Current evidence on the association of tongue strength with cognitive decline in older adults and the known risk factors of frailty, sarcopenia and nutritional health: a scoping review protocol

Abstract

Introduction
Evidence suggests that the pathology underlying cognitive decline leading to dementia begins 15–20 years before cognitive symptoms emerge. Thus, identifying biomarkers in this preclinical phase is critically important. Age-related decrease in muscle mass and strength, a known risk factor for sarcopenia, frailty and cognitive decline, also affects the tongue. This paper describes an a priori protocol by a multidisciplinary team to address the following questions relating to adults ≥50 years of age: (1) What is the current evidence on the association of tongue strength with cognitive decline? (2) How does tongue strength associate with frailty and sarcopenia? (3) What is the association of tongue strength with nutritional health?

Methods and analysis
Search terms will be identified then multiple electronic databases (PubMed, PsycINFO (Ovid), Scopus, Embase (Ovid), CINAHL and Web of Science) searched systematically for peer-reviewed articles published in English that address the following inclusion criteria: (1) human studies, (2) participants ≥50 years of age and (3) studies with tongue pressure values measured in relation to at least one of the following: frailty, sarcopenia, nutritional health, cognitive function and dementia (Alzheimer’s, vascular, frontotemporal and Lewy body). Grey literature also will be searched to identify additional studies, clinical trials and policy papers appropriate for inclusion. The search will be from database inception. After removing duplicates, two research team members will independently screen abstracts and identify articles for full-text review. The team will use a data charting tool for data extraction. Data will be analysed quantitatively and qualitatively.

Ethics and dissemination
The scoping review does not require ethics approval as data will be from publicly available sources. Results will be disseminated in workshops and conferences and a peer-reviewed journal paper.

Full text

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YitbarekGY, etal. BMJ Open 2023;13:e076005. doi:10.1136/bmjopen-2023-076005
Open access
Current evidence on the association of
tongue strength with cognitive decline
in older adults and the known risk
factors of frailty, sarcopenia and
nutritional health: a scoping
review protocol
Getachew Yideg Yitbarek ,1,2 Jane Alty ,1,3,4 Katherine Lawler ,1,5
Lynette Ruth Goldberg 1
To cite: YitbarekGY, AltyJ,
LawlerK, etal. Current
evidence on the association
of tongue strength with
cognitive decline in older adults
and the known risk factors
of frailty, sarcopenia and
nutritional health: a scoping
review protocol. BMJ Open
2023;13:e076005. doi:10.1136/
bmjopen-2023-076005
►Prepublication history for
this paper is available online.
To view these les, please visit
the journal online (http://dx.doi.
org/10.1136/bmjopen-2023-
076005).
Received 25 May 2023
Accepted 22 September 2023
For numbered afliations see
end of article.
Correspondence to
Getachew Yideg Yitbarek;
getachewyideg. yitbarek@ utas.
edu. au
Protocol
© Author(s) (or their
employer(s)) 2023. Re- use
permitted under CC BY- NC. No
commercial re- use. See rights
and permissions. Published by
BMJ.
ABSTRACT
Introduction Evidence suggests that the pathology
underlying cognitive decline leading to dementia begins
15–20 years before cognitive symptoms emerge. Thus,
identifying biomarkers in this preclinical phase is critically
important. Age- related decrease in muscle mass and
strength, a known risk factor for sarcopenia, frailty and
cognitive decline, also affects the tongue. This paper
describes an a priori protocol by a multidisciplinary team to
address the following questions relating to adults ≥50 years
of age: (1) What is the current evidence on the association of
tongue strength with cognitive decline? (2) How does tongue
strength associate with frailty and sarcopenia? (3) What is
the association of tongue strength with nutritional health?
Methods and analysis Search terms will be identied
then multiple electronic databases (PubMed, PsycINFO
(Ovid), Scopus, Embase (Ovid), CINAHL and Web of Science)
searched systematically for peer- reviewed articles published
in English that address the following inclusion criteria: (1)
human studies, (2) participants ≥50 years of age and (3)
studies with tongue pressure values measured in relation to
at least one of the following: frailty, sarcopenia, nutritional
health, cognitive function and dementia (Alzheimer’s,
vascular, frontotemporal and Lewy body). Grey literature also
will be searched to identify additional studies, clinical trials
and policy papers appropriate for inclusion. The search will
be from database inception. After removing duplicates, two
research team members will independently screen abstracts
and identify articles for full- text review. The team will use a
data charting tool for data extraction. Data will be analysed
quantitatively and qualitatively.
