Sleep Quality, Pain, Worry, and Rumination in Fibromyalgia: Results from Mediation Analyses

Background/Objectives: Fibromyalgia (FM) is a chronic pain syndrome frequently associated with severe pain, sleep disturbances, worry, and depressive rumination. Although previous studies have shown links among these factors, no study has specifically examined the mediating role of sleep disturbances in the relationship between forms of Repetitive Negative Thinking (i.e., worry and rumination) and pain intensity. This study aimed to investigate whether sleep disturbances mediate the relationship between: (1) worry and pain intensity and (2) depressive rumination and pain intensity. Methods: An online cross-sectional survey was conducted with a sample of 867 Italian adults who reported having received an FM diagnosis from a rheumatologist or pain physician. After screening, 733 participants (97.3% female; mean age = 51.0 ± 9.95 years) were included in the analyses. Participants completed the Penn State Worry Questionnaire, the Ruminative Response Scale, the Brief Pain Inventory, and the Pittsburgh Sleep Quality Index. Mediation analyses were performed using Hayes' PROCESS macro (Model 4). Results: Depressive rumination was associated with pain intensity both directly (B = 0.021, 95% Confidence Intervals [CIs] 0.012, 0.030) and indirectly through sleep disturbances (B = 0.014, 95% CIs 0.010, 0.020), indicating partial mediation. In contrast, worry showed no direct effect on pain intensity (B = 0.011, 95% CIs -0.003, 0.025) but demonstrated a significant indirect effect via sleep disturbances (B = 0.018, 95% CIs 0.012, 0.025), consistent with full mediation. Conclusions: Pain intensity, sleep quality, worry, and depressive rumination are interrelated in FM. Depressive rumination plays a particularly strong role in pain perception, independent of sleep quality. Interventions that integrate cognitive-behavioral and metacognitive strategies with sleep-focused treatments may help improve both sleep and pain outcomes in individuals with FM.