Campbell, Tavis S. PhD; Stevenson, Andrea MSc; Arena, Ross PhD, PT; Hauer, Trina BPAS, MSc; Bacon, Simon L. PhD; Rouleau, Codie R. BA; Cannon, Colleen PhD, RPsych; Stone, James A. MD, PhD, FRCPC
Cardiovascular disease (CVD) is the leading cause of death and disability worldwide.1 Modifiable risk factors for CVD include dyslipidemia, tobacco use, psychosocial factors such as depression and stress, high blood pressure (BP), diabetes, abdominal obesity, a lack of daily consumption of fruits and vegetables, excessive alcohol use, and a lack of daily exercise.2,3 Combined, these account for >90% of the variance in initial acute myocardial infarction.4,5
Research has focused on the efficacy of behavioral and psychological interventions to modify these risk factors in patients with CVD,6–10 including stress management programs in cardiac rehabilitation (CR) settings. In a sample of CR patients randomized to receive exercise, stress management, or usual care, Blumenthal et al6 reported that CR patients who received exercise or stress management had greater improvements in symptoms of depression, relative to usual care. In a systematic review, Rees et al11 also reported improved symptoms of depression among CR patients receiving stress management. Overall, these results suggest that both stress management and exercise may be important for reducing symptoms of depression in CR patients. Moreover, Plüss et al12 compared physical health outcomes in 224 patients with coronary artery disease who were randomly assigned to either standard CR or expanded CR (including stress management). At a 5-year followup, patients in expanded CR had experienced fewer cardiovascular events and fewer hospital readmissions due to CVD and had spent fewer days hospitalized since program completion compared with those in standard CR. Although informative, this study does not make clear whether the benefits observed were due to stress management or due to the other aspects of the expanded CR program.
Other research on whether stress management can improve clinical outcomes remains limited by relatively small samples sizes, narrowly defined outcomes, and highly selected patient groups.13 Furthermore, although most multidisciplinary CR programs offer optional stress management classes, no studies to date have directly compared participation in both exercise and stress management (E + SM) with exercise only (E). The present investigation examined the incremental impact of a stress management class, relative to exercise, on mental and physical health outcomes immediately after completing a 12-week CR program and at 1-year followup. It was hypothesized that relative to patients who attended only the exercise component of CR, patients who attended E + SM would experience greater reductions in symptoms of depression and anxiety and greater improvements in quality of life, functional capacity, body composition, cholesterol profile, and BP at the 12-week followup.
Ethics approval was obtained from the university ethics board, and participants consented to have researchers access their personal health information for research projects. Participants were men and women who completed a CR program between February 2005 and November 2007 at a private health care facility specializing in cardiac wellness. Exclusion criteria for this study included (1) patients who attended only the education component of CR, (2) patients who completed only the baseline assessments, (3) patients in the stress management group who did not attend at least 3 of the 4 classes, and (4) patients primarily diagnosed with a congenital condition.
This study used a retrospective analysis and chart review of prospectively collected data from the CR program clinical database. Baseline measurements were completed when the patient attended a CR orientation session and a maximal exercise treadmill test before starting the 12-week exercise component. Patients who attended stress management completed the class during the 12-week exercise component. All physical and psychosocial health assessments were repeated at 12 weeks. Patients also completed a medical assessment and had their cardiometabolic fitness determined at 1 year following the completion of the program.
Cardiac Rehabilitation Program
The CR program provided a 12-week comprehensive exercise and risk factor modification program to individuals with CVD. The CR program was consistent with the Canadian Association of Cardiac Rehabilitation guidelines.14 Briefly, the program included a tailored supervised exercise program delivered twice a week for 12 weeks (and encouraged self-monitored exercise at least once per week), individual appointments with a physician, and optional health education classes including the stress management program that is the focus of this study.
