Sleep quality and its clinical correlates in axial spondyloarthritis: a cross‑sectional study with exploratory mediation modelling.

OBJECTIVE: Sleep disturbance is common in axial spondyloarthritis (axSpA) and is associated with impaired quality of life. However, the relationships between disease burden and sleep impairment remain incompletely understood. We studied the prevalence of poor sleep quality in patients with axSpA and examined the clinical and psychological factors associated with sleep disturbance. PATIENTS AND METHODS: A cross‑sectional study of 119 patients fulfilling the ASAS 2009 classification criteria for axSpA at a tertiary care centre in India. Sleep quality was assessed using the Pittsburgh Sleep Quality Index (PSQI) and daytime sleepiness via the Epworth Sleepiness Scale (ESS). Disease activity, functional status and spinal mobility were evaluated using the Bath Ankylosing Spondylitis Disease Activity Index (BASDAI), Ankylosing Spondylitis Disease Activity Score (ASDAS‑CRP), Bath Ankylosing Spondylitis Functional Index (BASFI) and Bath Ankylosing Spondylitis Metrology Index (BASMI). Psychological status was assessed using the Hospital Anxiety and Depression Scale (HADS). Associations between clinical variables and sleep quality were evaluated using correlation and multivariable regression analyses. Exploratory mediation modelling was performed to examine indirect statistical associations among disease characteristics, psychological variables, cervical mobility, and sleep quality. RESULTS: Sixty‑three patients (52.9%) were classified as poor sleepers. Poor sleep quality was significantly associated with higher disease activity, greater pain and fatigue, worse functional status and poorer quality of life. Depression and anxiety demonstrated strong associations with sleep impairment and remained independent predictors of higher PSQI scores in multivariable analysis. Daytime sleepiness was higher in poor sleepers compared to good sleepers (6.71 ± 2.11 vs. 3.52 ± 1.13, p < 0.001). Exploratory mediation modelling suggested that the indirect relationship between longer disease duration and poorer sleep quality was associated with higher levels of depression (ACME = 0.11), anxiety (ACME = 0.07), and reduced cervical rotation (ACME = 0.21). CONCLUSION: Poor sleep quality is common in axSpA and is closely associated with both disease burden and psychological distress. Depression and anxiety were strongly associated with sleep impairment. Our findings highlight the need for a comprehensive management approach in axSpA that includes attention to psychological wellbeing in addition to control of inflammatory disease activity.