Background: Depression is a frequent comorbidity in COPD. COPD symptoms such as dyspnea may play an important role in the causal relationship between COPD and depression. We investigated the interrelations among different aspects of dyspnea and other COPD parameters and symptoms of depression in COPD patients.
Methods: This is a secondary analysis of N = 590 COPD patients. At the beginning (T0) and the end (T1) of a 3-week inpatient pulmonary rehabilitation, dyspnea aspects intensity (BORG scale), frequency (2 CCQ items), functioning (CCQ-function) and cognitive/emotional response (2 SGRQ items) as well as cough (2 CCQ items), functional capacity (6MWD), lung function (FEV1) and symptoms of depression (PHQ-9) were assessed. Regression analyses with PHQ-9 sum score as dependent variable as well as network analysis using PHQ-9 single items were performed. Structural invariance over time was examined.
Results: Dyspnea frequency, function, and cognitive/emotional response showed conditional independent relationships with PHQ-9 sum score. Network analysis showed that dyspnea frequency and dyspnea functioning were primarily associated with somatic depression symptoms (for example, sleep problems, loss of energy), while cognitive/emotional response was primarily related to cognitive-affective depression symptoms (for example, feeling down/depressed/hopeless). Regression parameters, network structure and network global strength did not differ between T0 and T1.
Limitations: Models are based on between-person relationships. Results should be confirmed using time-series data.
Conclusions: Dyspnea and depression seem to be interrelated through a variety of different and complex pathways in COPD patients. Results may be used to explain intervention effects and develop new intervention strategies to reduce depression in COPD.
Keywords: Bridge symptoms; COPD; Depression; Dyspnea frequency; Dyspnea intensity; Functioning; Pulmonary rehabilitation.
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