Stress Management Class
The stress management class offered through the CR program consisted of weekly 2-hour sessions for 4 consecutive weeks with sessions offered either during the daytime or during the evening. The stress management class was available to all CR patients at no cost and on a self-referral basis. Patients were considered to have completed the stress management program if they attended at least 3 of the 4 classes. The class was taught by a clinical psychologist or social worker and involved a combination of didactic instruction, small- and large-group discussion, and activities. Homework assignments assisted patients in identifying stressors and developing skills to manage them. The class contained both behavioral and cognitive components of stress management. Special emphasis was placed on the relationship between stress and heart disease, communication skills, thought awareness and thought challenging, deep breathing, anger management, and building and maintaining support systems. These are common components of stress management within CR.15
Symptoms of depression and anxiety
The Hospital Anxiety and Depression Scale (HADS)16 is a 14-item self-administered questionnaire that detects and distinguishes between the symptoms of anxiety and depression and measures the severity of emotional disorder. It consists of 2 subscales (Depression and Anxiety), and scores range from 0 to 21. It is a well-validated measure with good reliability.17 Cutoff scores are used to indicate symptoms in the normal (0–7), mild (8–10), moderate (11–14), and severe (15–21) ranges.
Quality of life
The Short Form Health Survey (SF-12)18 is a 12-item self-administered questionnaire that assesses health-related quality of life via patient physical and psychosocial health perception. The SF-12 consists of 8 subscales—Physical Function, Role Physical, Bodily Pain, General Health, Vitality, Social Function, Role Emotional, and Mental Health—and 2 summary scales—Physical Component Summary (PCS) and Mental Component Summary (MCS). The PCS provides an overall assessment of patient-perceived physical health, including an evaluation of ability to function and perform physical activity. The MCS provides an overall assessment of patient-perceived mental health and is composed of psychological distress and well-being, social and role functioning, and overall vitality. The SF-12 is a well-validated, reliable, and widely used measure.18
Functional capacity was estimated using a maximal exercise stress test and expressed as peak metabolic equivalents (METs). Peak METs were calculated from treadmill speed and grade during the final stage of the exercise protocol. Heart rate, BP, and electrocardiogram were monitored throughout the exercise test and into recovery. Test termination criteria followed American Heart Association guidelines.19
Body composition, BP, and cholesterol profile
Anthropometric data (ie, height, weight, and waist circumference) were measured prior to the maximal exercise stress test and used to calculate body mass index (BMI). Resting BP was manually measured in the pretest period in both a supine position and a standing position, with the lowest value used as resting BP. Two weeks prior to the stress test, patients had blood drawn following a 10-hour fast to assess lipids and glucose.
To evaluate whether the 2 groups (E + SM and E) were comparable on demographic variables at T1, a series of independent-samples t tests and χ2 analyses was conducted. To test for the incremental effect of stress management, separate 2 (groups: E + SM and E) × 2 (time: 1 and 2) repeated-measures analyses of covariance (RM-ANCOVAs) were conducted to detect main effects of time and group as well as time-by-group interactions on each of the psychosocial and physical health outcome measures. To take into account potential floor effects, parallel analyses were conducted for the subgroups of patients above clinical cut points on each respective physical outcome measure (ie, baseline systolic BP ≥140 mmHg, diastolic BP ≥90 mmHg, total cholesterol >4 mmol/L, low-density lipoprotein-cholesterol [LDL-C] >2.0 mmol/L, high-density lipoprotein-cholesterol [HDL-C] <1 mmol/L, triglycerides >2 mmol/L, BMI ≥30 kg/m2, waist circumference ≥35 inches for women and ≥ 40 inches for men, and peak METs <5). When significant main or interaction effects were detected, simple effect pairwise comparisons were performed as required. The Bonferroni correction was used to adjust for the overall error rate with multiple comparisons.20 All data analyses were conducted using SPSS for Windows version 16.0 (SPSS Inc, Chicago, IL).
Among the 1577 eligible patients who composed the study sample, 1389 patients attended E only and 188 patients attended E + SM. Sample characteristics are presented in Table 1. The most common CVD diagnosis upon program entry was myocardial infarction (53.5%), followed by angina (23.3%); 43.6% were also diagnosed with coronary artery disease, 51.6% with hypertension, 74.7% with dyslipidemia, and 19.7% with type II diabetes.
