['Age at onset (AAO) in multiple sclerosis (MS) is an important marker of disease severity and may have prognostic significance. Understanding what factors can influence AAO may shed light on the aetiology of this complex disease, and have applications in the diagnostic process.', 'The study cohort of 22\u2005162 eligible patients from 21 countries was extracted from the MSBase registry. Only patients with MS aged ≥16\u2005years were included. To reduce heterogeneity, only centres of largely European descent were included for analysis. AAO was defined as the year of the first symptom suggestive of inflammatory central nervous system demyelination. Predictors of AAO were evaluated by linear regression.', 'Compared with those living in lower latitudes (19.0-39.9°), onset of symptoms was 1.9\u2005years earlier for those at higher latitudes (50.0-56.0°) (p=3.83×10'] Is higher latitude significantly associated with an earlier age of disease onset in multiple sclerosis?