Studies have focused on emotional distress after myocardial infarction. For example, Frasure-Smith et al1,2 have found substantial rates of depression in this group of patients. Fatigue and depression may be different expressions of the same phenomenon,3 but McGowan et al4 provided support for the idea that fatigue can be experienced by myocardial infarction patients without coexisting depression.
Earlier studies have primarily treated fatigue as a risk factor for developing coronary heart disease. The state "vital exhaustion," characterized by feelings of excess fatigue, lack of energy, irritability, and demoralization, has been postulated to be a precursor of a coronary event in otherwise healthy individuals.5,6 In a previous study of early readjustment from a first-time myocardial infarction, fatigue was found to be a common and bothersome health complaint affecting daily life functioning.7 Recent findings show that there may be a difference between pre- and post-myocardial infarction fatigue.8
Possible preventive and treatment measures for post-myocardial infarction fatigue may rely on gaining insight into the psychosocial factors associated with fatigue. One such factor may concern life orientation: the way people view life or expect their life course to develop. People differ widely in life orientation. It is assumed that optimism serves a protective function in the face of life's difficulties. Optimists expect things to go their way and generally tend to anticipate good outcomes, whereas pessimists expect things not to go their way and generally expect that bad things will happen to them.9 Optimism has been found to promote better recovery in patients with coronary heart disease10 and to be related to positive mood status in individuals undergoing coronary artery surgery.11 There are, to date, no studies on life orientation and fatigue in patients with coronary heart disease. Therefore, in the present study, we investigated the associations among optimism, depression, and fatigue 1 year after a first-time myocardial infarction. The hypothesis of this study was that patients with myocardial infarction who either possess or are able to develop an optimistic orientation toward life are protected from experiencing depression or fatigue in the readjustment process.
The sample included patients who had suffered a first-time myocardial infarction and were admitted to the coronary care unit at a Swedish rural hospital. Participants in this study were given information on coronary heart disease, risk factors, and lifestyle changes during their first week in the hospital. They were also invited to participate in weekly physical exercises led by a physical therapist. The present study investigates cross-sectional data from the 1-year follow-up of 98 patients, 33 women and 65 men (response rate, 74%). The mean (SD) age of the women and men was 71.4 (8.7) and 64.6 (9.8) years, respectively. One third of the total sample had a history of hypertension, and one fourth had a history of angina pectoris(Table 1).
The Hospital Depression Scale consists of two subscales, one for anxiety and one for depression. In this study, only the depression scale was used (seven questions). Items were scored on a four-point scale from normal (0) to severe depression (3). The Hospital Depression Scale was developed by Zigmond and Snaith12 for measuring mental distress in patients with physical illness and has been found to be a useful instrument with high reliability. Cronbach's α typically ranges between .80 and .9313; it was .81 in the present sample.
In the present study, the fatigue scale of the Somatic Health Complaints Questionnaire was used. This questionnaire includes 13 items concerning health problems common in cardiac patients. The items have been partly developed based on clinical experiences and partly modified from Rose et al.14 These questions have previously been used as separate items in several studies at Sahlgrenska University Hospital, Sweden.15 In a psychometric evaluation test of the Somatic Health Complaints Questionnaire, the subscale fatigue, containing four items, was identified (E. Brink, unpublished data). The fatigue items were general fatigue, weakness, lack of energy, and dizziness. Each item was answered using a six-point Likert scale, ranging from never experience (1) to always experience (6). Cronbach's α for the four-item subscale fatigue, in a myocardial infarction patient group, was .82, and in the present sample, .85.
The Life Orientation Test (LOT) was developed by Scheier and Carver9 to measure optimism. They found a Cronbach's α of .76. The LOT included eight items rated on a five-point scale, ranging from strongly disagree (0) to strongly agree (4). A high score indicates an optimistic tendency. This test has been used in several studies over the years and is found to be a reliable instrument associated with measures of coping, symptom reporting, and negative affect.16 In the present study, Cronbach's α for the scale was .79.
Besides means (SD) and Pearson's correlations, linear and curvilinear regression analysis models were used to describe and explore the associations between variables. The level of significance (α) was set at .05. A linear relationship occurs when an increase (decrease) in the independent variable is associated with a constant increase (decrease) in the dependent variable: y = b1x1 + c. There are, however, circumstances in which a nonlinear model is more suitable. For example, the knowledge improvement effect of reading the 1st course textbook is different from that of reading the 10th course textbook. Using a linear regression model on such data may indicate a weaker relationship than is actually the case. Instead, using a nonlinear model would create a curve whose shape more accurately models the effect of reading books on knowledge improvement. To create such a curvilinear model, a quadratic component is needed. A quadratic function is based on the square value of the independent value. By squaring all these values, a curved line is generated.17 This means that the relation between the independent and the dependent variable will become either U-shaped or an inverse-U shape: y = b1x1 + b2x21 + c.
