Coronary artery bypass grafting (CABG) is a surgical treatment option for patients with advanced atherosclerotic coronary heart disease. The quality of life of patients awaiting CABG is poor and is affected by physical factors, such as poor physical health1 and severity of angina,2 and mental health,3 including low self-efficacy.4 High levels of self-efficacy have been shown to promote health behavior change, support self-management, and improve health status through reducing symptom burden and physical limitations in patients with coronary artery disease.4–8 Socioeconomic deprivation is also a predictor of poor cardiovascular outcomes in patients undergoing CABG.9,10
Self-efficacy as a concept is derived from Bandura's Social Cognitive Theory of Behavior, defined as an individual's confidence in his/her ability to perform a given task.11,12 The theory of self-efficacy proposes that an individual's perceptions of his/her ability to perform certain health behaviors influence his/her health outcomes.11,12 Patient recovery and adjustment after CABG, although largely determined by their physical condition and treatment, may be influenced by perceived self-efficacy. Patients with similar levels of physical impairment may achieve different functional outcomes, depending on their perceived self-efficacy.13,14 Furthermore, a spouse's or partner's confidence in the patient's capabilities can influence health-related outcomes as well.15,16
There may be differences between patients' and caregivers' perceptions of patient self-efficacy, and this could influence the level of support provided to the patient, as well as patient and caregiver outcomes.17,18 Poorer quality of relationship between caregiver and patient, greater patient symptoms, and caregiver strain are associated with caregivers overestimating patient self-efficacy.17 Although substantive research has examined the patient and caregiver relationship in heart failure,19–23 and whether spouse confidence predicts patient survival after heart failure,24 the effect of self-efficacy in patient-partner dyads in CABG has been rarely examined.14 Previous self-efficacy research has mostly involved a single assessment of either patients or caregivers.5–7,14,25–30 Such an individualized approach ignores the interdependency of behaviors or beliefs within the patient and partner relationship.31
Because patients and family caregivers are affected by patients' health status, interactions in patient and caregiver dyads are inevitable. The relationship between patient and caregiver is nonindependent. The Actor-Partner Interdependence Model, based on the Interdependence theory, allows investigators to examine the interrelatedness of variables in dyads.32 It provides insights into dyadic interactions by taking both the individual and family caregiver contribution into account in a single regression model. In this model, the association between a predictor (independent variable) and outcome (dependent variable) for members of a dyad is composed into 2 distinct parts: The actor effect is the impact of a person's own predictor variable on his/her outcome. The partner effect is the impact of a person's predictor variable on his/her dyadic partner's (family caregiver's) outcome.32–34
No preoperative studies of CABG were found that examined the relation between patients' and caregivers' perceptions of patient self-efficacy and quality of life at the dyadic level. The specific aims of this study were to compare patients' and caregivers' perceptions of patient self-efficacy and quality of life before CABG and to examine whether patients' and caregivers' perceptions of patient self-efficacy were related to their own and their partner's quality of life before CABG.
Design, Sample, and Setting
This was a secondary analysis of cross-sectional data from a study of patients and family caregivers recruited from a regional cardiology center in Scotland.13 The population consisted of patients due to have a first-time elective CABG procedure, aged 40 to 80 years, with stable angina pectoris (Canadian Cardiovascular Score II, III, or IV), or grade II to IV moderate to severe coronary artery disease, confirmed by coronary angiography as greater than 70% stenosis or 50%, if left main stem disease was present. Spouses, partners, and close family members (hereafter referred to as family caregivers) were invited to participate in the study providing they lived in the same household as the patient and were identified by them as their primary carer. Patients were excluded if they were having emergency surgery, and patients and caregivers were excluded if there were any major comorbidities, such as stroke or cancer, or psychological or communication limitations likely to affect their ability to consent.
After we received approval from the university and local research and ethics committees, patients and their family caregivers were recruited before their first visit to the surgical outpatient clinic. Study information and consent forms were mailed to the participants with the patient's clinic appointment card. After receipt of the signed consent forms, questionnaire packets were distributed to the participants at the clinic visit or mailed to their home address. Patients and caregivers were asked to complete the questionnaires separately from each other and to refrain from discussing their answers. Completed questionnaires were returned to the investigator by mail or at the clinic. A reminder letter was sent after 2 weeks.
