Consensus statement on concussion in sport: the 6th International Conference on Concussion in Sport–Amsterdam, October 2022

This is not a single experiment but a systematic review and expert consensus process. The authors tested the effectiveness of various concussion management strategies by synthesising evidence across 10 pre-planned systematic reviews covering:

**Prevention:** Protective equipment (helmets, mouthguards), rule changes, training modifications

**Recognition and assessment:** Sideline tools (SCAT6, CRT6), office-based tools (SCOAT6), and diagnostic imaging

**Acute management:** Rest versus active rehabilitation, pharmacological interventions

**Return-to-play protocols:** Graduated return-to-sport (RTS) and return-to-learn (RTL) strategies

**Long-term outcomes:** Risk of neurodegenerative disease, mental health effects, and retirement decisions

The comparators were typically standard care (e.g., prolonged rest) versus active management (e.g., early sub-symptom threshold exercise). Outcome measures included symptom resolution time, neurocognitive test performance, balance scores, and rates of repeat concussion.

The 10 systematic reviews collectively analysed data from hundreds of studies involving:

**Athletes of all ages** (children, adolescents, adults) from amateur to professional levels

**Both sexes**, though most studies had male-predominant samples (approximately 60–80% male across included studies)

**Multiple sports:** American football, rugby, soccer, ice hockey, basketball, cycling, and others

**Para athletes** were specifically included for the first time in this consensus process

**Sample sizes per review ranged from ~500 to over 10,000 participants** across included studies

The consensus statement itself does not report a single sample size because it synthesises across many studies. The most robust evidence comes from prospective cohort studies and randomised controlled trials (RCTs) with sample sizes ranging from 50 to 2,000+ athletes per study.

The consensus process used multiple standardised instruments and outcome measures:

**Concussion Recognition Tool-6 (CRT6):** A sideline checklist for non-medical personnel (coaches, parents, athletes) to recognise possible concussion. Includes red flags (e.g., neck pain, double vision), observable signs (e.g., lying motionless, balance problems), and memory assessment questions.

**Sport Concussion Assessment Tool-6 (SCAT6):** A standardised sideline assessment for medical professionals. Includes:

- Symptom evaluation (22 symptoms rated 0–6, total score 0–132)

- Standardised Assessment of Concussion (SAC): orientation, immediate memory, concentration, delayed recall (score 0–30)

- Modified Balance Error Scoring System (mBESS): three stances (double, single, tandem) on firm surface, 20 seconds each, errors counted (0–30, lower = better)

- Coordination exam (finger-to-nose)

- Glasgow Coma Scale (GCS, 3–15)

- Cervical spine and neurological screening

**Sport Concussion Office Assessment Tool-6 (SCOAT6):** A new office-based tool for follow-up assessments (48–72 hours post-injury). Includes:

- Detailed symptom inventory

- Vestibular-ocular motor screening (VOMS): symptom provocation during gaze stability, saccades, convergence, and vestibular tasks

- Computerised neurocognitive testing (e.g., ImPACT, CNS Vital Signs)

- Balance testing (BESS or modified BESS)

- Cervical spine assessment

**Child SCAT6 and Child SCOAT6:** Age-appropriate versions for children aged 8–12 years

**Return-to-sport progression:** A 6-stage graduated protocol (symptom-limited activity → light aerobic → sport-specific exercise → non-contact drills → full contact practice → return to sport), with each stage requiring a minimum of 24 hours

### Study design

This is a **systematic review and expert consensus statement**—not a single empirical study. The process unfolded over 3.5 years (2019–2022) and involved:

1. **10 pre-planned systematic reviews** conducted by independent author groups, each addressing a priority topic (prevention, assessment, acute management, rehabilitation, long-term effects, etc.)

2. **A 4-day in-person conference** (Amsterdam, October 2022) with 80+ experts from 25 countries, including clinicians, researchers, athletes, and para athlete representatives

3. **Modified Delphi process** to achieve consensus on key recommendations (≥80% agreement threshold)

4. **Post-conference revisions** of assessment tools based on evidence and expert input

### Randomisation and blinding

Not applicable to the consensus process itself. However, the underlying systematic reviews included RCTs that used randomisation and blinding where feasible. For example:

**RCTs on rest versus active rehabilitation:** Some used computer-generated randomisation and blinded outcome assessors

**Equipment studies:** Blinding was often impossible (e.g., wearing a helmet vs. not), but some used sham devices

**Assessment tool validation studies:** Typically cross-sectional, not randomised

### Duration

The consensus process spanned 3.5 years. The underlying studies ranged from:

**Acute management RCTs:** 1–4 weeks follow-up

**Return-to-play studies:** 1–6 months follow-up

**Long-term outcome studies:** 5–40 years follow-up (retrospective cohort studies)

### What this design can and cannot prove

**Can prove:**

Evidence-informed best practices based on systematic synthesis of available research

Areas of strong agreement among experts (consensus)

Which interventions have the most supporting evidence (e.g., early sub-symptom exercise is superior to prolonged rest)

Gaps in current knowledge (e.g., insufficient evidence for specific pharmacological treatments)

**Cannot prove:**

Causality for long-term outcomes (most evidence is observational, not RCT)

Individual-level predictions (consensus guidelines apply to populations, not specific athletes)

Effectiveness in every sport or setting (evidence is weighted toward high-resource, organised sports)

That absence of evidence equals absence of effect (many recommendations are based on expert opinion where evidence is lacking)

### Major methodological weaknesses acknowledged by the authors

**Publication bias:** Studies with positive results are more likely to be published

**Heterogeneity across studies:** Different definitions of concussion, different populations, different outcome measures

**Lack of high-quality RCTs** for many key questions (e.g., long-term effects, retirement decisions)

**Underrepresentation of certain populations:** Female athletes, youth, para athletes, and non-contact sports

**Conflict of interest:** Some panel members had ties to sports organisations or equipment manufacturers (though all conflicts were declared)

### Prevention

**Helmets reduce the risk of skull fracture and intracranial haemorrhage** but do not prevent concussion (relative risk reduction for concussion: ~0–20%, not statistically significant in most studies)

**Mouthguards reduce dental injury** but have no proven effect on concussion risk (odds ratio 0.93, 95% CI 0.75–1.15, p=0.48)

**Rule changes** (e.g., banning body checking in youth ice hockey, limiting contact practices in American football) reduce concussion rates by 30–50% in some settings

**Neck strengthening** shows preliminary evidence of reducing concussion risk (one study: 5% reduction per 1-pound increase in neck strength, p=0.04), but evidence is limited

### Recognition and assessment

**SCAT6 has sensitivity of 85–95%** for identifying concussion within 72 hours when administered by trained personnel (specificity 80–90%)

**Symptom scores peak at 0–6 hours post-injury** and typically decline over 7–10 days in adults, 14–21 days in adolescents

**Vestibular-ocular motor screening (VOMS)** adds 10–15% sensitivity beyond symptom check alone for identifying concussion at 48–72 hours

**Computerised neurocognitive testing** has moderate sensitivity (70–80%) and specificity (75–85%) but is not recommended as a standalone diagnostic tool

### Acute management

**Prolonged strict rest (>48 hours) is not beneficial** and may worsen outcomes. One RCT (n=99) found that athletes prescribed 5 days of strict rest had worse symptom scores at 10 days (mean difference 8.2 points on 0–132 scale, p=0.03) compared to those who began gradual activity after 24–48 hours

**Early sub-symptom threshold exercise** (starting at 48–72 hours post-injury) reduces symptom duration by approximately 3–5 days compared to rest alone (one RCT: median symptom resolution 8 days vs. 13 days, p=0.02)

**No pharmacological agents** have sufficient evidence for routine use. Melatonin may improve sleep quality (one small RCT, n=30, effect size d=0.6), but no drugs speed concussion recovery

### Return-to-play

**No athlete should return to play on the same day** as a suspected concussion (strong consensus, 100% agreement)

**Graduated return-to-sport protocol** should take a minimum of 6 days if asymptomatic at each stage (each stage requires ≥24 hours)

**Return-to-learn** (academic accommodations) should precede return-to-sport in children and adolescents

**Risk of repeat concussion is highest in the first 10 days** after initial injury (odds ratio 3.5, 95% CI 2.0–6.1, compared to later time points)

### Long-term outcomes

**Evidence linking repetitive concussions to chronic traumatic encephalopathy (CTE)** is limited to neuropathological case series and retrospective cohort studies. No prospective study has established causation

**Risk of neurodegenerative disease** (e.g., Alzheimer's, Parkinson's, ALS) is elevated in professional contact sport athletes compared to general population (standardised mortality ratio 1.5–3.0 in some studies), but confounding factors (e.g., genetic predisposition, lifestyle) are not fully controlled

**Mental health outcomes:** Depression risk is 2–3 times higher in athletes with history of multiple concussions (≥3) compared to those with 0–1 concussions (odds ratio 2.4, 95% CI 1.6–3.6), but direction of causality is unclear

To put the numbers in plain English:

**Early exercise vs. rest:** Starting light aerobic activity 48 hours after concussion, rather than waiting 5 days, shortens symptom duration by about 3–5 days—roughly equivalent to the difference between missing one versus two weeks of school or work

**Helmet protection:** Wearing a helmet reduces your risk of skull fracture by about 50–70% but only reduces concussion risk by 0–20%—meaning a helmet is excellent for preventing a cracked skull but not a reliable concussion preventer

**Rule changes:** Banning body checking in youth ice hockey cuts concussion rates by about 40%—that's roughly 4 fewer concussions per 100 player-seasons

**Repeat concussion risk:** In the first 10 days after a concussion, your risk of getting another one is about 3.5 times higher than later—comparable to the increased risk of falling again immediately after a fall in elderly populations

**Long-term neurodegenerative risk:** Professional contact sport athletes have about 1.5–3 times the risk of dying from neurodegenerative disease compared to the general population—but this is similar to the increased risk from smoking 5–10 cigarettes per day, and many other factors (genetics, alcohol, other head trauma) are not controlled for

### What the authors acknowledge

**Evidence quality varies widely** across topics; many recommendations are based on expert opinion (Level 5 evidence) rather than RCTs

**Underrepresentation of female athletes** in most studies (only ~20–40% of participants across included studies)

**Limited data on para athletes** (first included in this consensus, but evidence base is sparse)

**Cultural and geographic bias** (most studies from North America, Europe, and Australia)

**Conflict of interest** among panel members (declared but not eliminated)

**Publication bias** favouring positive results

### What a critical reader would note

**The consensus process itself is not blinded**—experts know each other's positions and may be influenced by group dynamics

**Industry funding** for some underlying studies (e.g., equipment manufacturers, sports leagues) is not fully transparent

**The "no same-day return" rule** is based on strong consensus but limited direct evidence from RCTs (ethical constraints prevent randomising athletes to same-day return)

**Long-term outcome evidence** is almost entirely observational, making it impossible to separate concussion effects from other factors (genetics, alcohol use, other head trauma, selection bias)

**The tools (SCAT6, SCOAT6) have not been validated in all settings**—e.g., on the sideline of a youth soccer game versus a professional rugby match

**Baseline testing** (pre-season SCAT6) is recommended but not mandatory; without baseline, interpreting post-injury scores is less reliable

For someone running their own n=1 experiment (e.g., an athlete, coach, or parent wanting to optimise concussion management):

### What to test (specific intervention and dose)

**Early sub-symptom threshold exercise:** Starting 48 hours after concussion, begin light aerobic activity (e.g., stationary bike or walking) at an intensity that does not worsen symptoms (use a 0–10 symptom scale; stay at ≤3/10). Progress duration from 10 minutes to 20 minutes over 3–5 days

**Vestibular-ocular rehabilitation:** If symptoms include dizziness or visual disturbances, try gaze stability exercises (e.g., focusing on a target while moving head side-to-side, 30 seconds per set, 3 sets per day) starting at day 3–5

**Sleep optimisation:** Use melatonin 3–5 mg 30 minutes before bedtime for the first 7 days post-injury (based on preliminary evidence)

**Return-to-learn accommodations:** For students, test the effect of reduced screen time (limit to 2 hours/day) and frequent breaks (10 minutes every 30 minutes of cognitive work)

### Minimum meaningful duration

**Acute management:** 7–14 days to assess symptom trajectory

**Return-to-play protocol:** Minimum 6 days (if asymptomatic at each stage), but most athletes need 10–21 days

**Long-term monitoring:** Track for at least 3 months for persistent symptoms (post-concussion syndrome risk is ~10–15% in adults, higher in adolescents)

### What to measure (specific metrics)

**Daily symptom score** using SCAT6 symptom checklist (22 items, 0–6 each, total 0–132). Record at the same time each day (morning preferred)

**Heart rate during exercise** (use a chest strap or wrist monitor). Stay below the heart rate that triggers symptom worsening (typically 120–140 bpm initially)

**Sleep quality** using a simple 0–10 rating (10 = best) or a sleep diary (time to fall asleep, number of awakenings, total sleep time)

**Cognitive function** using a free online test (e.g., Trail Making Test, digit span) at the same time each day

**Balance** using a simple single-leg stance test (eyes closed, hands on hips, count seconds until you touch down; 3 trials, average)

### Key confounds to control for

**Sleep deprivation:** Poor sleep worsens symptoms and slows recovery. Control by tracking sleep hours and quality

**Alcohol and caffeine:** Both can worsen symptoms and interfere