Physical fitness in patients treated with maintenance dialysis: a cross-sectional study

doi:10.21203/rs.3.rs-4014563/v1

Background: Low physical fitness has been associated with deterioration in overall health outcomes, resulting in increased hospitalization, morbidity, and mortality in patients treated with maintenance dialysis. This study aimed to compare self-reported physical fitness between patients treated with maintenance dialysis and those without chronic kidney disease (CKD).

Methods: In this cross-sectional study, patients treated with maintenance dialysis (n=674) and individuals without CKD (control, n=518) self-reported physical fitness by responding to the International Fitness Scale (IFIS). Binary Logistic Regressions were adjusted for sex, age, schooling, diabetes, smoking, physical activity, sedentary behavior, and body max index.

Results: Patients undergoing chronic hemodialysis are more likely to self-report lower general PF (OR=2.03; 95% CI: 1.35 to 3.05; p = 0.001), cardiorespiratory fitness (OR=3.18; 95% CI: 2.27 to 4.46; p<0.001), strength (OR=2.51; 95 % CI: 1.71 to 3.68; p<0.001) and agility (OR=1.83; 95% CI: 1.26 to 2.64; p=0.001) than the control group. Patients undergoing chronic hemodialysis who self-reported higher levels of physical activity were 5.64 times more likely to self-report high overall physical fitness (OR=5.64, 95% CI: 1.93 to 16.45, p<0.002).

Conclusion: Patients treated with maintenance dialysis were twice as likely to self-report lower general physical fitness compared to individuals without kidney disease. Considering the consequences related to these factors, strategies to improve it, like initiatives related to the practice of physical exercises with this population, including strategically during hemodialysis, may be interesting.

Kidney Dialysis

Physical activity

Chronic Kidney Failure

Cardiorespiratory Fitness

Muscle strength.

Chronic kidney disease (CKD) is characterized by abnormalities in kidney structure or function for at least 3 months¹. Patients with CKD present reduced ability to maintain metabolic and hydroelectrolytic balance². Thus, these individuals are exposed to several factors which may contribute to the progressive worsening of general health³.

CKD is an independent risk factor for functional impairment and frailty⁴. In patients treated with maintenance dialysis, lower physical fitness has been associated with a series of complications that may culminate in increased hospitalizations⁵ morbidity and mortality in this population⁶.

Physical fitness is defined as the ability to perform physical efforts, such as daily, occupational and leisure activities without excessive fatigue, and is considered as one of the strongest protective factors for the development of chronic diseases⁷.

Yurdalan etl. al (2007) verified a significant reduction in all physical fitness components evaluated in patients treated with maintenance dialysis (n = 90)⁸. Bučar and Pajek (2018) reported greater functional deficits in balance, flexibility, and lower limb function. (n = 140). Both studies carried out an objective assessment of participants' physical fitness through the application of physical tests to measure their outcomes. Nevertheless, due to the challenges inherent in objectively assessing physical fitness through physical tests, it is not always viable to incorporate this variable in studies involving a large cohort of individuals ⁹.

Yet, relying solely on the isolated objective assessment of participants' physical fitness may present a snapshot of a situation that could be atypical. Factors such as the timing of the physical tests and potential fluctuations in the well-being of patients can influence these outcomes. Additionally, self-reporting of physical fitness provides a subjective perspective on individuals' abilities and their perceived sufficiency, highlighting the relativity of these assessments. Therefore, this study seeks to compare self-reported levels of physical fitness between patients undergoing maintenance dialysis and individuals without chronic kidney disease (CKD).

Sample and ethics

This cross-sectional study (survey) was conducted from October 2021 to July 2022. The recruitment of patients undergoing maintenance dialysis was actively carried out across a network of hemodialysis clinics located in Brazil. A total of 35 treatment units agreed to participate in the study. The online survey was shared with the multidisciplinary team at each clinic, who forwarded it to their patients to respond after formal consent.

Patients with diagnoses of CKD on G5, undergoing chronic hemodialysis treatment at least twice a week for at least 3 months, from both sexes and older than 18 years were invited to answer the online survey. Healthy individuals over 18 years of age from both sexes, were invited to answer the online survey through social media, namely Facebook, Instagram, and WhatsApp. Individuals with diagnosis of CKD, but not undergoing hemodialysis, were not included in the sample.