Ethics and dissemination The scoping review does not
require ethics approval as data will be from publicly available
sources. Results will be disseminated in workshops and
conferences and a peer- reviewed journal paper.
INTRODUCTION
Current evidence suggests that the process of
neuropathological change underlying cogni-
tive decline leading to dementia occurs 15–20
years before the symptoms of dementia,
particularly those associated with Alzheimer’s
disease (AD), become apparent.1 2 A period
of 15–20 years is known as the preclinical
stage of dementia. In this preclinical stage,
abnormal accumulation of proteins such as
amyloid- beta (Aβ) and phosphorylated tau
(p- tau) accumulate in the brain.3 Developing
accessible biomarkers to facilitate early identi-
fication of dementia risk is critically important
to prevent up to 40% of dementia cases and
delay the progression of the condition.4
There is now a protocol of blood- based and
brain imaging biomarkers to detect preclin-
ical AD. While valuable, these biomarkers are
invasive and/or expensive, and frequently
difficult to access. There is increasing urgency
to identify non- invasive, affordable and readily
STRENGTHS AND LIMITATIONS OF THIS STUDY
⇒The review will be based on articles retrieved from
six large databases and a broad range of grey litera-
ture, including clinical trials and government reports.
⇒The review will be reported in compliance with
Preferred Reporting Items for Systematic Reviews
and Meta- Analyses Extension for Scoping Reviews
guidelines for scoping reviews to ensure complete-
ness and transparency.
⇒Healthcare providers and experts working in the
eld, particularly at the Wicking Centre’s ISLAND
Cognitive Clinic, ISLAND Project (Island Study
Linking Ageing and Neurodegenerative Disease) and
the Royal Hobart Hospital, will be involved through-
out the review process to identify evidence gaps and
ensure completeness.
⇒Critical appraisal of the quality of the included stud-
ies will be done.
⇒A limitation is that only literature published in
English will be included.
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accessible measures to assess people’s risk for dementia.
Identified non- invasive biomarkers include changes in
movement (speed, rhythm, accuracy) and strength, specif-
ically in walking (gait),5 hand grip strength6 and finger
tapping variability.7 Changes in movement and strength
have also been documented in the tongue, affecting
swallowing and speech production.8 9 Results suggest
that such changes in the tongue could be further indi-
cators of cognitive decline, with neurological changes in
sensory, motor and language systems impairing cognitive
processing and task performance.9 10 Therefore, assessing
tongue strength could play a significant role in predicting
cognitive decline.
Measurement of tongue strength is important for
multiple reasons. Changes in the muscle mass and
strength of the tongue are recognised as an oral compo-
nent of sarcopenia.8 11 Sarcopenia, the physical mani-
festation of frailty, is evident in slower gait speed and
decreased grip strength, known biomarkers of preclinical
AD.5 6 Sarcopenia, including oral sarcopenia, appears
to predict cognitive decline and incident AD dementia,
thought due to cellular inflammation, and decreased
muscle function.12 13 The frailty underlying sarcopenia is
commonly identified through five criteria: unintentional
weight loss, exhaustion, low physical activity, slowness and
weakness, with combinations of at least three of these
criteria defining a ‘frailty phenotype’.14 Limited educa-
tion, adverse socioeconomic circumstances and malnu-
trition can increase the risk of frailty.15 16 Early detection
and reduction of frailty and sarcopenia can prevent many
of the significant adverse health outcomes experienced
by older people, hence potentially contributing to the
preservation of cognitive function.
