Recruitment and retention rates in randomised controlled trials of exercise therapy in people with multimorbidity: a systematic review and meta-analysis

A review of patient recruitment in randomised controlled trials of preoperative exercise

BACKGROUND

Randomised controlled trials (RCTs) are considered the gold standard design to determine the effectiveness of an intervention, as the only method of decreasing section bias and minimising random error. However, participant recruitment to randomised controlled trials is a major challenge, with many trials failing to recruit the targeted sample size accordingly to the planned protocol. Thus, the aim of this review is to detail the recruitment challenges of preoperative exercise clinical trials.

METHODS

A comprehensive search was performed on MEDLINE, Embase, The Cochrane Library, CINAHL, AMED and PsycINFO from inception to July 2021. Randomised controlled trials investigating the effectiveness of preoperative exercise on postoperative complication and/or length of hospital stay in adult cancer patients were included. Main outcomes included recruitment rate, retention rate, number of days needed to screen and recruit one patient and trial recruitment duration. Descriptive statistics were used to summarise outcomes of interest.

RESULTS

A total of 27 trials were identified, including 3656 patients screened (N = 21) and 1414 randomised (median recruitment rate (interquartile range) = 53.6% (25.2%-67.6%), N = 21). The sample size of the included trials ranged from 19 to 270 (median = 48.0; interquartile range = 40.0-85.0) and the duration of trial recruitment ranged from 3 to 50 months (median = 19.0 months; interquartile range = 10.5-34.0). Overall, a median of 3.6 days was needed to screen one patient, whereas 13.7 days were needed to randomise one participant. Over the trials duration, the median dropout rate was 7.9%. Variations in recruitment outcomes were observed across trials of different cancer types but were not statistically significant.

CONCLUSION

The recruitment of participants to preoperative exercise randomised controlled trials is challenging, but patient retention appears to be less of a problem. Future trials investigating the effectiveness of a preoperative exercise programme following cancer surgery should consider the time taken to recruit patients. Strategies associated with improved recruitment should be investigated in future studies.

School-based physical activity interventions: which intervention characteristics are associated with participation and retention? A meta-analysis

OBJECTIVE

Many school-based intervention studies are conducted to increase students' physical activity (PA). Recruitment and retention problems potentially impact the robustness of RCT findings. We conducted a meta-analysis to summarize recruitment and retention rates in long-term secondary school-based PA intervention studies and examined associated participant and intervention characteristics.

METHODS

Web of Science, Pubmed, Medline, and PsychInfo were searched until March 20th 2023. We included studies on secondary school-based PA interventions ≥12 weeks, aimed at typically developing adolescents. We abstracted number of schools and students invited, randomized, and participating at follow-up to calculate pooled recruitment and retention rates; participant and intervention characteristics were abstracted to execute subgroup or meta-regression analyses.

RESULTS

Recruitment rates were 51% for invited schools and 80% for invited students, the retention for schools was almost 100% and for students 91%. Interventions with fixed and flexible components, executed in Asia and South America, and from later publication years had higher student recruitment rates. Students' retention rates were lower for interventions which had flexible components, were theory/model-based, used an accelerometer, had a longer intervention duration, and included more females.

CONCLUSION

Recruitment and retention rates in school-based PA interventions are high. Some participant and intervention characteristics influence these rates: flexibility of the intervention, theory/model-based intervention, accelerometer use, intervention duration, continent, and number of females. Researchers should consider these characteristics in intervention development to achieve optimal balance between intervention effectiveness, recruitment, and retention.