Visually impaired, illiterate, or individuals who felt unable to independently respond to the online survey were assisted by third parties. For chronic hemodialysis patients with visually illiterate or impaired conditions, the multidisciplinary team provided assistance in completing the questionnaire.

This study was approved by the Ethics Committee of the Federal University of São Paulo (UNIFESP) (CAAE: 48533321.1.0000.5505, opinion: 5,384,426). All procedures were carried out by national law and the Helsinki Declaration. All participants provided informed consent prior to the study.

Procedures

Volunteers answered an electronic questionnaire (Google Forms) composed of 45 questions (52 for patients treated with maintenance dialysis). Both questionnaires have 6 sections: section 1: Free and Informed Consent Form; section 2: demographic, behavioral, clinical, and social characterization; section 3: physical fitness; section 4: level of physical activity; section 5: eating habits; and section 6: questioning how the questionnaire was completed (with or without help). For patients treated with maintenance dialysis, a link was provided so they could complete the survey either at home or at the dialysis unit, using their personal electronic devices. Individuals who were visually impaired, illiterate, unable to answer independently, lacked access to an electronic device or internet received assistance from either the researchers or a member of the multidisciplinary team to complete the forms. After filling in the questionnaire, the entire form was redirected to a spreadsheet generated by Google, in Microsoft Excel format, for further analysis.

Only the main researcher had access to the identified responses, which is stored in a personal computer protect by passwords. The other researchers had only access to non-identified data.

For the present study, the answers and questions present in sessions 1, 2, 3, and 4 were analyzed. The details of these domains are also described below.

Instrument

Self-reported physical fitness was assessed throughout IFIS, which is a self-report scale, validated for the Brazilian population, composed of five questions of the "Likert" scale, ranging from 1 (very bad) to 5 (very good). IFIS questions the individual about the perception he/she has about his/her general physical fitness, cardiorespiratory fitness, muscle strength, speed-agility, and flexibility, and the person should classify these components as "very bad", "bad", "or medium", "good" and "very good". The higher the score, the higher the self-reported physical fitness ^9,10.

The IFIS is a validated instrument that has been translated into nine different languages, including Portuguese. Furthermore, the IFIS questionnaire is a good alternative to assess physical fitness in young adults and older adults^24,25. This population is capable of comprehending the terminology and stating their perceptions accurately and clearly regarding overall physical fitness, cardiorespiratory fitness, muscular strength, speed-agility, and flexibility. The subjective perception of general physical fitness and fitness objectively measured by a battery of physical tests indicated a high degree of agreement ²⁴.

Survey respondent characteristics

Demographic data were obtained: name (open question asking them to type name and surnames), age (open question), sex (possible answers: male or female), current mass (open answer requesting the answer in kilograms), current height (open answer asking for the answer in meters), city and state in which you currently live (open question), level of education (possible answers: complete or incomplete elementary, complete or incomplete middle, complete or incomplete higher education), whether you smoke (possible answers: yes or no), if a doctor had already said you have diabetes (possible answers: yes or no), if currently work (possible answers: yes or no) and income [possible answers: less than 1 minimum wage, 1 minimum wage, from 1 to 2 minimum wages (1,088 real to 2,176 real), from 2 to 3 (2,176 real to 3,264 real), from 3 to 4 of (3,264 real to 4,352 real) or from 4 to 5 or more (4,352 real to 5,440 or more)].

For the group of patients treated with maintenance dialysis, we also questioned the weekly frequency with which they underwent hemodialysis (possible responses: 2,3,4,5,6 or 7 times a week) and how long they had been undergoing treatment (possible answers: less than 3 months, less than 1 year, between 1 and 2 years, between 2 and 3 years, between 3 and 4 years or between 4 and 5 years or more). In the control group questionnaire, there was also the following question: "Have any doctors ever told you that you have chronic kidney disease?" (Possible answers: yes or no).

