We investigated the effects of the HIOH intervention, a home delivery variant of the peer led CDSMP, on patient chronic disease management self-efficacy, employing a variety of conditions. The main effect of HIOH delivered in participants’ homes resulted in a significant improvement in disease management self-efficacy relative to the control and telephone-delivered HIOH groups, with a peak effect size (.3) at 6 weeks (immediately post-intervention) that is comparable to that observed in prior studies of peer led disease management interventions (Foster, Taylor, Eldridge, Ramsay, & Griffiths, 2007
). However, the effect of the home intervention on self-efficacy had wanted by 6 months and had completely attenuated by 1 year. Ours was the first randomized controlled trial of face-to-face delivery of the CDSMP to follow patients as randomized for a full year; prior studies followed patients as randomized for only 4 – 6 months. The only prior one year randomized controlled trial of the CDSMP involved the Internet-delivered variant of the program (Lorig et al., 2006
). That study also found a significant short-term effect on disease management self-efficacy, but again the effect was no longer significant by 1 year. Taken together, these findings suggest the self-efficacy enhancing effects of the CDSMP are relatively short lasting. Such time-limited benefits have been observed with other behavioral interventions, like cognitive behavioral therapy (Escobar, Gara, Diaz-Martinez, Interian, Warman, Allen et al., 2007
) and suggest the need to explore ‘booster’ interventions as a way of potentially maintaining improved outcomes.
Consistent with prior observational research (Judge et al., 2002
; Williams et al., 2004
), we found that the lower self-efficacy was associated with higher levels of neuroticism and lower levels of conscientiousness, agreeableness, and extraversion. We further examined whether the FFM personality factors moderated (Kraemer et al., 2002
) the disease management self-efficacy enhancing effects of the HIOH intervention. We found that the disease management self-efficacy enhancing effect of HIOH was significantly higher among those high in Neuroticism and/or lower in Conscientiousness. However, consistent with the attenuation of the overall intervention effects, we also observed attenuation of the beneficial effects on self-efficacy among those with higher levels of neuroticism, and/or lower levels of conscientiousness The findings suggest that the greater potential for improvement outweighed the possibility of greater resistance to the intervention.
There are several possible explanations for our finding that the HIOH variant of the CDSMP was most effective in individuals high in neuroticism and/or those low in Conscientiousness. First, such individuals tended to have lower disease management self-efficacy at baseline than did other participants in our study, regardless of study arm. Thus, participants with higher levels of Neuroticism and/or lower levels of Conscientiousness appear to have the most room for improvement in self-efficacy, and when assigned to an intervention that aggressively targeted this deficit, they responded.
Additionally, patient personality factors might also moderate the effects of interventions like HIOH if dispositional tendencies affect the way participants perceive and respond to their specific components, demands, and features (Christensen, 2000
). For example, the negative self-perceptions such as poor self-esteem and vulnerability have been included in most definitions of Neuroticism (Costa & McCrae, 1992
), and these lower self-evaluations may affect one’s perceived ability to achieve desired outcomes (Judge et al., 2002
). Given the link between negative affect and self-efficacy, interventions such as HIOH, which includes modules on affective regulation, may lead to self-efficacy improvements among individuals relatively high in Neuroticism by helping them cope with difficult emotions. Likewise, the moderating effects of Conscientiousness might be understood in the context of this personality factor’s core elements of self-control, organization and goal-orientation. Low levels of these tendencies are likely to give rise to worse health behaviors within the disease self-management domain, including poor diet and exercise habits (Bogg & Roberts, 2004
; Goldberg & Strycker, 2002
; Roberts, Walton, & Bogg, 2005
). Several aspects of the HIOH intervention would appear particularly beneficial to individuals low in Conscientiousness. For example, the concept of ‘action planning,’ or setting personal health goals, with revision as needed, is emphasized weekly throughout the intervention. This instructive scaffolding may be particularly useful to less Conscientious persons who tend to be disorganized, have lower levels of self control and are less likely to set goals and/or follow through with them. However, while all of these hypotheses appear plausible, our study was unable to test them. Future studies will be required to examine whether particular components of peer led disease self-management interventions interface with participant dispositional tendencies such as personality factors.
