The principal finding in this study indicated that life event stress was associated with depressive symptoms and poor quality of life in both COPD and non-COPD participants (main effects), but showed a significantly stronger association among individuals with COPD than among non-COPD individuals (interaction), suggesting a disproportionately greater detrimental effect. To our knowledge, no other studies have reported demonstrating this relationship.
It should be noted that participants with COPD actually did not report greater frequency of occurrence or perceived stress score of non-illness-related life events than non-COPD participants. Instead, individuals with COPD appeared to experience the same number of non-illness-related life events and perceived them to be equally stressful as their non-COPD counterparts, yet showed disproportionately greater psychological distress and poorer quality of life. These results suggest that individuals with COPD may be more vulnerable to the adverse impact of stressful events than non-COPD individuals.
A greater detrimental effect of life event stress on psychological well-being and quality of life in COPD individuals may hypothetically be explained by the possibility that COPD individuals perceive and appraise stressful life events differently to individuals without COPD, or that COPD individuals have poorer coping skills or fewer social and economic resources, or both. We did not have measures of cognitive appraisal, coping resources and social support to explore these hypotheses directly, and this is a limitation of our study.
There are few studies that have investigated the relationship between cognitive appraisal of stressful events, coping strategies and psychological distress in COPD patients. A study by Andrenas and co-investigators24
have assessed how hospitalised patients with acutely exacerbated COPD appraised and coped with a recent stressful event and their level of psychological distress. They reported that half of the respondents tended to perceive their stressful event as representing a threat, 26% as harmful, 7.6% as a loss, 4.3% as a challenge and 11% characterised the stressful event in some other ways. However, the authors found that neither types of stressful event, stress intensity, primary or secondary appraisal, or number of coping strategies used were significantly related to psychological distress. Only problem-solving coping strategies were inversely related to psychological distress. This suggests that poor coping skills may be the principal psychological problem among COPD patients that contribute to their psychological distress and poor quality of life. However, further studies should be conducted.
Our secondary finding of the main effects of COPD on FEV1 was expected and thus not surprising. However, the association of COPD with more frequent cognitive problems was interesting, although the results for MMSE score were not significant after adjustment in two-way ANOVA, possibly due to sample size limitation. These results are consistent with clinical and population studies that indicate significant cognitive effects of COPD on deficits in abstract reasoning,25
complex visual motor process,26
and verbal learning,27
information processing speed29–31
and verbal learning and memory.30
The present study has strengths and limitations. The case definition for COPD is accurately based on symptom and postbronchial dilatation spirometric measures of chronic airflow obstruction that are diagnostic of COPD according to GOLD-recommended criteria. Results from this general population-based study are largely free of clinical selection bias, and also controlled for important confounding by demographic and psychosocial variables in the analysis. The measure of life event stress is modified to exclude illness-related stress from chronic diseases in this older population. However, a limitation of the life event inventory is inter-categorical variability and recall bias in the appraisal of the stressful life event.32
In a cross-sectional study, interpreting the causal relationship between stress- and the health-related functional outcomes can be uncertain. Further longitudinal studies are required.
have reported that mental health status, including anxiety and depressive symptoms, are better predictors of COPD-related quality of life than pulmonary function. The present study supports this observation and further indicates that life event stress has a starkly detrimental effect on mental health and quality of life in patients with COPD. More studies of the effects of stress management and coping strategy in psychological interventions in COPD should be investigated in randomised controlled clinical trials.
It is increasingly being recognised that the identification of mood and anxiety disorders, and psychological and psychosocial interventions to improve mood and reduce anxiety are important for improving patient-centred outcomes in COPD patients. However, in published clinical guidelines such as NICE, where the initial step care management by practitioners in primary care and general hospital settings includes low-intensity psychosocial interventions for patients with persistent subthreshold depressive symptoms or mild-to-moderate depression, there appears to be little attention given to identifying stressful life event(s) and supporting COPD patients experiencing stressful life events to prevent the onset of mood and anxiety disorders. In particular, group-based peer support, individual-guided self-help based on cognitive behavioural therapy (CBT) principles or computerised CBT to reduce patients’ vulnerability to stress may usefully include objective cognitive appraisal of stress, problem-solving coping skills and relaxation therapy to help support COPD patients experiencing stressful life events.
In conclusion, the present study found that life event stress was associated with more depressive symptoms and worse quality of life in individuals with COPD, much more than in those without COPD. Further studies should explore the role of cognitive appraisal of stress, coping resources and psycho-social support in this relationship.