Factors associated with pain-related functional interference in people with chronic low back pain enrolled in a physical exercise programme: the role of pain, sleep, and quality of life.

The study is cross-sectional, so it cannot prove that pain, sleep, or quality of life cause functional interference; it only shows they are associated. The participants were all able to perform physical exercise and were enrolled in a specific programme, so the findings may not apply to people with chronic low back pain who are too disabled to exercise. The sample size was relatively small (99 participants), which limits the generalisability of the results to the broader chronic low back pain population. Physical activity levels were measured using a self-report questionnaire (IPAQ), which can be prone to overestimation due to recall bias.

The authors declared no conflicts of interest. The work was funded by the Spanish Ministry of Science, Innovation and Universities, the Grünenthal Foundation, and the Biomedical Research and Innovation Institute of Cadiz.

Do not interpret the association between weak opioid use and lower functional interference as evidence that opioids improve function. This is an observational finding in people already enrolled in an exercise programme, and the study did not measure the causal effect of the medication on disability.