Decreased tongue strength also may reflect reduced
levels of brain- derived neurotrophic factor (BDNF), a
protein important in regulating and repairing neurons
and their connections in both the Central and Periph-
eral Nervous Systems.17 Evidence suggests that BDNF is
expressed and released by skeletal muscle, including the
tongue, and plays an important role in neuronal growth
and synaptic plasticity within neural circuits involved in
cognitive function.17 Maintaining muscle strength and
function plays a central role in the release of BDNF,
providing a potential link between muscle function and
brain function. In addition, decreased tongue strength
may be associated with cerebral blood flow in areas of the
brain responsible for cognitive functions.18
Further, decreased tongue strength can adversely affect
the management of food, including swallowing, with
consequences on nutritional health compounding sarco-
penia and frailty.19 20 Muscles of the tongue drive the swal-
lowing process. The loss of mass and strength in tongue
muscles can make ingestion of food more difficult, which
in turn can result in less food being consumed, thereby
contributing to malnutrition over time.21 The coordi-
nation of swallowing also may be affected, resulting
in aspiration of food, liquid and saliva, and increasing
vulnerability to aspiration pneumonia. Even if subtle,
chronic aspiration may result in respiratory insufficiency
and hypoxia, potentially affecting attention, executive
function and processing speed.22 Measuring tongue
strength is important in differentiating slowness and inco-
ordination in swallowing thought due to ageing (pres-
byphagia) compared with swallowing that is disordered
(dysphagia),21 22 with potential adverse effects on cogni-
tive function.
Similarly, measuring tongue strength is an important
component when assessing the degree of neuromus-
cular involvement to differentiate types of dysarthria (a
motor speech disorder).23 In addition, difficulties with
accurate speech movements related to tongue strength
may result in decreased social engagement and cognitive
decline.24–26 Decreases in tongue pressure in older adults
have been found to correlate with lower Mini- Mental
State Examination scores and decreases in ability to make
rapid movements of the tongue on request.26 Although
relationships appear complex, investigators have specu-
lated that the link between tongue strength and cogni-
tive function may centre in social engagement where
decreased tongue pressure and dexterity affect intelli-
gibility and ease of speech, with consequent decreased
social engagement and cognitive stimulation, resulting in
cognitive decline.26
For these multiple reasons, tongue strength may be an
important and overlooked factor in predicting cognitive
decline. This paper describes an a priori protocol to map
current evidence for the association of tongue strength
with cognitive decline leading to dementia in older adults
and known risk factors for cognitive decline: frailty, sarco-
penia and nutritional health. Findings from the scoping
review will provide additional perspectives to direct subse-
quent research and inform policymakers, ultimately bene-
fiting older adults primarily and the broader community
at large. Figure 1 depicts the proposed conceptual frame-
work for tongue strength and its association with cognitive
decline and the known risk factors of frailty, sarcopenia
and nutritional health.
Research questions
Three research questions will be addressed:
1. What is the current evidence on the association of
tongue strength with cognitive decline in adults aged
≥50 years?
2. How does tongue strength associate with frailty and
sarcopenia in adults aged ≥50 years?
3. What is the association of tongue strength with nutri-
tional health in adults aged ≥50 years?
METHODS AND ANALYSIS
Protocol design
The proposed review will be conducted based on the
methodological framework introduced by Arksey and
O’Malley27 and in accordance with the Joanna Briggs
Institute (JBI) methodology for scoping reviews.28 This
protocol and the corresponding scoping review will
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be reported according to the standards for Preferred
Reporting Items for Systematic Reviews and Meta- Analyses
Extension for Scoping Reviews (PRISMA).29 The protocol
is registered at the Open Science Framework (https://
osf.io/2fq69).
Review criteria
The criteria for the review will be based on JBI’s Partic-
ipants, Context and Concept approach. The following
inclusion criteria will be employed to select studies
relating to older adults (Participants) in relation to their
cognitive function, the factors that are known to increase
the risk of cognitive decline: frailty, sarcopenia and nutri-
tional health (Context), and the association between
these factors and tongue strength (Concept).
Inclusion criteria
Studies will be eligible if they satisfy these inclusion
criteria: (1) human studies, (2) participants ≥50 years of
age and (3) studies with tongue pressure values measured
in relation to at least one of the following: frailty, sarco-
penia, nutritional health, cognitive function, cognitive
decline and dementia (Alzheimer’s, vascular, frontotem-
poral and Lewy body and (4) peer- reviewed and published
in English.
