Self-reported head trauma predicts poor dual task gait in retired NFL players

Key points

1. 01Higher self-reported head trauma burden was linked to greater dual-task cost to stride time variability, the primary gait outcome
2. 02Players reporting loss of consciousness after a hit had 2.5 times greater dual-task cost to stride time variability than those who did not
3. 03Effects were independent of age, BMI, NFL career length, and history of musculoskeletal surgery
4. 04Single-task (normal) walking was not affected, suggesting cognitive-motor reserve is the sensitive domain
5. 05A validated smartphone app enabled fully remote, home-based gait assessment at scale

How it was conducted

Design

Cross-sectional observational study

Participants

64 retired professional NFL players (mean age 52.7 years, range 29-75) from the Football Players Health Study

Exposure measure

Self-reported symptomatic head trauma score: sum of hits to head or neck followed by any of 11 concussion-related symptoms; also a yes/no variable for loss of consciousness

Gait assessment

Validated smartphone app (TeamStudy) used at home; 45-second normal walking trial followed by 45-second dual-task trial (walking while performing serial subtractions of 3)

Primary outcomes

Dual-task cost to stride time and dual-task cost to stride time variability (coefficient of variation)

Statistical approach

ANOVA by trauma quartile, linear regression (continuous score), and ANOVA by loss-of-consciousness group, all adjusted for age, BMI, NFL seasons, and musculoskeletal surgeries

What they found

• Dual-task cost to stride time variability differed significantly by symptomatic head trauma quartile after adjustment (F=6.0, p=0.001)
• Players in the highest trauma quartile had 9.8 times greater dual-task cost to stride time variability than the lowest quartile (95% CI 3.5-27.9) and 4.4 times greater than the second quartile (95% CI 2.0-9.4)
• Linear regression: higher symptomatic head trauma score predicted greater dual-task cost to stride time variability, adjusted r2=0.20, p=0.003
• Players reporting at least 1 hit followed by loss of consciousness had 2.5 times greater dual-task cost to stride time variability (95% CI 1.6-3.9) than those who did not (adjusted F=4.5, p=0.001)
• Dual-task stride time variability was also greater in the highest 3 trauma quartiles vs the lowest: 1.3 times (95% CI 1.1-1.6), 1.4 times (95% CI 1.2-1.7), and 1.8 times (95% CI 1.5-2.2) respectively (adjusted p=0.03)
• Symptomatic head trauma was not associated with stride time or stride time variability during single-task walking
• Head trauma score was not correlated with age, NFL seasons, or PROMIS physical health (r2<0.02, p=0.30-0.65)
• Higher trauma score correlated with worse PROMIS mental health score (r2=0.09, p=0.01)

Limitations

• Small, self-selected subsample (n=64) who owned an iPhone, likely not representative of all retired NFL players
• Self-reported head trauma relied on recall of events many years in the past, introducing recall and reporting bias
• Cross-sectional design prevents causal inference; longitudinal data are needed
• Serial subtraction performance was not recorded, so cognitive task difficulty could not be controlled or compared across participants

Why it matters

For patients

Former football players who experienced repeated head trauma may develop subtle walking-while-thinking difficulties decades later, even when normal walking seems fine.

For clinicians

Dual-task gait assessment via smartphone can detect cognitive-motor deficits linked to prior head trauma burden, and may be a practical remote screening tool for this population.

For readers

Remote smartphone gait tests sensitive to long-term brain effects of sports-related head trauma could enable large-scale monitoring of at-risk athletes without clinic visits.