Can 6-minute walk test predict severity of obstructive sleep apnea syndrome?

Background: When considering the benefits of the 6-min walking test (6-MWT) in research fields and the need of treatment for moderate to severe obstructive sleep apnea (OSA) patients, research in this field is of great advantage and may have a significant role in therapeutic grounds. Methods: This cross-sectional study was conducted on 47 patients with confirmed diagnosis of OSA in the National Research Institute of Tuberculosis and Lung Disease, Masih Daneshvari Hospital. The 6-MWT was performed the day after polysomnography. The correlation between the 6-MWT and paraclinical findings during polysomnography in OSA patients was investigated. Results: In cases with moderate to severe OSA, the male sex displayed correlation with high PCO2. Ages of patients examined displayed reversed correlation with the distance in the 6-MWT by observing the O2 saturation (Sat) at the end of the 6-MWT, displaying direct correlation with the duration of O2 Sat <90% during sleep. The BMI also showed reversed correlation with the distance in the 6-MWT. Similarly, the severity of the OSA had reversed correlation with the expected distance in the test. However, patients with higher duration of O2 Sat <90% during sleep had a higher reduction in O2 Sat during and after the 6-MWT. Patients with higher duration of O2 Sat <90% during sleep also completed less overall distance in the 6-MWT (P values <0.05 for all). Conclusion: It appears that the 6-MWT can be used in patients with OSA to predict severity of the desaturation in OSA beyond functional capacity. Also, it can help predict the severity of disease and assist in follow up of the OSA patients in terms of functional capacity and selection of the most appropriate treatment strategy to increase the physical ability of the patients.