The overlap between randomised evaluations of recruitment and retention interventions: An updated review of recruitment (Online Resource for Recruitment in Clinical triAls) and retention (Online Resource for Retention in Clinical triAls) literature

BACKGROUND

The Online Resource for Recruitment in Clinical triAls (ORRCA) and the Online Resource for Retention in Clinical triAls (ORRCA2) were established to organise and map the literature addressing participant recruitment and retention within clinical research. The two databases are updated on an ongoing basis using separate but parallel systematic reviews. However, recruitment and retention of research participants is widely acknowledged to be interconnected. While interventions aimed at addressing recruitment challenges can impact retention and vice versa, it is not clear how well they are simultaneously considered within methodological research. This study aims to report the recent update of ORRCA and ORRCA2 with a special emphasis on assessing crossover of the databases and how frequently randomised studies of methodological interventions measure the impact on both recruitment and retention outcomes.

METHODS

Two parallel systematic reviews were conducted in line with previously reported methods updating ORRCA (recruitment) and ORRCA2 (retention) with publications from 2018 and 2019. Articles were categorised according to their evidence type (randomised evaluation, non-randomised evaluation, application and observation) and against the recruitment and retention domain frameworks. Articles categorised as randomised evaluations were compared to identify studies appearing in both databases. For randomised studies that were only in one database, domain categories were used to assess whether the methodological intervention was likely to impact on the alternate construct. For example, whether a recruitment intervention might also impact retention.

RESULTS

In total, 806 of 17,767 articles screened for the recruitment database and 175 of 18,656 articles screened for the retention database were added as result of the update. Of these, 89 articles were classified as 'randomised evaluation', of which 6 were systematic reviews and 83 were randomised evaluations of methodological interventions. Ten of the randomised studies assessed recruitment and retention and were included in both databases. Of the randomised studies only in the recruitment database, 48/55 (87%) assessed the content or format of participant information which could have an impact on retention. Of the randomised studies only in the retention database, 6/18 (33%) assessed monetary incentives, 4/18 (22%) assessed data collection location and methods and 3/18 (17%) assessed non-monetary incentives, all of which could have an impact on recruitment.

CONCLUSION

Only a small proportion of randomised studies of methodological interventions assessed the impact on both recruitment and retention despite having a potential impact on both outcomes. Where possible, an integrated approach analysing both constructs should be the new standard for these types of evaluations to ensure that improvements to recruitment are not at the expense of retention and vice versa.

Retention rates and reasons for non-retention in exercise oncology trials in the post-treatment phase-a systematic review

PURPOSE

Retention is a key marker of trial success. Poor retention can induce bias, reduce statistical power and minimise the validity of trials. This review examined retention rates in exercise trials in cancer survivors, reasons for non-retention and retention strategies utilised.

METHODS

A systematic review was conducted using a predefined search strategy in EMBASE RCTs, MEDLINE OVID, CINAHL, Web of Science-Core Collection and Cochrane Central Register of Controlled Trials (CENTRAL). The search was conducted on 27/03/2023. Title and abstract screening, full text review and data extraction were completed in duplicate.

RESULTS

Of 17,524 studies identified, 67 trials involving 6093 participants were included. The median overall retention rate immediately post-intervention was 89.85%, range (52.94-100%) and mean 87.36% (standard deviation 9.89%). Trials involving colorectal cancer survivors only had the highest median retention rate (94.61%), followed by breast (92.74%), prostate (86.00%) and haematological cancers (85.49%). Studies involving mixed cancer cohorts had the lowest retention rate (80.18%). The most common retention strategies were wait-list control groups, regular check-ins/reminders and free exercise equipment. Common reasons for non-retention were lost to follow-up, health problems, personal reasons including family/work commitments and travel burden, and disease progression.

CONCLUSIONS

Retention rates in exercise oncology trials are approximately 90% immediately post-interventions. Our previous work highlighted variable suboptimal recruitment rates of median 38% (range 0.52-100%). Recruitment rather than retention should be prioritised for methodology research in exercise oncology.

IMPLICATIONS FOR CANCER SURVIVORS

Optimising the quality of exercise oncology trials is critical to informing high quality survivorship care. PROSPERO registration number: CRD42023421359.

