Abstract
Background:
New or worsening frailty is a common problem in patients with end-stage renal disease (ESRD) during the prolonged time awaiting kidney transplantation. Structured physical activity in the dialysis setting has been shown to mitigate frailty, but little is known about the benefits of home-based exercise. The purpose of this systematic review was to summarize the effects of home-based exercise interventions on indicators of frailty (weakness, slowness, low physical activity, perceived exhaustion, and shrinking) among patients diagnosed with ESRD.
Methods:
We searched PubMed, MEDLINE, Scopus, CINAHL, Cochrane Central Register of Controlled Trials, Cochrane Database of Systematic Reviews, and Google Scholar using Medical Subject Heading terms and free text keywords including kidney failure, exercise, and frailty. We identified 13 relevant articles (eight randomized controlled trials, five quasi-experimental studies).
Results:
Our review found potential effectiveness of home-based exercise interventions on mitigating or preventing selected indicators of frailty (e.g., weakness, slowness, low physical activity, perceived exhaustion), particularly when the interventions combined aerobic walking, resistance exercise, and behavioral components and were delivered for at least 6 months. However, no published studies measured the effect of home-based exercise interventions on frailty as a whole.
Conclusions:
While existing studies suggest likely benefits of home-based exercise interventions among patients with ESRD, future research is warranted to develop and test home-based physical activity interventions that address all indicators of frailty.
The number of patients with end-stage renal disease (ESRD) has doubled since 2000, primarily because of the growing number of people with risk factors, such as diabetes and hypertension (Saran et al., 2020). Kidney transplantation (KT) is the treatment option with the greatest cost-effectiveness and survival benefit (Axelrod et al., 2018), but the rising number of patients diagnosed with ESRD leads to median wait times for a donated kidney as long as 48 months (Saran et al., 2019). During the prolonged KT wait time, increasing age and inflammatory processes related to dialysis contribute to worsening frailty over time, which can further impact access to transplantation (Haugen et al., 2019).
Frailty is a syndrome characterized by decreased ability to withstand health stressors and increased vulnerability to adverse health outcomes (e.g., falls, hospitalizations, and death) secondary to reduced strength and diminished physiologic reserve (Fried et al., 2001). Up to 73% of patients with ESRD experience frailty (Chowdhury et al., 2017), and of these, approximately half are ineligible for KT (Haugen et al., 2019). Moreover, 35% of patients with frailty initially deemed eligible for KT eventually lose their eligibility as they become frailer during the long KT wait times (Haugen et al., 2019). Thus, there is a pressing need for interventions that protect patients from worsening frailty while waiting for a kidney transplant.
In 2019, a task force of the International Conference of Frailty and Sarcopenia Research (ICFSR) published clinical practice guidelines and made recommendations for identifying and managing frailty in older adults (Dent et al., 2019). The task force noted that the most commonly utilized and well-validated approach to screening for frailty uses Fried and colleagues’ (Fried et al., 2001) description, requiring the presence of at least three of the five following physical characteristics or indicators: (1) weakness, (2) slowness, (3) low physical activity, (4) perceived exhaustion, and (5) shrinking. Frailty tends to begin with weakness resulting from muscle loss or sarcopenia (low muscle strength and/or diminished muscle quantity or quality) and with slowness or a decline in walking speed. Frailty subsequently progresses to self-reported low levels of physical activity and self-reported exhaustion or low energy. Finally, frailty leads to shrinking, as evidenced by unintended weight loss. Once the physical characteristic of weight loss occurs, it is difficult to improve or reverse the frailty status (Xue, 2011). This describes a possible progression of frailty, not the sole path of progression, that is imperative to identify early when it is still potentially reversible by intervention (Fried, 2016). The ICFSR task force agreed that first-line therapy for managing frailty should include a multi-component physical activity program with a resistance-based training component (Dent et al., 2019). Physical activity was viewed as the most feasible way to prevent and treat frailty (Fried, 2016), and it may be ideally suited for people with ESRD who are receiving dialysis and awaiting KT (Harhay et al., 2020). The ICFSR task force, however, acknowledged that evidence is not yet sufficient to identify the most favorable intensity, frequency, duration, or type of physical activity, as well as the optimal combination of aerobic and resistance physical activities necessary to treat/manage frailty (Dent et al., 2019).
