NEFL and neurodegenerative disease: Elevated levels of NfL in biofluids are considered a strong biomarker for the rate of neuronal turnover, e.g. due to death and degeneration (Wilke et al., 2022b; Benatar et al., 2023; Wilke et al., 2022a,b); therefore, NfL has been investigated as a biomarker in individuals affected by neurodegenerative diseases.