The Danish Child and Adolescent Musculoskeletal Pain (ChiBPS) Cohort: Protocol for a Prospective Nationwide Cohort Study in General Practice

Musculoskeletal (MSK) pain in adolescents is much more persistent than commonly appreciated. It has previously been described as a self-limiting condition, but several studies indicate otherwise. In a cohort study of 564 11-year olds with weekly MSK pain, 50% of the participants still reported pain after one year. Prospective cohort studies of adults in general practice show that 16-32% of patients with knee pain still have pain after a year. In accordance with this, Kastelein et al. found that 21% of 12 to 35-year-old patients had knee pain six years after initial general practitioner (GP) contact. Collectively, these studies highlight that a significant proportion of adolescents will continue to report pain even years after the initial onset of pain.

Can the adolescents with a high risk of MSK pain at follow-up be investigated? Our recent systematic review on children and adolescents with MSK pain indicates that female sex, depression, anxiety, and parental pain are associated with a higher risk of MSK pain at follow-up. However, the validity of these prognostic factors may be questioned as they have been tested in single cohorts and not validated in new external cohorts. Moreover, in accordance with our results, other studies identify emotional problems, psychological symptoms, and frequent exercise associated to a higher risk of MSK pain at follow-up. Given the paucity of high-quality evidence for prognostic factors in childhood and adolescent MSK pain, robust studies are needed to further explore prognostic factors in this population. The investigators want to follow up on this need and conduct a cohort study with a similar aim as in their review; to investigate prognosis in youth MSK pain. In this cohort study, the investigators will limit their participant group to those who are 8-19 years old, because the participants have to be able to provide self-reported data on a questionnaire. Participants aged 0-7 years will not be included as they will have difficulties in doing so and because they i) only represent 2% of all patients consulting GPs in Denmark, with a musculoskeletal complaint and ii) were sparsely represented in our systematic review which included a total of 23.933 patients.

At present we lack age-specific prognostic factors in adolescents with MSK pain, although multiple prognostic factors have been identified in adult MSK pain. One systematic review found that higher pain severity upon presentation to the GP, longer pain duration, multiple-site pain, anxiety and/or depression, higher somatic perceptions and/or distress, low social support, higher baseline disability, and greater movement restriction were all associated with a poor prognosis. Systematic reviews on adult knee pain suggest an association between low/middle education level, non-skeletal comorbidity, duration of knee symptoms of > 3 months, bilateral knee symptoms, self-reported warm knee, history of non-traumatic knee symptoms, valgus alignment and an unfavorable prognosis. Similar to findings in patients with adult low back pain, there was high evidence that fear-avoidance beliefs and meagre social support at work were associated with an poor prognosis.

If future studies are to tailor and target treatment for the adolescents with the highest risk of long-standing MSK pain, there is a need to identify prognostic factors for an unfavorable prognosis. The aim of this prospective cohort study is to identify the most important prognostic factors for adolescents with MSK pain in general practice.