There has been a lot of recent press regarding the presence of cognitive impairment and even dementia in NFL players who have suffered repeated head trauma and concussions.
But this is not a new story. Indeed, the observation that head trauma could cause dementia was first made in the 1920s when the term "dementia pugilistica" was coined to describe the occurrence of dementia in boxers who suffered repeated head trauma. In the modern era, head trauma (particularly with loss of consciousness) was recognized as a risk factor for Alzheimer's disease more than 25 years ago.
Other studies have shown that head trauma is associated with increased amyloid production and neurofibrillary tangles, the classic pathological hallmarks of Alzheimer's disease, providing a scientific basis for the relationship. This makes sense; beta-amyloid is probably produced in the brain in response to injury, and the "tangles" are markers of neuronal injury.
Like other chronic diseases, there are multiple risk factors for cognitive decline and dementia from Alzheimer's disease. Head trauma from any source, including all forms of athletics, is very likely one of these. Preventing head trauma, especially the kind associated with concussions, could help to prevent Alzheimer's disease.