Original article
Illness representations are associated with fluid nonadherence among hemodialysis patients

https://doi.org/10.1016/j.jpsychores.2009.08.010Get rights and content

Abstract

Objective

Patients with end-stage renal disease are required to limit fluid and salt intake. We examined illness representations [common-sense model (CSM)] among a sample of hemodialysis (HD) patients, investigating whether fluid-adherent patients held illness representations different from those of nonadherent patients. We also explored the utility of illness perceptions in predicting fluid nonadherence after controlling for clinical parameters, including residual renal function (KRU).

Methods

Illness perceptions were assessed [Revised Illness Perception Questionnaire (IPQ-R)] in 99 HD patients. Clinical parameters were collected and averaged over a 3-month period prior to and including the month of IPQ-R assessment. Depression scores, functional status, and comorbidity were also collected. Fluid nonadherence was defined using interdialytic weight gain (IDWG) and dry weight (ideal weight). Patients in the upper quartile of percent weight gain were defined as nonadherent (IDWG≥3.21% dry weight).

Results

Nonadherent patients had timeline perceptions significantly lower than those of adherent patients. Logistic regression models were computed in order to identify predictors of fluid nonadherence. After several demographic and clinical variables, including age, gender, and KRU, had been controlled for, lower consequence perceptions predicted nonadherence.

Conclusions

Illness representations appear to predict fluid nonadherence among HD patients. Extending the CSM to investigate specific perceptions surrounding treatment behaviors may be useful and merits attention in this setting.

Introduction

Dialysis is required in end-stage renal disease (ESRD) to remove accumulated toxins and excess fluid resulting from renal failure, which, without treatment, would inevitably prove fatal. Hemodialysis (HD) is the most common form of dialysis, typically requiring the patient to attend hospital three times per week to undergo a 3- to 4-h dialysis treatment session. The complications of ESRD require numerous other treatments, including multiple drugs to facilitate the management of blood pressure, anemia, abnormalities of mineral metabolism, and other problems related to extrarenal comorbidities. A potential significant stressor is the need to restrict the dietary intake of phosphates and potassium-rich foods, and to reduce salt and fluid intake. Adherence to these regimens can be categorized into the following facets: (a) medication, (b) dietary/fluid intake, and (c) dialysis prescription [1]. Adaptation to and maintenance of these requirements are crucial in disease management.

This article focuses on fluid nonadherence, which is associated with adverse clinical outcome, including left ventricular hypertrophy, cardiac failure, and premature death [2]. Fluid intake is driven by thirst which is strongly related to the body's sodium balance. Estimates of fluid nonadherence are varied and largely dependent on methodology and definition. Typically, fluid intake is evaluated by interdialytic weight gain (IDWG). IDWG refers to the amount of fluid gained between two dialysis treatment sessions and is estimated by subtracting postdialysis weight from the predialysis weight of the following treatment session. Although IDWG serves as a suitable physiological proxy of fluid adherence [3], the heterogeneity of definitions used has had a major impact on reported estimates of nonadherence. Critically, IDWG alone is insufficient to define adherence [4]. IDWG is influenced by residual renal function (KRU; the amount of remaining intrinsic renal function of the patient) [3] and dry weight (the patient's “ideal weight” when free of excess fluid) [4], [5], [6]. Both of these confounding factors were considered in the current study.

Section snippets

Leventhal et al.'s common-sense model (CSM) of illness representations

Several factors have been associated with nonadherence among dialysis patients, including age, gender, psychological factors including health beliefs [7], [8], [9], social support [10], [11], personality factors [12], locus of control [4], [7], self-efficacy [13], and depression [4], [14]. Cognitive factors may be more predictive than emotional variables [15], although it is likely that these factors have complex interactions and vary with different behavioral demands [4]. The application of

The present study

This study investigated whether there were significant differences between fluid-adherent patients' and nonadherent patient's illness representations, as measured by the Revised Illness Perception Questionnaire (IPQ-R) [19]. In addition, we investigated whether illness representations predicted fluid nonadherence. Our definition of fluid nonadherence involved computing IDWG as a percentage of a patient's dry weight, thus reducing potential confounding in our measure of nonadherence. Although

Patients

A random sample of adult HD patients from the renal service of the East and North Hertfordshire NHS Trust was approached for inclusion in a larger ongoing study, provided they satisfied the following criteria: (a) fluency in verbal and written English language; (b) not hospitalized at the time of assessment; (c) had been receiving HD for >6 months; (d) no evidence of cognitive impairment, as assessed by an age-adjusted score of <22 on the Mini Mental State Examination (MMSE) [36]; and (e)

Results

One hundred eighteen patients were approached for inclusion in an ongoing study. One hundred patients provided informed consent (17 refused and 1 was excluded after the administration of MMSE). One patient was excluded, as the patient had been receiving dialysis only twice a week during the past 3 months. Data on 99 patients are presented, of which the demographic and clinical characteristics are shown in Table 1 (N=99). The mean IDWG was 1.77 kg [standard deviation (S.D.)=0.85]. Patients'

Discussion

The goal of this investigation was to examine illness representations across fluid-adherent and nonadherent HD patients. Specifically, we were keen on defining “nonadherence” as a clinically relevant group of patients who would be at risk for fluid-related complications. Furthermore, we considered dry weight and KRU, both of which are significant factors associated with the definition of fluid nonadherence based on weight gain [4]. In univariate analysis, nonadherent patients reported

Acknowledgments

This study was kindly supported by a joint British Renal Society–Kidney Research UK Fellowship awarded to J. Chilcot. We wish to thank Prof. Diana Kornbrot for comments on earlier versions of this manuscript, and all patients for their participation.

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