In the present study, a hierarchical multiple regression analysis was performed, entering a linear regression analysis in step 1 and a quadratic component in step 2.
Means, SDs, and ranges for depression, fatigue, and LOT are displayed in Table 2. The theoretical ranges of scale scores were well covered by observed responses for the depression and fatigue scales. For LOT, the lowest theoretical scores were not covered by observed range scores, showing that no patient had an extremely pessimistic view. Also, LOT had the lowest standard deviation of the three variables measured (Table 2).
We found that fatigue and life orientation were correlated, which indicated a linear relationship (Table 3). The linear regression analysis (linear trend) between fatigue and life orientation showed an explained variance of R2 = 0.24 (P < .001; see Table 4 and Figure 1). Furthermore, when the quadratic term (b2x21) was added (curvilinear trend), it showed that this nonlinear model was an improvement upon the linear model, resulting in R2 = 0.27 (P< .05). The explained variance increased by three percentage points in the curvilinear model (see Table 4 and Figure 2), showing that the curvilinear model fit the data significantly better than the linear model did.
Depression was not significantly correlated with LOT, which indicates the absence of a linear relationship (Table 3). Also, a linear regression analysis with life orientation as the independent variable and depression as the dependent variable showed very low associations (0.9% explained variance). Adding a quadratic term did not improve the relationship, indicating that there was neither a linear nor a curvilinear relationship between depression and life orientation.
This study showed associations between fatigue and optimism in patients with myocardial infarction. Instead of accepting a linear model of the relationship between fatigue and optimism, we also tested a curvilinear model. The result showed an increase of three percentage points in the explained variance. This leads us to conclude that a pessimistic view of life may have more negative consequences, such as leading to the manifestation of fatigue, than an optimistic view of life has positive consequences. Our results are in line with a general finding in psychology that "bad" is more influential than "good." In a review of the literature, evidences were found for the phenomenon that when equal measures of good and bad are present, the psychological effects of the bad outweigh those of the good.18
However, others have found that an optimistic life orientation has been shown to protect health. In a study of patients undergoing coronary artery bypass graft surgery, optimism was predictive of a lower rate of rehospitalization.10 In a meta-analysis of LOT, optimism was found to be associated with decreased report of physical symptoms.16
One limitation of our result showing a nonlinear relationship between optimism and fatigue is that it is based on a small sample. Results are relevant for individuals with first-time myocardial infarction treated in a selected coronary care unit in a rural hospital. To conclude that our findings are valid for the population at large, further investigations using larger samples at several national and international coronary care units would have to be conducted. Another limitation is the cross-sectional design of the study, which makes it difficult to draw conclusions about cause and effect. However, our results do indicate associations between life orientation and post-myocardial infarction fatigue.
Given that fatigue is such a common and bothersome health problem after acute myocardial infarction, we found it important to deepen our understanding of this phenomenon. Many questions concerning fatigue symptoms after a heart attack remain unanswered. It may be essential to separate this from our knowledge of vital exhaustion, an independent risk factor for coronary heart disease. Also, McGowan et al4 concluded that future studies should investigate fatigue instead of vital exhaustion as a risk factor for poor prognosis in patients with myocardial infarction. In our study, the association between depression and fatigue was weak, which is not in line with the idea of Wojciechowski et al3 that fatigue and depression mirror the same phenomenon. Rather, based on our data, support is given to McGowan et al,4 who stated that fatigue may be experienced by myocardial infarction patients without coexisting depression.
Contrary to our hypothesis, optimism was not associated with depression. If we had used a larger sample, including a wider range of depression scores, we might have found a relationship between an optimistic life orientation and depression. Also, a longitudinal analysis could have revealed relationships between optimism and depression, in line with Scheier and Bridges,19 who found that pessimism is a prospective predictor of changes in depressive symptoms over time.
Implications for Nursing Practice
With respect to the process of readjustment after myocardial infarction, methodologically varied intervention research suggests that psychological interventions may improve heart disease prognosis.20-22 However, post-myocardial infarction fatigue is not explicitly focused on in such programs. According to Appels,6 if patients with coronary heart disease complain about tiredness, the health professional should tell them that this is not abnormal but avoid giving information on severe fatigue because this condition must be investigated further and understood better.
In the present study, variations in degree of pessimism and fatigue showed a stronger association than did variations in degree of optimism and fatigue. If life orientation (optimism-pessimism) has a causal impact on fatigue measures, then helping highly pessimistic individuals become less pessimistic would decrease fatigue more than would helping rather optimistic individuals become even more optimistic. Thus, with regard to the clinical implications of this study, one way to decrease postmyocardial fatigue could be to focus on steps that cause the most pessimistic individuals to feel less pessimistic.
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Keywords:© 2006 Lippincott Williams & Wilkins, Inc.
depression; fatigue; myocardial infarction; optimism