Study design

This systematic review follows the Preferred Reporting Items for Systematic Review and Meta-Analysis Protocols (PRISMA). The PRISMA guidelines provide items informed by empirical research for systematic reviews and meta-analyses [27].

Search strategy and selection criteria

The sources of information that were used are Medline through PubMed, Scopus, Cumulative Index to Nursing and Allied Health Literature (CINHAL), PsycINFO, and EMBASE, covering the period from database inception to March 15, 2023. The search strategies for this review were established by applying Boolean operators ‘AND’ and ‘OR’ to effectively connect the descriptors, facilitating a focused yet exhaustive search. These descriptors were derived from keywords and MeSH terms search (in PubMed) in each database’s metadata system. Therefore, the strategy was carefully developed for each database, considering its unique indexing system and search functionalities to guarantee the identification of the most pertinent and extensive collection of literature.

The search terms covered a spectrum of terms relating to home exercise programs, adherence, diverse influencing factors and cerebral palsy. To ensure the inclusion of a wide range of studies, the search incorporated terms with prefixes. The sample query for PubMed was constructed as follows: ("exercise" OR "therap*" OR "physiotherap*" OR "home physiotherap*" OR "home exercise*" OR "rehabilitation exercise*" OR "physical therapy") AND ("adheren*" OR "complian*" OR "involvement") AND ("psychosocial factor*" OR "psychological factors" OR "motivat*" OR "barrier*" OR "facilitat*") AND ("cerebral pals*" OR "neurodevelopmental disorder*" OR "pediatric neurology").

Two separate researchers independently conducted the search and evaluated studies for eligibility based on the inclusion criteria (JN, LU) using the Covidence database (www.covidence.org). During instances of disagreement, a dedicated reviewer panel (a team of MN, LC, and FC) was engaged to achieve consensus. Studies were considered eligible for inclusion if they (i) involved parents of children with CP who were younger than 18 years; (ii) described exercises that were assisted by a caregiver rather than performed independently by the patient; and (iii) were published in English. Notably, studies that presented both clinic and home-based exercise adherence data were included, provided the home-based data were reported separately. Exclusions were made for (i) review articles; (ii) studies involving children without a confirmed CP diagnosis; (iii) studies not available in full text; and (iv) computer-based rehabilitation studies due to a lack of reported data on psychosocial determinants of adherence from parents’ perspectives, which was a critical focus of our review.

The selection process began with the Boolean combination of descriptors, followed by a review of titles, abstracts, and finally, full texts. All references were imported into Covidence for deduplication and screened for eligibility based on the established criteria. The number of articles identified through electronic databases and the reasons for exclusion were rigorously documented in Fig 1. Following identification of relevant papers, their reference lists were manually searched for additional pertinent literature. At the conclusion of the selection phase, chosen papers were organized for data extraction, tabulation, and analysis, and subsequent interpretation and reporting.

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Fig 1. “Flow chart of study selection” should be placed here.

https://doi.org/10.1371/journal.pone.0305432.g001

Data extraction and management

The study characteristics and outcome data were extracted by one reviewer using a pre-designed data extraction spreadsheet. The information extracted for analysis was divided into three categories: study data, data about children with CP, and data about the parents. The following study details were extracted: study title, author(s), publication year, country of study, study design, participant characteristics (e.g., child’s age range, parents’ mean age) and the measure of adherence to the home exercise program. If some of the articles did not contain all the data required for the review, we included the available data (Table 1).

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Table 1. Summary of the main study characteristics and the key findings.

https://doi.org/10.1371/journal.pone.0305432.t001

Quality assessment

For quantitative studies, we utilized the Newcastle-Ottawa Scale (NOS) adapted for cross-sectional studies. This decision was informed by the nature of the review studies, which were explicitly of this type [28]. The NOS evaluates the methodological quality of studies based on three critical domains: Selection, comparability, and outcome. Stars are awarded in these categories according to the guidelines provided in the NOS coding handbook, with up to five stars might be given for selection, two for comparability, and three for outcome. The total number of stars a study receives serves as an indicator of its quality.

In assessing the qualitative studies, the Critical Appraisal Skills Programme Tool (CASP) for Qualitative Research. The tool encompasses 10 criteria aimed at appraising a study’s methodological rigour and validity [29]. We adopted a rating approach to gauge the relative quality of these studies [30]. Those meeting at least eight criteria were deemed ’high quality’, those fulfilling 5–7 criteria were considered ’moderate quality’ if they met 5–7 of the criteria, and studies meeting four or fewer criteria were categorized as ’poor quality’.