Effect of Exercise on Mental Health and Health-related Quality of Life in Adults With Spinal Cord Injury: A Systematic Review and Meta-Analysis

OBJECTIVES

To determine the effect of exercise interventions on mental health and health-related quality of life (HRQoL) in individuals with SCI.

DATA SOURCES

We searched Embase, CINAHL, Medline, PsychINFO, and SPORTDiscus from inception to September 2023.

STUDY SELECTION

We included randomized controlled trials that (1) involved participants ≥18 years old with a SCI; (2) administered an exercise intervention; and (3) measured subjective well-being, psychological well-being, social well-being, and/or HRQoL as outcomes. We reported standardized means differences (d) with a 95% confidence interval (CI), assessed the risk of bias by using the Revised Cochrane Risk-of-bias Tool for Randomized Trials (RoB 2), and the certainty of the evidence using GRADE.

DATA SYNTHESIS

Nineteen studies (797 participants, mean age <65 years in every study) were included. Exercise improved overall well-being (d=0.494; 95% CI 0.268, 0.720; low certainty evidence), subjective well-being (d=0.543; 95% CI 0.270, 0.816; low certainty evidence), psychological well-being (d=0.499; 95% CI 0.193, 0.805; low certainty evidence), social well-being (d=0.452; 95% CI 0.151, 0.752; low certainty evidence), and HRQoL (d=0.323; 95% CI 0.072, 0.574; low certainty evidence). Four serious adverse events probably attributable to the interventions were reported in 3 studies.

CONCLUSIONS

Exercise interventions can improve well-being and HRQoL in adults with SCI <65 years of age. Additional research is needed to determine effectiveness in adults ≥65 years of age.

The effect of exercise on mental health and health-related quality of life in individuals with multiple sclerosis: A Systematic review and meta-analysis

BACKGROUND

A large body of evidence has tested the effect of exercise interventions on mental health and health-related quality of life (HRQoL) in individuals with multiple sclerosis (PwMS).

OBJECTIVE

To determine the effect of exercise interventions on mental health and HRQoL in PwMS.

METHODS

We searched four databases up to April 2023, and included randomized controlled trials that: 1) involved PwMS ≥18 years old; 2) delivered an exercise intervention; 3) measured subjective well-being, psychological well-being, social well-being, or HRQoL as outcomes. We reported standardized differences in means (d) with a 95 % confidence interval (CI), for continuous outcomes and an incidence rate ratio (IRR) with a 95 % CI for dichotomous outcomes.

RESULTS

Forty-nine studies (n = 2,057 participants) were included. Exercise improved overall well-being (d = 0.78; 95 % CI 0.483, 1.077; moderate certainty evidence), subjective well-being (d = 0.666; 95 % CI 0.405, 0.928; moderate certainty evidence), social well-being (d = 1.046; 95 % CI 0.569, 1.523; low certainty evidence), and HRQoL (d = 0.568; 95 % CI 0.396, 0.74; moderate certainty evidence).

CONCLUSION

Exercise interventions can improve well-being and HRQoL in PwMS. Future studies should focus on PwMS ≥ 65 years or with higher level of impairments.

Does Osteopathic Heart-Focused Palpation Modify Heart Rate Variability in Stressed Participants with Musculoskeletal Pain? A Randomised Controlled Pilot Study

Heart rate variability (HRV) describes fluctuations in time intervals between heartbeats and reflects autonomic activity. HRV is reduced in stressed patients with musculoskeletal pain and improved after osteopathic manipulative treatment and mind-body interventions. Heart-focused palpation (HFP) combines manual and mind-body approaches to facilitate relaxation. This randomised controlled pilot study investigated the feasibility and sample size for a future randomised controlled trial and the effect of a single treatment with HFP or sham HFP (SHAM) on short-term HRV. A total of Thirty-three adults (47.7 ± 13.5 years old) with stress and musculoskeletal pain completed the trial with acceptable rates of recruitment (8.25 subjects per site/month), retention (100%), adherence (100%), and adverse events (0%). HFP (n = 18), but not SHAM (n = 15), significantly increased the root mean square of successive RR interval differences (p = 0.036), standard deviation of the NN intervals (p = 0.009), and ratio of the low-frequency to high-frequency power band (p = 0.026). HFP and SHAM significantly decreased the heart rate (p < 0.001, p = 0.009) but not the stress index and ratio of the Poincaré plot standard deviation along and perpendicular to the line of identity (p > 0.05). A power analysis calculated 72 participants. Taken together, the study was feasible and HFP improved HRV in stressed subjects with musculoskeletal pain, suggesting a parasympathetic effect.

