This protocol is being reported according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses Protocol 2015 (PRISMA-P) checklist [see Additional file 1][48]. This protocol has been registered on the PROSPERO database(CRD42020173988).
Criteria for considering studies for this review
Types of studies
We will include all randomized controlled trials that compare different cognitive rehabilitation interventions in treating people with cognitive impairment after stroke. Studies published from inception in any language will be included.
Types of participants
For study patients, we will include adults (aged over 18) of either sex and any ethnicity, with the presence of cognitive impairment after being diagnosed with stroke. In this review, we will accept the diagnosis of cognitive impairment made by any validated neuropsychological tests, such as MMSE, MoCA, or other domain-specific cognitive tests. We will also accept the diagnosis of cognitive impairment made by experienced researchers.
Types of interventions
We will consider any pharmacological or nonpharmacological interventions delivered alone.
Pharmacological interventions may include:
- Anticholinergic therapy, e.g. donepezil.
- Antihypertensive, e.g. indapamide.
- Antiplatelet, e.g. dipyridamole.
- Antidepressants, e.g. escitalopram.
Nonpharmacological interventions may include:
- Conventional cognitive training
- Computer-assisted cognitive training
- Aerobic exercises
- Music therapy
- Virtual reality
- Noninvasive brain stimulation
- Acupuncture
- Educational therapy, e.g. intensive caregiver education program.
Comparison will be done among the interventions mentioned above.
Types of outcome measures
Primary outcomes
- Any clinical changes in the general or specific cognitive domain (e.g. executive function, attention, memory or perception), measured by any validated measures, including but not limited to screening instruments such as MMSE and MoCA, and validated measure of domain-specific cognitive function such as Trail Making Test A and B, as well as Stroop Test.
Secondary outcomes
- Adverse effects, e.g. stroke, disability, or mortality, as defined by the original researchers.
- Quality of life, measured by any validated measure.
Search strategy
Electronic searches
The following electronic databases for relevant studies will be searched, with no restrictions in publication date or language:
- Cochrane Central Register of Controlled Trials (CENTRAL), Cochrane Database of Systematic Reviews, and Cochrane Methodology Register in the Cochrane Library (latest issue)
- EMBASE (from 1974 to present)
- MEDLINE (from 1946 to present)
- PsycINFO (from 1887 to present)
- CINAHL (from 1974 to present)
- PubMed (from 1966 to present)
Also, we will also search US National Institutes of Health Ongoing Trials Register ClinicalTrials.gov (www.clinicaltrials.gov/) for ongoing trials register. An experienced librarian has developed the detailed draft search strategy for the MEDLINE database [see Additional file 2] and then adapted it for searching studies in other databases. The search strategy has been revised by another experienced librarian.
Searching other resources
We will also search the reference lists of included trials, systematic reviews, and meta-analyses identified during the screening process to identify other eligible trials. Grey literature, such as conference proceedings will also be searched.
Data collection and analysis
Selection of studies
We will store citations using the EndNote software (https://www.endnote.com/) with duplicates removed. The screening and selection will be completed in two levels. In level one, two review authors (JL and XW) will independently screen the titles and abstracts of every record from the list of results of our literature searching activity to identify all potentially relevant trials. In level two, the full text of all potentially relevant records from level one screening will be retrieved, and the same two reviewers will independently examine these and the reasons for excluding the ineligible trials will be recorded. We will calculate inter-rater reliability from a pilot study before each screening level using a predesigned test form [see Additional file 3][49], and then launch the formal screening if the high agreement (≥80%) between two reviewers can be achieved. If discrepancies are found on study selection, the two review authors will further discuss, and a third review author (TW) will be consulted if necessary. The study selection process will be shown in a PRISMA flow diagram [see Figure 2][50].
Data extraction and management
All study data will be recorded using a data extraction form created in Excel. Two review authors (JL and XW) will independently extract data from all included studies. The following detailed trial characteristics will be extracted: study characteristics (e.g. date of publication, study design, settings, country), characteristics of the patient: (e.g. number enrolled in each group, age, gender, types of stroke, duration after stroke), interventions (e.g. types of interventions, comparison), outcome results (e.g. clinical changes in cognition, adverse effects and specific measure of the quality of life). Similar to study selection, inter-rater reliability will also be calculated for conformation of high agreement (≥80%). Any disagreements on data extraction will be resolved through discussion, or by recourse to a third review author (TW).
