Due to the subjectivity of fatigue, currently fatigue is mainly assessed according to the self-reporting questionnaires. MFI-20 is one of the multi-dimensional scales for the assessment of fatigue, which has the advantages including simple, easy to understand, and high validity and reliability, and could accurately and objectively reflect the state of fatigue in patients. In this study, the fatigue in patients on PD and HD was assessed by MFI-20, and the nutrition and inflammation related indicators were also measured. The difference of fatigue between patients on the two different dialysis methods was compared, and the correlation of fatigue with nutrition and inflammation was explored, which could provide theoretical bases for future studies on fatigue in patients on dialysis.
The findings of this study demonstrated that the prevalence of fatigue was 97.5% and 98.9% in patients on PD and HD, respectively, both of which mainly consisted of moderate fatigue. The prevalence of fatigue was higher than previously reported. Comprehensive analysis of the possible reasons are as follows: First, most of the dialysis patients in this study are farmers with no job and low income, low ability of daily activities and excessive dependence on others' care, which are more likely to produce negative emotions and aggravate the sense of fatigue; Second, the selected patients generally have low education level, which makes it difficult to identify the early state of the disease, and pay insufficient attention to the treatment of dialysis, which is easy to aggravate the disease and affect fatigue; Third, the diversity of fatigue measurement tools leads to different fatigue assessment tools often produce different results. The results of this study indicate that fatigue in dialysis patients is caused by multiple factors. The severity of fatigue in patients on PD was significantly lower than in patients on HD, and severities of general fatigue and physical fatigue were both lower in patients on PD than HD. Comparing with HD, PD has several advantages including stable hemodynamics, capability of preserving residual renal functions, and easy to perform, which could be self-applied in home [11, 12], all these factors could reduce the prevalence of fatigue.
Incidence of malnutrition is 18–75% and 10–50% in patients on HD and PD, respectively, which is one of the important factors influencing the quality of lives of CKD patients [13, 14].The insufficiency of ALB and PALB could reduce the energy of patients and consequently worsen the fatigue. Ozdemir et al. demonstrated that the ALB level in patients with fatigue was significantly reduced [15]. Anemia could influence the normal physiological functions, inducing cardiovascular diseases such as left ventricle hypertrophy or dilation, arrhythmia, and myocardial ischemia, consequently worsen the fatigue in patients, and reduce the capability of daily activities [16, 17]. Previous studies have demonstrated that the HB level in patients on PD that accompanied with fatigue is decreasing significantly and continuously [18, 19]. These findings indicated actively improve the HB levels in patients on dialysis to normal level could alleviate fatigue in patients. Serum iron is an essential substance for the synthesis of HB, and insufficient SI could induce iron-deficiency anemia [20, 21]. The findings of this study demonstrated that fatigue in patients on PD was correlated with SI, with higher SI level associated with lower fatigue severity. These findings indicated that in addition to increase the HB level, correcting the insufficiency of SI could also help alleviating fatigue of patients.
Chronic inflammation plays an important role in the occurrence of fatigue in patients on long-term dialysis. In patients on dialysis, the interaction between blood and dialysis membrane could activate the peripheral monocytes and induce the release of pro-inflammatory cytokines (such as IL-1 and IL-6) [22]. Cytokines could directly activate the central nervous system, hypothalamus, pituitarium, and adrenal gland to induce fatigue, and also indirectly induce fatigue through inducing sleep disorders, depression, and anxiety [23]. The levels of IL-6 and C-reactive protein are significantly elevated in dialysis patients with fatigue [24]. The findings of this study demonstrated that fatigue in patients on PD and HD was positively correlated with WBC, general fatigue in patients on PD was positively correlated with N%, and the fatigue in patients on HD was also positively correlated with PLT. These findings indicated inflammation is one of the risk factors for fatigue in patients on dialysis, with higher inflammation indicators associated with higher severity of fatigue.
PD and HD have different associated risk factors. HD is a reliable method to remove toxins in the body, but by the interference of the aperture of the dialysis membrane, the body macromolecular toxins cannot be effectively removed. At the same time, the central venous catheterization mode of HD increases the contact opportunity of dialysis pipeline and blood, and then activates monocyte macrophages and causes inflammatory factor release. Uremia patients widespread micro inflammation state, the cause and renal function is impaired, hindered the removal of inflammatory cells, iron overload, oxidative stress response, end-stage glycated glycosylation products, and with the progress of microinflammatory state can further lead to malnutrition, atherosclerosis related cardiovascular and cerebrovascular diseases, and renal anemia. PD uses the patient's peritoneal membrane as the dialysis membrane, which is beneficial for inflammatory factors to enter the peritoneal dialysis fluid through diffusion and ultrafiltration, and then discharged from the body, with ideal dialysis stability. At the same time, the materials used in PD have a strong adsorption effect, which can remove urinary toxins and macromolecular inflammatory substances in the body, protect the residual kidney function, maintain the balance of water and electrolyte, and the norm-al nutrient intake. PD reduce nutrients loss, and then improve the body's nutritional status, reduce the risk of complications such as malnutrition and anemia.
In summary, this cross-sectionals study in our center demonstrated that the fatigue severity of patients on PD was lower than patients on HD, and PD could be the preferred renal replacement therapy for such patients. Malnutrition and chronic inflammation could worsen the fatigue in dialysis patients, while improving nutrition and inflammation status in patients could help alleviating fatigue in patients. However, as a single-center, cross-sectional study, the findings of this study could not correctly reflect the overall level of fatigue in dialysis patients in China. More multi-center clinical studies are needed to further verify the fatigue state of different subgroups of patients on dialysis from different regions.