Four recent systematic reviews summarized the outcomes of physical activity interventions in patients with ESRD receiving dialysis (Chan & Cheema, 2016; Clarkson et al., 2019; Ferreira et al., 2020; Young et al., 2018). The physical activity interventions included aerobic training, resistance training, or both, delivered primarily during dialysis or on non-dialysis days. None of the reviews mentioned frailty as a syndrome, although they examined outcomes consistent with selected frailty indicators.
Chan and Cheema (2016) identified 16 progressive resistance trials focusing on upper or lower body strength. Overall, the studies showed evidence that resistance exercise (with free-weights, equipment, or elastic bands) increased muscle volume and lower body strength. However, among the six studies measuring walking capacity, only one showed improvement in the 6-minute walk test. Self-reported physical activity, measured in three studies, did not increase significantly. One study examined depression as an outcome and two studies evaluated fatigue; all showed non-significant trends toward improvement. The systematic review by Clarkson et al. (2019) included 27 physical activity trials (including 11 aerobic, eight resistance, four both). Eight trials contained exercises conducted during dialysis, whereas two trials included a home-based component. Aerobic physical activity included cycling during dialysis, home-based walking, or swimming, and resistance physical activity included free weights or bands. The authors concluded that, regardless of physical activity modality (aerobic or resistance), improvement occurred in outcomes as diverse as the 6-minute walk test and grip strength.
Ferreira et al. (2020) identified eight aerobic physical activity interventions (two aerobic only, one resistance only, three aerobic plus resistance, two Pilates/breath training), of which five were conducted in the dialysis unit and three were conducted outside the unit (involving Pilates, home-based walking, or breathing training). Depression, a potential indicator of exhaustion (Dent et al., 2019), improved with these interventions. A review by Young et al. (2018) included 13 studies, all of which were conducted within the dialysis unit and involved cycling. A meta-analysis of two of these studies demonstrated significant improvement in the 6-minute walk test; however, the quality of the evidence was relatively poor, with a high risk of bias. In contrast to the conclusions of the other review authors, Young's team (2018) concluded that the evidence was insufficient to support the use of cycling in the dialysis unit to improve cardiac capacity, physical function, or quality of life.
Although the findings from these systematic reviews of physical activity for patients with ESRD receiving dialysis are inconsistent, they provide some evidence suggesting that aerobic and resistance physical activity may be beneficial for improving the frailty symptoms of weakness (reduced strength) and slowness (reduced walking speed), as well as mental health symptoms (e.g., depression and anxiety) that may impact perceived exhaustion. However, these previous reviews provided little to no data regarding frailty outcomes related to self-reported physical activity, exhaustion, or shrinking. There remains a need to systematically consider the effects of physical activity on all five indicators of frailty to facilitate the development of physical activity interventions for people with ESRD that can prevent adverse health outcomes, as well as improve quality of life and access to KT.
Current knowledge about outcomes of physical activity interventions in people with ESRD is based primarily on interventions conducted within dialysis units. Physical activity interventions within these units are costly in terms of equipment and supervision time, producing difficulties with maintaining these interventions (Ma et al., 2012). Further, they may not promote continued exercise following successful KT. Physical activity in the home setting, however, has several key advantages: (1) respect for patients’ autonomy, (2) not dependent on the type of dialysis, and (3) potential sustainability following KT. We are unaware of any previously published review examining the benefits of home-based physical activity for preventing or mitigating frailty in patients with ESRD. Thus, the purpose of this review is to summarize and synthesize the effects of home-based exercise interventions on indicators of frailty (i.e., weakness, slowness, low physical activity, perceived exhaustion, and shrinking) among patients with ESRD.
Method
Design
A systematic review was conducted to synthesize reports of home-based exercise intervention studies evaluating frailty indicators in patients with ESRD. This review is reported in accordance with the guidelines for the Preferred Reporting Items for Systematic Reviews (Page et al., 2021).