Patients' and caregivers' perceptions of patient self-efficacy were assessed using the 16-item Cardiac Self-Efficacy Scale,35 containing 2 subdomains: self-efficacy for controlling symptoms (SE-CS) and self-efficacy for maintaining functioning (SE-MF). All items are rated on a 5-point Likert scale ranging from 0 (not at all confident) to 4 (completely confident). The scores for SE-CS range from 0 to 32, and the scores for SE-MF range from 0 to 20, with higher scores indicating greater self-efficacy. The scale measures patients' belief in their ability to perform certain behavior rather than the actual measure of a given behavior. In this study, the introduction of the scale was modified to fit the context relevant to caregivers. The validity and reliability of the Cardiac Self-efficacy Scale have been established in research.26–29,35 No studies were found that had used the scale with caregivers. In this study, the Cronbach's α for SE-CS was .75 for patients and .74 for caregivers, and that for SE-MF was .79 for patients and .76 for caregivers.
Quality of Life
Patients' and caregivers' own quality of life was assessed using the Medical Outcomes Short-Form 12 Health Survey (UK),36 which contains a physical component score and mental component score. Rated items reflect what the individual is able to do functionally, how they felt, and how they evaluated their health status. Quality of life was regarded as a multidimensional construct, to include subjective evaluation of the individual's physical and mental health, and social functioning. The physical and mental components scores were converted to t scores and standardized against UK population data. Totalled scores ranged from 0 to 100, with higher scores indicating better physical or mental health. The psychometric properties of the Medical Outcomes Short-Form 12 Health Survey have been well established in research.37,38 In this study, the Cronbach's α for the physical component score was .77 for patients and .72 for caregivers, and that for the mental component score was .78 for patients and .78 for caregivers.
Sociodemographics and Clinical Characteristics
Sociodemographics and medical history were collected in brief separate interviews with the participants, using a structured questionnaire. Occupation was identified in accordance with the Office of National Statistics.39 Social deprivation was identified using an index that takes account of income, residential postcode, and others.40 Categories range from 1 (most affluent) to 7 (most deprived). Clinical characteristics were identified from the patient's clinical records.
Sociodemographics, self-efficacy, and quality of life were compared using the paired sample t test, or chi-square statistics. Pearson's product moment correlations were used to identify associations among continuous variables. Multilevel dyadic modelling, that is, the Actor Partner Interdependence Model regression for distinguishable dyads, was used based on interdependence theory.32–34 In this study, the actor effect measured the impact of patient self-efficacy on his/her own quality of life and the impact of caregivers' perception of patient self-efficacy on his/her own quality of life. The partner effect examined the impact between each person's perceptions of patient self-efficacy on his/her partner's quality of life.
For the dyadic analysis, all data were restructured to a pairwise dyadic data set. Grand-mean centered scores were created that were standardized using z scores to obtain unstandardized and standardized regression coefficients for the actor and partner effects. The residual structure was treated as heterogeneous compound symmetry.32 Four separate models were computed; physical health was regressed on SE-MF; mental health was regressed on SE-MF; physical health was regressed on SE-CS; and mental health was regressed on SE-CS. All analyses were performed using Statistical package for the social sciences version 21.0 for Windows, with P < .05 indicating statistical significance. A power calculation was not performed as this was a secondary analysis of data. The data came from a study of 84 patients having CABG and their caregivers.13 In this analysis, we used multilevel dyadic modeling, that is, the Actor Partner Interdependence Model to evaluate perceptions of self-efficacy on the quality of life of patients and family caregivers. Previous research using this model has shown that 40 dyads were sufficient for conducting the dyadic analysis.23
Characteristics of the Participants
A total of 84 patient-caregiver dyads participated in the study (Table 1). There were 79 patient-spouse or partner pairs and 5 patient-family pairs. Most patients were men (85%), mean age 64.5 years (SD, 9.22 years). Most caregivers were women (87%), mean age 61.0 years (SD, 10.80 years). Additional information on the participants' characteristics is shown in Table 1.
Differences for Perceptions of Self-efficacy and Quality of Life
Patients' SE-CS was low and caregivers perceptions of patient's SE-CS was similarly low (P = .164) (Table 1). Patients' SE-MF and caregivers' perceptions of patient SE-MF were particularly low; there was a significant difference between them for perceptions of SE-MF (t = 2.51, P = .014), but not for SE-CS (t = 1.40, P = .164) (Table 1).