Data synthesis

The first plan was to do a meta-analysis. Unfortunately, there was little data provided in the studies found by this review, and the data that was gathered was inconsistent in terms of measures employed (7 out of 9 were self-designed) and analysis undertaken. As such, it was decided to conduct a narrative synthesis rather than a meta-analysis to synthesize the data in the most meaningful way possible, guided by the concepts described by Popay and colleagues [31]. A narrative synthesis approach was used to describe, compare, and combine findings from multiple studies.

This method concentrates on textual summaries and results descriptions with the primary goal of "telling the tale “of the findings from the included research [31]. The elements of this process in this review included: developing a preliminary synthesis to organize the findings from the included studies; exploring relationships within this data to understand and explain patterns or differences; and assessing the robustness of the synthesis by considering the strength, quality, and generalizability of the included data.

Characteristics of included studies

The search yielded 432 records. After removing duplicates, we screened a total of 342 titles and abstracts, leading to the exclusion of 326 records due to irrelevance. We then assessed the full texts of the remaining 16 records for eligibility, excluding three that did not meet the criteria. This process resulted in 13 relevant records. The flow chart of the literature search process is illustrated in Fig 1. We contacted the corresponding and last authors of these 13 records to inquire about any related studies, receiving responses from 8 (59%) authors who responded with either a suggestion or no additions at all, resulting in two additional records already included in the initial 13 records.

Our final review included eleven quantitative and two qualitative studies that explored factors influencing parents’ AHEP (Table 1). These studies were conducted across various countries: three studies were conducted in Spain, two in Turkey, two in the USA, and one each in Saudi Arabia, Ethiopia, Israel and Palestine. Publication dates ranged from 2000 to 2023, with three studies published between 2000 and 2005, and the remaining 10 studies between 2013 and 2023. Although the samples in all studies were mixed, participants were predominantly female, making up between 51% to 99% of the total sample. Sample sizes varied significantly, from 17 to 446 participants. The average age of parents across was approximately 34 years, while the age range for children spanned from 0.5–18 years. Adherence measures relied on participant self-report, with results often dichotomized into ’adherent’ and ’non-adherent’ individuals for analysis or expressed as a percent of the recommended exercise done.

Quality assessment of the included articles

In appraising the quantitative studies, two studies were awarded nine stars, one study was received eight stars, four were awarded seven stars, and the remaining four studies also awarded seven stars (Table 1). The primary concern identified during the quality assessment was the universal use of convenience sampling across all studies, suggesting that participants might not accurately represent the target research population. Except for one study [32], none conducted power analyses or provided sample size estimates to justify their sample sizes. While there are no universal guidelines for determining the optimal sample size for multivariate analyses, a small sample size can undermine confidence in the findings [33]. However, given the nature of the target population, the use convenient sample is understandable, yet it necessitates the authors adapting appropriate their analyses to the quality of their sample. Consequently, variations in study sample sizes might account for the inconsistencies in significant findings regarding specific factor. Moreover, response rates were generally low across the studies, with no insights into the characteristics of non-responders. This omission makes assessing the representative of the participants challenging [25]. It is plausible that parents who were most adherent to HEP may have been more willing to participate in the research because they saw it as relevant and valuable. In contrast, non-adherent parents might have chosen not to discuss their experiences and abstain from the research [25].

A notably issue was the frequent use of non-validated measures for various concepts, and the reliability evaluations of the scales for the specific samples were either not consistently conducted [24, 34, 35] or did not consistently demonstrate adequate reliability. Furthermore, all studies relied on self-report methods to assess AHEP and its associated factors, which depends on individuals accurately recalling and reporting their exercises routines. This approach exposes the data to potential social desirability and memory biases, possibly leading to an overestimation of adherence. This observation aligns with a previous systematic review that found that all 61 identified self-report measures lacked psychometric validity [36]. The current review also noted that factors such as social support and self-efficacy were sometimes assessed using a single item derived from related validated scales, which may not effectively capture the target concepts [32, 35, 37]. Other research efforts have tried to mitigate these issues by developing new measures based on existing scales or theories in the scientific literature [22, 35, 37] or by pre-testing and piloting the scales.

Conversely, the two qualitative studies included in the review demonstrated high quality in their approach to participant recruitment, data collection, and analysis (Table 1). These studies adequately considered the role of the researcher and how they might influence the study results.