Study Eligibility
For inclusion in this review, studies were required to meet these criteria: (1) subjects were diagnosed with ESRD and receiving renal replacement therapy (including hemodialysis or peritoneal dialysis), (2) subjects were aged 18 years or older, (3) home-based exercise interventions were evaluated, (4) the outcome measures represented at least one indicator of frailty, (5) the study design was a randomized controlled trial (RCT) or quasi-experimental study, and (6) the report was written in English. The frailty indicators were based on those described by Fried et al. (2001) and included the following: (1) weakness/reduced strength (e.g., sit-to-stand, stair-climb descent, timed up and go, hand grip strength, Short Physical Performance Battery); (2) reduced walking speed (e.g., 6-minute walking distance [6MWD], incremental shuttle walk test [ISWT], gait speed); (3) low physical activity (e.g., self-report of physical activity, physical activity monitoring device, cardiorespiratory fitness [peak oxygen consumption, VO2 peak]); (4) exhaustion (e.g., self-reported exhaustion or fatigue); and (5) shrinking (weight loss). Review articles, study protocols for clinical trials, and conference abstracts were excluded.
Search Strategy
We searched PubMed, MEDLINE, Scopus, CINAHL, Cochrane Central Register of Controlled Trials, Cochrane Database of Systematic Reviews, and Google Scholar in April 2020. We also reviewed the reference lists of key published studies to identity other relevant studies. Combinations of controlled vocabulary using Medical Subject Heading (MeSH) terms and free text keywords were developed for three main categories: (1) kidney failure, (2) exercise, and (3) frailty. For kidney failure, we included the terms kidney failure (MeSH), ESRD (MeSH), and pretransplantation (free text). The search terms for the exercise category were exercise (MeSH), physical activity (free text), and rehabilitation (free text). We intentionally used the term “exercise” to maximize the probability of capturing home-based exercise. For the category of frailty, we used the search terms frailty (MeSH), frail elderly (MeSH), and sarcopenia (free text). Both MeSH terms and keywords in the title or abstract field were searched. A reproducible search strategy is presented in the Supplemental Materials. The initial search results were imported into Covidence, an online platform for managing systematic reviews and screening literature (Covidence systematic review software, Veritas Health Innovation, Melbourne, Australia). Using this platform, two authors (J.Y. and T.R.) independently screened the titles and abstracts for eligibility. Any conflicts between these two authors regarding study eligibility were resolved by discussion and consensus. The full text of each potentially eligible study was reviewed for final eligibility, and data were extracted from the studies meeting the inclusion criteria for this systematic review.
Risk of Bias
Risk of bias was assessed by two authors (J.Y. and T.R.) using the Critical Appraisal Tools from the Joanna Briggs Institute (Moola et al., 2015) that were appropriate for the research design of each type of eligible study (i.e., RCTs or quasi-experimental studies). Discrepancies between the reviewers’ risk of bias assessments were resolved through discussion and consensus. The risk of bias of each study was categorized as follows: “low” if yes for ≥ 70% of the items, “moderate” if yes for 50%–69% of the items, and “high” if yes for < 50% of the items (Goplen et al., 2019; The Joanna Briggs Institute, 2016).
Data Analysis
Where possible, we linked study outcomes to each of four indicators of frailty (reduced strength, slowness, low physical activity, exhaustion) according to the theoretical definitions of each outcome. For example, strength in Fried’s criteria is operationally defined by hand grip strength. For this review, any measure addressing strength of the lower or upper extremities, such as changes in the sit-to-stand test (measuring lower extremity strength), was used as a strength indicator. Walking speed according to Fried’s criteria is assessed as the time necessary to walk 15 feet. For this review, any outcome related to walking capacity, such as the 6MWD and ISWT, were considered measures of walking speed. Physical activity in Fried’s frailty criteria is defined as kilocalories of activities during a 1-week period based on a subjective measure, such as the abbreviated version of the Minnesota Leisure Time Activity questionnaire. For our purposes, physical activity using self-report (e.g., total active minutes/day) and objective devices (e.g., steps) were considered physical activity outcome measures. In addition, cardiorespiratory fitness (VO2 peak) was included as an indirect measure of physical activity (Buchholz et al., 2013). Exhaustion in Fried’s criteria is measured by two questions from the Center for Epidemiologic Studies Depression (CES-D) scale. Any tool measuring anxiety, depression, or fatigue, as well as CES-D, was considered an indicator of exhaustion.
In addition to describing the characteristics of study interventions and the authors’ findings, we also calculated effect sizes (standardized mean difference, expressed as Cohen’s d) for each relevant frailty outcome. Effect sizes were calculated using Comprehensive Meta-Analysis software (Biostat, Inc., Englewood, NJ, USA). Because the included studies were a combination of controlled studies and single-group pre/post studies, it was not methodologically appropriate to combine individual study effect sizes in a meta-analysis.
