Predicting intentions and adherence behavior in the context of organ transplantation: Gender differences of provided social support

Abstract

Objectives

Medication non-adherence is a common problem in organ transplantation patients with severe consequences for the patients' health. This study aimed at examining the determinants of intention formation and adherence behavior based on the Theory of Planned Behavior (TPB). Moreover, to account for the role of patients' partners, provided social support by partners was included. Here, support provided by female partners was hypothesized to be more effective than support provided by male partners.

Method

This cross-sectional study comprised 121 heart, liver, lung, and kidney transplant recipients (n = 81 men; mean age = 54.32, SD = 13.32) and their partners (mean age = 51.99, SD = 13.67). Patients completed a questionnaire with TPB variables and a validated measure of self-reported adherence. Partners reported their provided social support with regard to medication adherence of the patients.

Results

For the prediction of intention to adhere to medication, the non-significant main effect of provided social support was qualified by partners' gender: Support provided by women was positively related to patients' intention to adhere, whereas support provided by men was slightly negatively related to the intention to adhere in their female spouses. Intentions in turn emerged together with relationship quality as the most important predictor of adherence behavior.

Conclusion

The beneficial effects of support provided by women could be replicated within the framework of the TPB in the context of organ transplantation. Interventions should focus on increasing the effectiveness of support provision of male partners and on promoting relationship quality.

Introduction

According to the World Health Organization poor adherence in long-term therapy is surprisingly common with up to 50% nonadherence in developed countries [1]. With regard to adherence after organ transplantation, study reports of non-adherence range between 20% and 50% (e.g., [2]. As in 2010, a total of 504 patients underwent organ transplant surgery in Switzerland [3], potentially 252 of these patients will suffer from severe complications, lose the graft or die due to medication non-adherence.

As a consequence, it is of crucial importance to identify the core modifiable determinants of adherence behavior in order to develop effective interventions for medication adherence after organ transplantation. So far, a broad number of studies exist, focusing on non-modifiable factors that are related with adherence-behavior (such as gender, marital status, etc., see e.g., [4], [5]. Relatively fewer studies focus on modifiable factors, such as self-efficacy [5], social support [2], attitudes [6], or anxiety or depressive disorders [7]. Again even fewer studies refer to an established theoretical framework in the domain of health behavior, such as the Theory of Planned Behavior, TPB, [8] that aims at explaining the underlying processes of adherence behavior.

The core determinants of behavior in the TPB are attitudes, subjective norms, and perceived behavioral control for predicting intentions. Intentions in turn are together with perceived behavioral control specified as predictors of behavior. Attitudes are defined as the expected positive or negative outcomes of a behavior. Subjective norms reflect whether or not a person's beliefs that significant others want him/her to change his/her behavior. Finally, perceived behavioral control is seen as an indicator of the actual control a person has over his/her behavior. According to Ajzen [9], perceived behavioral control can be operationalized as self-efficacy. Self-efficacy has originally been introduced by Bandura [10] and refers to a person's perceived capabilities to perform a certain behavior in spite of existent barriers. As self-efficacy has been proven to be of key importance for immunosuppressive adherence behavior (e.g., [5], we included self-efficacy as the indicator of perceived behavioral control in the present study.

The TPB has been successfully applied in the context of adherence to medical regimens, such as hypoglycaemic medication in Type 2 diabetes patients [11] or malaria chemoprophylaxis [12]. There is only one study so far, however, that applied the TPB to the context of medication adherence in organ transplant patients [13]. This cross-sectional study's findings indicate that attitudes and perceived behavioral control were the only substantial predictors of intentions. Intentions and past behavior in turn emerged to be the most important predictors of adherence behavior. Thus, overall, the TPB has proven to be able to partly explain adherence behavior in transplant patients.

With its construct subjective norm the TPB is the only theory that includes a variable of social influence. However, subjective norm refers to a person's own perceptions of significant others' expectations. Thus, a direct indicator of social influence, for example social support, is lacking so far in theories of health behavior.

Most studies addressing the association between social support and adherence behavior, target perceived social support. Perceived social support comprises the potential availability of social support from the social network. It is a prospective measure, which is known to be relatively stable, and to depend relatively little on actual support transactions. In contrast, provided social support refer to retrospective reports of actual support transactions by the support provider [14].

Studies on the association between perceived social support and adherence to medical regimens usually report a positive relationship (e.g.,[2]). However, studies focusing on actual support transactions by examining effects of provided social support are very rare. Thus, the present study aimed at examining the effects of partner provided social support on intention formation and medication adherence in organ transplant patients.

In the literature on the association between social support and well-being of support recipients, prominent gender differences emerge in that support provided by women seems to be more effective than support provided by men [15], [16]. In line with these reported gender differences are studies in the domain of social support and health behavior: Here again, female provided social support seem to be more beneficial for support recipients than male support provision (e.g.,[17], [18]. To the best of our knowledge, no studies exist that examine gender differences of the effectiveness of the provision of social support on adherence behavior in the context of organ transplantation.

This study's aim was to examine the added value of partner provided social support to the variables of the Theory of Planned Behavior for the prediction of intention and adherence behavior in organ transplant patients. In particular, we hypothesized that men would benefit more from the social support provided by their wives than vice versa with regard to both intention formation and adherence behavior.