NEFL and amyotrophic lateral sclerosis: As regards the association of higher sNFL levels with female sex, it is worth mentioning that, in agreement with our study, both a difference in blood (serum or plasma) NFL levels in ALS patients and a smaller difference in NHCs have been previously reported (Lu et al., 2015; Benatar et al., 2020; Simrén et al., 2022).