Results
Search Outcome
A total of 2,688 citations were retrieved in the initial search, which were reduced to 1,813 citations after removing duplicates (Figure 1). Next, the titles and abstracts were examined to screen for potential eligibility according to the inclusion criteria. After excluding 1,754 citations based on this screening, 59 potentially eligible studies were retrieved for full-text screening. Upon full-text screening, 50 studies were excluded for these reasons: 42 did not include home-based exercise, five lacked frailty indicators as outcomes, one did not include patients with ESRD, and two studies did not evaluate intervention effectiveness. Four additional studies meeting the inclusion criteria were identified from the reference lists of eligible studies. The search process therefore resulted in a total of 13 studies included in this systematic review.
PRISMA 2020 flow diagram of literature search and retrieval process and results.
Study Characteristics
Country and design
The studies were conducted mainly in Europe (n = 6), followed by North America (n = 3), Asia (n = 3), and Australia (n = 1) (Table 1). Among the 13 eligible studies, eight were RCTs and five were quasi-experimental studies.
Characteristics of Studies Examining the Effects of Home-Based Exercise.
Note. CKD = chronic kidney disease; HD = hemodialysis; KT = kidney transplant; PA = physical activity; PD = peritoneal dialysis; RCT = randomized controlled study.
a.Baggetta et al. (2018) was from the secondary analysis of data of Manfredini et al. (2017).
Sample
Age criteria for inclusion were provided for 11 studies, of which 10 included participants ≥18 to 20 years of age and one included participants only ≥ 65 years of age. The participants for all studies had been receiving dialysis for ≥ 3 months to ensure hemodynamic stability for exercise interventions. All studies excluded participants with any limitation to participating in exercise because of a physical condition (e.g., ambulatory issue) or medical condition (e.g., unstable vital signs, multiple comorbidities). Three studies excluded participants with a relatively high degree of walking capacity or physical activity at baseline, such as a walking > 550 meters in 6 minutes (Baggetta et al., 2018; Manfredini et al., 2017) and self-reporting ≥120 minutes of moderate-intensity physical activity per week (Koh et al., 2010).
The study sample sizes ranged from 47 to 227 for RCTs and from 20 to 194 for quasi-experimental studies. Among the 13 studies, more male participants were included in the home-based exercise groups.
Intervention/control
All 13 studies included home-based aerobic exercise. Five also included resistance training, and eight also contained a behavioral component. Overall, two studies included only aerobic exercise, three studies included aerobic plus resistance exercise, six studies included aerobic plus behavioral components, and two studies included aerobic, resistance, and behavioral components. The most common aerobic exercise was walking (n = 8). Other forms of aerobic exercise were cycling (n = 1), Tai Chi (n = 1), combined treadmill and cycling (n = 2), and self-selection of the preferred exercise modalities (n = 1). The intensity of exercise was predominantly self-reported using the Borg scale, with a recommended intensity of 11–15 on the Borg scale; however, two studies used participants’ maximal heart rates as an objective measure of exercise intensity. The frequency of aerobic exercise was three times per week in most studies (n = 8). Instead of frequency, one study set a goal of 10,000 steps per day, whereas another study set the goal of increasing the step count 10% above that of the previous week. One study implemented cycling ergometers 5 days per week, and one study involving Thai Chi set no limitations on the frequency of exercise. In the 10 studies reporting the duration of each aerobic exercise session, the duration ranged from 10 to 50 minutes, with a median of 25 minutes.
In the five studies that included resistance training, the training was typically accomplished with resistance bands (n = 2), bodyweight exercises (n = 2), or a combination of both (n = 1). The frequency of resistance exercise was two times per week (n = 2) or 3 times per week (n = 2); one study did not specify the frequency. Only one study specified the duration of resistance exercise, which was 20 minutes (Greenwood et al., 2012). The other studies indicated the number of repetitions.
In the eight RCTs, home-based exercise was compared to intra-dialysis cycling exercise (n = 3), usual care (n = 4), or exercise in a research center (n = 1). Among the five quasi-experimental studies, home-based exercise was compared to intra-dialysis cycling exercise (n = 2) and usual care (n = 1). Two quasi-experimental studies compared the effects of a home-based exercise intervention between patients diagnosed with ESRD and recipients of a kidney transplant. Usual care in control groups mainly involved general advice to maintain an active lifestyle.
