Patients with ankylosing spondylitis (AS) do not have a higher prevalence of obstructive sleep apnea (OSA) than comparable control participants; However, patients with AS and OSA have higher body mass index (BMI), are older, and have less chest expansion, suggesting more severe AS, according to study results published in Clinical Rheumatology.
Researchers attempted to examine the prevalence of OSA in patients with AS compared to control subjects, and to assess whether disease-related and non-disease-related factors were associated with the development of OSA in patients with AS.
Radiological changes in the spine were assessed based on the modified Stoke Ankylosing Spondylitis Spinal Score (mSASSS). Additional ratings 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 on the fourth intercostal level. High sensitivity CRP, erythrocyte sedimentation rate, and blood lipid levels were also measured.
Patients with AS were enrolled in the backbone study, with control subjects enrolled from Sweden’s nationwide CardioPulmonary BioImage Study (SCAPIS). For each of the participants with AS, 4 control participants were matched according to age, gender, height and weight. OSA was defined as an apnea-hypopnea index (AHI) of at least 5 events per hour.
A total of 63 of 155 patients with AS were assessed with home sleep monitoring during one night; 179 controls were assigned to 46 patients between the ages of 45 and 70 years.
A total of 47.8% (n = 22) of the patients with AS vs. 50.8% (n = 91) of the control participants had OSA (P = 0.72). No differences in sleep measurements were observed in patients with AS compared to controls.
Additionally, 39.7% (n = 25/63) of patients with AS who had fully completed sleep monitoring at home had an OSA and 14.3% (n = 9/63) of them had OSA syndrome that as AHI from at. a minimum of 5 events per hour combined with an Epworth Sleepiness Scale (ESS) of 10 or higher was defined.
Patients with AS with vs without OSA had higher mSASSS, BASMI, BASFI, and ESS scores and less breast expansion.
One of the limitations of the study was the lack of the gold standard for diagnosing sleep disorders (i.e., polysomnography).
The researchers concluded, “The patients [with AS] with OSA had more daytime sleepiness, a higher BMI, were older and, above all, had less breast expansion, which reflects a more severe AS disease compared to patients without OSA. These are the most important factors to consider when identifying OSA in patients with AS. “
Wiginder A, Sahlin-Ingridsson C, Giejer M, Blomberg A, Franklin KA, Forsblad-d’Elia H. Prevalence and factors associated with sleep apnea in ankylosing spondylitis. Clin Rheumatol. Published online September 28, 2021. doi: 10.1007 / s10067-021-05924-z