Tanuja Chitnis, MD, Brigham and Women’s Hospital, Boston, MA, outlines the details of a recently published study investigating the association between serum neurofilament light (sNfL) levels and age at different stages of multiple sclerosis (MS). sNfL has recently emerged as a promising biomarker of disease activity in MS, but it is influenced by several factors, including age. 94 patients were assessed during remission and after a gadolinium-enhancing (Gad+) lesion. Once adjusted for treatment use and sex, the models generated demonstrated a positive association between age and sNfL level during remission but a negative association after a Gad+ lesion, suggesting younger patients have a greater rise in sNfL levels in response to a Gad+ lesion. This interview took place during the ACTRIMS Forum 2021.