|Home | About | Journals | Submit | Contact Us | Français|
Patients with end-stage lung disease experience significant decrements in quality of life (QOL). Although coping strategies are related to QOL in patients with end-stage lung disease, the extent to which specific native lung disease moderates this relationship is unknown.
We investigated the relationship between coping, native lung disease, and QOL among 187 patients awaiting lung transplantation, including 139 patients with chronic obstructive pulmonary disease (COPD) and 48 patients with cystic fibrosis (CF). Participants completed a psychosocial battery assessing psychological QOL, physical QOL, and coping strategies.
For both COPD and CF patients, higher levels of Active Coping (P < .0001) and lower levels of Disengagement (P < .0001) were associated with better psychological QOL. For physical QOL, we observed a native disease by coping interaction (P = .01) such that Active Coping was associated with better physical QOL in patients with COPD but not in patients with CF.
The relationship between coping and QOL may vary as a function of native lung disease. In order to develop effective interventions to help patients cope successfully with end stage lung disease, patients’ native disease may need to be considered.
Lung transplantation can be the only remaining treatment option for patients with end-stage lung disease, but it is not without considerable risk. Transplant recipients face high rates of infection, graft rejection, and mortality following transplantation  and, despite improvements in surgical techniques, 5-year survival remains below 50% [2,3]. Because of the limited survival following transplant and the taxing nature of the transplantation process, quality of life (QOL) considerations have become increasingly important when weighing the benefits and risks of transplantation [4–6]. Much of the QOL literature has focused on the substantial decrements in QOL that are experienced by patients with end-stage lung disease, including impairments in both the physical and mental health QOL domains [7–14]. Furthermore, elevated rates of psychiatric illness in lung transplant candidates have been well-documented [11,15–17].
Accordingly, the strategies that lung transplant candidates use to cope with these many challenges have important implications for their well-being. The association between coping and QOL has been described in other solid organ transplant candidates  and in a variety of other disease groups [16,18]. In lung patients, avoidance coping, characterized by thoughts and/or actions to minimize the experience of a stressor , has been associated with poorer global QOL and work performance [20,21], as well as higher levels of depression, pain, and psychological distress , although negative findings also have been reported . In contrast, active coping, characterized by an active engagement in dealing with stressful events, has been associated with better QOL . Understanding the relationship between coping and QOL may be particularly important because certain coping strategies, particularly avoidance coping, have been associated with increased psychiatric illness [23–25] and noncompliance  following transplantation.
Consideration of the impact of native disease may be important in understanding the relationship of coping and QOL because of the distinct pathophysiologies and demographic characteristics associated with different lung diseases . These differences are particularly evident when comparing cystic fibrosis (CF) and chronic obstructive pulmonary disease (COPD), which represent two of the most common conditions necessitating lung transplantation . COPD is diagnosed in adulthood and smoking has been identified as a causal agent in 75–85% of all cases . In contrast, CF is an autosomal recessive genetic disorder that is typically diagnosed in the first year of life. Accordingly, it is not surprising that there are important psychosocial differences, including differences in QOL, between CF and COPD patients awaiting transplantation .
Despite the clinical and psychosocial differences between these disease groups, the influence that native disease has on the coping and QOL relation remains unclear. Native disease could have an important moderating effect on the relationship between coping and QOL, which would have major implications for psychosocial intervention and clinical management strategies between native disease classifications. Although individually-tailored psychosocial interventions among lung transplant candidates have gained recent attention , the more fundamental question of whether coping strategies may be differentially effective for different types of lung patients has not yet been examined. Similarly, despite native disease differences in coping and QOL, no studies, to our knowledge, have systematically examined whether native disease may moderate the coping and QOL relationship. Therefore, the purpose of the present study was to examine a) the relation between coping and QOL and b) to determine whether this relation is affected by the nature of the lung disease.
Patient selection and exclusion criteria have been previously described . Briefly, patients listed for lung transplantation at Duke University Medical Center and Washington University between September, 2000 and August, 2004 were initially contacted to be part of the larger clinical trial, known as the INSPIRE study . Patients were listed for lung transplant if they were 18 or older, had an expected survival of two years or less without transplant, and had no other significant extrapulmonary organ dysfunction. Patients also had to demonstrate an absence of substance abuse or active psychiatric disease, adequate social support, and adequate nutritional and exercise status. One hundred eighty seven patients with end-stage lung disease (139 with COPD and 48 with CF) were selected from the initial trail sample based on a primary diagnosis of COPD or CF. Patients with other forms of lung disease were excluded from the current analysis. All participating patients provided written informed consent approved by their respective Institutional Review Boards.
