Abstract
BACKGROUND: Singing for Lung Health (SLH) was non-inferior to physical exercise training in improving 6-minute walking test distance (6MWD) and quality of life (St. George's Respiratory Questionnaire (SGRQ)) within a 10-week pulmonary rehabilitation (PR) programme for COPD in our recent randomised controlled trial (RCT) (NCT03280355). Previous studies suggest that singing improves lung function, respiratory control and dyspnoea, however this has not yet been convincingly confirmed. Therefore, this study aimed to explore the impact of SLH on physiological parameters and the associations with achieving the minimal important difference (MID) in 6MWD and/or SGRQ. METHODS: We conducted post hoc, per-protocol analyses mainly of the SLH group of the RCT, exploring associations with 6MWD and SGRQ results by stratifying into achieving versus not-achieving 6MWD-MID (≥30 m) and SGRQ-MID (≤-4 points): changes in lung function, inspiratory muscle strength/control, dyspnoea, and heart rate response using logistic regression models. Further, we explored correlation and association in achieving both 6MWD-MID and SGRQ-MID (or in neither/nor) using Cohen's κ and Cochran-Mantel-Haenszel Test. RESULTS: In the SLH study group (n=108), 6MWD-MID was achieved by 31/108 (29%) and in SGRQ by 53/108 (49%). Baseline factors associated with achieving MID in either outcome included short baseline 6MWD and high body mass index. Achieving 6MWD-MID was correlated with improved heart rate response (OR: 3.14; p=0.03) and achieving SGRQ-MID was correlated with improved maximal inspiratory pressure (OR: 4.35; p=0.04). Neither outcome was correlated with significant spirometric changes. Agreement in achieving both 6MWD-MID and SGRQ-MID was surprisingly insignificant. CONCLUSIONS: This explorative post hoc study suggests that SLH is associated with physiological changes after short-term PR for COPD. Future physiological studies will help us to understand the mechanisms of singing in COPD. Our study furthermore raises concern about poor agreement between subjective and objective benefits of PR despite state-of-the-art tools.