To assess the level of physical activity, the participants were asked the following questions: "Do you currently practice physical activities?" (Possible answers: yes or no); "Currently what kind of physical exercise do you perform?" [Possible answers: I don't perform physical exercise; walking; bodybuilding; functional exercises (jumping, squatting, spinning, running, pushing, pulling)]; "Currently how many times a week do you perform physical activity?" (Possible answers: none to seven times); "How long is each physical activity session?" (Possible answers: I do not practice physical activity; less than 30 min; between 30 and 60 min or more than 60 min) and "What is the intensity of this physical activity?" [Possible answers: I don't practice physical activity; light (considering the following examples given: bathing, shaving, driving, washing dishes, making the bed); moderate (considering the following examples given: gardening, playing volleyball, water aerobics, pedaling, fast walking); intense/vigorous (considering the following examples given: climbing stairs, swimming, jumping rope, playing football, running).

Based on the answers, the time spent during each physical activity session during the study was multiplied by the number of days of the week in which the participant exercised.

The sedentary behavior was also evaluated through the following question: "On average how many HOURS do you spend sitting or lying down in a day? Don't consider the hours you spend sleeping" (open question).

Statistical analysis

The data were stored and analyzed using SPSS 25.0. Data normality was verified by the Shapiro-Wilks test. The results are presented as median and interquartile range for continuous variables and frequency (absolute and relative – %) for categorical ones. Comparison between groups was performed using the Mann-Whitney and Chi-square tests. Binary Logistic Regression was used to verify the association between undergoing chronic hemodialysis and reporting low physical fitness adjusted for sex, age, education level, diabetes, smoking status, sedentary behavior (SB), and body mass index (BMI)]. In the binary logistic regression analysis, low physical fitness was defined as a score below 3 on the International Fitness Scales (IFIS). With the exception of age and sedentary behavior (treated as continuous variables), the variables: sex, education level, diabetes, smoking status were treated in a categorized manner. All variables were entered together into the model. For the analysis of physical activity, the participants who added 150 minutes or more of moderate to high-intensity physical activity were classified as physically active, whereas those who did not reach this threshold were classified as inactive^36,37. Binary Logistic Regression was also used to verify the association between physical activity and self-report fitness level in dialysis patients (considering the same adjustment variables), but contemplating only participants undergoing hemodialysis with physical activity as a comparator factor (inactive adopted as reference)^36,37. Significance was set at p < 0.05 and 95% confidence interval (95%CI).

A total of 674 patients treated with maintenance dialysis and 518 without CKD participated in this study.

The number of patients according to the dialisys vintage was: less than 1 year: 116 (17.2%), between 1 and 2 years: 117 (17.4%), between 2 and 3 years: 91 (13.5%), between 3 and 4 years: 103 (15.3%), between 4 and 5 years or more: 247 (36.6%). The number of patients according to the weekly frequency with which they underwent chronic hemodialysis was: 3 times a week: 604 (89.6%), 5 times a week: 15 (2.2%), 6 times a week: 11 (1.6%), 4 times a week: 32 (4.7%), twice a week: 12 (1.8%). Among patients treated with maintenance dialysis, 373(55.3%) answered the questionnaire with help, while 301(44.7%) answered alone.

Regarding the way in which the participants in the control group filled out the questionnaire, 70 (13.5%) answered it with help, while 448 (86.5%) answered it alone.

Patients treated with maintenance dialysis were older, with lower BMI, engaged in fewer moderate to vigorous physical activities, had fewer sedentary behavior, and higher frequency of diabetes when compared to participants who did not undergo hemodialysis (Table 1).

Table 1

**Sample characterization.**
	Hemodialysis (n = 674)	No hemodialysis (n = 518)
Variables	Median (IR)	Median (IR)	P
Age (Years)	57.00 (21.00)	41.00 (32.00)	< 0.001
Mass (kg)	70.50 (21.00)	72.00 (20.00)	0.333
Height (cm)	167.00 (13.00)	165.00 (14.00)	0.010
BMI (kg/m²)	25.28 (6.59)	25.81 (6.14)	0.015
MVPA (min/week)	0.00 (0.00)	60.00 (150.00)	< 0.001
SB (hours/day) Sex (% Female/%Male)	8.00 (6.00) 41/59	9.00 (8.00) 68/32	< 0.001
Education	%(95CI)	%(95CI)
Incomplete fundamental	30.3 (26.8–33.7)	7.9 (5.5–10.2)
Complete fundamental	11.3 (8.8–13.6)	5.2 (3.3–7.1)
Incomplete high school	7.1 (5.1-9.0)	3.1 (1.6–4.5)
Complete high school	28.5 (25.0-31.9)	17.0 (13.7–20.2)	< 0.001
Incomplete graduate	7.4 (5.4–9.4)	18.0 (14.6–21.2)
Graduated	15.4 (12.7–18.1)	48.8 (44.5–53.1)
Cardiovascular risk factors	%(95CI)	%(95CI)
Diabetes	35.6 (31.9–39.2)	9.3 (6.7–11.7)	< 0.001
Smoking	9.6 (7.4–11.9)	9.5 (6.9–12.0)	1.000