Openness was not found to moderate the effects of HIOH in our study. The initial hypothesis that it would had been based on the results of prior studies linking lower openness to lower general self-efficacy (Judge et al., 2002
), yet it is also the case that, of all the FFM personality factors, openness has had the most inconsistent and lowest associations with general self-efficacy (Judge et al., 2002
). Furthermore, in our study openness was not associated with the baseline disease management self-efficacy. Thus, the degree of correlation between self-efficacy and openness may depend on the self-efficacy domain (e.g. general versus disease management) and/or study sample (e.g. chronically ill individuals versus others) being considered. Another possibility is that disease management self-efficacy could he positively correlated with some aspects of Openness but negatively with others, in effect ‘canceling out’ at the level of the higher order trait. Again, these possible explanations appear worthy of formal study.
Strengths of our study included rigorous RCT methodology, use of a well-validated and comprehensive personality taxonomy and measure, and repeated measurement of self-efficacy, the outcome of interest, which allowed for clear assessments of changeover time. Our study also had several limitations. We recruited individuals who had at least one of six target chronic conditions and who also had functional impairment and/or active depressive symptoms. The extent to which the sample reflects the broader chronic disease-burdened population in the US is unknown, so generalizations must be considered in this context. Women were somewhat over represented in our sample compared with the general primary care population, in part due to the higher prevalence of depression (one of our six study diagnoses) in women relative to men (Kuehner, 2003
). Randomization appeared successful in distributing other measured individual differences equally across groups, but the possibility of randomization failure on unmeasured confounders — although unlikely given the large sample size — cannot be ruled out. Additional studies examining the role of personality factors in moderating responses to other types of interventions, and which involve study samples with characteristics different from our sample, would be helpful in assessing the generalizability of the current findings.
Disease management self-efficacy is associated with significant short-term health outcomes (Foster et al., 2007
; Lorig et al., 1999
), highlighting the importance of understanding who is most likely to benefit from peer led disease management programs. Our results extend prior work on the CDSMP by demonstrating that the self-efficacy enhancing effects of such programs may be of relatively short duration, and by specifying the manner in which the intervention interacts with fundamental axes of personality variation. Two contributions of these findings are theoretical: (a) in the course of assessing in whom the intervention works, hypotheses may be generated about why or how it works, or what components drive its effectiveness; and (b) the study explicates the relationship of FFM personality factors to self-efficacy in the context of an intervention designed to increase self-efficacy.
However, another contribution is practical: identification of patients more or less likely to benefit can facilitate allocation of resources towards suitable candidates, improving the intervention’s efficiency (Issel, 2004
), or ratio of clinical benefit to delivery effort. The utility of targeting medical interventions to those most likely to benefit is well established, though it has heretofore been employed primarily to direct prescription drug therapy. An example is the widely employed evidence-based algorithm to determine the need for and intensity of drug therapy for hyperlipidemia, which encourages careful consideration of each individual’s overall risk for cardiovascular disease rather than reacting to serum lipid values in isolation (National Cholesterol Education Program, 2001
). Our findings suggest a similarly individualized approach might be fruitfully employed to better target health behavior change interventions to those most likely to benefit. The availability of personality assessment measures for all needs and purposes (DeRaad & Perugini, 2002
) make expedient factor-based screening feasible in many medical settings. Future trials of peer led disease self-management interventions may wish to block or stratify on personality factors (Kraemer et al., 2002
), and/or include alternative versions of the interventions targeting those who our results suggest are unlikely to respond favorably to the ‘standard’ program. The moderating role of personality factors in the effectiveness of other psychosocial health interventions may also deserve further study. Ultimately, the most important future questions for psychosocial health interventions for people with chronic conditions may not be whether or not the intervention ‘works,’ but in whom it is likely to work most effectively, and for how long.