INTRODUCTION

In recent decades, non-communicable chronic diseases have reached epidemic proportions and consolidated Chronic Kidney Disease (CKD) as an important public health problem^1,2, substantially contributing to the burden of the disease in the world, since CKD presents diabetes and hypertension as the main causes^2,4.

It is estimated that 9% of the world population has CKD². In Brazil, 8% of the population has some degree of the disease, with an increase of 34.78% of individuals on dialysis in 10 years, corresponding to 133,464 individuals⁴. Of this total, 92.30% undergo hemodialysis (HD)⁴.

The benefit of HD in prolonging the patient’s life and improving the clinical picture is known, however, patients on HD are subject to hemodynamic and metabolic changes, due to numerous factors, from disorders caused by the disease itself to side effects of treatment and medications⁵, in addition to daily activities and social changes⁶. Such changes severely impact the Quality of Life (QoL) of this population^7-9.

In the health area, QoL is aimed at the perception of physical, psychological and social limitations, influenced by the disease, treatment and other health problems¹⁰. With the increase in chronic diseases and life expectancy, QoL has gained greater importance, in addition to being a predictor of mortality in patients with CKD1^11,12. It has also become a measure of health outcome¹³.

In chronic diseases, QoL depends on several factors such as the type and duration of the disease, its treatment and side effects, the severity of symptoms, medication effects, patient age, limitations and self-care capacity⁹. Add to this, the social inequality, an important problem in Brazil, which both predisposes to CKD and worsens the outcomes of those with the disease¹⁴. In this scenario, the socioeconomic level becomes a determinant of QoL. Added to the low level of education, the observed social inequality is closely related to the QoL of this population^16,17.

Although the relationship between Low QoL and CKD is well established^18-20, it can be deepened through the biopsychosocial model that concerns the commitment of each biological, social and clinical domain that affects the quality of life of these individuals²¹. Mainly because this approach can help in understanding the various aspects involving CKD, hemodialysis treatment and social support, as well as their impact on the well-being of individuals with CKD. Therefore, to identify QoL predictors of patients on HD, it is imperative to consider the multidimensionality that involves the topic. In addition to sociodemographic variables, we also studied life habits and clinical characteristics, including disease time since diagnosis, years of HD treatment, number of medications and complications, variables little explored in their correlation with the dimensions of QoL. Thus, the aim of this study is to assess the association between QoL and socioeconomic, lifestyle and clinical factors of patients on HD.

METHODS

RESULTS

Of the 1,024 individuals in the study, the average age was 54.7±14.7 years and most individuals (51.56%) were aged between 30 and 59 years.

According to the sociodemographic profile, most individuals had less than 8 years of education (n=523, 51.62%), were of mixed race/color (n=496, 49.06%), and had family income between 1 and 2 minimum wages (n=441, 43.70%). Most were retired or on leave due to chronic kidney disease (n=547, 54.21%), and used the public health system (n=774, 75.65%).

QoL assessed by the SF-36 domains, showed that the lowest score was physical functioning (26.78) and the highest score was mental health (72.16). Regarding the physical and mental components summaries, a higher score was obtained for the mental component summary (47.98) when compared to the physical component summary (35.19).

Table 1 shows the sociodemographic data according to the 8 domains and 2 components of QoL.

Regarding gender, with the exception of the emotional aspect domain, there was a statistical difference in all domains and between the physical and mental components, in which males had better QoL.

Regarding age, young individuals aged 19 to 29 years old had better QoL in the physical capacity (p=0.001), physical aspect (p=0.005), pain (p=0.014), and physical component (p=0.001) domains. While the elderly, aged 60 years old or more, had better QoL in the domains of general health (p=0.001), mental health (p=0.003) and mental component (p=0.001). As for education, individuals that had between 8 and 11 years of schooling had better QoL in the domains of physical aspect (p=0.025), pain (p=0.025), vitality (p=0.001), social aspect (p=0.05), emotional aspect (p=0.001) and physical component (p=0.001). While individuals with more than 11 years of education had better physical capacity (p=0.001).

