In ataxic SCA3 patients, both age (0.012 log pg/ml per 1‐year increase; 95% CI 0.002, 0.022; p = 0.022) and number of CAG repeats (0.034 log pg/ml per 1‐repeat increase; 95% CI 0.004, 0.064; p = 0.025) accounted only for 4.2% of the variability in NfL. This evidence concerns the gene NEFL and Spinocerebellar ataxia type 3.