Participants completed standard pre-transplant clinical assessments, including measures of exercise tolerance and pulmonary gas exchange. Additionally, participants completed a battery of self-report psychometric measures designed to evaluate coping strategies as well as both psychosocial and physical components of QOL.
Exercise tolerance was determined using the Six-Minute Walk test, a standard procedure in which patients are asked to walk as far as possible on a measured course within a 6-minute time limit. An experienced physical therapist provided patients with enough oxygen to maintain saturations of 90% or greater, but no additional encouragement was provided. Arterial blood analysis was performed during pulmonary clinic visits and was used to determine partial pressures of carbon dioxide and oxygen gas (pCO2 and pO2).
A comprehensive psychological test battery was used to assess a broad range of both psychosocial and somatic/physical components of QOL. The following measures were selected because of their relevance for patients with advanced lung disease and established reliability and validity:
All statistical analyses were conducted using SAS statistical software version 9.1 (SAS Institute, Inc., Cary, NC). Differences in background and demographic factors between native disease classifications were examined using 1-way analysis of variance (ANOVA) for continuous variables and χ2 tests for categorical variables. In order to minimize the number of hypothesis tests, we preceded our primary analyses by performing a data reduction on the COPE inventory subscales. This was carried out using a principal components analysis with varimax rotation, the results of which are reported below in greater detail. The factor solution was interpreted based on Eigenvalues, a scree plot, a criterion of .40 as the minimum acceptable loading, and substantive interpretability. The principle components results yielded two composite variables which were labeled Active Coping and Disengagement. A second analysis examined native disease differences on mean levels of the two COPING composites. For this analysis, we used a MANCOVA in which the Active Coping and Disengagement composites were the joint dependent variables and native disease was the predictor.
Finally, in our primary analyses, we examined whether coping and native disease were related to the QOL variables. To this end we estimated two separate MANCOVA models: one in which Psychological QOL variables (PQLS-Psychological, SF-36 Psychological QOL, BDI, S-STAI, T-STAI, PSS, PSSS, and GHQ) served as the outcome and one in which Physical QOL variables (SF-36 Physical, PQLS-Physical, and SOBQ) served as the outcome. The predictors in each of these QOL models were native disease, Active Coping, and Disengagement. We then tested the moderation hypotheses by adding the Active Coping by native disease and Disengagement by native disease interaction terms simultaneously to the models. Each of the primary MANCOVA models included the following adjustment covariates, selected a priori: annual income (0 = under $15,000, 1 = $15,000 – $29,999, 2 = $30,000 – $44,999, 3 = $45,000–$59,999, 4 = $60,000 – $74,999, 5 = above $75,000); current use of psychiatric medication (0 = no, 1 = yes); education (0 = under 6 years, 1 = 7–9 years, 2 = 10–11 years, 3 = 12 years, 4 = 13–15 years, 5 = college degree, 6 = graduate or professional degree); ethnicity (0 = Caucasian, 1 = African-American, Native-American, Hispanic, Asian/Pacific Islander); current or previous psychological treatment (0 = no, 1 = yes); gender (0 = male, 1 = female); and six minute walk test (continuous). In all MANCOVAs, we first interpreted the multivariate test and, if significant, we examined the univariate ANCOVAs for each of the individual dependent variables.
Table 1 displays the background characteristics of the sample. The mean age of the sample was 50.4 (SD = 13.1) years and the majority of participants were Caucasian (92.5%) and female (56.6%).
Based on the Eigenvalues and scree test, we identified a plausible two component solution, which we labeled Active Coping and Disengagement. Table 2 shows the loadings for each component. With two exceptions, the Active Coping loadings were ≥ .70; loadings for the Disengagement component score ranged from .40 to .57.
MANCOVA results showed that CF and COPD patients did not differ in their use of Active Coping or Disengagement (Wilks’ lambda = 0.98, P = .22). Examination of the composite measures of coping showed that CF and COPD patients did not differ on either Active Coping (CF Mean = −.92, SD = 8.12; COPD Mean = .10, SD = 11.45) or Disengagement (CF Mean = .80, SD = 4.83; COPD Mean = .01, SD = 6.73).
