Study on the frequency and risk factors of moderate-to-severe sleep apnea syndrome in rheumatoid arthritis

We aimed to investigate the frequency of moderate-to-severe sleep apnea syndrome (SAS) that possibly influences long-term prognosis in patients with rheumatoid arthritis (RA), and to analyze the risk factors for this group.We examined respiratory disturbance index (RDI) by polysomnography in 62 hospitalized RA patients. Risk factors of moderate-to-severe SAS (RDI ≥20) were analyzed using a multivariate logistic regression analysis.RA was complicated by moderate-to-severe SAS in 13/62 (20.9%) cases. The highest stage of temporomandibular joint abnormality (TMJA) and a high value of health assessment questionnaire-disability index (HAQ-DI) were significant risk factors, according to the results of the multivariate logistic regression analysis (p < 0.0001 and p = 0.010, respectively). Contrary to these results, RDI was not related to the disease activity indexes of RA and other clinical characteristics.We clarified that the highest TMJA stage and a high value of HAQ-DI are novel important risk factors for moderate-to-severe SAS in RA patients.