Factors influencing the adherence to home exercise programs among parents of children with cerebral palsy

Our analysis identified several psychosocial and situational factors that have been considered in the literature to date, and were grouped into four conceptually related categories: Child related factors, caregiver-related factors, and therapist guidance and advice (Fig 2). We relied on the descriptive information supplied in the original articles to address our secondary research aim of identifying the specific factors that are perceived to be beneficial or detrimental in adhering to HEP among parents of C-CP.

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Fig 2. “Factors influencing the adherence to home exercise programs among parents of children with cerebral palsy” can be placed here.

https://doi.org/10.1371/journal.pone.0305432.g002

Child-related factors of HEPA

Gross motor function. Four quantitative studies showed an inverse relationship between gross motor function and HEPA [34, 35, 37, 38]. These studies evidenced that parents’ adherence appeared to be higher when the gross motor function was low.

Child age, gender, and weight. Four quantitative studies conducted showed mixed findings on the association between child age and HEPA [34, 35, 37]. While two studies revealed no associations between child age and HEPA [34, 37], one study showed a positive association, indicating that parents with younger children were more likely to adhere [35]. Two separate quantitative studies found no associations between the child’s gender [37], the child’s weight [34] and HEPA.

Parental-related factors of HEPA

Education level, age, and marital status. Four quantitative studies have consistently revealed that mothers’ educational status was positively related to adherence [24, 37, 40, 42]. These studies suggested that parental education helps parents feel less anxious about injuring or causing harm to their children. Further, the association between the caregiver’s age and HEPA was inconsistent [22, 34, 35, 39]. Only one study out of four indicated significant positive associations [34]. There was also strong evidence that marital status [22, 34, 35] and the household number of children were not related to HEPA among parents [22, 35, 37].

Depression and anxiety. Two quantitative studies showed significant negative associations between parental depression and anxiety, and HEPA [38, 42] and were complemented by one qualitative study [41]. These studies strongly evidenced that the severity of depression and anxiety symptoms were salient risks of non-HEPA. The only study where this association was not significant [34] is characterized by a weak methodological design (Table 1). This weakness can be traced to the sample predominated by fathers (51%) who are not usually involved in HEP [39] and a non-validated self-report measure of adherence [34].

Stress and emotional burden/exhaustion. Three articles highlighted that mothers’ sense of insecurity and doubts about their ability to complete exercises and burnout level [34, 41], level of stress, and family problems [24] were detrimental to parents’ HEPA.

Positive cognitions. Of 13 studies included in this review, five quantitative studies have investigated cognitive factors such as high self-efficacy, high knowledge and ability, and low perception of the barriers that enhance parents’ HEPA [32, 35, 37, 41]. According to these studies, all these factors are positively correlated with HEPA.

Social support. Social support is the perception and experience that one is taken care of, that supportive resources are available from others, and, most commonly, that one is part of a social network that is supportive. Although social support may involve several types of support, it was only assessed through one item and identified as a potential factor enhancing the likelihood of HEPA in four quantitative studies evidenced [22, 35, 37, 41]. The same result was reported in one of the qualitative studies included in the review [43] which was carried out through individual, face-to-face, and semi-structured interviews.

Family income and equipment. There were mixed findings on the positive association between family income and adherence in five quantitative studies, with some studies indicating significant positive associations [24, 35, 40] and no significance [22, 39]. Also, the availability of the home equipment necessary for the exercises did not affect the level of parental HEPA [35, 37]. Despite few studies conducted, these results indicate that parents do not any special equipment to adhere to HEPA.

Therapist guidance and advice

Amount of exercise. The number of exercises prescribed by health professionals was investigated by two studies: a quantitative study [24] and a qualitative study [44]. These studies highlighted that the more exercises prescribed, the less likely parents were to adhere to the recommendations. Healthcare professionals thus, need to take care of this while designing HEP for parents of C-CP.

Exercises that improve outcomes. There were consistent findings on the positive associations between parental perception of the benefits and efficacy of exercise and HEPA in five quantitative studies [24, 32, 35, 40, 41] and complemented by one qualitative study [44] which may support the generalisability of the findings. In this case, it is thought that parents are highly motivated and hopeful when their children’s conditions improve thanks to exercises performed [40, 41].

