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Self-Efficacy as a Predictor of Adult Adjustment to Sickle Cell Disease: One-Year Outcomes

Departments of Psychology (R.E.) and Maternal and Child Health (J.T., H.C.) and School of Nursing (J.L.), University of Alabama at Birmingham, Birmingham, Alabama.

Address reprint requests to: Joseph Telfair, DrPH, MSW, University of Alabama at Birmingham, 1530 3rd Avenue South, RPHB 320, Birmingham, AL 35294-0022. Email: jtelfair{at}uab.edu

	ABSTRACT

TOP ABSTRACT INTRODUCTION METHODS RESULTS DISCUSSION APPENDIX ACKNOWLEDGMENTS REFERENCES

 
OBJECTIVE: The present study prospectively investigated the role of self-efficacy in predicting disease symptomatology and health services utilization for adult patients with sickle cell disease.

METHODS: These data are derived from a 12-month prospective cohort study of African American adults with sickle cell disease. Disease-specific perceptions of coping self-efficacy and indices of disease severity, health care utilization, and psychosocial adjustment were assessed by use of standardized questionnaires administered by trained clinicians.

RESULTS: Perceptions of self-efficacy for coping with sickle cell disease were moderately stable across the 12-month study period. At baseline (N = 147), significant inverse relationships, measured with Pearson correlations, were noted between self-efficacy and the following variables: physical symptoms, psychological symptoms, pain severity, and number of physician visits over the preceding 12 months (p < .01). Similar relationships with self-efficacy were noted at the 1-year follow-up (N = 104) period for measures of physical symptoms, psychological symptoms, and pain severity (p < .01). In multiple-regression models, baseline self-efficacy scores predicted changes over the 1-year study period in physical and psychological sickle cell disease symptomatology. Moreover, changes in self-efficacy from baseline to 1-year follow-up were significantly and independently related to changes in physical symptoms, psychological symptoms, and pain ratings from baseline to 1-year follow-up.

CONCLUSIONS: Self-efficacy beliefs among African American adults with sickle cell disease are inversely related to reported disease symptomatology, and these relationships persist across time. Future investigations should examine the mechanisms through which relationships between self-efficacy and adjustment to sickle cell disease are effected, as well as the feasibility and effectiveness of enhancing self-efficacy beliefs as a means of improving adjustment to sickle cell disease.

Key Words: sickle cell disease • self-efficacy • chronic illness • longitudinal

Abbreviations: SCD = sickle cell disease; SCSES = sickle cell self-efficacy scale

	INTRODUCTION

TOP ABSTRACT INTRODUCTION METHODS RESULTS DISCUSSION APPENDIX ACKNOWLEDGMENTS REFERENCES

 
SCD is an inherited blood disorder that affects approximately 50,000 to 65,000 individuals, generally of African descent, in the United States (1). Individuals with SCD are at increased risk for significant health complications as a result of the production of abnormally sickle-shaped red blood cells. Characteristic symptoms of SCD include pain, stroke, anemia, pulmonary dysfunction, and major organ complications (2). The most frequent intractable problem encountered by persons with SCD is painful tissue ischemia that results from vaso-occlusive episodes (3). Areas of reported pain often include the abdomen, chest, low back, joints, and extremities. In addition to physical complications, individuals with SCD are more likely to report emotional and psychosocial difficulties such as depression, anxiety, and social isolation (4, 5). The direct and indirect costs of SCD treatment are substantial (5), and studies are needed to identify predictors of adjustment to SCD to enhance quality of life and reduce medical costs in this population.

Although the constellation of SCD symptomatology tends to be similar for most individuals with the disease, significant interindividual variability in the reported frequency, intensity, and impact of symptoms also has been noted (5, 6). As a result of this considerable variability in SCD-related physical and psychological symptomatology, many researchers have turned their attention to the investigation of factors that may account for such variability. These studies have concluded that, in general, disease severity and related illness parameters tend to account for little of the variance in SCD adjustment (6–9), which suggests that psychosocial variables may play a more influential role in determining adjustment to SCD (5, 6, 9, 10). In this regard, several studies have found that psychosocial variables such as coping, stress, depression, and worry may relate to SCD adjustment (4, 5, 11). However, this literature is relatively limited, with an emphasis on the role of coping strategies in the prediction of children and adolescents’ adjustment to SCD (7, 8, 12). Because most children with SCD now survive far into adulthood (13, 14), researchers need to examine psychosocial factors that affect adjustment to SCD among adults as well as children.

