Optimizing Quality of Life in Kidney Transplant Recipients Through Structured Exercise: A Systematic Review and Evidence-Based Guidelines

Introduction

It is recognized that kidney transplantation is the best treatment in renal replacement therapy [1–3]. Compared with hemodialysis, renal transplantation has certain advantages in survival and economic cost [4–6]. However, after transplantation, patients still have to face negative results, such as adverse reactions caused by immunosuppressant treatment [5] and potential high cardiovascular risk [2,7]. Exercise is an attractive option to address these potential risks and to help patients prevent post-transplant weakness and cardiovascular disease [2,8]. Several studies have shown that exercise training has short-term benefits for kidney transplant recipients [9–11]. On the other hand, quality of life (QOL) is the comparison between expectation and reality, and it is also an important index to judge the prognosis of kidney replacement therapy [5,12]. There is also evidence that kidney transplant recipients can improve their QOL through exercise [3]. The most important thing is that patients can maintain long-term renal allograft function and have a good QOL [8].

Consequently, in the present study, the existing evidence about the impact of structured exercise training on renal transplant recipients’ QOL was collected under the guidance of the 5 steps of evidence-based practice, to provide suggestions for clinical decision making on implementing exercise training and promoting further research in this field.

Answerable Practice-Based Questions in PICO Format

Evidence-based practice is a combination of the best research evidence and preferences to help health professionals make clinical decisions [13]. The first step of evidence-based practice is to turn information requirements into answerable clinical questions constructed from PICO elements [13]. The following clinical question is answered: Compared with routine postoperative recovery without exercise training (comparison), can exercise training (intervention) improve the QOL (outcome) of recipients after renal transplantation (population)? In the present study, the best evidence for this clinical question was sought by identifying, evaluating, and synthesizing the existing literature.

Eligibility Criteria

In the literature review, articles that considered 3 types of PICO questions were retrieved.

First, the type of population was considered: This review considered recipients after kidney transplantation regardless of age, sex, and country. Second, the type of interventions were considered: This review included articles on exercise training, to improve the kidney transplant recipients’ QOL. Additionally, “exercise training” means a subset of planned, structured, repetitive, and purposeful physical activities conducted to improve or maintain health [14]. Therefore, the types of exercise training such as “aerobic exercise”, “resistance exercise”, and “strength training exercise therapy” were included. Third, the type of outcome measurement was considered: This review considered and evaluated any objectively measured or self-reported quantitative data on QOL.

Search Strategy

The second step of evidence-based practice is to find the best evidence [13]. Therefore, the databases MEDLINE Complete, CINAHL Complete, Academic Search Complete, Health Source: Nursing/Academic Edition of EBSCO, and PubMed were retrieved. The search strategy was to design alternative terms for each component of the PICO. Each database was searched based on 3 key concepts: “renal transplant patients”, “exercise training”, and “quality of life” and their synonyms. During the retrieval process, the Boolean operator “OR” to combine keywords and alternative terms was used. Then, the article was obtained using the Boolean operator “AND” to the historical results of the vital concept retrieval. Finally, the reference list of articles closely related to the topic was manually searched, identifying qualified papers that may be left out. The restrictions imposed by the literature included the release of (1) years between 2000 and 2023; (2) an English-language document; (3) peer-reviewed literature; and (4) full text (Table 1).

Study Selection

Articles that were initially determined based on the search strategy were stored in the Zotero database. The retrieval result was 470 articles. First, duplicate content was identified and merged, and then potential articles were screened according to the title and abstract. The included studies must have met the following: (1) investigated the effects of exercise training on kidney transplant patients of any age; (2) the results of the study must have included an assessment of “quality of life”; (3) the study was designed only for kidney transplant patients, excluding experimental controls with other diseases, such as hemodialysis and chronic kidney disease. The study excluded letters to editors, editorials, and research protocols or conducts only counselling on physical activities. Consequently, 5 eligible studies were selected to be included in the evidence-based practice assignment (Figure 1).

