Development and validation of a model predicting post-traumatic headache six months after a motor vehicle collision in adults

Importance: The prognosis of post-traumatic headache is poorly understood.

Objective: To develop and validate a prognostic model to predict the presence of post-traumatic headache six months after a traffic collision in adults with incident post-traumatic headache.

Design: Secondary analyses of adults with incident post-traumatic headache injured in traffic collisions between November 1997 and December 1999 in Saskatchewan, Canada (development cohort); and between January 2004 and January 2005 in Sweden (validation cohort).

Setting: The Saskatchewan cohort (development) was population-based (N = 4162). The Swedish cohort (validation) (N = 379) were claimants from two insurance companies covering 20 % of cars driven in Sweden in 2004.

Participants: All adults injured in traffic collisions who completed a baseline questionnaire within 30 days of collision. Excluded were those hospitalized >2 days, lost consciousness >30 min, or reported headache <3/10 on the numerical rating scale. Follow-up rates for both cohorts were approximately 80 %.

Predictors: Baseline sociodemographic, pre-injury, and injury factors.

Outcome: Self-reported headache pain intensity ≥3 (numerical rating scale) six months after injury.

Results: Both cohorts were predominantly female (69.7 % in Saskatchewan, 65.2 % in Sweden), with median ages 35.9 years (Saskatchewan), and 38.0 years (Sweden). Predictors were age, work status, headache pain intensity, symptoms in arms or hands, dizziness or unsteadiness, stiffness in neck, pre-existing headache, and lower recovery expectations. With a positive score (i.e., ≥0.75 probability), the model can rule in the presence of post-traumatic headache at six months (development: specificity = 99.8 %, 95 % CI 99.5 %-99.9 %; sensitivity = 1.6 %, 95 % CI 1.0 %-2.6 %; positive likelihood ratio (LR+) = 8.0, 95 % CI 2.7-24.1; negative likelihood ratio (LR-) = 1.0, 95 % CI 1.0-1.0; validation: specificity = 95.5 %, 95 % CI 91.1 %-97.8 %; sensitivity = 27.2 %, 95 % CI 20.4 %-35.2 %); LR+ = 6.0, 95 % CI 2.8-13.2; LR- = 0.8, 95 % CI 0.7-0.8).

Conclusions and relevance: Clinicians can collect patient information on the eight predictors of our model to identify patients that will report ongoing post-traumatic headache six months after a traffic collision. Future research should focus on selecting patients at high risk of poor outcomes (using our model) for inclusion in intervention studies, and determining effective interventions for these patients.

Keywords: Craniocerebral trauma; Neck injuries; Post-traumatic headache; Prognosis.