Exclusion criteria
Studies will be excluded if they meet the following
criteria: (1) animal studies, (2) participants younger
than 50 years or age not reported, (3) articles, clinical
trials, government reports, commentaries, conference
presentations, abstracts, letters, reviews and editorials
with no information on tongue strength measurement,
(4) tongue strength measured in relation to cachexia,
or other progressive neurological motor conditions, that
is, multiple sclerosis, Parkinson’s disease, amyotrophic
lateral sclerosis and (5) publications not written in
English.
Information sources
Six major databases will be searched from inception and
no publication date restrictions will be applied. The data-
bases are PubMed, PsycINFO (Ovid), Scopus, Embase
(Ovid), CINAHL and Web of Science. Grey literature also
will be searched to identify additional studies, clinical trials
and policy papers appropriate for inclusion. Reference
lists of key articles will be searched to identify additional
studies appropriate for inclusion. Handsearching of liter-
ature not available on electronic databases (websites of
key organisations and related professional associations)
also will be included.
Search strategy
The search strategy will be developed in an iterative
process by the research team. An academic librarian at
the University will be consulted to advise on a stepwise
searching process. The plan is to search with a combina-
tion of the following terms: (“Oral function” OR “tongue
strength” OR “tongue pressure” OR “tongue weakness”
OR “lingual pressure” OR “oral motor function” OR “oro-
motor” OR “oral hypofunction”) AND (dysphagia OR
presbyphagia, OR “deglutition disorder” OR “nutrition
disorder” OR undernutrition, OR “weight loss” OR frailty
OR “pre- frail” OR sarcopenia OR “muscle atrophy” OR
“muscle weakness” OR “muscle mass” OR “muscle func-
tion” OR “intramuscular fat” OR dementia OR “cognitive
dysfunction” OR “cognitive decline” OR cognition) AND
(ag?ing OR “older adults” OR aged OR frail elderly OR
elderly) (table 1). A pilot search to test the appropriate-
ness of key terms is presented in table 2.
Study records
Data management
JBI methodology for scoping reviews will be followed
to ensure that the review is conducted systematically,
transparently and rigorously. Searching will be made in
different databases and will be exported to both EndNote
and Covidence software to remove duplicates and find
full text articles. Covidence software will be used to screen
the articles. Data will be collected in a structured form
and entered into a Microsoft Excel database.
Selection process
The results of the database searches will be integrated,
and duplicates removed by the first author. Two members
of the research team will independently screen the titles
and abstracts of the identified papers to exclude those
that do not satisfy the inclusion criteria. Titles and
abstracts of the articles with questionable eligibility will
be reviewed by the research team. Disagreements about
eligibility will be discussed between the reviewers until a
Figure 1 Conceptual framework for tongue strength and
its association with cognitive decline in older adults, and the
known risk factors of frailty, sarcopenia and nutritional health,
developed after a comprehensive literature search.
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consensus is reached; an independent reviewer will arbi-
trate if necessary.
Full- text articles will be retrieved for the remaining
articles (or articles not excluded during title and abstract
screening) and reviewed independently by two members
of the research team to ensure they meet eligibility.
Disagreements will be resolved via consensus or arbitra-
tion with a third reviewer. Articles continuing to meet the
eligibility criteria will be included in the review. A Kappa
score will be calculated to identify the level of agreement
between reviewers while selecting the title/abstract and
full- text article.30 A moderate level of agreement between
Table 1 Suggested keywords and MeSH terms to be used in the nal database search
Search terms
Keywords and MeSH
terms Combination of keywords and MeSH terms
Tongue strength (Concept) Keywords Oral function, tongue strength, tongue pressure, tongue
weakness, lingual pressure, oral motor function, oromotor, oral
hypofunction
Swallowing ability (Context) Keywords Dysphagia, presbyphagia
MeSH Deglutition disorder (MeSH)
Malnutrition (Context) Keywords Nutrition disorder, undernutrition, weight loss
MeSH terms Nutrition disorder (MeSH)
Frailty (Context) Keywords Frailty, pre frail
MeSH terms Frailty (MeSH)
Sarcopenia (Context) Keywords Sarcopenia, muscular weakness, muscle mass, muscle function,
intramuscular fat
MeSH terms Sarcopenia, muscular weakness, muscular atrophy
Dementia (Context) Keywords Dementia, cognitive dysfunction, cognition, cognitive decline,
cognitive impairment
MeSH terms Dementia, cognitive dysfunction
Older adults (Population) Keywords Older adult, ag?ing, elderly
MeSH terms Older adult, aged, frail elderly
?: truncation used.
