Post-traumatic neck pain is common, representing a substantial human and societal burden. About 15%–25% of individuals involved in an accident causing whiplash continue to experience moderate-to-severe symptoms and functional impairment 1 year post-trauma. Factors such as age, high pain intensity, hypersensitivity to pain and early post-traumatic hyperarousal are associated with persistent neck pain. However, multiple questions remain unanswered regarding how best to improve early care. As such, research on recovery patterns (including indicators for health economic burden) and their predictors is still needed, including biomarkers for pre-traumatic and peri-traumatic stress, and the value of early prediction tools.

This prospective cohort study will include 100 participants (≥18 years) suffering from post-traumatic neck pain sustained within 72 hours of an accident. At baseline (a combination of inclusion and 1 week assessment), eligible participants will undergo a thorough evaluation, including assessment of descriptive characteristics, self-reported variables (eg, pain, disability, sleep quality and post-traumatic stress), biomarkers (eg, heart rate variability (HRV) and hair cortisol) and clinical tests (eg, cervical range of motion). Follow-up will be conducted at 3, 6 and 12 months post-trauma. Further, register data (eg, data on labour market attachment) will be added for the period. Among other methods, a receiver operating characteristic (ROC) curve and multivariable regression analyses will be used to evaluate performance and associations of the prediction tools and their associations with measures of HRV.

The sample size calculation is based on previous studies, estimating that 15% of participants will develop moderate-to-severe ongoing symptoms. Using a conservative estimate, 64 participants are needed to achieve a statistical power of 90% with an expected area under the curve of 0.80. Accounting for a 25% loss to follow-up, 80 participants are required. For regression analysis, 100 participants will be included. The prediction tool will be validated using ROC analysis, sensitivity and specificity. Logistic regression models will be performed with and without biomarkers and pain sensitivity. Health economic costs will be compared across groups. Multivariable regression will examine the link between HRV and post-traumatic stress disorder, adjusting for confounders and a moderation analysis will assess hair cortisol as a potential moderator.

The study is approved by the Regional Committee on Health Research Ethics of Southern Denmark (S-20230037). Due to the acute nature of recruitment, the study design does not allow for a 24-hour reflection period; however, this approach has been approved by the Committee.

Study results will be published in peer-reviewed journals and disseminated through non-scientific outlets, including patient and professional publications, press releases and social media. If effective, workshops for clinicians will be organised. Results will be published regardless of outcome, with coauthorships following ICMJE guidelines.

NCT06176209.