Pulmonary Impairment Does Not Limit Exercise Capacity in Patients with Ankylosing Spondylitis with Low Disease Activity

Abstract

ABS TRACT Objective: To evaluate aerobic capacity and pulmonary function in patients with ankylosing spondylitis (AS) and compare these to the healthy controls and to investigate the possible relationship between aerobic capacity, pulmonary function and disease-specific measures. Material and Methods: Fourteen AS patients and 14 healthy controls were included in this prospective study. Clinical disease indices (BASDAI: Bath Ankylosing Spondylitis Disease Assessment Index, BASFI: Bath Ankylosing Spondylitis Functional Index, BASMI: The Bath Ankylosing Spondylitis Metrology Index) were assessed. Participants completed questionnaires assessing physical activity level and quality of life. Aerobic capacity was assessed by submaximal treadmill test with breath-bybreath gas analysis. Aerobic capacity and pulmonary function tests were performed by an ergospirometry system. Results: The results of exercise tolerance test were similar in both groups (VO2max for AS and control group; 40.03±6.11 and 40.28±4.54). AS patients had significantly lower vital capacity (VC) (4.42±0.72 and 5.37±0.72), and forced vital capacity (FVC) (4.36±0.82 and 5.32±0.71) and forced expiratory volume at first second (FEV1) (3.57±0.74 and 4.20±0.58) than healthy controls. Pulmonary function test results were not correlated with the disease duration, chest expansion and other clinical variables. In AS patients, only BASMI score showed significant association with FVC, FEV1, VC and chest expansion. No association between aerobic capacity and pulmonary function test variables, chest expansion, BASDAI, BASMI, BASFI was observed. There was no significant difference between groups in terms of physical activity level. Physical function, physical role limitations and bodily pain scores were significantly lower in AS group (p<0.05). Conclusion: These results indicated that aerobic capacity in AS patients is not influenced by the reduced pulmonary function, probably due to the maintenance of an active life style.