Patients with chronic kidney disease (CKD) often require regular hemodialysis (HD) to prolong life. However, between HD sessions, patients have to restrict their diets carefully to avoid excess accumulation of potassium, phosphate, sodium, and fluid, which their diseased kidneys can no longer regulate. Failure to adhere to their renal dietary regimes can be fatal; nevertheless, non-adherence is common, and yet little is known about the psychological variables that might predict this dietary behavior. Thus, this study aimed to assess whether dietary adherence might be affected by a variety of psychological factors including stress, personality, and health locus of control, as well as dietary knowledge, in chronic HD patients. Fifty-one patients (30 men; age range 25–85) who had undergone HD for at least 3 months and had been asked to restrict at least one of potassium, phosphate or fluid, were recruited from a hospital renal unit. Measures of adherence to each of potassium, phosphate, and fluid were derived from standard criteria for these physiological indices in renal patients. Knowledge of food/drink sources of these dietary factors, and their medical implications in relation to HD and CKD were assessed by a bespoke questionnaire. Psychological factors including stress, personality and health locus of control beliefs were measured by standardized questionnaires. Having to restrict a particular nutrient was associated with better knowledge of both food sources and medical complications for that nutrient; however, greater dietary knowledge was not linked to adherence, and knowledge of medical complications tended to be associated with poorer adherence to potassium and phosphate levels. Adherence to these two nutrient requirements was also associated with lower reported stress in the past week. Adherence was associated with differences in locus of control: these differences varied across indices although there was a tendency to believe in external loci. For potassium, phosphate, and fluid restriction, adherers were less likely to be sensation seekers but did not differ from non-adherers on impulsivity, anxiety sensitivity, or hopelessness. In conclusion, the links between dietary adherence and stress, locus of control and personality suggests that screening for such psychological factors may assist in managing adherence in HD patients.

Dietary restriction of K, phosphate and fluid are commonplace in patients with end-stage renal failure. Previous studies have shown that patients on haemodialysis (HD) exhibit poor dietary compliance (1) . The aim of the present study is to explore knowledge of food sources and dietary compliance in patients on HD.Thirty-nine patients attending a HD unit completed the study over four consecutive weeks in 2007; they were on HD for >3 months and had received advice from the renal dietitian. Patients completed a modified twenty-six-item renal knowledge questionnaire (2) . Adherence to the dietary restrictions was monitored by serum K, phosphate and inter-dialytic weight gain (IDWG) over the previous three 1-month periods.The patients were aged between 25 and 85 years (twenty-six males and thirteen females). The length of time on HD ranged from 3 months to 16 years. Twenty-three (59 %) patients reported fully understanding the dietary advice and sixteen (41 %) requested further dietary advice, predominately relating to K and phosphate. Correct responses to questions relating to foods high in: K Phosphate Na Fluid n % n % n % n % 26 67 21 54 29 74 29 74Patients were most knowledgeable about foods high in Na and fluid. Patients varied in their compliance: K, n 24; phosphate, n 26; fluids, n 18. Knowledge of food sources high in K or phosphate did not impact on whether they were compliant (P > 0.05). Knowledge of foods high in Na or fluid also did not influence compliance, although there were more patients who were non-compliant based on IDWG who had poor knowledge of Na-containing foods (ten v. five).Patients had a variable knowledge of foods containing high levels of electrolytes and fluids, which highlights a potential need for reinforced dietary advice. However, there was no clear relationship between knowledge of food sources high in electrolytes and fluids and dietary compliance, in agreement with previous findings (2) . The present findings suggest other factors, such as stress, health locus of control, and personality, may have a greater impact on dietary compliance when compared with knowledge of food sources. However, it should be noted that a certain level of knowledge must be required to enable the patients to choose appropriate foods within the renal diet. However, common psychological factors may mediate both knowledge and compliance and further investigation into patients with poor dietary knowledge is warranted. Future studies are needed to help elucidate what factors influence dietary compliance, and thus health outcomes, in patients on HD.

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