MeSH, Medical Subject Heading.
Table 2 Pilot search, completed on 12 February 2023, on PubMed database to test the appropriateness of key terms
Search Query Results
#10 (#9) NOT (animal) 373
#9 (((#1)) AND (#7)) AND (#8) 375
#8 ((((#2) OR (#3)) OR (#4)) OR (#5)) OR (#6) 1 034 413
#7 (((((Older adults[MeSH Terms]) OR (aged(MeSH Terms))) OR (frail elderly(MeSH Terms))) OR
(Older adult*[Title/Abstract])) OR (ag?ing[Title/Abstract])) OR (elderly*[Title/Abstract])
3 535 786
#6 ((((((Dementia[Title/Abstract]) OR (cognitive dysfunction[Title/Abstract])) OR (cognition[Title/
Abstract])) OR (cognitive decline[Title/Abstract])) OR (cognitive impairment[Title/Abstract]))
OR (Dementia(MeSH Terms))) OR (cognitive dysfunction[MeSH Terms])
397 865
#5 (((((((Sarcopenia[Title/Abstract]) OR (muscular weakness[Title/Abstract])) OR (muscle
mass[Title/Abstract])) OR (muscle function[Title/Abstract])) OR (intramuscular fat[Title/
Abstract])) OR (muscular atrophy[MeSH Terms])) OR (sarcopenia[MeSH Terms])) OR
(muscular weakness[MeSH Terms])
67 976
#4 ((Frailty[Title/Abstract]) OR (pre frail[Title/Abstract])) OR (frailty[MeSH Terms]) 24 056
#3 (((((Nutrition disorder[MeSH Terms])) OR (Nutrition disorder[Title/Abstract])) OR
(undernutrition[Title/Abstract])) OR (weight loss[Title/Abstract]))
493 959
#2 ((dysphagia[Title/Abstract]) OR (presbyphagia[Title/Abstract])) OR (Deglutition
disorder[MeSH Terms])
76 122
#1 ((((((Oral function[Title/Abstract]) OR (tongue strength[Title/Abstract])) OR (tongue
pressure[Title/Abstract])) OR(tongue weakness[Title/Abstract])) OR (lingual pressure[Title/
Abstract])) OR (oral motor function[Title/Abstract])) OR (oral hypofunction[Title/Abstract])
2120
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reviewers will be considered the minimal requirement. If
the agreement is less, the eligibility criteria will be revised
and used consistently. The process of study selection will
be reported using a PRISMA flow chart.
Data collection process
A data extraction form will be created by the team based
on the preliminary scoping phase. The form will include
all the variables identified to answer the research ques-
tions (table 3). The data will be charted in Microsoft
Excel.
All reviewers will complete a pilot test of the extraction
form on a sample of the included studies. Discrepancies
in extracted data will be discussed between reviewers until
consensus is reached or by arbitration of another inde-
pendent reviewer, if required. Consistent use of the form
between reviewers will be checked. The extraction form
will be revised as needed.
Data items
Alongside standard bibliographical information (ie, age
group, mean age, authors, title, journal and year of publi-
cation), objectives of each included article, outcomes
assessed and conclusions and recommendations in rela-
tion to tongue strength will be extracted. Information
on tongue strength, the device used to measure tongue
strength, characteristics of the study populations, defi-
nitions and measurements of frailty, sarcopenia and
nutritional health, measurement of muscle mass, muscle
strength and any factors associated with tongue strength
status will be documented. Tools used to assess cogni-
tive function, including any neuropsychological battery,
and their relationship with tongue strength status will be
documented. The level of tongue strength according to
cognitive function: normal cognitive function, preclinical
stage, subjective cognitive impairment, mild cognitive
impairment and dementia, will also be documented.
Authors or coauthors of the retrieved articles will be
contacted if the information sought is missing in the full-
text paper.
Outcomes and prioritisation
Analysis of the extracted data will provide information on
the body of research that has been conducted on tongue
strength in relation to cognitive decline and the factors
that are known to increase the risk of cognitive decline:
frailty, sarcopenia and nutritional health. Analysis also
will identify areas that require further investigation.