Exercise without adverse effects on children. The perceived adverse effects or pain of the exercises on C-CP were found to be negatively related to HEPA in two quantitative studies [24, 42]. This finding was complemented by the qualitative study, which recognized pain as detrimental to HEPA [44]. Therefore, it can be concluded that the presence of pain or adverse effects during exercise plays a crucial role in executing and adhering to HEP.

Easy and enjoyable exercises. Three quantitative studies continually reported enjoyable and easy exercises [24, 41, 42] as potential factors of HEPA, demonstrating a largely positive relationship in multivariate analyses. This was also confirmed in one qualitative study [44]. As such, an effective home treatment program should contain easy, understandable, and entertaining exercises that are suited to daily activities.

Physiotherapist’s support. The relationship between support from the physiotherapist and HEPA was investigated in seven quantitative studies [22, 32, 35, 37, 38, 41, 42] and a qualitative one [44]. There was mounting and consistent evidence that parents were more likely to adhere to home exercises when they were satisfied with the care from their therapist [35, 37, 38, 40] and informed about the progress and clarification of doubts [35, 37]. Further, parents who were motivated by the therapist advised to insert exercises into daily routines, assessed their skills, or asked about adherence at home by their therapists were more likely to comply with home exercises [22, 35, 37, 41, 42, 44]. Yet, some authors [45] have highlighted the risk that this follow-up may lead to stress and feelings of guilt in parents. Similarly, Lillo-Navarro and his colleagues [37] suggested that healthcare providers must be aware of this circumstance to be perceived as a source of assistance rather than a judgemental bystander.

Study strengths and limitations

This review was rigorous and used a strong methodological approach to discover, appraise, and synthesize significant findings. The search parameters were intentionally broad to locate research examining a wide variety of factors that may impact HEPA among parents of children with cerebral palsy. It also used a robust quality criteria tool to assess the articles included in the synthesis.

Nevertheless, our findings should be interpreted considering the methodological limitations of included studies and the review itself. First, a small number of studies exploring several factors, studies’ methodological constraints, changes in concept formulation and operationalization, and contradictions across findings have all made it difficult to draw firm conclusions regarding the predictive power of these factors. Second, the difficult measuring of home exercise adherence deserves special attention. As revealed in the previous reviews, the absence of verified and standardized methodologies is a significant methodological restriction in this field of research [25, 36], making it difficult to compare findings across studies.

Moreover, noting that all studies included in the syntheses applied the cross-sectional design, it’s not possible to make conclusions about causal effects. Longitudinal studies are strongly recommended to draw definitive causal effects and confirm the presence or absence of associations. Lastly, only published full-text English language publications were considered, which may have created a publication bias given that unpublished studies may be more likely to have reported different findings. It might also be argued that the review did not consider differences in adherence metrics between studies sufficiently.

Implications for research and practice

In terms of research, further studies are warranted to determine the nature of the relationships between HEPA and each of the five identified consistent predictors. It is crucial to understand whether certain groups of parents or specific circumstances amplify these predictors’ effects, and to what extent other factors may mediate or moderate the relationship. Coupled with the expanding research on behaviour modification techniques [50], these findings may guide the development of highly effective strategies to boost HEPA. Identifying the most impactful adherence behaviour factors allows for a targeted approach in selecting of behaviour modification strategies for these interventions. Furthermore, despite acknowledging computer-based rehabilitation’s increasing role in managing cerebral palsy and its influence on adherence, there is a noticeable gap concerning its psychosocial dimensions. This observation underscores the necessity for research focused on the psychosocial aspects of adhering to such rehabilitation modalities. Finally, future studies addressing the methodological limitations identified in this review, particularly the challenges in monitoring home-exercise adherence, is essential for enhancing the evidence base regarding HEPA predictors.

In terms of practice, the review’s findings have implications for practitioners implementing HEP programs with parents of C-CP. Considering that stronger parental self-efficacy, high knowledge, and ability to perform the exercises, low perceived barriers, social support and therapist guidance, high gross motor function, and low psychological distress tend to predict higher HEP Adherence. Therefore, assessing these domains beforehand may uncover any risk factors for poor adherence. These findings give significant insights into how therapists and other stakeholders working with parents of C-CP may take a more active role in protecting against the alarming rate of HEP non-adherence by ensuring that appropriate assistance is in place or prioritizing currently accessible help. Priority areas should be reinforcing guidance of health professionals to parents, strong peer support networks, psychological support, and training of the parents to increase high self-efficacy, high knowledge, and ability to promote HEPA.