The increase in risk of dementia or Alzheimer's Disease is anywhere form twice as likely to as much as 18 times more likely. The NFL players with strong histories of concussions develop Alzheimer's at 18 times the normal rate.

pbob, I am glad to see you use the term sub-concussive blows. That is a new term that has been promoted by just a few doctors. These doctors have noticed that many concussion subjects will develop symptoms from minor impacts that do not cause any concussion symptoms at the time of the impact.

They have coined the term sub-concussive because of the lack of immediate symptoms. Their research and direct experience shows that there is substantial damage done by these sub-concussive blows, especially when there are multiples of them.

There is research with soccer players that shows more injury from the many sub-concussive blows of a heading drill than the occasional strong header. Soccer research also shows that soccer players who routinely head the ball have a 10% lower IQ.

The important issue to understand with concussions or other impacts to the head is that they defy logic. The long held belief that degree of impact was directly related to degree of injury has been shown to be wrong. Even length of Loss Of Consciousness (LOC) has minimal impact on degree of injury, except when this LOC leads to a coma. Post Traumatic Amnesia (PTA) also has no direct relationship to degree of injury, especially residual injury.

The recent studies of sports concussions has suggested that only one in ten concussions is reported. Many are so short term in immediate symptoms that they are dismissed by the player as not a concussion.

The NFL is looking at a helmet system that records the impact forces. Dr Robert Thatcher is developing a wearable mini-EEG system that will record the interruptions to brain function. As technology advances, the ability to track concussions is improving.

There are some with hope for a radical cure to injured brains but those with the most understanding of the brain's capabilities to heal are not holding their breath. The direction is heading toward prevention of concussions in sports and early detection so that therapies that stop the cascade of damage can be started. The auto accident insurance industry is fighting to deny concussion as causing long term symptoms but the personal injury attorneys are learning how to win.