserve function in pwMS.