Association between chronotype and central sensitization in patients with non-specific low back pain.

Low back pain is a leading cause of disability, with over 85% of cases classified as non-specific (NSLBP). Beyond mechanical causes, central sensitization (CS) has been recognized as a key mechanism in chronic pain. This study investigated the relationship between chronotype (morning, intermediate, evening) and CS severity in NSLBP patients, and whether chronotype is associated with pain intensity and disability. A total of 131 patients (aged 18-65) were assessed using the Morningness-Eveningness Questionnaire (MEQ), Central Sensitization Inventory (CSI), Pain Catastrophizing Scale (PCS), Beck Depression Inventory (BDI), Pittsburgh Sleep Quality Index (PSQI), Visual Analogue Scale (VAS), and Roland-Morris Disability Questionnaire (RMDQ). Three-way ANCOVA (controlling for age, gender, and occupation) revealed that evening-type individuals had significantly higher CSI, PCS, BDI, PSQI, and RMDQ scores (all p < 0.05). Hierarchical regression analysis showed that evening chronotype (β = 0.193, p = 0.004), pain catastrophizing (β = 0.508, p < 0.001), and depressive symptoms (β = 0.435, p < 0.001) were independent predictors of CS severity. These findings suggest that eveningness is associated with more severe central sensitization and adverse psychosocial outcomes in NSLBP. Chronotype may play a role in pain modulation and should be considered in assessment and management strategies.