As dialysis technology improves and kidney disease patients live longer, healthcare providers are placing greater emphasis on patients’ HRQOL.
A recent meta-analysis involving 147 studies reported a pooling mean HRQOL score for patients undergoing dialysis was 64.25 (95% CI 55.67 to 72.82) [22]. In the present study, the overall mean score of HRQOL was modestly lower than the results mentioned above. The reason may be that the average age of the patients enrolled in this study was older (58.57 ± 12.07). As described in the study by Ishiwatari et al., dialysis patients' quality of life decreased over time, especially among those older adults [23].
From the viewpoint of all dimensions, except MCS, all are lower than a large sample of the USA data [24], where only Symptom/Problem is not statistically significant, see Fig. 1. This may be related to the faster development of dialysis technology in the United States [25]. In addition, the results of low scores in each dimension may be related to the kidney disease itself, as well as existing comorbidities and related disease complications. The lowest burden of kidney disease score was similar to the results of the Peritoneal and Dialysis Outcomes and Practice Patterns Studies [26], indicating that disease burden is an important cause of lower quality of life for dialysis patients. As concluded by Abeywickrama et al., the symptoms burden score independently influenced all HRQOL (PCS: β=-0.417; MCS: β=-0.464) [27].
In the univariate analysis, dialysis type, dialysis vintage, and physical activity represented predictors for HRQOL in dialysis patients. Unlike previous studies [28], the results of this study showed that the HRQOL scores of hemodialysis patients were 4.443 (OR: 1.363, 7.523; P = 0.005) higher than those of peritoneal dialysis patients, but similar to the results of Gonçalves et al. [29] and de Abreu et al. [30] This happened because the limited sample size and the different inclusion criteria.
Regarding dialysis vintage, we found that patients with longer dialysis vintage had lower HRQOL scores than those with shorter ones. Early studies have shown that patients with kidney disease quality of life tend to decrease year by year after dialysis initiation [31, 32]. This is because the number of medications and co-morbidities increases with dialysis vintage, further eroding quality of life [33]. Therefore, Boini et al. emphasized that HRQOL at dialysis initiation is significantly influenced by the quality of predialysis nephrology care and that emphasis should be placed on disease management [34].
The relationship of interest between physical activity and the prognosis of dialysis patients has been widely recognized [35]. As in previous studies, the results of this study showed that patients who participated in higher levels of physical activity had higher HRQOL scores compared to those who were less physically active than recommended. Previous studies have shown that physical activity increases the HRQOL of dialysis patients by improving cardiovascular health, inflammatory status, physical fitness, and reducing disease-related symptoms [36–38].
Moreover, in the current study, a significant positive interrelation was found between exercise self-efficacy and HRQOL. This positive relationship corroborates the social cognitive model proposed by McAuley et al. that exercise self-efficacy has a positive effect on PCS and MCS [39]. Self-efficacy has been reported to be the most dominant factor in the uptake and maintenance of exercise in populations with chronic conditions [40, 41]. Furthermore, self-efficacy is an essential determinant of health behavior, associated with a positive quality of life among patients living with chronic illnesses [42, 43].
In the stratified regression analysis, our study presented that physical activity remained statistically significant positive correlation with HRQOL. Also, physical activity as a predictor variable can explain an additional 9.8% of the variation in HRQOL. Most of the studies found a positive relationship between physical activity and HRQOL as well as a negative relationship between sedentary behavior and HRQOL among dialysis patients [44–46]. The present study further confirmed this positive finding. Moreover, we found that exercise self-efficacy was an important predictor of HRQOL in dialysis patients. Exercise self-efficacy is a strong determinant of behavior in physical activity and other health domains and has been shown to correlate with HRQOL in other populations [17, 18, 47]. The results of this study reinforce existing evidence on the importance of self-efficacy as a determinant of HRQOL in patients with chronic disease. Therefore, interventions aiming at increasing the HRQOL of dialysis patients should consider physical activity and exercise self-efficacy in these populations.
Our study has several limitations. Firstly, conducted in single-center, the results limit generalizability. Meanwhile, this study focused only on a sample of the dialysis population and has limited universality to non-dialysis CKD patients. Secondly, self-administered questionnaires were used to assess physical activity; an inaccurate estimation and recall bias was unavoidable. Thirdly, this study used a cross-sectional design and could not infer a causal relationship between exercise self-efficacy and HRQOL. Finally, we were unable to control the intensity of physical activity, and since we did not collect relevant data, this may have confounded the relationship between key variables.