Sleep in ankylosing spondylitis and non-radiographic axial spondyloarthritis: associations with disease activity, gender and mood.

The study aims were to assess the prevalence of good or poor sleep in a cohort of axial spondyloarthritis patients and to investigate its correlation with a range of objectively and subjectively measured variables in order to develop a model for distinguishing good from poor sleepers. Five hundred ninety-eight patients with ankylosing spondylitis and 61 with non-radiographic axial spondyloarthritis completed the Jenkins Sleep Evaluation Questionnaire. Measures of disease activity, mobility, function, mood, fatigue, quality of life, work productivity, night-time pain and general health were gathered. Patients with ankylosing spondylitis or non-radiographic axial spondyloarthritis were initially compared. With the exception of waking up tired less often and having lower mobility and functioning, the two groups were similar so were combined for subsequent analysis. Twenty-nine percent of all patients were classified as good sleepers and 19% as poor sleepers. Poor sleepers had higher disease activity and fatigue scores and more night-time back pain than good sleepers. They reported poorer quality of life, general health, mood and work-related measures. A model incorporating mood, gender, fatigue and objective and subjective judgements of disease activity correctly classified 87.3% of good and poor sleepers. Poor sleep was strongly associated with poor mood, female gender, greater fatigue, greater disease activity (specifically, spinal pain and stiffness) and better mobility; however, the direction of causality between poor sleep and markers of active disease was undetermined. This study also highlights the need to standardise the measurement of sleep disturbance in axSpA to facilitate comparisons between patient groups and interventions.