One important psychosocial variable that may influence coping among persons with SCD is self-efficacy (15, 16). Self-efficacy refers to personal judgments concerning one’s ability to engage successfully in specific behaviors that lead to specific, desired outcomes. Ample evidence exists concerning the utility of the construct of self-efficacy. In particular, self-efficacy beliefs have been noted to play an important role in adjustment to such chronic conditions such as fibromyalgia (17), arthritis (18), chronic low back pain (19), diabetes (20), cystic fibrosis (21), multiple sclerosis (22), and chronic obstructive pulmonary disease (23). In these studies, higher levels of self-efficacy were associated with reduced physical symptomatology (eg, severity of pain) and improved psychosocial functioning (eg, lower levels of depression, stress, and anxiety). The results of these investigations suggest that high levels of self-efficacy for coping with or reducing disease symptomatology may act as a buffer for individuals with chronic conditions. Although the mechanisms that underlie the positive benefits of self-efficacy for adjustment to chronic illness remain unclear, self-efficacy beliefs may exert their effects, in part, by facilitating positive health behaviors and reducing the impact of stressors associated with a chronic condition (24, 25).

Recent data have suggested that self-efficacy for the management of chronic illness not only influences current levels of symptomatology but also may affect the course of disease across time. In other words, enhanced self-efficacy beliefs at a given time point may be associated with future decrements in disease symptoms and improvements in adjustment. Indeed, longitudinal studies have documented the beneficial effects of enhanced self-efficacy over a period of months or years in such populations as cardiac patients (26), patients with arthritis (27), patients with cancer (28), older adults (29), and patients with fibromyalgia (30). Results from these investigations suggest that higher baseline levels of self-efficacy are associated with fewer physical and emotional problems at various follow-up periods.

Collectively, recent studies indicate that self-efficacy is an important factor in psychosocial and physical adjustment for persons with a chronic medical condition. Thus, the potential utility of the construct of self-efficacy in SCD is evident. To date, however, only four investigations have examined the role that self-efficacy may play in psychosocial adjustment to SCD. In the first study (31), higher efficacy expectations were associated with improved psychological adjustment (operationalized as lower scores on the Symptom Checklist-90, a self-report measure of general distress) in a sample of adults with SCD. In the second study (9), although self-efficacy beliefs were associated with lower levels of distress at the baseline assessment, baseline self-efficacy did not predict psychological adjustment as measured at the 20-month follow-up. In the third study (11), efficacy expectations were inversely associated with the degree of psychopathology in a sample of children with SCD. Although these three studies provide support for the positive relationship of self-efficacy to SCD adjustment, none incorporated use of a psychometrically validated measure of self-efficacy for coping with SCD, because no such measure was available at the time. Furthermore, measurement of efficacy beliefs was typically accomplished by use of single-item responses, which are less reliable and sensitive than multi-item scales as indices of self-efficacy (32).

Finally, a recent study by our research group (33) tested the reliability and validity of a nine-item scale that assesses self-efficacy for coping with and managing SCD in adults. The SCSES demonstrated good internal consistency and showed significant positive relationships with the related constructs of self-esteem, mastery, and internal locus of control. In addition, we noted inverse relationships between self-efficacy for coping with SCD and such variables as pain severity, SCD-related physical symptoms, and health-care utilization in a sample of adults with SCD. Of the studies that have examined the role of self-efficacy in psychosocial and physical adjustment to SCD, only the most recent (33) used a psychometrically validated, disease-specific measure of self-efficacy for coping with and managing SCD. The present investigation was designed to extend previous work by assessing the role of disease-specific self-efficacy in the prediction of SCD symptomatology and health-care utilization at multiple time points.

