A newly published study has provided further evidence linking participation in American football with a degenerative neurological condition called Chronic Traumatic Encephalopathy (CTE), which is thought to be triggered by repeated blows to the head. Initially referred to as "punch drunk syndrome" due to its prevalence among boxers, CTE occurs when repeated head trauma leads to an accumulation of tau proteins in the brain, and sets in motion a progressive degradation of brain tissue.

Symptoms of the condition, which include memory loss, confusion, aggression, depression and – eventually – progressive dementia, have been known to manifest themselves anywhere from months to decades after the last occurrence of brain trauma.

The research, which analyzed the brains of 202 deceased American football players, displayed a staggeringly high percentage of CTE occurrences, including a 99 percent diagnosis rate for athletes who had played in the NFL.

The brains used in the study make up what is known as a convenience sample, meaning that they were selected due to necessity and accessibility rather than under a more targeted scientific criteria. In this case, the samples were drawn from a brain bank created to store the brains of individuals who had repeatedly suffered head trauma, and so would be useful to studies of CTE.

Of the brains used in the study, two belonged to individuals who played pre-high school level football, 14 high-school, 53 college level, 14 semi-professional players, 8 Canadian Football League (CFL) players, and 111 NFL players.

The team analyzed the sample brains, applying a stringent set of neuropathological criteria to determine whether an individual had suffered from CTE, and to what extent. The effort was informed where possible by medical questionnaires and forms completed by the deceased before they passed.

It was discovered that 177 of the 202 subjects (87 percent) suffered from various stages of CTE. Whilst no pre-high school subjects, and only 3 high-school players exhibited the condition, an alarming 48 (91 percent) college players, 9 semi-professionals, 7 CFL players, and all but one of the NFL athletes were posthumously diagnosed with the condition.

The paper lists many symptoms of CTE that affected the deceased players. For example, of the 84 participants diagnosed with severe CTE, 89 percent had behavioral or mood issues, 95 percent exhibited cognitive symptoms, and 85 percent showed signs of dementia.

The findings themselves, though possibly alarming due to the percentage of individuals found to be affected by the condition, are of no great surprise. Previous research has established a solid link between American football and brain injury, and the NFL has acknowledged the link between participation in the sport and CTE.

It is also worth noting that the study itself is to be approached with a degree of caution. Whilst the research does serve to further strengthen the link between playing American football and CTE, it is important to remember where the brains used in the study came from.

The public has been made very aware of the health risks linked to American football. It is possible that the study was saturated with football players that suffered from CTE because the kin that donated the brains for study knew of the condition, and suspected it to be an element of the passing of their relative. Therefore, the sample brains used in the study may not be representative of American football players in general.

Sadly, the fact remains that, no matter how much money is poured into the development of safer helmets, or the number of rules put in place to protect against needless hits, head trauma will always be a serious and troubling aspect of the sport. Studies such as the one highlighted above play a significant role in highlighting the dangers to prospective players, and advancing our understanding of CTE.