Objectives: To assess sleep quality, and its associations with physical function, cardiorespiratory fitness, and spinal mobility, in axial spondyloarthritis (axSpA) patients.
Method: Baseline data from the Exercise for Spondyloarthritis trial were used. Assessments included [Pittsburgh Sleep Quality Index (PSQI), 0-21, 21 = worst], performance-based physical function [Ankylosing Spondylitis Performance Index (ASPI), seconds, higher = worse], patient-reported physical function [Bath Ankylosing Spondylitis Functional Index (BASFI), 0-10, 10 = worst], cardiorespiratory fitness [peak oxygen uptake (O2peak), mL/kg/min, lower = worse], and spinal mobility [Bath Ankylosing Spondylitis Metrology Index (BASMI), 0-10, 10 = worst]. Associations were examined in separate models using multiple linear regression.
Results: Ninety-nine patients with axSpA were included, 53% female, mean age 46 years, and 72% with high disease activity (ASDAS-C-reactive protein ≥ 2.1), of whom 84 (85%) had reduced sleep quality. Sleep disturbance was most frequently reported (65%), followed by poor subjective sleep quality (53%), daytime dysfunction (41%), and increased sleep latency (41%). Positive associations were observed between PSQI and ASPI [β = 0.10, 95% confidence interval (CI) 0.01, 0.19] and PSQI and BASFI (β = 0.85, 95% CI 0.51, 1.20), and there was an inverse association between PSQI and O2peak (β = -0.14, 95% CI -0.27, -0.01), adjusted for age and sex. There was no association between PSQI and BASMI.
Conclusion: Reduced sleep quality was common in axSpA patients with moderate to high disease activity. Better sleep quality was associated with better physical function and higher cardiorespiratory fitness. There was no association between sleep quality and spinal mobility.
Trial registration: ClinicalTrials.gov NCT02356874.