Using a longitudinal, prospective design, we investigated self-efficacy for coping with SCD as a predictor of SCD adjustment at two time points separated by 1 year. We used multiple dependent measures to assess physical and psychological symptomatology as well as behavioral responses to SCD symptoms (ie, health care utilization) to represent the multidimensional construct of adjustment (12, 25, 26). The present study sought to examine (1) the relationships between self-efficacy and SCD adjustment at each time point, (2) the ability of baseline levels of self-efficacy to predict 1-year outcomes, and (3) the relationship between changes in self-efficacy over 1 year and changes in SCD adjustment over that same year. On the basis of the initial findings from our original cross-sectional study (33), as well as the work of Thompson and colleagues (11, 31), we anticipated that self-efficacy would be positively related to adjustment at both time points, that baseline measures of self-efficacy would predict 1-year follow-up adjustment, and that changes in self-efficacy from baseline to follow-up would be positively associated with changes in adjustment over that same period.

	METHODS

TOP ABSTRACT INTRODUCTION METHODS RESULTS DISCUSSION APPENDIX ACKNOWLEDGMENTS REFERENCES

 
Patient Sample
Patients were recruited from a regional Sickle Cell Association in Greensboro, North Carolina. Inclusion criteria for the study were 1) age of at least 18 years old and 2) a confirmed positive diagnosis of SCD. Of the eligible clients of the Sickle Cell Association, 147 provided informed consent and completed an extensive psychosocial interview. No information was available regarding individuals who were contacted but did not participate. The data presented in this study concern those 147 individuals who completed baseline assessments and 104 subjects (71% of original sample) who also completed assessments 12 months later. The remaining 43 participants (29% of original sample) were unreachable by phone or mail because of relocation with no forwarding address or disconnection of phone service. All of the research procedures described in the present study were approved by the Sickle Cell Disease Association of the Piedmont’s project oversight staff.

Procedure
Potential subjects were contacted by phone by one of two trained nurse interviewers who described the nature of the study and obtained preliminary consent to interview the subjects. After providing written and verbal informed consent, participants were interviewed by one of the nurses. See Edwards et al. (33) for a more detailed description of the study protocol.

Measures
Self-efficacy. Self-efficacy for the perceived ability to engage in daily functional activities despite having SCD was measured with the nine-item SCSES. The SCSES provides an overall index of self-efficacy by summing item scores; higher scores indicate greater self-efficacy. Response categories for each item range from "not at all sure" to "very sure." Please refer to the Appendix for a complete list of items comprising the SCSES. We have documented the reliability and validity of the SCSES in a prior study (33).

SCD adjustment. Disease-specific symptomatology was measured with three indices, composed of a total of 20 items. The first index required patients to rate the severity of their SCD pain for the preceding 30 days along a 10-point Likert scale (1 = no pain to 10 = very severe pain). For the second symptom index, patients rated the frequency of 11 physical symptoms over the preceding 6 months: weakness, yellowing of skin or eyes, vomiting, nausea, pain, heart problems, gall stones, eye trouble, kidney problems, swelling of hands or feet, and shortness of breath. Response categories were 1 = never or rarely (zero or one time), 2 = not very often (two or three times), 3 = often (four or five times), or 4 = very often (six or more times). An overall physical symptom index was created by summing all item scores, with greater scores indicating higher levels of reported physical sympotmatology. Cronbach’s alpha for these 11 items was 0.81, which indicates good internal consistency. For the third index, patients rated the frequency of eight psychological symptoms over the preceding 6 months: feeling sad, feeling tense or nervous, feeling short-tempered, feeling worried or concerned, problems coping, problems sleeping, problems eating, and problems paying attention. Response categories for items comprising this index were identical to those described above (ie, 1–4). A total psychological symptom index was calculated by summing responses to all eight items, with higher scores indicating more reported psychological symptomatology. Cronbach’s alpha for these items was 0.84, which reveales good internal consistency. Previous studies (4, 8, 31, 33) have used similar measures of physical and psychological symptomatology.

A gross measure of health-care service utilization was assessed with a single item: the number of physician visits in the past 12 months. Previous research with patients who have SCD has indicated that self-report of health care utilization is highly correlated with actual utilization, as documented by medical record review (4).