To further examine differences between patients' and caregivers' perceptions of patient self-efficacy, new variables were computed for each patient and caregiver dyad by subtracting the caregiver score from the patient score. Based on qualitative observations of scores being the same, higher, or lower, patient-caregiver dyad members with the same score (ie, no difference in self-efficacy) were coded as 0; 1 person (ie, the caregiver) in the dyad with a higher score in self-efficacy than the patient was coded as 1; and 1 person (ie, the patient) in the dyad with a higher score in self-efficacy than the caregiver was coded as 2. Forty-three patients (51%) had higher scores for SE-CS than the caregivers; 33 caregivers (40%) had higher scores for SE-CS than the patients; and 8 patient-caregivers (9%) had the same score. Thirty-nine caregivers (46%) had higher scores for SE-MF than the patients; 25 patients (30%) had higher scores for SE-MF than the caregivers; and 20 patient-caregivers (24%) had the same score.
The patients' physical health was particularly poor preoperatively, and poorer still compared with the caregivers (t = 7.48, P < .001) (Table 1). The patients' and caregivers' scores for mental health were similarly low (t = 1.10, P = .275).
Correlations Between Ratings of Self-efficacy and Quality of Life
Both patients' and caregivers' ratings for patient SE-MF were positively weakly correlated with the patients' physical health (r = 0.39, P < .001 and r = 0.29, P = .007, respectively) (Table 2). In addition, caregivers' ratings for patient SE-MF were weakly positively correlated with their own mental health (r = 0.23, P = .005). There were moderate to strong positive correlations for patients' and caregivers' perceptions of patient SE-CS and SE-MF. There were significant correlations between patients' physical health and mental health, between patients' mental health and caregivers' physical and mental health, and between caregivers' physical and mental health (Table 2).
Self-efficacy and Quality of Life in Dyadic Relationships
Patients' SE-MF exhibited an actor effect on their mental health (Table 3, Figure). The Figure shows the actor effect of the patient's SE-MF on his/her own mental health. Patients with higher SE-MF had better mental health. There was no partner effect of the patient's SE-MF on the caregiver's mental health (Table 3). Thus, patients' SE-MF did not impact the caregiver's mental health. With respect to the caregiver's perception of patient SE-MF, there was no actor effect on their own mental health, or partner effect on the patient's mental health (Table 3, Figure). Thus, caregivers' perception of patient SE-MF did not impact their own or the patients' mental health. There were no actor effects or partner effects found for patients' and caregivers' SE-MF on their own or their partner's physical health (Table 3), Also, there were no actor effects or partner effects found for patients' and caregivers' SE-CS on their own or their partner's physical or mental health (Table 3).
This study was unique in that we compared patients' and caregivers' perceptions of patient self-efficacy and quality of life before CABG. We also examined interdependence between patients' and caregivers' perceptions of patient self-efficacy. Patients' SE-MF was particularly low, which may be linked to their poorer physical health before CABG.3,41 Previous research has shown that patients' low self-efficacy is related to increased symptom burden, impaired physical function, and poorer quality of life, independent of disease severity and depression.35 Evidence from the Heart and Soul Study showed that patients with stable coronary artery disease have low SE-MF.7 Our patients awaiting CABG had lower scores for SE-MF compared with previous research.7,42 In this study, our patients also reported low SE-CS, which may be related to symptom burden and poor mental health. It is possible though that patients' poorer mental health came first and contributed to their low self-efficacy.8,26 However, previous research4,7 and clinical experience indicate that patients awaiting CABG often have low self-efficacy. Use of a quality of life measure and a Cardiac Self-efficacy Scale may help in deciphering this relationship as part of preoperative assessment.
Our results indicate that there were some similarities and differences between patients and caregivers in their perceptions of patient self-efficacy, based on our qualitative observation of scores being higher or lower. Only 9% of patient-caregiver dyads had the same scores for SE-CS, although more patient and caregiver dyads (24%) had the same scores for SE-MF. Notably, 46% of caregivers rated patient SE-MF higher than the patients themselves did, indicating some overoptimism on the part of the caregiver, which could have a detrimental effect on the patient.14 In contrast, 51% of patients scored higher for SE-CS than the caregivers did, suggesting some underestimation of the patient's capacity to self-manage. Our findings are consistent with other studies that have found patient and caregiver incongruence.21 Such incongruence may cause conflict and distress in relation to self-care and advance care planning.21 Our findings reiterate the significance of considering both patients' and caregivers' perspectives, which is especially important in the education and preparation of patients awaiting CABG.
