Chronic kidney disease (CKD) and end-stage renal disease (ESRD) are major medical and public health problems worldwide and a serious challenge for many developing countries (1, 2). In Iran, like in other developing countries, diabetes mellitus and hypertension are the leading causes of ESRD. Other common causes of ESRD include glomerulonephritis, polycystic kidney disease, and obstructive uropathy (3–8). ESRD represents a progressive clinical condition in which an irreversible loss of endogenous renal function below a sufficient degree is established, imposing permanent dependency on renal replacement therapy (RRT) to avoid life-threatening uremia and other complications. Treatment of this disease is affected through RRT, including peritoneal dialysis (PD), hemodialysis (HD), or kidney transplantation (KT) (9–11).

Kidney transplantation has been accepted as the best RRT, contributing to the best prognosis, regarding either survival or quality of life in ESRD patients. However, owing to rapid increase in the prevalence of ESRD and the long waiting list for kidney transplantation, most patients with ESRD would go through a period of using any of the dialysis modalities in their life (12–15). It is a fact of clinical practice that while long-term survival is the center of attention of most physicians, ESRD patients care more about their health-related quality of life (HRQoL) and prefer to spend this time in satisfactory well-being, instead of achieving a longer life (16–19).

Quality of life (QoL) is a term that is difficult to define. It is both a subjective and multidimensional concept that is regarded as a useful indicator of individual’s well-being in both physical and mental aspects of health. According to the World Health Organization’s (WHO) definition of quality of life, it is individuals’ perceptions of their position in life in the context of the culture and value systems in which they live and in relation to their goals, expectations, standards, and concerns (20–25).

In recent years, more attention has been focused on the psychological consequences of maintenance dialysis therapy in patients with ESRD, and interests in HRQoL as an evaluative factor of responsiveness and effectiveness of treatment has grown significantly. Hence, evaluation of outcomes of ESRD treatment has gone beyond traditional assessments, such as morbidity, mortality, and hospitalization rate, and HRQoL has been accepted as an important outcome measure from both clinician and patient perspectives (9, 24, 26–29).

The present study comprised 173 CKD patients who underwent peritoneal dialysis for at least 3 months. The characteristics of patients of the study are shown in Table 1. The mean age of the patients was 56.14 ± 16.55 years, 107 (61.8%) were males, and 130 (75.1%) patients were married. Most of the patients were housewives (34.9%), and the level of education of most of them was elementary (48%).

The mean duration of kidney disease in all patients was 109.71 ± 99.9 months, and the mean duration of dialysis was 35.63 ± 35.04 months. The mean dialysis adequacy score was 1.91 ± 0.48, and their mean residual renal function was 2.64 ± 2.68. Most of the patients were dialyzed three (39.8%) or four (42.1%) times a day, and 115 (67.3%) of them had a separate room for dialysis at their home. Their mean hemoglobin level was 11.07 ± 2.06 g/dL. The most common comorbidity in the study participants was diabetes mellitus (35.9%). The overall QoL score of the participants was 50.28 ± 20.87 (Table 1).

Next, we assessed the association of demographic and dialysis-associated factors with QoL scores. Male patients had a higher QoL score, compared to female patients (58.18 [males] vs 48.18 [females]; P = 0.04). Considering the number of dialysis per day, a significant association was observed between frequency of dialysis and quality of life (P = 0.047), where three sessions of dialysis per day yielded the highest quality of life (QoL score = 59.62, P = 0.047). No statistically significant relationship was observed between quality of life and marital status, level of education, having comorbidities, solution type, or having a separate room for dialysis. As Table 1 shows, most of the patients were housewives. A higher QoL score in self-employed patients was ascertained, compared to housewives (60.95 [self-employed] vs 46.49 [housewives]; P = 0.001). In addition, no statistically significant association was discovered between QoL score and level of education (P = 0.36; Table 2).

As presented in Table 3, no statistically significant relationship was determined between the QoL score in peritoneal dialysis patients and age, BMI, hemoglobin level, disease duration, dialysis duration, and dialysis adequacy. Although residual renal function was associated with QoL scores in patients undergoing peritoneal dialysis (P = 0.013), a correlation coefficient of 0.230 accorded with a weak direct correlation between them (Table 3).

Next, controlling the effects of gender, age, and BMI, we investigated the association of dialysis-associated variables with QoL score. Only residual renal function significantly associated with QoL scores (regression coefficient = 2.17 (0.71, 3.64, P = 0.046). No other variables showed any significant association with QoL scores.

Next, we assessed the association of contributing factors with SF-36 questionnaire sub-scales, including physical functioning, role physical, bodily pain, general health, vitality, social functioning, role emotional, and mental health. Males and females were different in physical functioning, and males had a higher score (70 [males] vs 55 [females]; P = 0.010), they also had a better score for role physical (50 [males] vs 0 [females]), bodily pain (87.5 [males] vs 77.5 [females]), general health (50 [males] vs 40 [females]), and role emotional (66.66 [males] vs 0 [females]). However, marriage was not shown to be significantly associated with any of the sub-scales. BMI of patients also showed no significant association with any of the sub-scales. A significant association was found between age and physical functioning (P< 0.001). In addition, no significant association was discovered between comorbidities and any of the sub-scales. Self-employed patients yielded a better function in most of the domains, compared with housewives, and showed a better physical functioning (69.9 [self-employed] vs 49.71 [housewives], P = 0.003), role physical (75 [self-employed] vs 0 [housewives], P = 0 < 001), general health (54.18 [self-employed] vs 44.23 [housewives], P = 0.014), role emotional (66.66 [self-employed] vs 0 [housewives], P = 0.007), mental health (64.94 [self-employed] vs 59.23 [housewives], P = 0.007). They also suffered from less bodily pain (P = 0.042). Frequency of dialysis resulted in significant changes in general health (P < 0.001), vitality (P = 0.011), social functioning (P = 0.017), and mental health (P = 0.009), and three sessions of dialysis per day resulted in better general health (55.58), vitality (55.5), social functioning (75), and mental health (68.26). Having a separate room for dialysis also had a significant association with better scores of general health (50 [self-employed] vs 40 [housewives], P = 0.023), social functioning (75 [self-employed] vs 62 [housewives], P = 0.015), VT (55 [self-employed] vs 45 [housewives], P = 0.048), RE (66 [self-employed] vs 0 [housewives], P = 0.002), and MH (68 [self-employed] vs 54 [housewives], P = 0.014). No relation was observed between patients level of Hb and quality of life; however, higher levels of Hb in patients were associated with a better role physical (P = 0.007).