Intervention Duration/Interventionist/Theory
The duration of home-based exercise programs ranged from 8 to 24 weeks, with a median of 16 weeks. The interventionists included physical therapists (n = 2), a kinesiologist (n = 1), a nurse (n = 1), and unspecified study staff (n = 9). Only two studies reported that their intervention process was driven by theories: Cognitive Behavioral Theory (Greenwood et al., 2012) and Pender’s Health Promotion Model (Tao et al., 2015). The Cognitive Behavioral Theory guided the processes of setting goals, solving problems, and logging exercise to monitor adherence. The Health Promotion Model helped with identifying barriers, setting goals, solving problems, discussing action plans, and monitoring the safety of exercise.
Adherence to Intervention
Nine of the 13 included studies reported adherence to the intervention. Adherence to exercise intervention was defined as the percentage of exercise sessions completed (n = 6), time spent walking (n = 1), and meeting the goal of exercise duration or walking steps (n = 2). The percentage of exercise sessions completed ranged from 52% to 82%.
Frailty Indicators and Effect Sizes
None of the 13 included studies assessed frailty as a whole, and none measured all five indicators of frailty (reduced strength, slowness, low physical activity, exhaustion, and shrinking). Likewise, no study used the operational definitions of all five frailty indicators described by Fried et al. (2001; Table 2). Shrinking (weight loss) was not an outcome of interest in any of the 13 studies. Only the study by Greenwood et al. (2012) addressed four indicators of frailty. Walking speed was the most commonly measured frailty indicator (n = 10), followed by strength (n = 9).
Outcomes of Studies Examining the Effects of Home-Based Exercise.
Note. CES-D = Center for Epidemiological Studies Depression scale; DASI = Duke Status Activity Index; HADS = Hospital anxiety and depression score; ISWT = Incremental shuttle walk test; SCD = stair-climb descent; SPPB = short physical performance battery; STS60 = Sit-to-stand 60 seconds; TUAG = Timed up and go; 5STS = Sit-to-stand for five times; 6MWD = 6 minutes walking distance.
Strength
A total of nine studies measured strength of the upper extremities (e.g., hand grip strength) or lower extremities. Of the three studies measuring hand grip strength, none reported significant beneficial effects. Only one of these three studies included resistance exercise of the upper extremities (with TheraBands) in addition to walking. In contrast, lower extremity strength measured by a variety of sit-to-stand tests in four studies (two involving walking, one involving ergonomic cycling, one involving Tai Chi) showed significant positive effect sizes, with d values > 0.2.
Slowness (walking speed)
A total of 10 studies evaluated slowness, as determined by walking speed and measured by 6MWD (n = 7), ISWT (n = 2), and gait speed (n = 1). Among the seven studies measuring 6MWD, two with aerobic walking exercise interventions reported positive effect sizes when analyzing both pre- versus post-intervention results and intervention versus control groups. Only one study found positive effects on ISWT post-intervention; this intervention included exercise both at home and in an outpatient setting, with mixed aerobic exercise (treadmill/cycling) and resistance exercise (Greenwood et al., 2012). Measurement of normal and fast gait speed over a 10-meter distance showed positive effect sizes in both pre- versus post-intervention and intervention versus control analyses when participants participated in mixed aerobic (walking, jogging, or cycling) and resistance exercises.
Low physical activity
Five studies reported the participants’ level of physical activity: two used patient self-reported physical activity (Duke’s activity status index [DASI] and weekly physical activity), one used a device with the average daily step counts, and two used VO2 peak. DASI showed a positive effect size in one study using a combination of at-home exercise and exercise at a center. The average daily step counts in one study were significantly increased with a positive effect size after home-based exercise intervention. VO2 peak indicated a positive effect size in one study that implemented cycle ergometer exercise.