Data Collection

These 5 articles were all quantitative studies of randomized controlled trials (RCT), which have the advantage of being in second place in the hierarchy of evidence [13]. All 5 studies evaluated the health outcomes of the kidney transplant recipients’ QOL after exercise training. Additionally, the 5 studies were conducted in 3 countries: 2 articles in Canada [15,16]; 2 articles in the United States [17,18]; and 1 article in the United Kingdom [19]. Specific information about research variables were extracted from the included articles (Table 2).

Appraisal of the Evidence

The third step of the evidence-based practice process is to critically evaluate the evidence’s validity, impact, and applicability [13]. Melnyk et al specify that the ability to appraise evidence critically plays a vital role in evidence-based practice [20]. Therefore, in the present study, the Critical Appraisal Skills Program (CASP) was used to evaluate the 5 studies. The CASP checklist was developed based on the National Health Service Public Health Resource Unit in the United Kingdom [13]. CASP checklists for different types of experiments can be easily and quickly obtained free of charge through the website https://casp-uk.net. The CASP assessment tool can simply and effectively guide students to evaluate the quality of literary works and critical evidence critically [21]. The CASP website shows that the checklist for RCTs consists of 11 questions in 4 sections. Section A is about evaluating the experiment’s validity; section B verifies whether the research method is reasonable; section C evaluates the research results’ impact and clinical applicability; and section D helps readers think systematically. Only when the validity of section A is determined can the reader move on to the next part.

Hoffmann, Bennett, and Del Mar pointed out that attention should be paid to the bias that can distort quantitative research results. They state that the common bias in quantitative research includes selection or sample bias, allocation bias, performance bias, attrition bias, and detection bias [13]. The questions in the RCT CASP checklist also evaluate the study against these deviations. The 5 studies’ appraisal results all passed section A of the CASP checklist, which proved that the selected articles’ research design was effective. All studies randomly assigned the samples and reported the method of random allocation. Also, the participants’ baseline characteristics were analyzed to ensure that the study groups were similar. However, because the intervention was the particularity of exercise training, the participants were not blinded to the intervention. Therefore, this leads to a higher risk of performance bias in all 5 articles.

On the other hand, the 5 studies explained why participants dropped out of the study, such as lack of interest in the project, conflicts with working hours, and medical problems. Among them, 4 articles analyzed the data on intervention compliance and dropout [16–19]. Participants in both studies with a follow-up period of 12 months had higher dropout rates [17,18]. This shows that the failure of extended follow-up leads to a high risk of study attrition deviation, which affects the study’s quality. However, it is worth noting that Tzvetanov et al indicated that, in the study of personalized exercise training, although the withdrawal rate of the control group was very high, the compliance of the participants in the intervention group reached 100% [18]. Moreover, in section C about the sample size, the 5 studies’ power calculations are not clear. Also, there was only 1 article with a lower risk of detection bias [19]. However, all 5 studies’ reports were unbiased. Overall, none of the studies reached an excellent level.

Participant Characteristics

The populations in the 5 studies were all patients after kidney transplantation. Overall, the sample size ranged from 20 to 97 patients. A total of 113 patients participated in an exercise training intervention. The patients ranged in age from 26 to 65 years old. The transplant time for the participants ranged from 6 weeks to 18 years. Moreover, Karelis et al focused on kidney transplant recipients who were sedentary and had cases complicated by new-onset diabetes [16]. Tzvetanov et al recruited renal transplant recipients with obesity (BMI >30) in their study [18]. The other 3 studies used similar exclusion criteria to determine the final included renal transplant recipients. For example, participants with mental illness and exercise contraindications or restrictions were excluded.

Exercise Training Characteristics

The types of exercise training adopted in the 5 studies were different. The exercise training programs of 2 studies were resistance exercise, with an exercise duration of 12 months and 16 weeks, respectively [16,18]. One study tested 12 months of aerobic training [17]. One article assigned participants to aerobic or resistance exercise training for 12 weeks [19]. One study conducted 12 weeks of endurance and strength training, a combination of aerobic and resistance exercise [15]. Also, the exercise intervention group was compared with the routine nursing group in the 5 studies. Additionally, exercise training was monitored in 4 studies, with 1 study excluded [17]. In the 5 studies, the frequency of exercise training was repeated 2 to 4 times a week, the exercise time was 30 to 60 min, and the duration of the exercise study was 12 weeks to 12 months (the median duration was 7.5 months). Karelis et al performed resistance exercise training as early as 6 to 8 weeks after transplantation [16]. No adverse safety incidents or injuries were reported in all studies after the implementation of sports training. The exercise intensity of these studies was also different, and 2 studies used maximum heart rate to determine the exercise intensity [17,19]. Riess et al used the peak of the uptake of oxygen to determine exercise intensity [15].

