Does combining the STarT Back Tool with a polygenic risk score for chronic low back pain improve prediction of work disability over two years?

Chronic back pain (CBP) is a leading cause of work disability worldwide, yet identifying individuals at risk remains difficult due to its multifactorial etiology. This study investigated whether integrating a polygenic risk score (PRS) for CBP with the STarT Back Tool (SBT)--a widely used psychosocial screening instrument--could improve the prediction of work disability, measured as disability leave days over a two-year follow-up. We analysed data from 1,938 participants in the Northern Finland Birth Cohort 1966 with complete genotyping, SBT responses, and registry-linked disability records. A zero-inflated negative binomial regression model was applied to account for the highly skewed distribution of work disability days. Results showed that both SBT and CBP genetic risk independently predicted the cumulative number of disability leave days. While SBT was also associated with the likelihood of having no disability leave, CBP genetic risk was not, suggesting that polygenic risk contributes specifically to the burden of disability among affected individuals. Participants in the highest CBP genetic risk quartile experienced significantly more work disability days, supporting a dose-response relationship. The two tools captured complementary domains: SBT reflected modifiable biopsychosocial risks, while the PRS represented fixed genetic liability. This distinction supports the value of integrating a CBP PRS into existing screening frameworks, particularly for early CBP management.