The multivariate results showed that higher levels of Active Coping were related to better Psychological QOL (Wilks’ lambda = 0.75, p = .0001), while higher levels of Disengagement were related to poorer levels of Psychological QOL (Wilks’ lambda = 0.57, P = .0001). Figure 1 shows the relation between Psychological QOL and Active Coping and Figure 2 shows the relation between Psychological QOL and Disengagement.
The unstandardized linear model coefficients from the univariate models for each of the dependent Psychological QOL variables are shown in the upper portion of Table 3. Higher levels of Active Coping were associated with better scores on all Psychological QOL subtests. In contrast, higher levels of Disengagement were associated with poorer Psychological QOL on all subtests, except for the PSSS. With respect to native disease differences, CF patients demonstrated higher Psychological QOL compared to COPD patients (Wilks’ lambda = 0.87, P = .005) (Table 4). Specifically, CF patients demonstrated lower levels of anxiety and better PQLS-psychological QOL compared to COPD patients, whereas there were no differences between CF and COPD patients on the BDI, SF36-Psychological, STAI-T, PSS, PSSS, and GHQ scales.
The multivariate analysis revealed that Active Coping was not significantly related to Physical QOL as a main effect (Wilks’ lambda = 0.97, P = .221). The multivariate effect for Disengagement, however, was statistically significant (Wilks’ lambda = 0.93, P = .007). Finally, CF and COPD patients differed significantly in Physical QOL (Wilks’ lambda = 0.89, P = .0005). The linear model coefficients from the univariate models for the three individual Physical QOL variables are shown in the lower portion of Table 3. Consistent with the multivariate tests, none of the individual Physical QOL variables was related to Active Coping. Disengagement, however, was associated with worse SOBQ scores. Native disease was related to all three measures of Physical QOL, with CF patients reporting better QOL than COPD patients.
The Active Coping by native disease interaction term was significant for Physical QOL (Wilks’ Lambda = 0.85, P = .01), indicating that the relation between Active Coping and Physical QOL depended on native disease category. Figure 3 displays the observed Active Coping score plotted against the model fitted values of a Physical QOL composite score for CF and COPD patients, suggesting that the association between Active Coping and Physical QOL was greater for COPD patients compared to CF patients. Specifically, among COPD patients, Active Coping was associated with better SOBQ, PQLS, and SF36-Physical. In contrast, Active Coping was not significantly associated with Physical QOL among CF patients.
The primary goal of the present study was to examine the relationship of coping to QOL, and to evaluate whether this relationship was moderated by native disease. Results showed that higher levels of Active Coping and lower levels of Disengagement were associated with better psychological QOL. However, Active Coping was associated with better physical QOL only among patients with COPD and was not associated with better physical QOL among patients with CF.
We found that higher levels of Active Coping and lower levels of Disengagement were associated with better psychological QOL. Specifically, Active Coping was associated with lower levels of depression, state and trait anxiety, stress, pulmonary-specific psychological QOL, and general well-being, as well as higher levels of social support. Disengagement, in contrast, was associated with higher levels of depression, state and trait anxiety, stress, pulmonary-specific psychological QOL, and general well-being. Our finding that higher levels of Active Coping and lower levels of Disengagement are associated with better psychological QOL is consistent with previous research among patients awaiting lung transplant [20,21], as well as other solid organ transplant candidates  and other chronic disease groups [18,44,45]. For example, a pilot study from our group  found that teaching Active Coping skills was associated with better QOL during the pre-transplant period. Similarly, Burker and colleagues  found that lung transplant candidates with higher levels of Disengagement experienced impaired QOL on a variety of outcome measures, including anxiety, depression, and overall disability.
In contrast to our Psychological QOL findings, we found that higher levels of Active Coping were associated with better Physical QOL only among COPD patients. Specifically, COPD patients who reported greater Active Coping exhibited better SOBQ, PQLS, and SF36-Physical. The finding that Active Coping was not related to better physical QOL in CF patients was unexpected and suggests that, for a subset of lung transplant candidates, psychosocial functioning such as coping may influence QOL through different mechanisms. This finding also suggests that native disease differences in Active Coping may be clinically meaningful insofar as for every standard deviation increase in Active Coping, COPD patients exhibited a 4.7 point decrease in SOBQ scores, indicating less breathing difficulty, whereas CF patients exhibited a 5.2 point increase in SOBQ scores, suggesting greater shortness-of-breath. Although the magnitude of these effects may seem relatively small, a 5-point change on the SOBQ has shown to be associated with clinically meaningful differences in pulmonary function among patients with COPD . This finding may be particularly important because coping has been identified as a psychosocial risk factor that may be modifiable with treatment .