Documentation of the limitations of each of the reported
studies will guide and direct the next research steps.
Risk of bias in individual studies
A formal quality assessment will be conducted for each
of the included articles. The quality of evidence will be
documented using the Grading of Recommendations,
Assessment, Development and Evaluation (GRADE)
framework.31 The JBI critical appraisal tool for randomised
controlled trial and observational studies28 will be used
for risk of bias assessment of each included article.
Condence in cumulative evidence
Three reviewers will be involved to assess quality of
evidence and resolve any disagreement. For each
included article, each reviewer will follow the four
levels of evidence defined in the GRADE protocol31
(high, moderate, low, very low). Evaluation of the
type of study design will determine an initial ‘high’
(randomised controlled trial) or ‘low’ (observational)
Table 3 Proposed data extraction form for each of the included studies
Parameters Details Remark
Bibliographic information Authors, year of publication, country of publication.
Study characteristics Objective(s) of the study, study design, sample size, mean age, mean/
median tongue strength, tongue strength assessment device.
Study context Sarcopenia Diagnostic methods (European Working Group on Sarcopenia in
Older People, Asian Working Group for Sarcopenia or any criteria
used) or subcomponents (walking speed, grip strength and skeletal
muscle mass index) considered to dene sarcopenia.
Cognitive decline Data in relation to the stage of the disease (preclinical, SCI, MCI,
dementia and type of dementia).
Frailty The specic criteria used to assess frailty. Percentage of frail and not-
frail population in relation to tongue strength status.
Nutritional status The nutritional assessment method employed and the cut- off value
used to rank nutritional status.
Outcomes Key ndings related to the review questions: tongue strength status
of participants in relation to cognitive decline, frailty, sarcopenia and
nutritional health.
Quality assessment Recommendations and limitations reported from each study, along
with independent quality assessment.
MCI, mild cognitive impairment; SCI, subjective cognitive impairment.
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quality rating. Evaluation of risk of bias, inconsis-
tency, indirectness, imprecision and publication bias
may lower the quality rating. Evaluation of reported
effect size, dose response and control of confounding
variables may increase the quality rating. The GRADE
framework, applied to each included article, will ensure
confidence that a careful and systematic approach has
been undertaken to document the quality of current
evidence on the association of tongue strength with
cognitive decline in older adults in relation to frailty,
sarcopenia and nutritional health.
Data synthesis
Data from the included studies will be summarised and
results presented in tables and figures, as appropriate.
Quantitative analysis will be conducted using descrip-
tive methods, including frequencies, means and
medians; qualitative data will be analysed thematically
in four major categories relating to tongue strength
(cognitive decline, frailty, sarcopenia and nutritional
health). Gaps and limitations of the included studies
also will be documented.
Consultation
The Arksey and O’Malley methodological approach
includes an optional consultation with stakeholders
and experts throughout the review process.27 To
ensure this scoping review is relevant, comprehen-
sive and meaningful to those who will use or benefit
from the outcomes, an interdisciplinary team of a
speech pathologist, neurologist and physiotherapist
will guide the review. This interdisciplinary team will
seek ongoing input from community members, policy-
makers, researchers and healthcare providers who are
working to reduce dementia risk. These consultants
will include staff working at the Wicking Centre’s
ISLAND Cognitive Clinic,32 the Wicking Centre’s
ISLAND Project33 and at the Royal Hobart Hospital.
All will be invited to three meetings to discuss and
provide feedback on 1) the proposed review process
and study design, (2) results of the search and (3)
plans for dissemination of the results.
Patient and public involvement
No patients were involved in the development of this
protocol. Members of the public are involved and are
included in the consultants described in the previous
section.
Changes to the protocol
Due to the wide- ranging and investigative nature of
a scoping review, alterations to the protocol may be
necessary as new data come to light. Any discrepancies
or enhancements to the protocol, along with an expla-
nation for these adjustments, will be explicitly noted
in the reporting of the results of the reviews.
Ethics and dissemination
Because the scoping review methodology will synthesise
evidence from publicly available sources, this study does
not require ethics approval.
