For example, a matched case–control study nested in three large prospective US cohorts (the Nurses’ Health Study, the Health Professionals Follow-up Study, and the Multiethnic Cohort Study) revealed that plasma NfL is elevated in individuals who were later diagnosed with ALS, with increases generally being observed 12–24 months before an ALS diagnosis [83]. This evidence concerns the gene NEFL and amyotrophic lateral sclerosis.