The relationship between coping and QOL has gained increasing importance because coping has been identified as a psychosocial risk factor amenable to intervention in lung transplant candidates . In our recent interventional trial of 328 lung transplant candidates , we found that a 12-week coping skills training intervention delivered over the telephone was associated with higher QOL. Given the prognostic association between QOL and medical outcomes such as compliance, organ rejection, and mortality [49,50] in solid organ transplant populations, interventions that improve coping ability may have important implications for post-transplant outcomes. Our findings indicate that such interventions may benefit from the additional consideration of native disease classification. For example, it may be appropriate to continue teaching Active Coping skills in interventions targeting COPD patients, while other alternatives may need to be explored in order to optimize patient care among individuals with CF.
This study had several limitations: the cross-sectional design prevents an analysis of the causal relationship between coping and QOL. Coping strategies can be both a cause and consequence of poor quality of life. It is unclear from the current study whether CF and COPD patients would respond differentially to a coping intervention, which focuses on active methods of coping. Second, the label selected for the Disengagement factor may not appear entirely appropriate because the Disengagement factor includes the venting of negative emotions subscale. Intuitively, it would not seem that venting of emotions is consistent with a disengagement strategy. Finally, because age is confounded with native disease—patients with CF are younger and patients with COPD are older—it is possible that the coping and QOL differences observed were the result of age and/or developmental differences and not characteristics of the native disease, per se. For example, in addition to peer relationships, the relationships that CF patients have with their parents may influence the effects of Active Coping . Because CF patients require a complex and demanding medical regimen, they must rely upon their parents to manage their treatment throughout their childhood and adolescence. This may influence the parent-child relationship with respect to gaining and exercising independence among CF patients. For example, when the time comes for children with CF to transition to adult CF care, parents’ most salient concern is their child’s ability to manage his or her condition independently, while CF patients themselves do not report significant concern in this area . Transplantation requires heavy reliance on a caregiver once again and, because CF patients are younger and less likely to be married, they may be more likely than COPD patients to name a parent as their primary caregiver. It is possible that the necessity of continuing to rely on a parent for instrumental and emotional social support during the transplantation process, when most CF patients are already well into adulthood, causes some degree of distress that was not accounted for by the psychosocial measures used in the present study.
It is also possible that the observed differences in the relationship between coping and physical QOL are due to the fact that CF is an inherited disorder that is likely viewed as an uncontrollable stressor, whereas the vast majority of COPD cases are linked to the controllable risk factor of smoking. Because problem-focused (i.e. active) coping strategies can be more effective when stressors are controllable versus uncontrollable , Active Coping may confer physical QOL benefits for COPD patients but not for CF patients. Due to the relatively early diagnosis of CF, it is possible that coping strategies may have less relevance for CF patients given the chronicity of this diseases progression. Alternatively, it is possible that physical differences in the end-stage disease characteristics may influence the effectiveness of active coping strategies. CF patients exhibit much higher rates of bone fractures  and pain  compared with other end stage lung patients, for example, and it is possible that active coping behaviors may be associated with exacerbation of these physical symptoms. It is less likely that the current results are explained by differences in psychological QOL given the scarcity of differences found in our study (Table 3) as well as existing QOL literature in this population .
In summary, results of this study indicate that coping is related to psychological QOL and that the relationship between coping and physical QOL in patients awaiting lung transplantation is moderated by native lung disease. These findings may have important implications for the management of patients with end-stage lung disease (ESLD), who comprise a pathophysiologically and demographically heterogeneous population. Specifically, psychosocial interventions among patients with ESLD may benefit from selecting treatment targets specific to native disease classifications. Future studies should investigate the relationship between coping, native disease, and QOL prospectively in order to determine their causal relationship and identify additional opportunities for intervention.
This study was support by grant HL 065503 from the National Institutes of Health, Bethesda, Maryland.
Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.