Regarding race/color, individuals of white race/color had better QoL for the emotional aspect domain (p=0.011). For family income, individuals with income above 5 minimum wages had better QoL, with a significant difference in all domains (p<0.005), with the exception of general health. And with regard to occupation, employed individuals had better QoL in the physical capacity (p=0.001) and physical component (p=0.001) domains. In relation to health care, individuals who used private care showed better QoL in the emotional aspect domain (p=0.031).

Table 2 presents the data on lifestyle habits in relation to the QoL domains. Of the total number of individuals, 95 (9.3%) reported consuming alcoholic beverages, 36.3% (n=372) reported being smokers in the past, and 76.4% (n=766) reported not practicing physical activity.

The smoking habit, represented by the smoking load, showed that individuals with a low smoking load had better QoL for the functional capacity domain (p=0.007). Regarding alcohol consumption, individuals who did not consume alcoholic beverages had significantly better QoL in the physical capacity (p=0.001), physical aspect (p=0.044) and emotional aspect (p=0.031) domains.

Regarding the habit of practicing physical activity, all QoL domains and the two components (physical and mental) obtained significant results (p<0.05).

Table 3 presents data on clinical variables in relation to QoL domains. For CKD time, 51.5% (n=525) reported having the disease for less than five years, and 48.5% (n=494) for more than five years. As for HD time, most individuals 38.1% (n=368) undergo hemodialysis for less than two years, while 26.1% (n=252) undergo hemodialysis between three to five years, 20.5% (n=198) between six and ten years, and 15.4% (n=149) for more than 10 years. Regarding the use of medications, it was found that the majority 70.4% (n=664) used less than five medications, while 29.6% (n=280) used more than five medications.

Most individuals 68.1% (n=697) reported having 3 or more diseases and 78.8% (n=807) reported having 2 or more complications. Individuals with the disease for less than 5 years had better QoL in the pain (p=0.003) and vitality (p=0.026) domains. On the other hand, individuals with the disease for more than 5 years had better QoL in the physical aspect domain (p=0.036).

For the duration of HD, individuals with 6 to 10 years of treatment had better QoL in the physical aspect (p<0.001) and emotional aspect (p=0.007) domains. Among individuals with 2 years of treatment or less, they had better QoL in the pain domain (p=0.010).

Regarding the number of medications used, individuals who used more than 5 medications had better emotional aspects (p=0.040). With regard to the number of diseases and complications, individuals with three or more diseases and three or more complications showed significantly worse QoL for all domains.

After adjustment for multiple linear regression, male gender was a predictor of better functional capacity (β= 0.147, p<0.001), pain (β= 0.174, p<0.001) and summary of the physical component (β= 0.138, p<0.001). The age group from 30 to 59 years old and over 60 years old were predictors of worse functional capacity (β= -0.184, p=0.008 and β= -0.370, p<0.001), physical aspect (β= -0.215, p=0.003 and β= -0.199, p=0.008) and physical component summary (β= -0.188, p=0.008 and β= -0.277, p<0.001), respectively. The categories of education above 8 years of schooling were predictors of better functional capacity. Family income strata were predictors of better functional capacity, physical aspect and summary of the physical component. The profession was a predictor of worse functional capacity among retired/on leave (β= -0.069, p=0.038) (Table 4).

For the domains related to mental health, after adjustment, male gender was a predictor of better QoL for vitality (β= 0.087, p=0.009), social aspect (β= 0.093, p=0.007), mental health (β= 0.134, p<0.001) and mental component summary (β= 0.072, p=0.048). The age group over 60 years old was a predictor of better mental health (β= 0.188, p=0.009) and summary of the mental component (β= 0.214, p=0.008). Education between 8 and 11 years of schooling was a predictor of better vitality (β= 0.102, p=0.003), emotional aspect (β= 0.083, p=0.034), mental health (β= 0.188, p=0.031) and summary of the mental component (β= 0.076, p=0.042), while education above 11 years of schooling was a predictor of worse social status (β= -0.122, p=0.002). Family income categories were predictors of better social appearance (Table 5).

For lifestyle habits related to the physical health domains, the absence of physical activity was a predictor of worse QoL for all domains: functional capacity (β= -0.272, p<0.001), physical aspect (β= -0.099, p= 0.004), pain (β= -0.081, p=0.018), general health status (β= -0.167, p<0.001) and summary of the physical component (β= -0.221, p<0.001). The high smoking burden was a predictor of worse functional capacity (β= -0.060, p=0.049) (Table 6).

