The Illness Intrusiveness Model in Male Veterans with Chronic Heart Failure
Background: Individuals suffering from chronic heart failure (CHF) experience adaptive and psychosocial challenges that originate from disease symptoms, and these symptoms often disrupt individuals’ valued lifestyles and activities; this interference is called illness intrusiveness. The illness intrusiveness theoretical model proposes that the relation of disease factors to psychological wellbeing is mediated by illness intrusiveness. The model also proposes that illness intrusiveness produces negative psychological effects by reducing individuals’ sense of personal (internal) control over valued life activities, with personal control serving as a mediator of the relation of illness intrusiveness to psychological wellbeing.
Researchers who have examined the illness intrusiveness model have operationalized personal control in two ways. Consistent with the illness intrusiveness model, personal control has been assessed in terms of the extent of control individuals believe they have over various domains of functioning or their valued life activities, which can be construed as a direct consequence of the illness itself (e.g., Poochikian-Sarkissan, Sidani, Wennberg, & Devins, 2008). However, other researchers have operationalized personal control as health locus of control (HLC), which refers to individuals’ beliefs regarding to what extent with their actions they can make a difference in the progression of their disease (e.g., Talbot, Nouwen, Gingras, Belanger, & Audet, 1999). HLC can be construed as a personality predisposition consistent with Julian Rotter’s (1966) Locus of Control theory. A study that examined internal HLC control as a mediator of the relation of disease factors to psychological wellbeing operationalized the construct similar to Rotter’s original definition. Their results indicated that internal HLC contributed little variance to depression and that the model including personal control as a mediator was not the best fit for the data (Talbot et al., 1999). The illness intrusiveness model also proposes that psychological factors may moderate the relationship between illness intrusiveness and wellbeing. Therefore, it is possible that internal HLC assessed as a personality predisposition (e.g., a psychological factor) will moderate, rather than mediate, the relationship between illness intrusiveness and anxiety symptom severity. Purpose: No published studies were located that assessed whether patients’ perceived level of internal HLC over the progression of their disease might moderate the relationship between illness intrusiveness and anxiety symptom severity in Veterans diagnosed with CHF. Thus, the purpose of this study was to examine among Veterans diagnosed with CHF illness intrusiveness as a mediator of the relation between disease severity and anxiety symptom severity, and internal HLC as a moderator of the relation between illness intrusiveness and anxiety symptom severity. The hypotheses were a) that illness intrusiveness would mediate the relation between HF severity and anxiety symptom severity, and b) the relationship between illness intrusiveness and anxiety symptom severity would be strengthened for Veterans with
a lower endorsement of internal HLC, and that either a non-significant or less strong relationship would occur with a higher endorsement of internal HLC. Methods: Archival data of approximately 116 adult male Veterans (ages 49-88; see demographic variables in Table A1) from two Veterans Affairs hospitals in the United States who participated in a baseline screening for an ongoing effectiveness/implementation trial of brief cognitive behavioral therapy (bCBT) were used for the study. Participants in the database were diagnosed with CHF, chronic obstructive pulmonary disease (COPD), or both, and comorbid symptoms of anxiety and/or depression; however, only data from Veterans diagnosed with comorbid CHF and anxiety were used in this study. The Kansas City Cardiomyopathy Questionnaire (KCCQ; Green, Porter, Bresnahan, & Spertus, 2000) was used to assess disease severity, the Beck Anxiety Inventory (BAI; Beck & Steer 1990) was used to assess anxiety symptom severity, the Heart Failure Illness Intrusiveness Rating Scale (HF IIRS; Devins et al., 1983; Devins, 2010) was used to assess illness intrusiveness, and the Internal Health Locus of Control subscale of the Multidimensional Health Locus of Control Scale, Form C (MHLC; Wallston, Stein, & Smith, 1994) was used to assess the internal HLC construct. Preliminary analyses were conducted to examine the bivariate correlations of the variables included in the study. To examine the first hypothesis, a simple mediation model was tested using a non-parametric, bias-corrected bootstrapping procedure to examine the indirect effect of illness intrusiveness on the association between CHF severity and anxiety symptom severity using macros provided by Preacher and Hayes (2004; 2008). Age was used as a control variable because research indicates differences in distress levels from the effects of illness intrusiveness in younger versus older patients. To examine the second hypothesis, hierarchical regression analysis was used to examine to what extent internal HLC moderates the relation of illness intrusiveness to anxiety symptom severity. Two steps were involved in this analysis to test for moderation. Step 1 included the control variable of age, as well as illness intrusiveness and internal HLC to test for the main effects of the predictor and moderator. In Step 2, the interaction term (e.g. illness intrusiveness by internal HLC) was included to examine to what extent it explains additional variance in anxiety over and above the variance explained by the others (Baron & Kenny, 1986).
Results: Bivariate correlations showed that age and internal HLC were not related to any of the variables of interest; however, the other variables of anxiety, illness intrusiveness, and CHF severity were related to each other as expected (see Table A2). Results of the first analysis indicated that illness intrusiveness significantly mediated the relation of CHF severity to anxiety symptom severity in this sample; this finding is consistent with existing research and supports the first hypothesis of the study. Results of the second analysis showed that although the overall model was significant and the combination of illness intrusiveness and internal HLC share approximately 14% of the variance with anxiety, the change in R2 from step one to step two was not statistically significant. This finding indicates that the relation of illness intrusiveness to anxiety is not moderated by internal HLC in this sample, thereby not supporting the second hypothesis of this study. Conclusion: The results of this study are consistent with existing literature and suggest that illness intrusiveness mediates the relationship between CHF severity and anxiety symptom severity. These findings highlight the importance of examining and treating CHF patients’ level of illness intrusiveness in order to hopefully reduce their level of anxiety. Future research on the illness intrusiveness theoretical model using a larger sample size will allow clinicians and other health professionals to appropriately assess and treat patients diagnosed with CHF in an attempt to increase their quality of life.