The views and experiences of people with myeloma referred for autologous stem cell transplantation, who declined to participate in a physiotherapist-led exercise trial: a qualitative study

BACKGROUND

Recruitment rates to rehabilitation trials are variable among cancer survivors, and deeper investigation into the causes for declining participation is needed. The aim of this study was to qualitatively explore the experiences of people with myeloma referred for autologous stem cell transplant who were approached to take part in a physiotherapist-led exercise trial but declined.

METHODS

Participants were asked to participate in this qualitative study after declining to participate in a trial conducted at a UK tertiary cancer center. Semi-structured interviews were conducted. Data was analyzed inductively using reflexive thematic analysis.

RESULTS

Interviews from 18 myeloma patients (56% male, mean age 62 years) were analyzed. Four themes were identified: 1) Traveling to the specialist center is challenging, not just logistically; 2) Individualized approach valued but recall of research information variable; 3) Being less active has profound impact yet ameliorative support is lacking; and 4) Common side-effects of treatment are expected and endured but personal impact underestimated and unaddressed.

CONCLUSION

A number of barriers to participation were identified. Travel, a commonly cited reason for declining research participation, is more than a logistical issue for cancer survivors experiencing side-effects and the time burden of clinical appointments. Expectation or knowledge of the typical side-effects from myeloma and its treatment may lead to under-reporting of concerns to care providers, despite their impact upon daily activities and quality of life. Approaches used for research recruitment should consider the timing and consequences of ongoing cancer treatment to reduce potential barriers to participation.

Safety and feasibility of exercise interventions in patients with hematological cancer undergoing chemotherapy: a systematic review

OBJECTIVE

Exercise during and after cancer treatment has established quality of life and health benefits. However, particularly for patients with hematological cancer clear recommendations regarding the safety and feasibility of exercise are under-investigated. The aim of our systematic review was to summarize the literature regarding the feasibility and safety of exercise interventions in patients diagnosed with hematological cancer undergoing chemotherapy.

METHOD

A systematic literature review was conducted using PubMed, SPORTDiscus, MEDLINE, Science Direct, and Web of Science electronic databases. Eligible studies were scientific publications reporting the feasibility and/or safety of an exercise intervention program carried out in inpatient patients diagnosed with hematological cancer undergoing chemotherapy.

RESULT

Out of 12 studies (six RCTs) included in this review, six investigations reported results with regard to safety and 10 with regard to feasibility. While all studies claim that their exercise interventions were safe and/or feasible, it is noteworthy that this claim often remains unsupported as detailed information on how the feasibility of the intervention was asserted is missing.

CONCLUSION

Exercise appears to be safe and feasible in hematological cancer patients. However, due to a striking lack of information on how the feasibility of the intervention was asserted, contextualizing the results and deducing recommendations for further studies remains challenging. Further research should therefore incorporate information on the execution of the exercise intervention in more detail.

