did you even read? the bulk happened at collegiate level

also there are studies on this

McKee et al. (2023) – Neuropathologic and Clinical Findings in Young Contact Sport Athletes Exposed to Repetitive Head Impacts (JAMA Neurology) [https://jamanetwork.com/journals/jamaneurology/fullarticle/2...]

Alosco et al. (2017) – Age of First Exposure to Tackle Football and Later-Life Cognitive Impairment and Neuropsychiatric Symptoms (Translational Psychiatry) [https://doi.org/10.1038/tp.2017.197]

even intl football headers have concerns