For the domains related to mental health, the absence of physical activity and its occasional practice were predictors of worse vitality, (β= -0.241, p<0.001 and β= -0.086, p=0.007) respectively, of social aspect (β= -0.096, p=0.005) and mental health (β= -0.117, p<0.001). The non-consumption of alcoholic beverages was a predictor of worse mental health (β= -0.062, p=0.047) (Table 7).

For clinical characteristics associated with the physical health domains, the number of complications was a predictor of worse QoL for all domains. The categories of time on HD were predictors of better physical appearance and over 10 years of HD was the worst predictor of pain (β= -0.123, p=0.005) (Table 8).

For the domains related to mental health, except for the emotional aspect, the number of complications was a predictor of worse QoL for all domains. Time on HD between 6 to 10 years (β= p=0.013) and the use of more than 5 medications (β= 0.081, p=0.020) were predictors of better emotional appearance.

DISCUSSION

The results demonstrate that QoL is multidimensional and it can be affected by inherent individual’s characteristics and by clinical conditions. The determining factors were male gender, age, education, physical activity and the number of intradialytic complications are highlighted as factors associated with both physical and mental health and, therefore, important predictors of QoL in this population.

Mental health represented the best QoL of the individuals in the study, while the worst QoL was represented by the physical aspect. This data is corroborated by the summaries of components, in which the mental component obtained higher scores in relation to the physical component. Better mental health at the expense of physical health is a common finding in this population, and it is related to the chronic nature of the disease, in which the individual adapts not only to the disease, but psychologically to his reality over time, influencing QoL^17,26-28.

Advanced age is related to the gradual decline in physical health²⁹, however, the older the patient, the greater the adherence to treatment²⁶. Elderly individuals value social and emotional support, regardless of the state of frailty³⁰, influencing their perception of QoL. In this context, it was observed in this study that while being young (19 to 29 years old) was a predictor of better functional capacity and physical aspect, being elderly (≥ 60 years old) was a predictor of better mental health. Similar results were found in other studies^31,32.

Despite the high mental health of the general population in the study, there was a low QoL for females when compared to males. Low QoL among women is also observed in other studies^29,31. Gerogianni et al., (2017)³³, identified higher levels of anxiety and depression in women undergoing hemodialysis when compared to men, a result attributed to the social context in which the women find themselves, for various daily responsibilities that impact QoL.

In this social context, socioeconomic factors also stand out. In this study, education was configured as a predictor of mental health and functional capacity, a result similar to previous studies^17,31,32. Higher levels of education allow greater access to information and better economic status, enabling a more assertive assessment of QOL¹⁶. It is also assumed that individuals with a higher level of education tend to develop more intellectual than physical activities²⁹, which explains the better functional capacity of individuals over 8 years of schooling in our findings.

Therefore, it is noted that social inequities such as low education, which are responsible for increasing the risk of CKD, continue to influence on their QoL even after HD treatment. In this context, racial disparities also become a determinant of health^34,35. In our findings, in accordance with other studies^35,36, there was a predominance of non-white individuals (71.97%), and the negative impact of black and mixed race/color, as a predictor of worse emotional appearance.

Added to this scenario, the socioeconomic level is reported by different studies as a determining factor of QoL^13,17,38. Low socioeconomic status both increases the risks that predispose to CKD, as well as worsens the outcomes of those with the disease¹⁵. In this study, most individuals (43.1%) had a family income between 1 and 2 minimum wages, and the lower the income, the worse the QoL. Therefore, there is a greater association of socioeconomic level with physical health domains, as well as profession, which is a predictor of better QoL for functional capacity among employed individuals.

Thus, the set of associations of sociodemographic characteristics allow us to assume that individuals with higher education and better socioeconomic status develop more intellectual activities, requiring less physical effort, preserving physical health, in addition to presenting better economic conditions and greater clarification to deal with the disease^16,17,32,38.

Besides socioeconomic factors, the lifestyle habits of hemodialysis population also impact QoL^39,31,40. Smoking and alcohol consumption are poorly studied habits in this population, however some studies demonstrate their low prevalence in patients on HD^36,40. In this study, even considering a minority with high smoking burden, it negatively affected their functional capacity. Moreover, the consumption of alcoholic beverages, despite negatively affecting their functional capacity, positively impacted their mental health.