Sex Differences in the Feasibility of Aerobic Exercise Training for Improving Cardiometabolic Health Outcomes in Adults with Type 2 Diabetes

Females with type 2 diabetes (T2D) have a 25-50% greater risk of developing cardiovascular disease compared with males. While aerobic exercise training is effective for improving cardiometabolic health outcomes, there is limited sex-segregated evidence on the feasibility of aerobic training in adults with T2D. A secondary analysis of a 12-week randomized controlled trial examining aerobic training in inactive adults with T2D was conducted. Feasibility outcomes were recruitment, retention, treatment fidelity, and safety. Sex differences and intervention effects were assessed using two-way analyses of variances. Thirty-five participants (14 females) were recruited. The recruitment rate was significantly lower among females (9% versus 18%; p = 0.022). Females in the intervention were less adherent (50% versus 93%; p = 0.016), and experienced minor adverse events more frequently (0.08% versus 0.03%; p = 0.003). Aerobically trained females experienced clinically meaningful reductions in pulse wave velocity (-1.25 m/s, 95%CI [-2.54, 0.04]; p = 0.648), and significantly greater reductions in brachial systolic pressure (-9 mmHg, 95%CI (3, 15); p = 0.011) and waist circumference (-3.8 cm, 95%CI (1.6, 6.1); p < 0.001) than males. To enhance the feasibility of future trials, targeted strategies to improve female recruitment and adherence are needed. Females with T2D may experience greater cardiometabolic health improvements from aerobic training than males.

Study protocol for a multicenter randomized controlled trial of personalized exercise therapy and self-management support for people with multimorbidity: The MOBILIZE study

Background

Despite the great individual and societal burden associated with multimorbidity, little is known about how to effectively manage it.

Objective

The aim of this multicenter randomized controlled trial (RCT) is to investigate the 12-month effects of a personalized exercise therapy and self-management support program in addition to usual care in people with multimorbidity.

Design

This is a protocol for a pragmatic, parallel-group (1:1 ratio), superiority RCT conducted at five intervention sites (two hospitals, a private practice physiotherapy clinic and two municipal rehabilitation centers) in Region Zealand, Denmark. A total of 228 persons with multimorbidity aged 18 years or older, will be randomly allocated to one of two groups. Both groups will receive usual care, defined as routine care for multimorbidity at the discretion of the treating doctor, while the intervention group will also participate in a 12-week exercise therapy and self-management support program tailored to people with multimorbidity at one of the intervention sites. The primary outcome will be the between-group difference in change in EQ-5D-5L from baseline to the follow-up at 12 months. Secondary outcomes include objectively-measured physical function and physical activity, inflammatory markers, disease and treatment burden, anxiety, depression, stress, sleep, pain and other self-reported parameters. In parallel with the RCT, an observational cohort will follow persons aged ≥18 years with multimorbidity not adhering to all eligibility criteria, as well as people fulfilling all eligibility criteria, but unwilling to participate in the RCT. This study was approved by the Regional Committee on Health Research Ethics for Region Zealand (SJ-857) and results will be communicated in scientific papers, at relevant conferences and to a broader audience.

Discussion

Exercise therapy and self-management support is safe and effective in people with single conditions. However, it is still unclear whether this holds true for individuals with multimorbidity. This pragmatic, multicenter RCT will provide high-quality evidence on the benefits and harms of exercise therapy and self-management support and, if the results support it, lead to the development of a plan for implementation in clinical practice.

Personalised exercise therapy and self-management support for people with multimorbidity: feasibility of the MOBILIZE intervention

BACKGROUND

Exercise therapy is safe and effective in people with single conditions, but the feasibility in people with two or more conditions is unclear. Therefore, the aim was to evaluate the feasibility of exercise therapy and self-management in people with multimorbidity prior to a randomised, controlled trial (RCT).

