In our study we found that 49 (57%) of the kidney patients were adherent to immunosuppressive medications, and in the liver sample 28 (56%) were adherent to immunosuppressive medications, according to the ITAS. Our adherence rates are similar to the currently reported adherence rates in the literature. Depending upon the method and the operational definition used, the incidence of medication nonadherence in the adult renal transplant recipients ranges from 4.7% to 53%.3
According to a recent study using self-report, the incidence of nonadherence in the liver transplant population is about 50%.24
It is important to note that the ITAS is a self-report instrument that has its limitations, as are described in other publications, including a long recall period of 3 months and a broad range of nonadherence scoring options.
As previously stated, prior research found that poor social support, a history of alcohol abuse, and being young, non-white, and male are all strong predictors of nonadherence in lung, liver, or heart transplant recipients.9
The current study adds an association between patient nonadherence and the presence of depression, select personality traits (low openness), and poor physical function in the kidney transplant patients. In addition, we found that as liver transplant patients become older their adherence improves.
The factors associated with nonadherence are different for the liver and kidney transplant recipients, possibly due to the differences these two samples exhibit. In our kidney sample, 33 (38.4%) of the patients were taking prednisone, whereas none of the liver transplant patients was taking prednisone. Administration of prednisone is associated with depression in the transplant population.25
It is likely that more kidney transplant patients became depressed pretransplant due to the exposure to prednisone. At baseline, eight (9.3%) and ten (20%) of the kidney and liver patients were depressed, respectively. Post-transplant, 52 (60%) and 36 (52%) of the kidney and liver transplant patients had minimal to mild depression, respectively. Severe depression was observed in eight (9.8%) and three (6%) of the kidney and liver patients, respectively. We cannot exclude the possibility that more kidney patients became depressed post-transplant, resulting in depression being associated with nonadherence in the kidney transplant population.
Previous investigators have evaluated psychiatric factors and their association with adherence. A recent study from 2009 by Dobbels et al26
evaluated some of the same psychosocial factors as our study and their association with patient adherence. Their study examined which pretransplant psychosocial factors (depression, anxiety, personality traits, social support, per-transplant medication adherence, and smoking status) predicted post-transplant nonadherence with immunosuppressant medications and clinical outcomes in heart, liver, and lung transplant recipients. They found that pretransplant self-reported medication nonadherence, receiving lower social support, a higher education, and lower “conscientiousness” were independent predictors of post-transplant nonadherence. It is important to note that this study was done in a Belgian pretransplant population on the waiting list for a transplant, and the surveys for measuring depression and personality were administered before they received their transplant. Also, their reported outcomes were for the combination of lung, liver, and heart transplant recipients with up to 1-year post-transplant follow-up.
A study by Cukor et al13
in 2008 was the first study to investigate a correlation between depression and adherence to immunosuppressant medications in kidney transplant recipients. This study found higher levels of depression correlated with missing more medication doses. Jindal et al12
using the United States Renal Data Service data in 2009, conducted a retrospective cohort study of 32,757 Medicare primary renal transplant recipients. A strong association between depression and nonadherence was found using this database, regardless of whether the depression was diagnosed pre or post-transplant. The results of our study with regard to the kidney transplant population are consistent with the findings in these two previous reports.
Only one study to date, from 2009 in Portuguese liver transplant candidates, has been designed to determine whether there is an association between adherence and personality. This is a study in pre-liver transplant candidates. The authors measured adherence by a Multidimensional Adherence Questionnaire developed and validated by them. They found that multidimensional adherence positively correlated with the personality trait of agreeableness. In our study we found that a low level of openness was associated with nonadherence to medications in the kidney transplant recipients.
No prior studies have been conducted to determine the association between quality of life and nonadherence in the adult transplant population. In our study, possibly due to the small sample size, we did not find an association between quality of life and adherence to immunosuppressant medications in the liver or kidney transplant population.
From the available data it is clear that depression and personality traits are associated with nonadherence to immunosuppressant medications. Strategies need to be incorporated to address these factors. Physicians need to be advised to screen for pre and post-transplant depression, as this may affect adherence and therefore transplant outcomes. Diagnosed depression needs to be treated appropriately, and patients need to be monitored. Depressed patients need to receive special attention by transplant clinic health care providers to facilitate the development of good medication-taking behaviors. For example, extensive medication adherence counseling and use of a medication adherence tool could be administered to these at-risk individuals. There is only one previously published study that evaluated the association of personality traits with adherence.14
That study and ours indicate an association between low agreeableness or low openness and nonadherence. Consideration should be given to administration of a pretransplant personality assessment to facilitate identification of individuals with personality traits associated with medication nonadherence. More studies are needed to determine whether quality of life is associated with adherence to immunosuppressant medications. This association has been demonstrated only in studies of adolescent patients.10
It is important to identify targeted interventions to improve adherence rates so that costs resulting from nonadherence can be reduced or avoided. Previous adherence research has led to several different strategies for increasing adherence to medications in patients with chronic disease states.
Identification of these patients will allow appropriate resource allocation to ensure intensive patient education and medication adherence monitoring.
Medication nonadherence is a significant problem in the transplant populations. Enhanced understanding of the impact of personality traits, depression, and quality of life on medication-taking behaviors is an important step in the development of novel strategies to improve medication adherence and, ultimately, patient outcomes.