In our findings, the practice of physical activity was a predictor for all QoL domains, proving the benefit of practicing some exercise both for physical and mental health, for patients on HD. However, despite the Kidney Disease Outcomes Quality Initiative (KDQOI) guidelines recommending that HD patients be encouraged to increase their level of physical activity⁴⁰, studies have verified the low adherence to physical activity practice by this population, as well as this study, and have focused on proving the clinical and QoL benefits of the regular practice of physical activity^31,39,42.

The improvement in physical performance and QoL of patients on HD was verified after an exercise program for 6 months, safely allowing the encouragement of simple and sustainable physical activity in this population, with the aim of improving clinical outcomes⁴³.

Since frailty and physical malfunction are perhaps the most disabling disorders in patients on chronic dialysis^44,45, our findings, in agreement with the studies mentioned above, prove the practice of physical activity as a fundamental practice for QoL of patients on HD.

Clinical characteristics were also identified as predictors of QoL. The time on hemodialysis showed an inverse association with the physical aspect and pain domains, indicating worsening of pain and physical aspect, the longer the time on HD. On the other hand, individuals between 6 to 10 years of hemodialysis treatment presented better emotional aspects, reflecting once again the patient’s adaptation to the disease over the years. Previous studies have failed to prove the effect of hemodialysis time on QoL^38,40,47,48. However, Pan et al., (2018)³²observed that time on hemodialysis above 4.5 years was inversely associated with QoL, and a positive association was observed between longer dialysis time and the mental component, a result similar to our findings .

Another clinical feature predicting the emotional aspect was the number of medications. It is known that the population with CKD commonly has other associated diseases. Multimorbidity, the presence of two or more diseases in the same individual is frequently observed in this population, and has become a growing concern in the care of individuals with CKD, resulting in an increase in the treatment burden and contributing to polypharmacy^49,50.

Unlike previous studies^17,38,51 that identified that the greater the number of medications being used by the individual, the worse the QoL, this study showed that individuals using five or more medications had a better emotional aspect when compared to individuals using fewer medications. Thus, the drug load contributed positively to the study population, however, in addition to the impact of the disease itself, the patient with CKD on HD is subjected to the consequences of the treatment itself, which despite the benefits also causes complications⁵².

Intradialytic complications are frequently seen in patients on HD⁵² and play a significant role in worsening QoL³². In this study, most individuals (85.05%) had 3 or more complications, placing themselves as the clinical characteristic that is most associated with QoL. Therefore, the greater the number of complications, the worse the QoL, emphasizing the vulnerability of these individuals and the necessary intervention for this modifiable risk factor very present in this population.

Finally, this study has some limitations. Due to the cross-sectional nature of the study, it was not possible to determine a causal effect between QoL and the study variables. In addition, this study was carried out in a single state in Brazil, but the results may support further studies that point to a causal relationship. However, the strengths of the study help to circumvent this limitation. Since the metropolitan region surveyed concentrates the largest number of individuals undergoing HD in the state, provided us a large sample size. In addition, the use of all domains of QoL is highlighted, which allows exploring the influence of each variable studied on quality of life and precisely identifies the most effected domains.

CONCLUSION

Quality of life is impacted by different aspects involving CKD, such as social, clinical and lifestyle characteristics. Therefore, in addition to considering the various factors that influence quality of life, we demonstrate the importance of using quality of life in all its dimensions, identifying the positive or negative associations between each factor with each domain of quality of life.

The male sex is highlighted as a predictor of better physical and mental health, and the influence of age group characterizes elderly people with better mental health despite the impairment in physical health. Physical activity was an important predictor of QoL, highlighting that the absence of physical activity is associated with worse physical and mental health. Clinically, it was possible to observe how the number of complications negatively affects the QoL of HD patients, since having 3 or more complications was associated with worse physical and mental QoL. Encouraging the practice of physical activity and preventing intradialytic complications are modifiable factors that can promote the QOL of HD patients, contributing to a better health outcome. As low QOL is one of the main problems in this population, our findings highlighted the potential of QOL assessment for holistic clinical treatment.