This study assessed the effects of physical exercise programs on people with cognitive impairment. It is reported in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement [19]. A compiled PRISMA checklist is included in Table 1.
Table 1 Checklist of items to include when reporting a systematic review or meta-analysis
Section/topic
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#
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Checklist item
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Reported on page #
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TITLE
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Title
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1
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Identify the report as a systematic review, meta-analysis, or both.
|
2
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ABSTRACT
|
|
Structured summary
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2
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Provide a structured summary including, as applicable: background; objectives; data sources; study eligibility criteria, participants, and interventions; study appraisal and synthesis methods; results; limitations; conclusions and implications of key findings; systematic review registration number.
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2-3
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INTRODUCTION
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|
Rationale
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3
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Describe the rationale for the review in the context of what is already known.
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3-4
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Objectives
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4
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Provide an explicit statement of questions being addressed with reference to participants, interventions, comparisons, outcomes, and study design (PICOS).
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4
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METHODS
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|
Protocol and registration
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5
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Indicate if a review protocol exists, if and where it can be accessed (e.g., Web address), and, if available, provide registration information including registration number.
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-
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Eligibility criteria
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6
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Specify study characteristics (e.g., PICOS, length of follow-up) and report characteristics (e.g., years considered, language, publication status) used as criteria for eligibility, giving rationale.
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5-6
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Information sources
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7
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Describe all information sources (e.g., databases with dates of coverage, contact with study authors to identify additional studies) in the search and date last searched.
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6, Table 2
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Search
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8
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Present full electronic search strategy for at least one database, including any limits used, such that it could be repeated.
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Table 2
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Study selection
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9
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State the process for selecting studies (i.e., screening, eligibility, included in systematic review, and, if applicable, included in the meta-analysis).
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7, Fig 1
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Data collection process
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10
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Describe method of data extraction from reports (e.g., piloted forms, independently, in duplicate) and any processes for obtaining and confirming data from investigators.
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7-8
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Data items
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11
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List and define all variables for which data were sought (e.g., PICOS, funding sources) and any assumptions and simplifications made.
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-
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Risk of bias in individual studies
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12
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Describe methods used for assessing risk of bias of individual studies (including specification of whether this was done at the study or outcome level), and how this information is to be used in any data synthesis.
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7
Table 4
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Summary measures
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13
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State the principal summary measures (e.g., risk ratio, difference in means).
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7-8
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Synthesis of results
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14
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Describe the methods of handling data and combining results of studies, if done, including measures of consistency (e.g., I2) for each meta-analysis.
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8
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Risk of bias across studies
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15
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Specify any assessment of risk of bias that may affect the cumulative evidence (e.g., publication bias, selective reporting within studies).
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-
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Additional analyses
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16
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Describe methods of additional analyses (e.g., sensitivity or subgroup analyses, meta-regression), if done, indicating which were pre-specified.
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8
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RESULTS
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Study selection
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17
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Give numbers of studies screened, assessed for eligibility, and included in the review, with reasons for exclusions at each stage, ideally with a flow diagram.
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8, Figure 1
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Study characteristics
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18
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For each study, present characteristics for which data were extracted (e.g., study size, PICOS, follow-up period) and provide the citations.
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Table 3, 4
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Risk of bias within studies
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19
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Present data on risk of bias of each study and, if available, any outcome level assessment (see item 12).
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9
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Results of individual studies
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20
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For all outcomes considered (benefits or harms), present, for each study: (a) simple summary data for each intervention group (b) effect estimates and confidence intervals, ideally with a forest plot.
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Figure 2
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Synthesis of results
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21
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Present results of each meta-analysis done, including confidence intervals and measures of consistency.
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Figure 2
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Risk of bias across studies
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22
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Present results of any assessment of risk of bias across studies (see Item 15).
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-
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Additional analysis
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23
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Give results of additional analyses, if done (e.g., sensitivity or subgroup analyses, meta-regression [see Item 16]).
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9-10
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DISCUSSION
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Summary of evidence
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24
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Summarize the main findings including the strength of evidence for each main outcome; consider their relevance to key groups (e.g., healthcare providers, users, and policy makers).
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10-12
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Limitations
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25
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Discuss limitations at study and outcome level (e.g., risk of bias), and at review-level (e.g., incomplete retrieval of identified research, reporting bias).
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12
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Conclusions
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26
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Provide a general interpretation of the results in the context of other evidence, and implications for future research.
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13
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FUNDING
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Funding
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27
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Describe sources of funding for the systematic review and other support (e.g., supply of data); role of funders for the systematic review.
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15
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The PICO (population, intervention, comparisons, and outcomes) framework was used for framing the inclusion criteria (see below).
- Participants: people with a cognitive impairment being diagnosed with one of the standardized tools with a closed scale
- Intervention: activities requiring increased energy output excluding interventions combining both physical and cognitive training
- Comparisons: active or passive controls according to reported activities
- Outcomes: cognitive performance; focus on: type of exercise or control group activities, age and sex of participants, length of interventions, frequency of exercise, and severity of impairment
Inclusion criteria for this study
Based on the above-mentioned PICO framework, the following inclusion criteria were applied: only data from randomized trials (RCT) were used, and the participants had to be diagnosed with a cognitive impairment according to one of the standardized tools with a closed scale written in the English language. Following global cognitive function tests were considered appropriate: Cambridge Cognitive Examination (CAMCOG) [20], the Mini-Mental State Examination (MMSE) [21], the Rapid Evaluation of Cognitive Function (ERFC) [22], the Alzheimer Disease Assessment Scale–Cognitive Subscale (ADAS-Cog) [23], and the Montreal Cognitive Assessment (MoCA) [24].