Data Analysis
First, logistic regression was used to assess predictors of the availability of follow-up data. To determine the cross-sectional associations between self-efficacy scores and SCD adjustment variables at both baseline and 12-month follow-up, Pearson correlations were calculated. To control the type I error rate, only correlations significant at p < .01 were interpreted as statistically significant. Temporal stability of the variables employed in the present study was assessed by use of intraclass correlation coefficients, and changes from baseline to 12-month follow-up in self-efficacy and the dependent variables were assessed with repeated-measures analysis of variance. Prospective relationships between self-efficacy scores and changes in SCD adjustment from baseline to 12-month follow-up were investigated by calculating change scores (ie, the baseline value was subtracted from the value of the variable at 1-year follow-up) for each of the variables in the study. Next, we used multiple regression analysis to predict changes in physical symptoms, psychological symptoms, pain severity, and physician visits over the 1-year study period. After controlling for demographic variables (ie, age and gender) and baseline adjustment scores, both baseline SCSES scores and changes in SCSES scores were entered as predictor variables. Again, alpha was set to p < .01 to guard against inflation of type I error.

	RESULTS

TOP ABSTRACT INTRODUCTION METHODS RESULTS DISCUSSION APPENDIX ACKNOWLEDGMENTS REFERENCES

 
Sample characteristics are summarized in Table 1. A logistic regression analysis was performed that used demographic and study variables to predict the availability of follow-up data. The 104 patients who completed both baseline and 1-year follow-up assessments were coded as 1', and the 43 individuals who completed only the baseline assessment were coded as 2'. Results of this analysis appear in Table 2. Individuals who were lost to follow-up were more likely to be male (p = .04). No other study variables predicted the availability of follow-up data.

Temporal Stability
Descriptive data for the SCSES and for all dependent measures at both time points are provided in Table 3. Intraclass correlations between baseline and follow-up scores for the SCSES and all dependent measures were computed. SCSES scores were moderately stable over the 1-year study period (r = .46), as were scores for most dependent measures (intraclass correlations ranging from .37 to .57). Intraclass correlations were significant for all study variables (p < .01). Repeated-measures analyses of variance indicated that mean SCSES and dependent variable scores did not change from baseline to follow-up, although individual variability was considerable (Table 3).

Zero-Order Correlations Between Self-Efficacy and SCD Adjustment
Table 4 displays the zero-order correlations between self-efficacy and the four dependent variables (pain ratings, physical symptoms, psychological symptoms, and physician visits). SCSES scores were significantly associated with all four of the SCD adjustment variables at baseline and with three of the variables at 12-month follow-up (p < .01). At baseline, higher levels of self-efficacy were associated with fewer physical and psychological symptoms, less pain severity, and fewer physician visits. At the 1-year follow-up, higher SCSES scores were significantly related to fewer physical and psychological symptoms and decreased reports of pain severity.

Longitudinal Prediction of SCD Adjustment
Multiple regression analysis was used to determine relationships between self-efficacy and changes in dependent measures from baseline to 1-year follow-up. Specifically, we were interested in whether baseline levels of self-efficacy could predict future changes in symptomatology and health care utilization and whether changes in self-efficacy over the 1-year study period were independently associated with changes in these outcome variables. In separate analyses for each outcome measure, demographic variables (ie, age and gender) and the baseline value of the outcome measure were entered into the multiple regression analysis, with the change in the outcome measure (ie, physical or psychological symptoms, pain ratings, or physician visits) from baseline to follow-up as the dependent variable. Baseline SCSES scores were entered as well, to determine the unique ability of self-efficacy scores to longitudinally predict changes in SCD adjustment. Finally, changes in SCSES scores from baseline to follow-up were also included as predictor variables to examine independent relationships between changes in self-efficacy and changes in the outcome variables.

The multiple regression analyses revealed that baseline self-efficacy scores were inversely related to changes in physical symptoms (Table 5), psychological symptoms (Table 6), and pain ratings (Table 7) over the 1-year study period. That is, higher baseline self-efficacy was associated with decreases in physical symptoms, psychological symptoms, and pain severity as assessed 1 year later. Moreover, changes in self-efficacy were independently associated with changes in physical symptoms, psychological symptoms, and pain ratings, again in an inverse manner. Increases in self-efficacy from baseline to follow-up were related to decreases in symptomatology over the 1-year study period. Neither baseline self-efficacy nor changes in self-efficacy predicted changes in reported physician visits from baseline to follow-up (Table 8).

