Patients with ankylosing spondylitis (AS) do not have a higher prevalence of obstructive sleep apnea (OSA) compared with matched control participants; however, patients with AS and OSA have a higher body mass index (BMI), are older, and have lesser chest expansion, which is reflective of more severe AS, according to study results published in Clinical Rheumatology.
The researchers sought to explore the prevalence of OSA in patients with AS vs control participants, and to evaluate whether disease- and nondisease-related factors were associated with the development of OSA among patients with AS.
Spinal radiographic alterations were scored based on the modified Stoke Ankylosing Spondylitis Spinal Score (mSASSS). Additional assessments included the Bath Ankylosing Disease Spondylitis Activity Index (BASDAI), the Ankylosing Spondylitis Disease Activity Score with C-reactive protein (ASDAS-CRP), the Bath Ankylosing Spondylitis Metrology Index (BASMI), and the presence of metabolic syndrome. Chest expansion was measured at the fourth intercostal level. High-sensitivity CRP, erythrocyte sedimentation rate, and blood lipid levels were measured as well.
Patients with AS were included in the Backbone study, with control participants enrolled from the nationwide Swedish CardioPulmonary BioImage Study (SCAPIS). For each of the participants with AS, 4 control participants were matched for age, sex, height, and weight. OSA was defined as an apnea-hypopnea index (AHI) of at least 5 events per hour.
Overall, 63 of the 155 patients with AS were examined using home-sleep monitoring during 1 night’s sleep; 179 controls were matched with 46 patients aged between 45 and 70 years.
Overall, 47.8% (n=22) of the patients with AS vs 50.8% (n=91) of the control participants had OSA (P =.72). No differences were observed in sleep measurements among patients with AS compared with control participants.
Further, 39.7% (n=25/63) of the patients with AS who fully completed the home sleep-monitoring had OSA and 14.3% (n=9/63) of them had OSA syndrome, which was defined as an AHI of at least5 events per hour combined with an Epworth Sleepiness Scale (ESS) of 10 or higher.
Patients with AS with vs without OSA had higher mSASSS, BASMI, BASFI, and ESS scores, as well as lesser chest expansion.
One of the study limitations was the lack of using the gold standard for diagnosing sleep disorders (ie, polysomnography).
The researchers concluded, “The patients [with AS] with OSA had more daytime sleepiness, had a higher BMI, were older, and, importantly, had also lesser chest expansion, which reflects a more severe AS disease, compared with patients without OSA. These are the most important factors to consider when trying to identify OSA in patients with AS.”
Wiginder A, Sahlin-Ingridsson C, Giejer M, Blomberg A, Franklin KA, Forsblad-d’Elia H. Prevalence and factors related to sleep apnoea in ankylosing spondylitis. Clin Rheumatol. Published online September 28, 2021. doi:10.1007/s10067-021-05924-z