Abstract
Objective: Somatosensory abnormalities are linked to clinical pain outcomes in individuals with spinal pain. However, a range of factors might confound the relationship between altered somatosensory function and clinical pain outcomes. This systematic review aimed to evaluate the literature to assess the level of evidence of associations between psychological, social, physical activity, and sleep measures and somatosensory function (assessed via sensory psychophysical testing) among individuals with spinal pain. Methods: A comprehensive literature search was performed in 6 electronic databases from their inception to June 2018. Two reviewers independently assessed the methodological quality using a modified Quality in Prognostic Studies (QUIPS) tool and supplemented with recommendations from the Critical Appraisal and Data Extraction for the Systematic Review of Prediction Modelling Studies (CHARMS) checklist and the Quality Assessment of Diagnostic Accuracy Studies (QUADAS-2) tool. The level of evidence was assessed using the Grading of Recommendations, Assessment, Development, and Evaluations (GRADE) system. Data were pooled to evaluate the strength of the relationships of interest. Results: Among the 17 factors identified in the included studies, pain catastrophizing, depression, and pain-related fear have significant negative (small to fair) associations with pain thresholds. A "very low" to "moderate" quality of evidence was found for all the investigated factors. Subgroup analysis showed a smaller effect size for pain catastrophizing/fear of movement and pain thresholds in individuals with low back pain. Conclusions: Psychological factors are associated negatively with pain thresholds and they need to be adjusted when establishing predictive relationships between somatosensory function and pain outcomes in individuals with spinal pain.