Understanding the complex relationship between sleep and pain symptoms in people with chronic musculoskeletal pain -...

Although chronic musculoskeletal pain and sleep disturbances are often viewed as bi-directionally linked, intervention studies show only small effects of sleep-specific interventions on pain. This suggests a more complex relationship in which only certain sleep parameters may be causally relevant, while other factors such as depression or fatigue may confound the association. Network analysis is a promising statistical approach to disentangle the complex relationships between sleep and chronic musculoskeletal pain variables by identifying key associations between specific variables while accounting for others. This pre-registered study applied Gaussian Graphical Models to examine the complex network linking subjective sleep and pain variables in a sample of 1536 individuals with chronic musculoskeletal pain. Additionally, network structures were compared across subgroups with widespread pain and comorbid insomnia disorder versus controls to identify relevant differences. The results showed eleven direct associations between sleep and pain variables, all very weak (regularized partial correlation coefficients ≤0.07), with no indirect paths involving only one other variable. Findings were mostly comparable across subgroups, with no relevant differences in network structures. These results cautiously challenge the notion that subjective sleep and pain variables are tightly linked. While limitations of the applied methods should be considered, this may partially explain why sleep-focused interventions show only small effects on pain in chronic musculoskeletal pain populations. These findings underscore the need for future studies to apply transparent causal inference methods to move beyond statistical associations and to better understand potential causal relationships between sleep and chronic musculoskeletal pain. PERSPECTIVE: This study is the first to examine sleep-pain links within a complex network in chronic musculoskeletal pain, revealing weaker-than-expected associations. This may (partially) explain why interventions targeting subjective sleep improvements, such as cognitive behavioural therapy for insomnia, often show limited effects on reducing pain.