New Danish Study Tracks Who Recovers From Whiplash and Why

Post-traumatic neck pain, commonly known as whiplash-associated disorder, affects hundreds of thousands annually worldwide and carries enormous human and economic costs. While most patients recover, 15–25% experience moderate-to-severe symptoms and functional impairment one year after injury, placing them at risk of leaving the labour market. A 2008 estimate placed European insurance claims alone at $500 million. Despite this burden, early prediction and targeted intervention remain underdeveloped, motivating this new Danish prospective cohort study.

The study will recruit 100 adults (≥18 years) presenting to one of three emergency departments in Denmark within 72 hours of an accident causing neck pain. Baseline assessment combines self-reported measures (pain intensity via Neck Disability Index, disability, sleep quality, post-traumatic stress) with objective biomarkers including heart rate variability (HRV), resting heart rate, respiration monitoring, and hair cortisol for retrospective pre-trauma stress estimation. Quantitative sensory testing and cervical range of motion will also be performed. Follow-up occurs at 3, 6, and 12 months post-trauma, supplemented by register data on labour market participation and healthcare utilisation.

A central focus is validating two existing clinical prediction tools—Australia's WhipPredict (using age, NDI score, and hyperarousal symptoms) and Denmark's DWGRAS (based on neurological symptoms, pain severity, and cervical range of motion)—in a European acute-care context where neither has been extensively tested. The study will also explore whether adding HRV measurements improves predictive accuracy. Prior neurobiological research supports HRV as a marker of autonomic dysregulation; low HRV has been associated with post-traumatic stress disorder (PTSD) development, and one prior study found that HRV measured 2 days post-accident identified 72% of those who later developed PTSD.

Hair cortisol, reflecting cumulative cortisol secretion over weeks to months, will serve as a measure of pre-trauma stress—testing the hypothesis that pre-existing stress vulnerabilities moderate long-term recovery outcomes. Health economic analyses will compare costs between recovered and non-recovered groups (NDI <10% vs >32%) at 12 months. Statistical approaches include ROC curve analysis, logistic regression with and without biomarkers, and moderation analysis.

The sample size of 100 is justified for regression analyses; a minimum of 80 participants (accounting for 25% dropout) is needed to detect an AUC of 0.80 with 90% power based on an estimated 15% chronicity rate. The study is registered (NCT06176209) and ethically approved. If prediction tools prove effective, clinician workshops will be organised. Results will be published regardless of outcome, advancing the evidence base for early, personalised care in whiplash.