Quality of Life

In the assessment of QOL, a study used WHO-5 well-being scores and found that the QOL in the resistance exercise group was significantly better than that in the routine nursing group (P=0.02, 95% CI=5.37, 21.83) [16]. The other 4 studies used the most common tool for quantitative analysis of QOL, the short-form questionnaire SF-36 [22]. The score of the exercise group was also significantly higher than that of the control group, and the quantitative results showed statistical significance. However, one of the studies reported only the average value of the QOL questionnaire in the experimental group. There was no quantitative evaluation, which affected the quality of the study [18]. The other studies focused and reported on different aspects of QOL. For example, Riess et al report the overall score of QOL (P=0.02), comprehensive psychological score (P=0.04), and social function score (P=0.006) [15]. However, due to the different types and duration of exercise intervention, there are some methodological differences in the evaluation cycle of QOL in the 5 studies. Although the types of exercise training in the study were different, exercise significantly improved the participants’ QOL in various aspects.

Discussion

Based on the current evidence, it was found that exercise can significantly improve the QOL of renal transplant recipients in many aspects. Also, in the 5 studies, the implementation of exercise training was safe and feasible, and there were no adverse incidents. When considering using this evidence to help make clinical decisions, patients’ values, personal experiences, and different needs should not be ignored. The fourth step in evidence-based practice emphasizes the need to combine evidence with clinical knowledge, clinical practice, patient values and preferences, and environment [13]. Two studies also proved that after implementing personalized exercise counselling or training guidance, the compliance of the exercise group was higher, even up to 100% [17,18]. The participants in the latter study were kidney transplant recipients with obesity. Exercise may benefit patients with obesity more. However, the researchers also point out that coaches listen to the participants’ abilities during sports training and provide emotional support, enhancing their adaptability [18]. Therefore, in future clinical practice, more consideration should be given to patients’ own experience and different needs, and personalized sports training measures should be implemented. Also, qualitative research can be chosen as evidence to provide relevant information for the needs of patients [23]. The final step of evidence-based practice is auditing [13].

There are some limitations in the present study. First, the 5 studies featured a small number of participants. The primary bias in the evidence-based framework is that most published studies include only the lowest number of patients [23]. Additionally, the minimum size of the sample can be determined by power, which helps the study to get a clear result [13]. However, the power analysis is not described in the 5 studies; therefore, it is impossible to determine whether these studies have a sufficient sample size. The external validity of the research is affected. Second, the intervention measures of the 5 studies are different in exercise type, exercise frequency, exercise time, and exercise intensity, and there is high heterogeneity. In the case of these differences, it is difficult to compare the results, making it impossible to determine which exercise intervention can maximize patients’ QOL. Third, the intervention time of most studies is short. Two of the 12-month intervention studies impacted the quality of the research due to high-risk attrition bias [17,18]; there was a lack of evidence on the long-term effect of exercise training on QOL.

Moreover, Hoffmann, Bennett, and Del Mar stressed that researchers should focus not only on the statistical significance of the study but also on clinical significance [13]. Therefore, more attention should be paid to power and precision in future research so that the results are of clinical importance and applicability. Additionally, the risks and long-term effects of exercise need to be studied. Personalized and supervised exercise training for different renal transplant patients will also be the focus of future research.

Conclusions

In conclusion, this study raises a clinical question and critically evaluates evidence under evidence-based practice guidelines. The results show that exercise training can significantly improve the QOL of renal transplant recipients. It provides suggestions and evidence for sports training in clinical practice. Exercise advice and guidance should be incorporated into the routine treatment plan in medical care to help renal transplant recipients optimize their physical function to maintain the best results of surgery. However, it is impossible to determine the best exercise mode and time accepted by patients, and the long-term effect of exercise, which needs to be further studied.