The National Football League is just now coming to grips with a degenerative brain disease called CTE (chronic traumatic encephalopathy). It is commonly found in athletes that participate in contact sports with concussive injuries.
The scientists don't have a lot of data to understand how early in life these changes in the brain occur. It could be happening in peewee football or it may take years of repeated trauma. They don't have any tests yet that can diagnose it except for post mortem autopsy.
There has also been a lot of study recently about early onset dementia associated with hearing loss. Apparently when you can't hear very well your brain uses all of it's ram to assemble sounds into words.
What I am curious about is whether or not we will one day find a correlation between brain disease and CNC machinery. The high frequency motors sound a lot like electronic mosquitos. The sound is very jarring. Whenever I am around a CNC machine my ears seem to ring for a bit when I leave the environment. Is it possible that extended exposure to CNC might also have neurological health effects?