Effects of Inspiratory Muscle Training on Depressive Symptoms in COPD: Secondary Analysis of a Randomized Controlled Trial

Background Depressive symptoms are common in patients with chronic obstructive pulmonary disease (COPD) and are associated with worse clinical status and functional limitation. Inspiratory muscle training (IMT) improves inspiratory muscle strength and exercise capacity; however, its effects on depressive symptoms are not well established. This study evaluated the effects of IMT on depressive symptoms in patients with COPD. Methods This secondary analysis of a randomized, sham-controlled trial included patients with stable COPD and inspiratory muscle weakness. Participants were allocated to IMT or sham training for eight weeks. Depressive symptoms were assessed using the Patient Health Questionnaire-9 (PHQ-9). Secondary outcomes included functional exercise capacity measured by the six-minute walk distance (6MWD) and health status assessed by the COPD Assessment Test (CAT). Between-group differences at follow-up were analyzed using analysis of covariance adjusted for baseline values. Results Thirty-eight participants completed the study (IMT: n = 22; control: n = 16). Compared with controls, IMT resulted in a greater reduction in PHQ-9 scores (adjusted mean difference − 2.9; 95% CI − 5.3 to − 0.5; p = 0.016). Significant improvements were also observed in 6MWD (mean difference 39 m; p < 0.001) and CAT score (− 6.7 points; p < 0.001). Participants in the IMT group showed a shift from moderate to mild depressive symptom severity, whereas no relevant categorical change occurred in the control group. Conclusions In patients with COPD and inspiratory muscle weakness, IMT was associated with reductions in depressive symptoms and improvements in functional capacity and health status. These findings support the inclusion of IMT as part of comprehensive COPD management.