MVPA = minutes of moderate to vigorous physical activities/week; SB = hours of sedentary behavior/ day.

Multivariate Binary Logistic Regression analysis revealed that patients treated with maintenance dialysis were twice as likely to report lower general physical fitness. Similar findings were observed for cardiorespiratory fitness, muscular strength, and speed/agility. No associations were observed for flexibility (Table 2).

Table 2

Association between self-report fitness level in patients treated with maintenance dialysis and participants without chronic kidney disease (n = 1192).
Fitness Component	Reference Group	Outcome Definition	OR	95% CI	P-value
General Physical Fitness	High	Self-reported fitness level	Ref	Ref	Ref
	Low		1.86	1.22–2.83	0.004
Cardiorespiratory Fitness	High	Self-reported fitness level	Ref	Ref	Ref
	Low		3.04	2.14–4.34	< 0.001
Strength	High	Self-reported fitness level	Ref	Ref	Ref
	Low		2.34	1.58–3.46	< 0.001
Flexibility	High	Self-reported fitness level	Ref	Ref	Ref
	Low		1.14	0.78–1.65	0.491
Agility	High	Self-reported fitness level	Ref	Ref	Ref
	Low		1.75	1.20–2.57	0.004

Adjusted by sex, age, education level, diabetes, smoking status, physical activity, sedentary behavior, and BMI. Note: OR = Odds Ratio; CI = Confidence Interval; P-value indicates statistical significance.

In Fig. 1, we present the self-reported fitness levels of patients treated with maintenance dialysis and participants without chronic kidney disease.

Table 3 presents the associations between self-reported physical activity level and self-reported physical fitness level in patients undergoing dialysis. Higher self-reported physical activity level was independently associated with better self-reported physical fitness.

Table 3

Association between physical activity and self-report fitness level in dialysis patients (n = 674).
Fitness Component	Reference Group	Outcome Definition	OR	95% CI	P-value
General Physical Fitness	Inactive	Self-reported fitness level	Ref	Ref	Ref
	Active		5.64	1.93–16.45	0.002
Cardiorespiratory Fitness	Inactive	Self-reported fitness level	Ref	Ref	Ref
	Active		6.23	2.84–13.63	< 0.001
Strength	Inactive	Self-reported fitness level	Ref	Ref	Ref
	Active		6.29	2.19-18.00	0.001
Flexibility	Inactive	Self-reported fitness level	Ref	Ref	Ref
	Active		2.65	1.43–4.90	0.002
Agility	Inactive	Self-reported fitness level	Ref	Ref	Ref
	Active		4.89	1.99–12.03	0.001

Adjusted by sex, age, education level, diabetes, smoking status, sedentary behavior, and BMI. Note: OR = Odds Ratio; CI = Confidence Interval; P-value indicates statistical significance.

To the best of our knowledge, this is one of the very few studies to compare self-reported levels of physical fitness between patients undergoing maintenance dialysis and individuals without CKD. The main result is that patients treated with maintenance dialysis self-reported lower physical fitness in all assessed components, but flexibility, compared with individuals without CKD. The decline in physical fitness components in CKD patients reported in the presented study and in others, is related with adverse outcomes, including lower quality of life¹³, higher oxidative stress, a higher degree of inflammation¹⁴, an increase in hospitalizations⁵ and a higher mortality rate^14,15. Factors such as uremic neuropathy, anemia, heart disease, hypertension, fatigue, depression, and lower limb pain contribute to the observed reduction in physical fitness^15,16.

