Studies on the role of psychological factors in CR programs have merely focused on the role of negative affect. In contrast, little is known about the effects of positive affect in CAD. To the best of our knowledge, this is the first study to demonstrate that anhedonic patients, i.e. the lack of positive affect, reported more impaired health status and higher levels of health complaints prior to and after CR attendance compared with non-anhedonic patients. Furthermore, the current study pointed out that patients’ health status improved and somatic and cognitive symptoms decreased in both anhedonic as well as non-anhedonic patients over time. In addition, we found an interaction effect for anhedonia by time for somatic and cognitive symptoms, indicating that anhedonic patients reported more benefit from CR in terms of reduction in somatic and cognitive symptoms. The interaction effect for time by health status was not significant.
Our study was in line with previous findings, showing that CR may improve health status [2
] and diminish somatic and cognitive symptoms [28
]. However, in the present study, we were also able to identify a specific subgroup of patients—namely anhedonic patients—who consistently reported impaired health status and higher levels of somatic and cognitive symptoms despite CR attendance. The importance of anhedonia has been demonstrated previously in CAD, with anhedonia being a risk factor for major clinical adverse events following implantation of coronary-artery stents [18
], and the combined endpoint of adverse clinical events and all-cause mortality [17
]. The present study elaborates on these findings by showing that in a large sample of CR patients, patient-centered outcomes vary as a function of the level of anhedonia as well.
In addition, in this study, we replicated findings on the underlying factorial structure of the HADS. Originally, this instrument was developed to assess depressive and anxious symptomatology in hospitalized patients [20
]. However, two recent studies suggest that it is also possible to derive a measure of anhedonia from the HADS [18
]. Hence, with the HADS, it is possible to tap into several psychological constructs that have been shown to impact on patient well-being and prognosis in CAD without increasing patient burden, making it an opportune instrument to use in clinical practice. In line with these two other studies, we found that HADS assesses Negative Affect, Relaxed Affect, and Positive Affect. The construct validity of these subscales was confirmed by the significant medium to large correlations with the GMS, an instrument that previously has been shown to valid and reliably assess positive and negative affect [22
]. Furthermore, the three derived HADS scales were shown to be internally consistent (.83 < α < .67).
The notion of positive and negative affect not just merely being the opposite two ends of a continuum [10
], and the possibility that both types of affect can be present simultaneously, broadens the scope. The present study supports this notion, as the effects of anhedonia remained significant after controlling for the confounding effects of negative affect. The combined effects of negative and positive affect, i.e. the interaction between those two types of affect, might refine findings and contribute to a fuller understanding of the role of affect in the context of CAD.
Limitations of the current study must be acknowledged. First, we were not able to control for markers of disease severity, (e.g. left ventricular ejection fraction) as these were not consistently collected in the current study. Moreover, in the present study, we only evaluated the effect of anhedonia on short-term patient-centered outcomes. Whether these improvements remain over time is unknown, but it has been shown that the effects of CR on health status remain over time [35
]. Further, patients diagnosed with chronic heart failure were excluded in the current study, due to participation in another study. Results from the current study can therefore not be generalized to this specific patient group. Fourth, information on psychiatric diagnoses and objective outcomes, such as exercise capacity, are lacking. Finally, the present study was based on a between-subjects design and improvements in health outcomes cannot be attributed to CR, due to the lack of a control-group. Strengths of the study comprise the large sample size and the use of valid and reliable instruments to assess patient-centered outcomes. In addition, both generic as well as disease-specific questionnaires were administered to evaluate CR in CAD patients.
From a clinical point of view, studies on anhedonia pave the way for the development of new interventions for secondary prevention. Positive affect has been shown to be associated with biological indices of cardiac disease in healthy individuals, like salivary cortisol, systolic blood pressure, and inflammatory markers [37
]. However, up to now, most studies have focused on the detrimental effects of negative affective states, like distress [8
] and depressive symptoms [6
] on CR outcome. Our results indicate that anhedonia is also of importance in the context of CR. Consequently, incorporating and encouraging the development of skills to experience more positive affect might contribute to increased benefits from CR programs. Cognitive-behavioral therapy and mindfulness-based stress reduction have been shown to improve positive affect in medically ill patients [40
], and in older depressed patients at increased cardiovascular risk [42
], and might be effective in enhancing positive affect in patients attending CR.
Future studies are warranted to further determine the role of anhedonia on hard outcomes like (re-)hospitalization, major clinical adverse events (MACE), and survival. Anhedonia, or the lack of positive affect, independently predicted major clinical adverse events following implantation of coronary-artery stents [18
], and the combined endpoint of MACE and all-cause mortality in post-MI patients [17
] in previous studies. However, the current study is of importance as health status has been shown to predict mortality in CAD patients [43
], and patient-centered outcomes and the identification of its determinants have been advocated to bridge the gap between research and clinical practice [19
In conclusion, the present study showed that anhedonic CAD patients reported poorer health status and higher levels of somatic and cognitive symptoms prior to and after CR in comparison with non-anhedonic patients. Furthermore, health status improved and somatic and cognitive symptoms decreased in both anhedonic and non-anhedonic patients. Somatic and cognitive symptoms pre- and post-CR changed differentially for anhedonic and non-anhedonic patients, with anhedonic patients reporting more changes in somatic and cognitive symptoms. These findings underscore the importance of studying positive affect within the context of CR.