	DISCUSSION

TOP ABSTRACT INTRODUCTION METHODS RESULTS DISCUSSION APPENDIX ACKNOWLEDGMENTS REFERENCES

 
This study is one of the first systematic investigations of the impact of self-efficacy on short-term and long-term adjustment to SCD. Adults with SCD who reported lower levels of self-efficacy tended to report more physical and psychological SCD-related symptoms, more severe SCD pain, and more frequent physician visits (although this relationship was markedly less robust than relationships between self-efficacy and reported symptomatology) than did those patients who reported relatively greater levels of self-efficacy. Thus, levels of SCD-specific efficacy beliefs related negatively to levels of SCD symptomatology and health-care utilization. Moreover, similar results were observed at both baseline and 12-month follow-up assessments, which highlights the importance of ongoing assessment of efficacy beliefs in the context of a chronic illness such as SCD. These findings are in agreement with previous investigations of self-efficacy beliefs in SCD (9, 31, 33), as well as in other chronic conditions (24, 27, 34, 35).

Efficacy beliefs were moderately stable over the 1-year study period, as were measures used as outcome variables (physical and psychological symptoms, pain severity, and physician visits). Although several previous studies in patients with fibromyalgia and arthritis (27, 36) appeared to indicate that changes in self-efficacy were a better predictor of outcomes than baseline levels of efficacy beliefs, the present findings suggest that baseline levels of self-efficacy and temporal changes in self-efficacy are uniquely associated with changes over time in SCD symptomatology. After controlling for demographic variables and baseline values of the dependent measures, higher baseline self-efficacy was predictive of decreases in physical symptoms, psychological symptoms, and pain severity over the 1-year study period. Similarly, changes in self-efficacy, independent of baseline levels of self-efficacy, were inversely related to changes in symptomatology from baseline to follow-up. Overall, it seems that individuals with increasing levels of self-efficacy may be at reduced risk for poor SCD adjustment, as indexed by decreased levels of physical and psychological symptomatology. The present findings are somewhat inconsistent with the longitudinal study of psychosocial adjustment to SCD by Thompson and colleagues (9). Their results suggested that baseline efficacy beliefs were not associated with stable positive adjustment over 20 months. However, they did not use a validated disease-specific measure of SCD efficacy beliefs and efficacy was measured at only a single time point (baseline). The current data suggest that 1) self-efficacy beliefs at a single time point are inversely related to SCD symptomatology and health-care utilization; 2) present self-efficacy beliefs may be predictive of future changes in SCD symptomatology, with higher current self-efficacy predicting future decreases in physical and psychological symptoms; and 3) changes in SCD symptomatology are related negatively to changes in self-efficacy over a 1-year period. These results highlight the value of ongoing assessment of self-efficacy beliefs across multiple time points. The mechanisms by which efficacy beliefs might influence physical and psychosocial outcomes remain incompletely understood. Prior investigations have suggested that individuals’ efficacy beliefs influence a number of behavioral, cognitive, affective, and physiological variables (25, 37). For example, enhanced efficacy beliefs are associated with diminished perceptions of stress (38), activation of physiological events such as augmented release of endogenous opioids (39), use of more adaptive coping mechanisms (40), decreased anxiety (41), and better adherence to medical regimens (35). At present, it is not known which, if any, of these and related variables could account for the documented effects of self-efficacy on adjustment to a chronic illness such as SCD.

Bandura (15, 16) emphasizes that self-efficacy expectations are not stable personality traits but are malleable, situation-specific personal beliefs. Sources for self-efficacy beliefs include the individual’s perceived and actual performance level, cognitive state, and physical and emotional arousal level. Each of these sources, partially via effects on self-efficacy expectations, can shape adjustment in patients with SCD. By strengthening efficacy beliefs, the physical and psychosocial burden of SCD may be diminished, which ultimately may produce a diminished need for health services, with consequent decreases in direct and indirect treatment costs associated with SCD. A number of individual and group interventions have been shown to produce positive effects on self-efficacy in other populations (27, 35, 41). Moreover, several recent randomized, controlled trials have suggested that brief cognitive, behaviorally oriented counseling may improve patient’s self-efficacy and positively affect health outcomes in patients after myocardial infarction (42), patients with arthritis (43), patients with diabetes (44), patients with chronic pain (45), patients recovering from coronary artery bypass surgery (46), patients with fibromyalgia (47), and older adults with macular degeneration (48). In a recent trial that assessed the effects of coping skills training provided via educational videotapes to a sample of patients recovering from coronary artery bypass surgery (46), improvements in self-efficacy in the intervention group were shown to mediate the beneficial effects of the intervention (ie, improved health behaviors and shorter hospital stays).