Previously, Yurdalan et al. (2007) identified a significant reduction in all physical fitness components among patients undergoing maintenance dialysis using the Eurofit Test Battery³⁵. Similarly, Bučar and Pajek (2018) revealed functional deficits, in balance and flexibility⁸. Medeiros et al. (2002) highlighted gender-specific differences in cardiorespiratory fitness, strength, and flexibility. Kaysen et al. (2011) and Painter et al. confirmed impaired physical performance and exercise capacity in patients on maintenance dialysis^15,33. Even in agreement with these studies, the results here presented emphasized the importance of self-reported data, offering a more general assessment and eliminating biases associated with fluctuating well-being. Furthermore, individuals' self-perception of their physical fitness reflects their beliefs about their capabilities and introduces a relative aspect to the assessment. This nuanced analysis prompts reflection on vulnerability and may encourage greater engagement in physical exercise.

The analysis of Table 3 revealed positive correlations between the self-reported level of physical activity and self-reported physical fitness among patients treated with maintenance dialysis. It was found that patients undergoing maintenance dialysis who reported higher levels of physical activity were 5.64 times more likely to indicate high overall physical fitness (OR = 5.64, 95% CI: 1.93 to 16.45, p < 0.002). In line with our findings, Huang et al. (2020) showed in a pragmatic randomized controlled trial that engaging in moderate-intensity combined intradialytic exercise for 24 weeks can improve physical fitness³⁸.

To validate the representativeness of our samples, we compared our results with the Brazilian Dialysis Survey 2020 and general population data from the Brazilian Institute of Geography and Statistics (IBGE 2023). According to the Brazilian Dialysis Survey 2020, the sex of patients treated with maintenance dialysis was: 58% men and 42% women, conclusion of our study: 59% men and 41% women; According to the Brazilian Dialysis Survey 2020, the weekly frequency with which patients treated with maintenance dialysis underwent treatment: 90.8% of patients responded that they performed less than ≤ 4 sessions/week, finding of our study: 96.6% ≤ 4 sessions/week. According to the Brazilian Dialysis Survey 2020, the most prevalent age group was between 45 and 64 years old, representing 42.5%; finding of our study: the median age of the patients was 57 years old (IR:21). According to the Brazilian Dialysis Survey 2020, the region in Brazil with the highest number of patients treated with maintenance dialysis was Southeast; finding of our study: most of the individuals who responded to our questionnaire were from this region too^28,26. Despite certain limitations, our findings closely align with national demographic and treatment patterns.

The study acknowledges limitations, including expected differences in sample characteristics between the groups. Reported mass, sued to BMI calculations may not precisely represent the actual dry mass of patients, considering the complexities of CKD pathophysiology. The self-reported nature of data introduces potential biases in interpretation.

Given the high prevalence of low physical fitness in individuals with CKD and its associated consequences, our study underscores the necessity of implementing strategies to address these components. Initiatives related to the practice of physical exercises with this population, including strategically during hemodialysis, may be interesting^17–22.

Considering the high prevalence of low physical fitness in patients treated with maintenance dialysis, and the consequences related to these factors, strategies are necessary to work these components in these individuals. Initiatives related to the practice of physical exercises with this population, including strategically during hemodialysis, may be interesting

ETHICS APPROVAL AND CONSENT TO PARTICIPATE

This study was approved by the Ethics Committee of the Federal University of São Paulo (UNIFESP) (CAAE: 48533321.1.0000.5505, opinion: 5,384,426). All procedures were carried out by national law and the Helsinki Declaration. All participants provided informed consent prior to the study.

AVAILABILITY OF DATA AND MATERIALS

The datasets used and/or analysed during the current study available from the corresponding author on reasonable request.

COMPETING INTERESTS

The authors declare that they have no competing interests.

FUNDING

Not applicable.

DECLARATION OF CONFLICTING INTERESTS

The Authors declares that there is no conflict of interest.

AUTHORS' CONTRIBUTIONS

All authors were involved in all stages of the study.

ACKNOWLEDGEMENTS

Not applicable.

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No competing interests reported.

Physical fitness in patients treated with maintenance dialysis: a cross-sectional study

Status:

Version 1

Abstract

Figures

BACKGROUND

METHODS

Sample and ethics

Procedures

Instrument

Survey respondent characteristics

Statistical analysis

RESULTS

DISCUSSION

CONCLUSION

Declarations

AUTHORS' CONTRIBUTIONS

References

Additional Declarations

Status:

Version 1