Background Fatigue is a common symptom and an indicator of disease activity in AS, but its pathogenic basis is poorly understood.1 It is also a cardinal symptom of OSA.2 AS may contribute to OSA through reduction of upper airway size (10% involvement of temporomandibular joints-TMJ), cervical spine (CS) involvement leading to cord or medulla compression, or chest wall involvement leading to poor respiratory pattern.
Objectives Assessment of the prevalence of OSA in AS and its association with fatigue.
Methods 22 consenting, random AS out-patients were prospectively recruited. 3 did not attend for assessment. 19 patients [16 males, 3 females; age 43.7 years (31–69)] were assessed using: full clinical examination, Body Mass Index (BMI), Chest, CS and TMJ x-rays, Bath Ankylosing Spondylitis Activity Index (BASDAI), Hospital Anxiety and Depression Scale (HAD), Epworth Sleepiness Scale (ESS), Bed Partner Questionnaire, full Lung Function Tests, sleep studies (2 consecutive nights using EDEN Trace).
Results 11 patients had normal lung function, 6 had a typical and 2 a borderline restrictive pattern. ESS: mean 10 (2–20). 2 patients (10%) fulfilled criteria for OSA: one had retrognathia, the other no obvious cause. Both received CPAP therapy with great improvement in fatigue and Epworth Sleepiness Scale and normalisation of oximetry. There were no associations with AS duration or activity, HAD, CS involvement, TMJ involvement or BMI.
Conclusion OSA affects 2% of the general population.3 Its prevalence in AS appears higher, but no definite conclusions can be drawn from this study. In isolated AS cases, OSA may be an important contributor to fatigue and, in the presence of relevant symptoms, it should be actively investigated and treated.
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