Exhaustion
Ortega-Pérez de Villar et al. (2020) assessed the level of depression using the CES-D scale. The effect size of CES-D change between baseline and post-intervention was not significant for the group participating in home-based exercises; however, the effect size was medium (d = 0.52) for the group participating in exercise in a dialysis unit. Sheshadri et al. (2020) also found no significant effect on either the CES-D scale or fatigue scale of the Dialysis Symptom Index. Greenwood et al. (2012) reported medium pre- to post-intervention effect sizes for both anxiety (d = 0.43) and depression (d = 0.67), as measured by the Hospital Anxiety and Depression Scale. No study evaluated perceived exhaustion using a dedicated exhaustion instrument.
Risk of Bias
The risk of bias was determined for each domain of methodologic quality according to the study design. Of the eight RCTs, the risk of bias was low for two studies (Ortega-Pérez de Villar et al., 2020; Uchiyama et al., 2019) and moderate for the remaining six. All five quasi-experimental studies had a low risk of bias (Table 3).
Risk of Bias Assessment.
Discussion
Our systematic review of the literature identified four primary modes of home-based exercise: (1) aerobic exercise only, (2) aerobic plus resistance exercise, (3) aerobic exercise plus behavioral change components, and (4) aerobic exercise, resistance exercise, and behavioral change components. The reported outcomes included four of the five frailty indicators identified by Fried: reduced strength, slowness, low physical activity, and exhaustion. In general, the effect sizes for individual frailty indicators suggest a pattern of potential benefits from home-based exercise interventions to prevent or mitigate frailty when these interventions involve a combination of both aerobic (walking) and resistance exercise. We also found that the beneficial effects of home-based exercise on two frailty indicators (strength and physical activity) are not inferior to the effects of aerobic exercise (e.g., cycling) performed in a dialysis unit (Bohm et al., 2014; Konstantin et al., 2002). Walking, cycling at home, and Tai Chi exercises improved lower extremity strength and walking speed. Home-based treadmill/cycling plus resistance exercise, mixed with additional supervised exercise, effectively increased physical activity and decreased exhaustion. Overall, we found potential effectiveness for mitigating or preventing frailty when aerobic walking and resistance exercises were combined in a 6-month or longer program of exercising three times per week, for 25 minutes and at an intensity of “somewhat difficult,” and with behavioral components, including interventionists’ feedback regarding exercise plans, goal setting, and problem solving.
Despite these findings, we noted several limitations of the available literature regarding home-based exercise interventions. One limitation was that none of the studies addressed all five indicators of frailty as outcomes of interest for home-based exercise. Only three studies (Bohm et al., 2014; Greenwood et al., 2012; Koh et al., 2010) addressed three indicators. Shrinking was not evaluated in any of the 13 included studies. Exhaustion was not measured using a dedicated exhaustion measure, and depression was used as a proxy for exhaustion (Greenwood et al., 2012; Ortega-Pérez de Villar et al., 2020). Of note, frailty is not a status measured by a single domain; instead, it is assessed using multiple indicators that are interconnected and integrated into a syndrome of declining energy and reserves (Fried et al., 2001). Patients diagnosed with ESRD unavoidably experience frailty processes (Johansen et al., 2017). Measuring individual frailty indicators could be a practical way to show the effectiveness of physical activity interventions; however, a systematic assessment of all five indicators of frailty in patients with ESRD is important, as it would allow predictions of patient trajectories for adverse health outcomes and access to KT.
Another limitation of the available literature was that verification of adherence was difficult and inconsistent. The main home-based exercise was aerobic exercise (walking). In contrast to cycling during dialysis therapy, monitoring adherence to duration, frequency, and intensity of exercise in the home relied predominantly on patients’ self-reported exercise logs (Fang et al., 2019). Only two studies used objective device measures (pedometers) to assess adherence by determining the number of walked steps. For exercise intensity, the Borg scale, a subjective measure of perceived exertion during exercise, was the most commonly used approach (6 studies). Thus, adherence was defined inconsistently, and four studies did not even measure adherence. Wearable physical activity monitoring devices using motion sensors have recently become widely used for monitoring adherence to exercise prescriptions (Halloway et al., 2015), and future studies will hopefully use these devices to improve assessment of adherence to home-based exercise interventions.
A further limitation involved the quality of behavioral change strategies incorporated into home-exercise regimens. Without focusing on factors underlying health behavior changes and creating circumstances that promote autonomy, competency, and connection, motivation for physical activity is difficult to achieve and sustain (Brand & Cheval, 2019). Of the eight studies employing behavioral components, only two reported that their interventions were driven by health behavior theories (Cognitive Behavioral Theory; Pender’s Health Promotion Model), and application of these theories was not well described in these studies. Further, behavioral components across studies were neither consistent nor clear as to whether they promoted motivation. For patients with ESRD in need of KT, a desire to be free of dialysis therapy and live a normal life can be used as leverage to increase motivation for physical activity.
