The relationship between contact sports and CTE is a lot like smoking and lung cancer: the more exposure, the greater the risk. In science, that’s called a dose-response relationship. Recent research found that NFL players with long careers face a 4x higher risk of developing dementia. What makes this finding especially striking is the magnitude of the association compared with other recognized risk factors, including lead exposure and severe traumatic brain injury (TBI). As the science advances, one message is clear: exposure matters. Understanding the long-term risks of repetitive head impacts is critical to protecting athletes at every level.