On the other hand, not all such interventions enhance self-efficacy and improve long-term health outcomes. A recent trial of a self-monitoring intervention in patients undergoing hemodialysis found no difference between treatment and control groups in self-efficacy or physical health (49). In addition, a smoking prevention program in postpartum women did enhance their self-efficacy beliefs relative to the control group but had no effect on smoking status or health outcomes (50). Several other recent trials of psychosocial interventions in pregnant women have indicated no impact of education programs on patients’ health behaviors or health outcomes (51, 52). Thus, although a good deal of promising research suggests that brief, relatively low-cost interventions may enhance patients’ self-efficacy beliefs and facilitate health, such positive findings are not universal, and the capacity of a given intervention to promote improved efficacy and better health outcomes may depend on the population in which it is implemented. Although the effects of such interventions have not, to our knowledge, been documented in the population of adults with SCD, future longitudinal studies may wish to implement and study such interventions. Given the availability of interventions that have been demonstrated to enhance self-efficacy, it may be clinically beneficial to identify at-risk individuals low in self-efficacy to reduce adverse SCD impact. Although at least one recent randomized controlled trial found no benefit of additional psychosocial intervention for patients experiencing high levels of distress (53), the intervention employed in that study appeared to be composed of fairly nonspecific phone contacts by social workers. It may be the case that specific interventions targeted at enhancing self-efficacy for coping with chronic medical conditions are necessary to achieve the desired outcomes. Effective, relatively low-cost interventions such as psychoeducational groups, individual counseling, or group therapies (41) may facilitate increased efficacy beliefs and improved adjustment to SCD, thus increasing client and provider satisfaction.

Several limitations of the present study should be noted. First, there was a significant dropout rate, with only 71% of the original participants completing a 1-year follow-up assessment. Although dropout was generally not associated with the measured baseline variables (with the exception that nonreturners were more likely to be male), it is certainly possible that individuals who did not return for follow-up differed from those who did on important but unmeasured variables. Second, the present investigation relied entirely on participant self-report data, the many potential limitations of which have been well-documented (54). Although constructs such as self-efficacy, pain severity, and psychological symptoms such as distress are generally measured by self-report, several of the dependent measures such as the number of physician visits and physical complications of SCD are amenable to more objective evaluation. Future investigations may benefit from inclusion of multiple data sources (eg, behavioral observations, report of family members, medical chart review, etc.). Third, the present study does not identify specific mechanisms for the effects of self-efficacy on SCD symptomatology and adjustment. As indicated above, self-efficacy beliefs may have substantial impact on behavior, physiological processes, or affective states. The present study does not provide an examination of the potential mediators of the effects of self-efficacy. Finally, although the prospective design used in the present study provides evidence of the use of self-efficacy in predicting SCD adjustment, it does not demonstrate causal relevance. An experimental design is necessary to demonstrate a causal role for self-efficacy in facilitating improved SCD adjustment. Investigation of one or more of the interventions suggested above, such as psychoeducational groups, in conjunction with appropriate control groups, would provide a stronger causal demonstration and perhaps a more sensitive estimate of the effects of self-efficacy on SCD adjustment.

	APPENDIX

TOP ABSTRACT INTRODUCTION METHODS RESULTS DISCUSSION APPENDIX ACKNOWLEDGMENTS REFERENCES

 

	ACKNOWLEDGMENTS

TOP ABSTRACT INTRODUCTION METHODS RESULTS DISCUSSION APPENDIX ACKNOWLEDGMENTS REFERENCES

Received for publication May 10, 2000.

Revision received December 30, 2000.

	REFERENCES

TOP ABSTRACT INTRODUCTION METHODS RESULTS DISCUSSION APPENDIX ACKNOWLEDGMENTS REFERENCES

 

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