METHODS

This was a mixed-methods feasibility study performed in two general hospitals and one psychiatric hospital. 20 adult patients (8 females; mean age (SD) 67 (6.9)) with at least two long-term conditions and a score of ≥ 3 on Disease Burden Impact Scale for at least one condition (at least moderate limitations of daily activities) and of ≥ 2 for at least one other condition. Patients with unstable health conditions, at risk of serious adverse events (SAE) or with terminal conditions were excluded. Participants received 12 weeks of exercise (18 60-min group-based and 6 home-based sessions) and self-management support (6 90-min group-based sessions) supervised by physiotherapists. Pre-defined progression to RCT criteria were the primary outcomes and included recruitment rate (acceptable 20 participants in 3 months), retention through follow-up (75% retention), compliance (75% complete > 9 of exercise and > 3 self-management sessions), outcome burden (80% do not find outcomes too burdensome), improvement in quality of life (EQ-5D-5L) and function (6-min walk test; ≥ 50% experience clinically relevant improvements) and intervention-related SAEs (No SAEs). Furthermore, a purposeful sample including eleven participants and two facilitators were interviewed about their experiences of participating/facilitating. Qualitative data was analysed using thematic analysis.

RESULTS

Recruitment rate (20 in 49 days), retention (85%), outcome burden (95%), and SAEs (0 related to intervention) were acceptable, while compliance (70%) and improvements (35% in quality of life, 46% in function) were not (amendment needed before proceeding to RCT). The intervention was found acceptable by both participants and physiotherapists with some barriers among participants relating to managing multiple chronic conditions while caring for others or maintaining a job. Physiotherapists expressed a need for additional training.

CONCLUSIONS

Exercise therapy and self-management are feasible in people with multimorbidity. The subsequent RCT, amending the intervention according to progression criteria and feedback, will determine whether the intervention is superior to usual care alone.

TRIAL REGISTRATION

ClinicalTrials.gov registration: NCT04645732 Open Science Framework https://osf.io/qk6yg/.

Does Inspiratory Muscle Training Affect Static Balance in Soccer Players? A Pilot Randomized Controlled Clinical Trial

Inspiratory muscle training (IMT) is effective in improving postural stability and balance in different clinical populations. However, there is no evidence of these effects in soccer players. A single-blind, two-arm (1:1), randomized, placebo-controlled pilot study on 14 soccer players was performed with the main aim of assessing the effect of IMT on static balance, and secondarily, of examining changes in the respiratory muscle function. The experimental group (EG) received an IMT program with progressive intensity, from 20% to 80%, of the maximal inspiratory pressure (MIP). The sham group (SG) performed the same program with a fixed load of 20% of the MIP. Static balance and respiratory muscle function variables were assessed. A two-factor analysis of variance for repeated measures was used to assess differences after training. Statistical significance was set at p < 0.05. Significant increases were observed in the EG on length of sway under eyes open (from 2904.8 ± 640.0 to 3522.4 ± 509.0 mm, p = 0.012) and eyes closed (from 3166.2 ± 641.3 to 4173.3 ± 390.8 mm, p = 0.004). A significant increase in the maximal voluntary ventilation was observed for both groups (EG p = 0.005; SG p = 0.000). No significant differences existed between the groups. IMT did not improve the static balance in a sample of soccer players. Conducting a high-scale study is feasible and could refine the results and conclusions stemming from the current pilot study.

Development and feasibility of an inter-agency physical activity and education programme for adults with multimorbidity in primary care: Activ8

Background

While physical activity is widely recommended for many long-term conditions, it may be difficult to achieve for patients managing multiple conditions. We aimed to determine the feasibility of an inter-agency exercise and education programme for patients with multimorbidity in primary care.

Methods

We conducted an uncontrolled pilot study with adults with multimorbidity, recruited in two community healthcare organisations in an urban area in Ireland. The six-week pilot intervention combined an individually tailored gym-based exercise programme and education to support self-management. Feasibility of the Activ8 programme was assessed using a mixed methods process evaluation. Outcome measures at baseline and at 6 weeks included recruitment and retention, gait speed, grip strength, quality of life and self-efficacy. Focus groups and interviews explored participants and facilitators’ perceptions of the programme.