An examination of baseline (T1) patient characteristics revealed that relative to men, proportionally more women elected to attend E + SM than E only (see Table 1). Compared with those in the E-only group, patients in the E + SM group were younger, had smaller waist circumferences, reported more symptoms of depression and more symptoms of anxiety (as measured by the HADS), as well as poorer physical quality of life and poorer mental quality of life (as measured by the SF-12). There were no differences in medication use between the 2 groups. Waist circumference and age were included as covariates in subsequent analyses.
Associations Between SM and Psychosocial Outcomes
Results of the RM-ANCOVA revealed a time-by-group interaction for the HADS Depression subscale, F1,717 = 5.80, P = .016 (Figure 1; Table 2). Pairwise comparisons indicated that although the E + SM group had higher depression scores than the E-only group at T1, t(1) = 3.81, P < .001, both groups improved from T1 to T2, with no significant difference between groups at T2, t(1) = 1.74, P = .082. This indicates that the E + SM group had a greater decrease in depressive symptoms than the E-only group.
Similarly, a time-by-group interaction was observed for the SF-12 PCS subscale, F1,223 = 4.69, P = .031 (Figure 2). Pairwise comparisons indicated that although the E + SM group had lower physical quality of life scores than the E-only group at T1, t(1) = 3.00, P = .003, both groups improved from T1 to T2, with no significant difference between groups at T2, t(1) = 1.56, P = .120. The E + SM group showed a greater improvement in physical quality of life than the E-only group.
Main effects of group were observed for the HADS Anxiety subscale, F1,717 = 26.01, P < .001, and for the SF-12 MCS subscale, F1,229 = 5.24, P = .023, indicating that the E + SM group had higher anxiety scores and lower mental quality of life scores across time than the E-only group.
Associations Between SM and Physical Outcomes for the Entire Sample
RM-ANCOVA analyses indicated no time-by-group interactions for any of the physical outcome measures (Table 3). Overall main effects of time, F1,1447 = 5.97, P = .015, and group, F1,1447 = 16.28, P < .001, were observed for waist circumference. Patients in the E + SM group had smaller mean waist circumferences relative to those in the E-only group. Both groups had reduced waist circumferences from T1 to T2.
Analyses revealed main effects of time such that T2 was associated with an increased functional capacity, F1,1484 = 61.04, P < .001; decreased total cholesterol, F1,1286 = 4.20, P = .041; and decreased LDL-C, F1,1250 = 4.42, P = .036.
Main effects of group were observed for BMI, F1,1461 = 5.36, P = .021, and triglyceride levels, F1,1284 = 4.67, P = .031. Patients in the E + SM group had higher BMIs and lower triglyceride levels than those in the E-only group. There were no interaction, time, or group effects observed for HDL-C, systolic BP, or diastolic BP.
Association Between SM and Physical Outcomes for Patients With Clinical Elevations on Outcome Measures
Results of the RM-ANCOVA revealed a time-by-group interaction for systolic BP, F1,183 = 8.31, P = .004 (Figure 3; Table 4). Pairwise comparisons indicated a greater decrease in systolic BP from T1 to T2 for patients in the E + SM group relative to those in the E-only group, t(1) = 2.07, P = .040.
A similar time-by-group interaction was observed for waist circumference, F1,722 = 4.04, P = .045 (Figure 4). Pairwise comparisons indicated a greater decrease in waist circumference from T1 to T2 for patients in the E + SM group relative to those in the E-only group, t(1) = 2.12, P = .034.
Main effects of time were revealed for diastolic BP, F1,152 = 5.63, P = .019; functional capacity, F1,112 = 16.95, P < .001; and HDL-C, F1,383 = 14.37, P < .001. Specifically, diastolic BP decreased and functional capacity and HDL-C increased from T1 to T2. There were no interaction, time, or group effects observed for total cholesterol, LDL-C, triglyceride levels, or BMI.
