There is some evidence from Wales that multiple blows to the head experienced by rugby players may accelerate the rate of brain ageing and could potentially lead to early dementia.
Dementia fears for rugby players, academic warns. Wales: BBC Wales / BBC Health News, November 18th 2014.
Rugby’s top medic calls for rule change to make game safer. London: BBC News Scotland / BBC Health News, September 21st 2015.
Possibly of interest, over 70 doctors and academics have written to urge schools to ban tackling in rugby:
Sellgren, K. (2016). Doctors urge schools to ban tackling in rugby. London: BBC Health News / BBC Education News, March 2nd 2016.
Beattie, J. (2016). John Beattie meets former rugby players with dementia. London: BBC Health News / BBC Scotland, February 15th 2016.
Beattie, J. (2015). Is rugby bad for my brain? London: BBC Health News / BBC Scotland, September 21st 2015.