What is CTE and how does it differ from concussion?

CTE (chronic traumatic encephalopathy) is a progressive neurodegenerative disease caused by repetitive head trauma — not necessarily concussions with loss of consciousness, but the cumulative load of sub-concussive hits over time. Concussion is a single acute brain injury event; CTE is the disease that may develop over years from repeated sub-threshold impacts. It can only be definitively diagnosed post-mortem by examining brain tissue. Symptoms during life include memory problems, mood disturbance, impulsivity, and depression — but these overlap with many other conditions, which is why lifetime diagnosis remains a research challenge. There is currently no blood test or scan that can diagnose CTE with certainty in a living person.

Should children stop playing contact sport because of CTE risk?

The evidence on CTE risk in children and adolescents is less developed than in professional athletes, and current guidance from Australian sporting bodies generally focuses on minimising contact in training, using proper technique, and age-appropriate rule modifications rather than recommending avoidance altogether. What the current evidence supports most clearly is the importance of reducing the frequency of sub-concussive hits — particularly in training — and ensuring any concussion is properly assessed and goes through graduated return-to-play before full contact is resumed. The risk is real; it is also not simple, and structured sport has documented physical and mental health benefits that matter.

70% of head impacts in practice: what CTE research means for Australian sport

What just happened

Two pieces of CTE data surfaced this week, and together they reframe a question that Australian sport has been circling for years: where, exactly, is the problem occurring?

A study analysing head impacts in NFL players found that 70 per cent of impacts during the football season occurred in practice, not in games. This is a meaningful reframe. Most public discussion about head injury in sport focuses on game collisions — the visible hits, the high-impact tackles seen on television. The volume data says most of the cumulative trauma load is accumulating quietly, in training sessions, where cameras are rarely present and no referee is watching.

Separately, post-mortem analysis of brain tissue donated by NFL players and their families found signs of CTE — chronic traumatic encephalopathy — in approximately one in four players. CTE is a progressive brain disease caused by repetitive head trauma that can only be confirmed by examining brain tissue after death. There is no diagnostic blood test, no imaging biomarker, no way to identify it with certainty in a living person.

These findings are from American football in the United States. They are not Australian data, and applying NFL findings directly to AFL, rugby league, or rugby union requires care. But the underlying mechanism — repetitive sub-concussive head impacts causing cumulative brain change — is not specific to any sport or country.

Both-and

The selection bias that matters

The one-in-four figure for CTE in donated NFL brains is not the same thing as one-in-four NFL players having CTE. The brains that reach research centres are donated by families who typically seek donation because their loved one showed neurological symptoms — memory loss, mood disturbance, impulsivity, depression — during life. That is a systematically skewed sample. It over-represents the symptomatic end of the distribution.

Large systematic studies have attempted to correct for this. The research continues to find that former contact-sport athletes are at elevated risk of neurodegenerative disease compared to age-matched controls who did not play contact sport, and that risk appears to scale with years of play and cumulative exposure to head impacts. But the magnitude of risk for recreational-level players — the suburban AFL footballer, the weekend rugby forward, the junior NRL player — is genuinely less well characterised than the professional data suggests.

This is an important distinction for clinical conversations. The biology is the same; the exposure dose is different. A player who takes ten thousand sub-concussive hits in a professional career is in a different risk category from someone who plays district football for ten seasons and retires at 35. Conflating the two leads to advice that is either too alarming or dismissively reassuring.

What the 70 per cent practice finding actually changes

The policy implication of finding that most head impacts occur in training rather than games is direct: reducing full-contact activity in practice sessions could meaningfully reduce total career head impact exposure without changing the game itself. Some sports have already moved in this direction — limiting full-contact practice days, restricting certain blocking and tackling drills, scaling back pre-season contact volumes. If 70 per cent of the exposure is happening in training, training-level changes are where the leverage is.

Australian football codes have made incremental changes over the past decade — high-contact rules in AFL, modified tackle rules in junior NRL competitions, age-grade modifications in rugby union. Whether these changes have measurably shifted the concussion and long-term brain injury burden is still being studied.

The sub-concussive hit problem is harder to regulate than visible concussions, because there is no immediate symptom. A player who is repeatedly hit in tackling drills without ever losing consciousness, without showing concussion signs, is accumulating exposure that current monitoring systems are not designed to capture. This is what makes the training-session finding significant: it identifies where unmonitored exposure is occurring at scale.

Where CTE comes up in general practice

The CTE conversation arrives in general practice in a few specific ways. A parent asks directly after reading a story like this one and wants to know whether to let their child play contact sport. A former professional athlete presents in middle age with unexplained mood changes, memory difficulties, or impulsivity that has been attributed to everything except head injury history. An adolescent who has had three concussions wants to know whether to continue playing.

The honest clinical position in each case is that the science is real, the risk is not fabricated, but quantifying individual risk for a non-professional player is not yet possible with precision. The research that exists comes predominantly from professional athletes with career-level exposure. Recreational-level risk in adults, and risk in adolescents, is less well mapped.

What general practice can offer: accurate information about what the evidence actually says and does not say; clear guidance that any concussion warrants proper assessment and graduated return-to-play before contact resumes; and — for patients with a significant concussion history and new cognitive or mood symptoms — appropriate neurological referral and documentation of head injury history as part of the clinical picture.

My two cents

The 70 per cent practice finding is the more actionable number from this week’s research. It reframes where the problem is occurring and, by implication, what kinds of regulatory changes would move the dial. Game rules are televised and enforced. Training-room rules are coach-dependent, largely unmonitored, and historically more resistant to change.

For families making decisions about children in contact sport: the risk is real and the conversation is legitimate, but it is not binary. Structured sport — even contact sport played at appropriate intensity for age and development — carries documented benefits for physical fitness, mental health, social connection, and resilience. The question is whether the sport being played has adopted sensible contact-in-training rules, uses appropriate age-grade modifications, and has a clear and enforced return-to-play protocol after any head impact that shows symptoms.

If those things are in place, the risk profile is different from a sport where full-contact training happens daily and concussions are walked off without assessment.

Verdict: yes — the 70 per cent practice finding is a meaningful reframe, not a recycled CTE alarm. For Australian GPs the relevance is in the sport-safety conversations that are already arriving in consulting rooms.

Sources cited

CTE study finds 70pc of head impacts happening in sports practice. ABC News, 26 August 2026. https://www.abc.net.au/news/2026-08-26/cte-study-finds-one-in-four-nfl-players-had-brain-disease/107078502