Illness perceptions predict mortality in patients with predialysis chronic kidney disease: a prospective observational study

BACKGROUND Illness perceptions have been shown to predict a range of psychosocial and clinical outcomes in kidney disease; including quality of life, distress, treatment adherence and even survival in end-stage renal disease patients on dialysis. The aim of this study was to evaluate whether illness perceptions impact mortality in incident predialysis Chronic Kidney Disease (CKD) patients. METHODS Over the study period between September 2015 and June 2019, a total of 200 participants with predialysis CKD were recruited from the Nephrology Outpatient's clinics at Mater Dei Hospital, Malta. The participants were followed up until June 2019, and the mortality information was collected. Cox proportional hazards models were used to examine the association between illness perceptions, and mortality risk, after adjustment for covariates including distress, kidney function, co-morbidity and psychological distress. RESULTS Of the 200 cases available for analysis, there were 43 deaths. The mean survival time was 718.55 days (min. 3 days, max. 1297 days). The cumulative survival 1-year post the assessment of the Revised Illness Perceptions Questionnaire (IPQ-R) was 93%. Stronger identity beliefs (HR = 1.199, 95% CI: 1.060-1.357, p = 0.004), perceptions of a chronic timeline (HR = 1.065, 95% CI: 1.003-1.132, p = 0.041), personal control beliefs (HR = 0.845, 95% CI: 0.748-0.955, p = 0.007) and perceptions of control over the treatment (HR = 0.812, 95% CI: 0.725-0.909, p = 0.000) demonstrated a significant association with mortality after controlling covariates. In a subsequent saturated model, perceived identity, chronic timeline and treatment control perceptions remained significant predictors of mortality, together with serum albumin, comorbidities and urea. CONCLUSIONS CKD patients' perceptions of treatment control, perceptions of a chronic timeline and perceived illness identity predict survival independently of clinical prognostic factors, including kidney function and co-morbidity. Illness perceptions are important and potentially modifiable risk factors in CKD. Further studies are required to test whether the assessment and the implementation of psychological interventions aimed to modify maladaptive illness perceptions influence clinical outcomes in CKD.