Recent studies have concluded that the effects on improving the quality of life as well as on long-term survival should be considered when evaluating the effectiveness of the treatment in chronic diseases . Also, it is increasingly recognized that renal failure is associated with cognitive impairment . Among patients with CKD, the prevalence of mild cognitive impairment has been estimated to be as high as 30 to 63% as reported in studies by Murray et al. and Post et al., respectively, which is approximately twice as high as in the age-matched general population [24, 25].
Residual Kidney Function is the remaining kidney function in patients receiving renal replacement therapy. RKF may provide many benefits to patients on permanent RRT. RKF preservation is expected to contribute significantly to the improvement of quality of life, cardiovascular protection, and even better survival in this patient population . Therefore, this study was carried out to assess the impact of this issue on the quality of life and cognitive function in an Egyptian cohort of hemodialysis patients. There are recommendations for Residual Kidney function preservation as Avoidance of nephrotoxic agents, especially aminoglycosides, NSAIDs, CoX-2 (Cyclooxygenase-2) inhibitors and radiocontrast media, Avoidance of excessive ultrafiltration, routine use of biocompatible dialyzer membranes, routine use of bicarbonate- based dialysate, use of ultrapure water, hemodiafiltration, incremental hemodialysis, and a low-protein diet, as well as general care such as maintaining appropriate blood pressure, and better control of mineral and bone disorder parameters [27, 28].
As regards QOL domains according to RKF status, patients with RKF (urine output≥100 ml/day) had significantly higher scores (denoting better quality of life) for the symptom problem list, cognitive function, sleep, overall health, physical functioning, role limitations caused by physical health problems, pain, general health, role limitations caused by emotional health problems, social function, energy/fatigue and PCS in comparison with patients without RKF. Moreover, the measured RKF was positively correlated with the PCS. These findings match with the results of Abdel-Azim et al., who revealed that HD patients with preserved RKF had better physical functioning, role limitations caused by physical health problems, vitality, mental health, general health, PCS and MCS scores. Also, they observed that there was a statistically significant positive correlation between measured RKF and PCS, Symptom problem list, cognitive function, sleep, overall health, physical functioning, role limitations caused by physical health problems, pain, general health, role limitations caused by emotional health problems, social function and energy/fatigue scores . In addition, Hiramatsu et al. observed that preservation of urine volume showed a positive relationship with physical activity . However, when subjecting possible predictors of PCS to multivariate regression analysis, patients’ age was the only predictor for PCS. Such a result goes in agreement with, Seica et al. who demonstrated that age had a significant impact on HRQOL especially PCS of the SF-36, but not on MCS .
Sleep disturbances are widespread among HD patients, and they are frequently linked to pain, exhaustion, and sadness . Sleep disturbances were shown to be more common in HD patients lacking RKF in the current research. Psychological disorders, pulmonary edema from fluid overload, disturbances in the activity of the respiratory center from chronic metabolic acidosis and uremic toxins, abnormalities in dopaminergic pathways, anemia, and increases in calcium-phosphate product and PTH levels are all possible causes of sleep disorders in HD patients .
Cognitive impairment is a highly relevant clinical factor for disease progression in HD patients, possibly also affecting daily life activities, thereby impeding adherence to therapeutic regimes and compromising the quality of life . It was evident that cognitive impairment is more prevalent in individuals with CKD than in the general population .
As regards cognitive function domains according to RKF status, visuospatial, executive, attention, language, delayed recall and total score of MoCA were significantly higher in the RKF group compared to the non-RKF group. Also, there was a statistically significant positive correlation between the measured RKF and visuospatial, executive, attention, delayed recall and the total MoCA score. Moreover, the measured RKF, were proved to be one of the predictors of the total MoCA score by multivariate linear regression analysis. To the best of our knowledge, there are no available studies in the literature that had assessed the relation between MoCA score and RKF status. Most of the studies had assessed the relation between cognitive function and CKD and ESKD patients in general.
This study had limitations. First, a relatively small number of patients were studied. Second, the cross-sectional nature of the study. Third, absence of calculated Charlson or another comorbidity scores. However, assessing the relation between the measured residual kidney function and both the cognitive function and HRQOL in this specific group of patients is considered as a strength point in the current study.