The literature is also limited by the primarily moderate risk of bias of RCTs and substantial measurement heterogeneity between studies. Thus, it was not possible to form general conclusions regarding the effects of certain exercise types on frailty measures.
This systematic review itself has potential limitations. Every literature review is accompanied by the risk of missing relevant studies. We addressed this by using a thorough search strategy incorporating multiple electronic databases. Another potential limitation involved the definition of frailty. The physical frailty phenotype first described by Fried et al. (2001) has been the most commonly used definition of frailty for patients with kidney disease (Chowdhury et al., 2017). However, because none of the 13 included studies addressed frailty as a whole, it is unknown whether the participants of these studies met the criteria for frailty at the beginning or end of the intervention. The operational definitions of frailty according to Fried et al. (2001) are very specific for each of the five indicators, but they did not fit perfectly with the outcome measures of the included studies. As a result, it was necessary for us to fit the conceptual definitions of frailty indicators to the outcomes measured in the included studies. Ongoing discussion regarding how to best measure frailty is necessary.
Conclusion
To mitigate or prevent frailty among patients diagnosed with ESRD and seeking a new kidney, home-based exercise has the advantage of offering flexibility to accommodate the patients’ dialysis treatment modalities (e.g., types, schedules, duration) and other life activities. Although dialysis unit-based interventions facilitate the delivery of the prescribed exercise, monitoring of adherence, and following up on exercise progress, they are challenging to implement, and few dialysis units can provide exercise equipment for each patient, as well as trained staff members. Further, if home-based exercise is established prior to transplant, it may be easier to continue following KT.
Our review found that home-based exercise may have beneficial effects on selected indicators of frailty; however, no study of home-based exercise interventions measured frailty as a whole. Further research is necessary to develop and test home-based physical activity interventions designed to improve or mitigate frailty and tailored to the specific needs of ESRD patients awaiting KT. Future home-based exercise intervention studies should be designed using methods to measure all indicators of frailty, as well as monitor adherence to frequency, duration, and intensity of physical activity programs.
Supplemental Material
Supplemental Material, sj-docx-1-brn-10.1177_10998004211033031 - Effects of Home-Based Exercise on Frailty in Patients With End-Stage Renal Disease: Systematic Review
Supplemental Material, sj-docx-1-brn-10.1177_10998004211033031 for Effects of Home-Based Exercise on Frailty in Patients With End-Stage Renal Disease: Systematic Review by Jongwon Yoo, Todd Ruppar, JoEllen Wilbur, Arlene Miller and Jennifer C. Westrick in Biological Research For Nursing
Footnotes
Acknowledgments
The authors acknowledge the Office of Rush Mentoring Programs for providing support for the manuscript editing service.
Author Contributions
Jongwon Yoo contributed to conception and design, contributed to acquisition, analysis, and interpretation, drafted manuscript, critically revised manuscript, gave final approval, and agrees to be accountable for all aspects of work ensuring integrity and accuracy. Todd Ruppar contributed to conception and design, contributed to acquisition, analysis, and interpretation, drafted manuscript, critically revised manuscript, gave final approval, and agrees to be accountable for all aspects of work ensuring integrity and accuracy. JoEllen Wilbur contributed to conception and design, contributed to acquisition, analysis, and interpretation, drafted manuscript, critically revised manuscript, gave final approval, and agrees to be accountable for all aspects of work ensuring integrity and accuracy. Arlene Miller contributed to conception and design, contributed to acquisition, analysis, and interpretation, drafted manuscript, critically revised manuscript, gave final approval, and agrees to be accountable for all aspects of work ensuring integrity and accuracy. Jennifer C. Westrick contributed to conception and design, contributed to acquisition, analysis, and interpretation, drafted manuscript, critically revised manuscript, gave final approval, and agrees to be accountable for all aspects of work ensuring integrity and accuracy.
Declaration of Conflicting Interests
The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
Funding
The author(s) received no financial support for the research, authorship, and/or publication of this article.
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References
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