Patients in both the E + SM group and the E-only group reported significant improvements in waist circumference and functional capacity from baseline to 12-week followup. Similarly, diastolic BP, functional capacity, and HDL-C improved for patients with clinically elevated baseline values on these measures, regardless of the group. Although waist circumference, in general, is highly correlated with BMI,21 patients in the E + SM group had smaller waist circumferences but higher BMIs than those in the E-only group at both time points. There is no natural explanation for this finding, but it will be interesting to see whether a similar phenomenon appears in future research. Results from this study also demonstrate incremental benefits of stress management over exercise for 2 risk factors associated with CVD recurrence. Specifically, the findings are the first to indicate that participation in E + SM was associated with greater reductions in waist circumference and systolic BP for patients with baseline clinical elevations, relative to participation in E only. This suggests that participation in stress management may be beneficial for CR patients to improve efforts aimed at secondary and tertiary prevention. The incremental benefits of stress management on reduced waist circumstance and BP are not surprising given that stress can affect both biological mechanisms22,23 (eg, stimulating the release of inflammatory cytokines and “stress hormones” such as cortisol) and health behaviors24 (eg, reducing the likelihood of healthy eating and regular exercise) that may contribute to increased abdominal adiposity and elevated BP.
With respect to psychosocial functioning, patients in both the E + SM group and the E-only group reported significant improvement in symptoms of depression and physical quality of life from baseline to 12-week followup. Baseline depressive and anxious symptom severity in this sample is similar to that found in other studies that have administered the HADS prior to CR.25–28 Although the E + SM group had more symptoms of depression and lower physical quality of life than the E-only group at baseline, there were no differences between the groups at 12 weeks. Improvements in depressed mood after stress management in CR have been found in previous research.6,11 However, results to date on changes in quality of life following stress management have been equivocal. Specifically, only 2 of the 5 studies conducted have reported improvements in quality of life associated with stress management. A comparison of findings is difficult because of the different definitions, methodologies, and measurements of quality of life used in each study.29,30 The present study points to the efficacy of stress management for alleviating depressive symptoms and improving quality of life, but it must be interpreted with caution because of the nonrandomized, retrospective design.
This study has several limitations. Patients self-referred to the stress management program, so the results of this study may be applicable only to patients who are receptive to the idea of stress management, to patients who believe that stress is a modifiable risk factor for CVD prognosis, or to patients who are motivated to enroll in and complete a stress management class. It is noteworthy that only 12% of the total sample enrolled in stress management and, in general, <20% of patients attend optional classes at this CR program. This is possibly due to the additional time and burden associated with stress management and other optional classes. Nevertheless, the greater depressive and anxious symptoms and lower quality of life in the stress management group suggest that patients who self-refer to stress management have higher levels of general distress upon CR admission. Thus, the program is attracting individuals with significant levels of distress. Also, the majority of patients were men, which is generally consistent with other studies within the area of CR.31 This is especially important considering that depression and anxiety are more prevalent in women than in men, and it has been suggested that women may have different treatment needs than men.32–34 Furthermore, regression to the mean could account for some of the similarity between the E-only group and the E + SM group after program completion.
Future research should examine the characteristics of patients most likely to benefit from stress management to identify the factors that may influence goodness of fit between the individual and the stress management intervention. Randomized, controlled trials are needed to help understand the causal relations between stress management and physical and psychosocial health in CR populations. This is the objective of the ongoing ENHANCED study,35 in which 150 outpatients with a documented history of CVD will be randomly assigned to one of two 12-week programs: standard CR or stress management–enhanced CR. Cardiovascular biomarkers and quality of life will be assessed posttreatment, and clinical events will be assessed during a followup of 6 months to 4 years.
A key strength of this study is that it was performed in a clinical setting, which provides insight into the practical utility of stress management in CR programs. The main findings indicate that patients who chose to participate in stress management in addition to exercise had larger reductions in waist circumference and systolic BP if they had clinically elevated baseline values on these measures. This supports future research efforts aimed at uncovering the potential benefits of adding stress management as a core component of CR.
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anxiety; cardiac rehabilitation; depression; health-related quality of life; stress management
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