The scoping review will provide a comprehensive over-
view of current evidence on the association of tongue
strength with cognitive decline in older adults and the
factors that are known to increase the risk of cognitive
decline: frailty, sarcopenia and nutritional health. The
review will highlight areas where evidence is debatable
or lacking. Results will be disseminated in workshops and
through social media for those interested in dementia
risk reduction. A paper reporting the findings of the
review will be submitted to a scientific journal for publi-
cation and data will be presented at relevant conferences.
DISCUSSION
This scoping review aims to investigate the current
evidence on the association of tongue strength with
cognitive decline and dementia in older people and the
known risk factors of frailty, sarcopenia and nutritional
health. This review has substantial potential impact as
evaluating tongue strength may be an important, and
overlooked, factor in predicting cognitive decline leading
to dementia.
This protocol is strengthened by establishing a kappa
score to show the consistency between raters when
screening studies from their titles to abstracts and full
texts, and by using the GRADE framework to document
the quality of each included study to ensure confidence
that a careful and systematic approach has been under-
taken to document the quality of current evidence on the
association of tongue strength with cognitive decline in
older adults in relation to frailty, sarcopenia and nutri-
tional health.
A key limitation of the planned review is that it will
focus solely on articles published in English. If there are
any differences or deviations required in the implementa-
tion of this protocol, these amendments will be explicitly
described and justified in the published paper.
Author afliations
1Wicking Dementia Research and Education Centre, University of Tasmania, Hobart,
Tasmania, Australia
2Biomedical Sciences Department (Medical Physiology Unit), College of Medicine
and Health Science, Debre Tabor University, Debre Tabor, Ethiopia
3School of Medicine, University of Tasmania, Hobart, Tasmania, Australia
4Neurology Department, Royal Hobart Hospital, Hobart, Tasmania, Australia
5School of Allied Health, Human Services and Sport, La Trobe University, Melbourne,
Victoria, Australia
Twitter Jane Alty @janealty1, Katherine Lawler @KateLawlerPT and Lynette Ruth
Goldberg @LynGoldberg7
Contributors GYY, LRG and JA conceptualised the review idea, formulated review
questions, developed the search strategy, created the data extraction framework
and drafted the initial version of the review protocol. LRG and JA provided general
guidance to GYY and supervised the work. GYY, LRG, JA and KL critically revised the
protocol. All authors made substantial intellectual contributions to the development
and draft of this protocol and read and approved the nal review protocol
manuscript.
on October 29, 2023 by guest. Protected by copyright.http://bmjopen.bmj.com/BMJ Open: first published as 10.1136/bmjopen-2023-076005 on 28 October 2023. Downloaded from

7
YitbarekGY, etal. BMJ Open 2023;13:e076005. doi:10.1136/bmjopen-2023-076005
Open access
Funding This work is supported by funding from J.O. and J.R. Wicking Trust (Equity
Trustees).The funder has no direct involvement in the study design, data collection,
data analysis and manuscript writing. The work also is supported by a scholarship
for PhD study to the rst author by the College of Health and Medicine, University
of Tasmania.
Competing interests The authors have no potential conicts of interest with
respect to the research, authorship, and/or publication of this protocol.
Patient and public involvement Patients and/or the public were involved in the
design, or conduct, or reporting, or dissemination plans of this research. Refer tothe
Methods section for further details.
Patient consent for publication Not applicable.
Provenance and peer review Not commissioned; externally peer reviewed.
Open access This is an open access article distributed in accordance with the
Creative Commons Attribution Non Commercial (CC BY- NC 4.0) license, which
permits others to distribute, remix, adapt, build upon this work non- commercially,
and license their derivative works on different terms, provided the original work is
properly cited, appropriate credit is given, any changes made indicated, and the use
is non- commercial. See:http://creativecommons.org/licenses/by-nc/4.0/.
ORCID iDs
Getachew YidegYitbarek http://orcid.org/0000-0001-9823-9981
JaneAlty http://orcid.org/0000-0002-5456-8676
KatherineLawler http://orcid.org/0000-0002-1484-1113
Lynette RuthGoldberg http://orcid.org/0000-0002-8217-317X
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on October 29, 2023 by guest. Protected by copyright.http://bmjopen.bmj.com/BMJ Open: first published as 10.1136/bmjopen-2023-076005 on 28 October 2023. Downloaded from