Assessment of risk of bias in included studies
The risk of bias for each included study will be assessed independently by two review authors (JL and XW), conforming to the criteria outlined in Chapter 8 of the Cochrane Handbook for Systematic Reviews of Interventions[51]. Any discrepancies on assessment will be resolved by further discussion or by involving a third review author (TW). The risk of bias in the following domains will be assessed:
- Random sequence generation.
- Allocation concealment.
- Blinding of participants and investigators.
- Blinding of outcome assessment.
- Incomplete outcome data.
- Selective outcome report.
- Other bias.
We will grade the risk of bias of studies as low, high, or uncertain in each of these domains. Information from the study report will be provided with a justification for our judgment in the ‘Risk of bias’ tables.
Assessment of heterogeneity
We will measure heterogeneity among the trials in each analysis using the I2 statistic, and the heterogeneity will be considered as low (I2 = 0% to 40%), moderate (I2 = 40% to 70%) and substantial (I2 = 70% to 100%). If heterogeneity is found, we will explore the potential sources via subgroup analyses.
Dealing with missing data
If we encounter missing data, the authors of the original trials and studies will be contacted to request access to further study data. When this is impossible, we will conduct an imputation approach using informative missing odds ratio (IMOR) for dichotomous data and informative missingness difference of means (IMDoM) for continuous data[52, 53]. And we will then conduct a sensitivity analysis to ensure no bias of the final results is created.
Assessment of reporting biases
Published and unpublished studies will be searched comprehensively to minimize reporting biases. If we identify 10 or more studies, possible reporting biases (e.g. publication bias, time-lag bias, citation bias, and outcome bias) will be evaluated for all studies using a funnel plot. If less than 10 studies are included, reporting bias will be assessed qualitatively on the basis of characteristics of the included studies, instead of performing the funnel plots.
Data synthesis and analysis
If there are sufficient trials with clinically similar populations and outcome measures, a meta-analysis of primary and secondary outcomes will be carried out using Review Manager 5[54]. We will use the Mantel-Haenszel method to pool the treatment effect of dichotomous data as risk ratio (RR) with 95% confidence intervals(CI). We will express continuous data as mean difference (MD) with 95% CI using an inverse variance method. We will report the result narratively if only one study contributes data for an outcome. We will combine the data in a meta-analysis when data for an outcome can be contributed by two or more trials. A fixed-effects model will be used to assess the results for heterogeneity. But if substantial heterogeneity is found, a random-effects model will be used instead.
We can only assess the statistical significance of the efficacy of a specific intervention using conventional meta-analysis. However, conventional meta-analysis cannot assess the amount of evidence that we used to estimate the intervention effect. To fill this vacancy, we will conduct trial sequential analysis to assess whether sufficient studies are identified to draw a firm conclusion on the efficacy of a specific intervention in cognitive rehabilitation after stroke.
‘Summary of findings’ table
The following outcomes will be included in a summary of findings table [see Additional file 4]: clinical changes in general cognitive function, clinical changes in domain-specific cognitive function (e.g. executive function, attention, memory or perception), adverse effects (e.g. stroke, disability or mortality) and QoL.
We will assess the certainty of the body of evidence using the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) system. The following five GRADE considerations: risk of bias, consistency of effect, imprecision, indirectness, and risk of publication bias will be considered. We will conform to methods described in Chapter 14 of the Cochrane Handbook for Systematic Reviews of Interventions[51]. A narrative ‘summary of findings’ table format will be created to present results if meta-analysis is not feasible.
Subgroup analysis
The following trial characteristics were prespecified as of interest to explore reasons behind heterogeneity: ischemic stroke versus hemorrhagic stroke and pharmacological interventions versus nonpharmacological interventions. We will use the ‘test for subgroup differences’ in Review Manager 5[54] to evaluate differences between subgroups.
Sensitivity analysis
If the heterogeneity is substantial, we will exclude studies with high risk of bias and undertake a sensitivity analysis of the primary outcomes.