Results

19 participants with ≥2 chronic conditions were recruited over three-weeks with similar attrition at both sites (≤40%). Overall, the results indicate that Activ8 was feasible and acceptable to patients and practitioners. Quantitative outcome measures suggested improvements in most outcomes. Qualitative data analysis indicated that Activ8 addressed an overarching concept of patient-centeredness among participants. Three key themes included perceived personal programme impact, the personalised composition of the programme and the evolving nature of primary care practice.

Conclusion

While further definitive evidence is needed and attrition from the programme needs to be considered, the Activ8 Programme was acceptable to both patients and professionals in two different primary care areas with the potential for positive impacts for adults living with multimorbidity.

Personalised exercise therapy and self-management support for people with multimorbidity: Development of the MOBILIZE intervention

BACKGROUND

To our knowledge, there is no intervention which includes personalised exercise therapy and self-management support for people with multimorbidity, although these interventions may be as effective as for people with single chronic conditions. Therefore, we developed a novel intervention, including personalised exercise therapy and self-management support for people with multimorbidity.

METHODS

We followed the Medical Research Council framework and conducted one scoping review, five systematic reviews, two registry-based studies, one qualitative interview study and a mixed-methods feasibility study. Following an iterative approach, together with feedback from people with multimorbidity and relevant stakeholders, we developed the MOBILIZE intervention.

RESULTS

The intervention included 24 (60 minutes) sessions of personalised exercise therapy and 24 (30 minutes) sessions of self-management support twice a week for 12 weeks, delivered in small groups by specifically trained physiotherapists. The intervention targets physiological, psychosocial, behavioural, and contextual factors to improve health-related quality of life and physical function in people living with multimorbidity.

CONCLUSIONS

We developed a personalised exercise therapy and self-management support programme for people with multimorbidity. The intervention will be tested for its safety and effectiveness in a randomised controlled trial.

Retention in RCTs of physical rehabilitation for adults with frailty: a systematic review and meta-analysis

Background

Physical rehabilitation (PR) interventions can improve physical function for adults with frailty; however, participant retention rates in randomized controlled trials (RCTs) are unknown.

Objective is to summarize participant retention rates in RCTs of PR for adults with frailty.

Design is a systematic review and meta-analysis (DOI:10.17605/OSF.IO/G6XR2).

Participants are adults ≥ 18 years with frailty.

Setting consists of inpatient, outpatient and community-based interventions.

Intervention includes any PR intervention.

Methods

We searched 7 electronic databases from inception to April 15, 2020 for published RCTs. Our primary outcome was participant retention rate to primary outcome measurement. Secondary outcomes included retention by study group, participant retention to intervention completion, reported reasons for attrition and reported strategies for maximizing retention. We completed screening, data extraction and risk of bias (ROB) assessments independently and in duplicate. We conducted a meta-analysis, calculating retention rates and 95% confidence intervals (CIs) using fixed or random-effects models, as appropriate.

Results

We included 21 RCTs, enrolling 1685 adults with frailty (median age 82.5 years (79.0, 82.2), 59.8% female (57.5, 69.8)). Twenty RCTs reported retention data, of which 90.0% (n = 18) had high ROB. The pooled participant retention rate to primary outcome measurement was 85.0% [95%CI (80.0, 90.0), I² = 83.9%, p < 0.05]. There were no differences by group for retention to the primary outcome [intervention 87.0% (83.0, 91.0), p < 0.05, comparator 85.0% (79.0, 90.0), p < 0.05] or in retention to intervention completion [83.0% (95.0% CI (78.0–87.0), p < 0.05]. Of the 18 studies reporting 24 reasons for attrition, 51.3% were categorized as potentially modifiable by the research team (e.g. low motivation). Only 20.0% (n = 4) of studies reported strategies for maximizing retention.

Conclusions

In this review of 21 RCTs of PR, we identified acceptable rates of retention for adults with frailty. High retention in PR interventions appears to be feasible in this population; however, our results are limited by a high ROB and heterogeneity.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13063-022-06172-5.