Concerning the exercise programs, only exercise activities that required increased energy output without taking frequency or intensity into account were included. All intervention groups from studies with a combination of physical exercise and cognitive training were excluded. However, their control groups were included if they met our search criteria.
Exercise intervention and control group classification
Walking, stretching, toning, kinesiotherapeutic exercise, music-based dance therapy, ergometer cycling, as well as generally specified “aerobic exercise” were classed as aerobic exercise. When the intervention program included high-intensity functional exercise, strengthening exercise with own body weight, or exercise with dumbbells, we classed it as resistance exercise.
According to the activities that were prescribed, we divided the control groups into two categories - active and passive control groups. All the control groups with activities that could have potentially been beneficial for cognitive functions (for example, attention-control educational programs, social visits, or recreational activities such as card playing or home craftwork) were categorized as the active control groups. Control groups asked to maintain their usual activities were categorized as the passive control groups.
We also analysed information about the length of intervention, the duration of exercise per week, and female ratios.
Search strategy
The analysis was conducted by identifying relevant papers referenced in the Web of Science, Scopus, and PubMed. Search terms used in all databases are presented in Table 2.
Table 2 Search results in electronic databases
DATABASE
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KEY
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NUMBER
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Web of Science
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TITLE: (dementia) OR TITLE: ("Alzheimer disease") OR TITLE: ("cognitive function") OR TITLE: ("cognitive impairment") AND TITLE: ("physical activity") OR TITLE: (exercise) OR TITLE: (training) AND TOPIC: (randomized) OR TOPIC: (trial)
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489
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Scopus
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( ( TITLE ( dementia ) OR TITLE ( "Alzheimer disease" ) OR TITLE ( "cognitive impairment" ) OR TITLE ( "cognitive function" ) ) ) AND ( ( TITLE ( "physical activity" ) OR TITLE ( exercise ) OR TITLE ( training ) ) ) AND ( ( TITLE-ABS-KEY ( randomized ) OR TITLE-ABS-KEY ( trial ) ) )
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612
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PubMed
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Search (((((((dementia[Title]) OR "Alzheimer disease"[Title]) OR "cognitive impairment"[Title]) OR "cognitive function"[Title]))) AND (((("physical activity"[Title]) OR exercise[Title]) OR training[Title]))) AND ((randomized[Title/Abstract]) OR trial[Title/Abstract])
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329
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Data extraction and quality assessment
All potential papers were first downloaded into EndNote. Then, our three reviewing authors (LS, AT, and MS) deleted all the duplicates and scanned the titles and abstracts of the papers in order to identify studies that had the potential to meet the eligibility criteria. Full texts were subsequently assessed for eligibility. Any disagreements among the reviewers (KD, and IH) were resolved through discussions. We used the Physiotherapy Evidence Database (PEDro) scale to assess the methodological quality of the included studies [25].
We collected the following data for both the exercise groups and control groups separately: baselines and after intervention means with 95% confidence interval (CI) and/or standard deviation (SD); and if described, also the mean of post-pre intervention score with SD or 95% CI were collected. Additionally, for factors or covariates for general linear models, we collected information about the type of exercise or control group activities, age of participants, sex of participants, length of interventions, and frequency of exercise.
Cognitive impairment classification
We divided the participants into three categories according to the level of their cognitive impairment: mild, mild to moderate, and moderate to severe impairment. In the classification, we used a 95% CI of the baseline mean in the standardized 100 points scale. Mild cognitive impairment = the lower 95% CI > 65.0 points, mild to moderate cognitive impairment = the lower 95% CI > 57 to points, and moderate to severe impairment = the upper 95% CI < 60 points. This division was in concordance with the standard diagnostic of cognitive impairment according to MMSE [26]. We could say with 95% certainty that in the mild impairment group there were not participants with less than 20.1 points, in the mild to moderate impairment group there were not participants with less than 17.1 points and in the moderate to severe impairment group, there were not any participants with higher than 18 points.
Data analysis
The sample size and mean post-pre intervention score with standard deviation (SD) from intervention as well as control groups were used to calculate the standardized mean differences (SMD). The random effect models were used for all the analyses [27]. To assess the heterogeneity I2 was considered. A rough guide to the interpretation of I2 is as follows: 0 to 40% might not be important, 30% to 60% may represent moderate heterogeneity, 50% to 90% may represent considerable heterogeneity, and 75% to 100% represents substantial heterogeneity [28]. Additionally, we standardized all the mean of the baseline score and post-pre intervention score from all the groups separately onto the 100 points scale. Then generalized linear models were used to estimate the influences of selected factors and covariates to the standardized post-pre intervention score as the continual dependent variable. We calculated an unstandardized coefficient beta (B), standard error (SE) and 95% CI. B represents the amount by which dependent variable changes if we change independent variable by one unit keeping other independent variables constant. If 95 % CI does not cross the 0 then the result is statistically significant. Statistics were calculated using RevMan 5.3 and IBM SPSS Statistics 24.