Although the duration of dialysis did not demonstrate significant association with any of the QoL sub-scales, dialysis adequacy established a significant association with vitality (P = 0.06) and social functioning (P = 0.029), where higher dialysis adequacy provided better outcomes. Duration of disease was also associated with physical functioning (P = 0.017), and patients with a shorter duration of kidney disease had a better physical functioning. In addition, residual renal function was significantly associated with better role physical (P = 0.24) and mental health (P = 0.035) (see Table 4).

The mean sub-scale scores across contributing factors are presented in Table A1.

This study discovered that the most significant characteristics independently associated with quality of life were gender, employment, frequency of dialysis, and residual renal function. In the present study, males had a higher total QoL score than females (58.18 in males, compared to 48.18 in females). On the other hand, in subgroup analysis, males had a better score for physical functioning than females (70 in males, compared to 55 in females). Similar to our findings, studies in North America showed males to be associated with better quality of life (32, 33). In addition, some European studies using the SF-36 discovered an association between males and better QoL (34, 35). In contrast, other studies conducted in the United Kingdom and Turkey determined that scores for males were independently associated with a lower score for all QoL dimensions (9, 24). Previous studies demonstrated that faster decline in kidney function in males than in females could have a negative impact on HRQoL in males, while changes in the hypothalamic–pituitary–gonadal hormones status could make females more prone to problems such as sleep disorders, depression, and cognitive dysfunction (36, 37). On the other hand, males socialized in a different manner than females, more independent and self-controlled, especially in Middle East cultures, while females are taught to be more emotionally expressive, dependent, and concerned with their physical appearance to be accepted by the society (38). It seems that gender roles are not rigid or fixed and depend on some qualitative issues, such as ethnicity, culture, family dynamics, coping mechanisms, educational and social factors as well as physiologic hormonal status. Further studies are required to explore gender roles on quality of life in PD patients. In the present study, notwithstanding the previous studies (34, 39), married patients had no significantly better quality of life, indicating that most patients, either single or married, experienced good support through family ties, maybe due to traditional Iranian culture. According to results of the present study, frequency of dialysis was significantly associated with quality of life. It was not surprising to observe the negative effects of frequency of dialysis on the quality of life of patients because of the time required to spend on dialysis. Self-employed patients were significantly associated with a higher QoL score in our population. It was documented that employment not only provided economic benefits but increased self-esteem, sense of control, and social value (24, 40). On the other hand, the Brazilian peritoneal dialysis multi-center study demonstrated that quality of life was not significantly associated with family income (41), while other aspects of working beyond financial matters might influence more the quality of life. In the present study, patients who were self-employed and could schedule their working time themselves, experienced better quality of life than those working for others. Another factor that was not associated with QoL score in our population was education. However, poor educational status was shown to have a negative effect on the quality of life of PD patients in other studies (24, 33–35). The most common comorbidity in patients of the present study was diabetes mellitus. In the present study, comorbidities were not associated with any sub-scale of quality of life, while another study showed that diabetic patients scored significantly worse on the physical function scale. Although in certain surveys, some comorbidities were related to some QoL sub-scale scores, other possible reasons could be observed for lacking a significant association between the QoL sub-scale scores and diseased condition (24, 34). It appeared that quality of life was not determined merely by the absence or presence of comorbidities; however, it was influenced by patients’ perception of their position in different aspects of life, and many non-disease health-related factors play important roles (42). Besides, the severity of comorbidities should be considered in the future studies. Our study demonstrated no significant association between age and QoL score. However, a Spanish study showed that advanced age adversely affects the QoL score (34). It is important to note that in the present study, a significant association between mental health sub-scale and residual renal function was established. This result was consistent with the results of previous studies, indicating that higher residual renal function was associated with improved HRQoL of PD patients, particularly in mental health domains (43, 44). Dialysis adequacy was significantly associated with social functioning and vitality sub-scales. Scarce data were available regarding the effect of dialysis adequacy on the physical and mental domains of quality of life (45, 46), whereas other studies showed no significant association (24, 47).

In contrast with other studies, no statistically significant relationship was observed in the present study between Hb level and the QoL score in peritoneal dialysis patients (2, 48, 49). However, higher Hb levels were associated with a better score of role physical sub-scale (P = 0.007). This result was consistent with another study, where greater Hb concentration was related to better QoL scores on physical dimension (35).

Our study showed that the most significant characteristics that were independently associated with patient’s quality of life were gender, employment, residual renal function, and frequency of dialysis. Evaluation of quality of life should be incorporated in clinical follow-up of PD patients The above-mentioned factors should be considered to a greater extent for implementing strategies and possible interventions to improve certain aspects of quality of life in our population.