The strongest weighted protein in the brain aging model was neurofilament light chain (NEFL; Fig. 2f), which increases with age and is a clinical biomarker of neurodegeneration that is often measured in clinical trials for Alzheimer’s disease10,11 and was recently approved as a surrogate endpoint for a clinical trial to treat superoxide dismutase 1 amyotrophic lateral sclerosis (SOD1-ALS)12,13. Here, NEFL is linked to amyotrophic lateral sclerosis.