This study found that self-efficacy is important for understanding pain and behavioral adjustment in overweight and obese OA patients. Moreover, our analyses revealed that the contribution of self-efficacy was domain specific, as self-efficacy scales demonstrated significant associations with corresponding outcomes and not outcomes in general. Consistent with our hypotheses, associations were found between self-efficacy for controlling pain and pain, self-efficacy for performing physical activities and physical disability, self-efficacy for managing other (emotional) symptoms related to OA and psychological disability, and self-efficacy for restricting eating and eating behaviors. In addition, self-efficacy for restricting eating was associated with psychological disability. These results suggest that clinicians working to manage pain, disability, and eating behaviors in overweight OA patients need to assess patients’ perceptions of their self-efficacy for each domain.
One of the most interesting findings of this study was that the self-efficacy variables explained as much or more variance in pain, disability, and eating behaviors than demographic and medical variables (with the exception of the association between the impact of number of comorbid medical disorders and physical disability). Traditionally, medical variables such as BMI and disease severity, and demographic factors, such as age and sex, have been considered important in understanding pain and disability in this population (Jordan et al., 1996
; Larsson & Mattsson, 2001
). Indeed, in the present study, several of these factors did emerge as significant predictors. However, what is striking about our findings is that self-efficacy variables explained a significant proportion of the variance in outcomes even after statistically controlling for demographic and medical variables. These findings suggest that analysis of pain, disability, and eating behaviors in overweight and obese OA patients should not only examine medical and demographic factors, but also self-efficacy variables.
For overweight and obese OA patients, weight control is important for managing pain and reducing disability (Barofsky et al., 1997
; Bunning & Materson, 1991
; Creamer et al., 2000
). Thus, it is important for these patients to manage their eating and increase physical activity. This study found that self-efficacy for physical function explained a significant portion of variance in physical disability. Prior studies have found that self-efficacy for function is related to physical disability in arthritis patients (Harrison, 2004
; Maly, Costigan, & Olney, 2005), but to our knowledge this study is the first to examine the associations of self-efficacy to physical function in a sample of overweight and obese OA patients. Interestingly, the effects of self-efficacy for physical function were apparent even after controlling for BMI and pain. BMI was not associated with physical disability suggesting that physical disability in overweight and obese OA patients may depend more on self-efficacy beliefs than on patients’ body weight. In other words, OA patients may be overweight, yet if they retain a sense of self-efficacy for function, they may be less physically disabled by their arthritis. Therefore, maintaining confidence in one’s ability to engage in daily functional activities may be quite important for overweight and obese OA patients. Those patients who are able to maintain a high level of self-efficacy in the face of obesity may be much more likely to maintain their involvement in daily activities, which in turn can potentially contribute to increased strength, muscle conditioning, pleasant activities, and positive affect, all of which are important factors in adjustment to OA (Keefe et al., 1990
; Ikeda, Tsumura, Torisu, 2005
To our knowledge, the present study is one of the first to examine the degree to which self-efficacy for resisting eating is related to eating behaviors and psychological disability in overweight and obese OA patients. Our results indicated substantial variability in self-efficacy for resisting eating, suggesting that not all overweight and obese OA patients report difficulties controlling their eating. This is consistent with results showing that overweight and obese individuals, regardless of OA status, vary in their reports of self-efficacy for resisting eating (Clark et al., 1991
). Interestingly, those patients who reported higher self-efficacy for resisting eating had lower levels of psychological disability. There may be several reasons why self-efficacy for resisting eating is a significant predictor of psychological disability in this population. First, overweight and obese OA patients may feel that they should be able to resist eating, and those who feel they fail in this regard (i.e., who experience lower self-efficacy for resisting eating) may suffer greater psychological distress and negative affect compared to those with greater self-efficacy for resisting eating. Alternatively, patients who experience higher levels of psychological disability may have more difficulty controlling their eating because eating represents a way to cope with negative affect (Linde et al., 2004
). However, after statistically controlling for demographic and medical characteristics, there was no association between psychological disability and eating behaviors in this sample.
A limitation of the present study is that it utilizes a correlational design, which prevents us from drawing causal attributions about the effects of self-efficacy on pain, disability, and eating behaviors. Future studies employing longitudinal designs need to be conducted to examine causal relationships between changes in domain specific self-efficacy and changes in corresponding outcomes for overweight and obese OA patients. In addition, generalizability of our findings to the broader population of overweight OA patients may be limited because we included only those patients who had a body mass index between 25 and 42. There is an increasing number of OA patients who have a BMI greater than 42 (Must et al., 1999
), and this group of extremely obese patients may be different from less obese patients in important ways. Finally, our findings may be less generalizable because data were obtained from OA patients voluntarily seeking participation in a treatment study that targets weight loss and pain reduction. It would be interesting to determine whether a general population study of overweight OA patients would yield similar findings.
The design of this study allowed us to examine the relative importance of self-efficacy in explaining pain, disability, and eating behaviors in overweight and obese OA patients. We found that self-efficacy was domain specific, as self-efficacy scales significantly contributed to variance in corresponding outcomes and not outcomes in general. These findings suggest that strategies for enhancing domain specific self-efficacy are important for managing pain, disability, and food intake. Self-efficacy can be enhanced through a variety of sources, including accomplishments, verbal persuasion, observation of others, and development and practice of relevant skills (Bandura, 1977
). Intervention protocols for overweight and obese OA patients could benefit from including strategies designed to enhance self-efficacy for pain, physical function, emotional symptoms, and resisting eating (e.g., goal setting with self-monitoring of achieved goals, group-based behavioral rehearsal of pain coping skills, guided treatment- and home-based practice sessions). It may not be adequate to focus on general feelings of efficacy or to focus solely on one domain of self-efficacy in this population. For example, overweight and obese OA patients receiving only a weight management intervention may drop out prematurely or fail to maintain exercise behaviors due to perceived inability to control pain or perform physical activities. Combining pain coping skills training with behavioral weight management techniques may be more beneficial than either intervention alone for this population. We are currently evaluating this in a randomized clinical trial.