Furthermore, our results indicate that both patients' and caregivers' perceptions of patient SE-MF were significantly positively correlated with the patients' physical health. Previous longitudinal research has shown that spousal confidence in the patient's ability to perform specified behaviors is related to patient outcomes.15,24 The caregivers' ratings for patient SE-MF were correlated with their own mental health. No dyadic studies of patients awaiting CABG were found for comparison of our results. Previous studies of self-efficacy have mainly focused on its role in cardiac rehabilitation42,43 or after myocardial infarction8 or coronary revascularization.35,44 In caregivers, studies of self-efficacy or caregivers' confidence in their partner (ie, the patient) have rarely been conducted.14–16 The importance of patient and caregiver dyads in heart failure has been given much more attention,21,24,45 and there have been studies of heart failure dyads using the Actor Partner Interdependence Model, which have identified actor-partner effects of self-care and depression and anxiety on quality of life.19,20,23
Our study was novel in that it used the Actor Partner Interdependence Model as a way of examining the dyadic effect of self-efficacy on patient and family caregiver quality of life in CABG. The results revealed an actor effect of patients' SE-MF on his/her own mental health but not the caregivers' mental health. This indicates that self-efficacy was based more on the “self” than on the dyad, which is consistent with Bandura's proposal that personal information has the most potential to impact self-efficacy beliefs.12 Other studies have found that patients and caregivers influenced one another's mental and physical health, but not their self-efficacy.18
Our finding of an actor effect of patients' SE-MF on their mental health is consistent with previous research that has identified that patient self-efficacy is significantly related to their mental health.14 It was an interesting finding that patients' SE-MF and their physical health were significantly correlated in simple correlation, but yet there were no actor or partner effects. Other studies have found positive correlations between self-efficacy and physical health, albeit postoperatively, and the Actor Partner Interdependence Model was not used.43 This may be explained by the fact that in this type of analysis, the researcher is examining associations controlling for both partner and role, so it is possible for a nonsignificant simple correlation to be a significant regression coefficient. To our knowledge, this is the first study to examine cross-sectionally preoperative cardiac self-efficacy and quality of life in patients and caregivers at the dyadic level. Further research using the Actor Partner Interdependence Model is needed, which may lead to a better understanding of the interaction in dyad members. The aim would be to work with the dyad to build self-efficacy and optimize the patient's physical and mental health and functioning before surgery.
There were limitations to this study. First, it was a secondary data analysis using cross-sectional data, which meant that the direction of causality of associations could not be determined. Second, the study sample was relatively small, which limits the generalizability of the findings. This makes it difficult to know whether our null results, that is, no partner effects, indicate unimportant dyadic relations or insufficient power. Further study is needed to support or refute our findings. Third, length of marriage or cohabitation and marital quality of the respondents were not known.
Patients' SE-MF was particularly low preoperatively, which may be related to perceptions of impaired physical function and poorer quality of life. Differences between patients' and caregivers' perceptions of patient SE-MF should be addressed before surgery to help promote patient functioning. Although the patients' SE-MF predicted their own quality of life using the Actor Partner Interdependence Model, there was no dyadic effect. Further research is needed in this area.
What's New and Important
- Patients' self-efficacy for maintaining function was particularly low before coronary artery bypass grafting (CABG), which may be linked to their impaired physical function and perceived quality of life. Use of a quality of life measure and the Cardiac Self-efficacy scale may be useful as part of preoperative assessment.
- Differences between patient and caregiver dyads in their perceptions of patient self-efficacy may lead to caregivers underestimating the patient's capacity to self-manage. Addressing these differences is especially important in the education and preparation of patients awaiting CABG.
- Patients' self-efficacy for maintaining function impacted on their own mental health, but not the caregiver's mental health. There were no other actor effects or partner effects of self-efficacy on quality of life. More dyadic research is needed in this area.
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Keywords:Copyright © 2019 Wolters Kluwer Health, Inc. All rights reserved
Self-Efficacy; Quality of life; Coronary artery bypass grafting; Family caregivers; Statistical Models