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Archives of Gerontology and Geriatrics 117 (2024) 105181
Available online 6 September 2023
0167-4943/© 2023 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).
Towards an operational denition of oral frailty: A e-Delphi study
Karl G.H. Parisius
a
,
b
,
*
, Merel C. Verhoeff
a
, Frank Lobbezoo
a
, Limor Avivi-Arber
c
, Joke Duyck
d
,
Hirohiko Hirano
e
, Katsuya Iijima
f
, Barbara Janssens
g
, Anastassia Kossioni
h
, Chia-Shu Lin
i
,
Gerald McKenna
j
, Frauke Müller
k
, Martin Schimmel
k
,
l
, Anita Visser
m
,
n
,
o
, Yutaka Watanabe
p
,
Robbert J.J. Gobbens
b
,
q
,
r
,
s
a
Department of Orofacial Pain and Dysfunction, Academic Centre for Dentistry Amsterdam, ACTA, University of Amsterdam, The Netherlands
b
Faculty of Health, Sports and Social Work, Inholland University of Applied Sciences, The Netherlands
c
University of Toronto, Canada
d
Department of Oral Health Sciences, KU Leuven, Belgium
e
Tokyo Metropolitan Institute for Geriatrics and Gerontology, Japan
f
Institute for Future Initiatives, Institute of Gerontology, The University of Tokyo, Japan
g
Department of Oral Health Sciences, Gerodontology, ELOHA (Equal Lifelong Oral Health for All) research group, Ghent University, Belgium
h
Division of Gerodontology, Department of Prosthodontics, Dental School, National and Kapodistrian University of Athens, Greece
i
Department of Dentistry, National Yang Ming Chiao Tung University, Taiwan
j
Centre for Public Health, Queen’s University Belfast, Northern Ireland United Kingdom
k
Division of Gerodontology and Removable Prosthdontics, University Clinics of Dental Medicine, University of Geneva, Switzerland
l
Department of Reconstructive Dentistry and Gerodontology, school of Dental Medicine, University of Bern, Switzerland
m
Department of Gerodontology, Center for Dentistry and Oral Hygiene, University of Groningen, The Netherlands
n
University Medical Center Groningen, The Netherlands
o
Department for Gerodontology, College of Dental Sciences, Radboud University Nijmegen Medical Centre, The Netherlands
p
Gerodontology, Department of Oral Health Science, Faculty of Dental Medicine, Hokkaido University, Hokkaido, Japan
q
Zonnehuisgroep Amstelland, The Netherlands
r
Department Family Medicine and Population Health, Faculty of Medicine and Health Sciences, University of Antwerp, Belgium
s
Department of Tranzo Academic Centre for Transformation in Care and Welfare, Faculty of Behavioural and Social Sciences, Tilburg University, The Netherlands
HIGHLIGHTS
•This study establishes a consensus on an operational denition of oral frailty.
•An international expert panel assessed 55 potential components of oral frailty.
•Oral frailty constitutes mastication, swallowing, oral motor skill, and salivation.
•Based on these ndings a revised method for assessing oral frailty is recommended.
ARTICLE INFO
Keywords:
Oral frailty
Oral function
Operational denition
Modied e-Delphi study
International consensus
ABSTRACT
Objectives: Building upon our recently developed conceptual denition of oral frailty (the age-related functional
decline of orofacial structures), this e-Delphi study aims to develop an operational denition of oral frailty by
identifying its components.
Methods: We used a modied e-Delphi study to reach a consensus among international experts on the components
of oral frailty. Twelve out of fteen invited experts in the eld of gerodontology participated. Experts responded
to three rounds of an online 5-point scale questionnaire of components to be included or excluded from the
operational denition of oral frailty. After each round, scores and rationales were shared with all experts, after
which they could revise their position. A consensus was reached when at least 70% of the experts agreed on
whether or not a component should be included in the operational denition of oral frailty.
* Corresponding author at: Department of Orofacial Pain and Dysfunction, Academic Centre of Dentistry Amsterdam (ACTA), University of Amsterdam and Vrije
Universiteit Amsterdam, Room 3N-75, Gustav Mahlerlaan 3004, 1081 LA Amsterdam, The Netherlands.
E-mail address: k.g.h.parisius@acta.nl (K.G.H. Parisius).
Contents lists available at ScienceDirect
Archives of Gerontology and Geriatrics
journal homepage: www.elsevier.com/locate/archger
https://doi.org/10.1016/j.archger.2023.105181
Received 29 July 2023; Received in revised form 1 September 2023; Accepted 4 September 2023
Archives of Gerontology and Geriatrics 117 (2024) 105181
2
Results: The experts achieved a high level of agreement (80 – 100%) on including eight components of oral frailty
and excluding nineteen. The operational denition of oral frailty should include the following components: 1)
difculty eating hard or tough foods, 2) inability to chew all types of foods, 3) decreased ability to swallow solid foods,
4) decreased ability to swallow liquids, 5) overall poor swallowing function, 6) impaired tongue movement, 7) speech or
phonatory disorders, and 8) hyposalivation or xerostomia.
Conclusion: This e-Delphi study provided eight components that make up the operational denition of oral frailty.
These components are the foundation for the next stage, which involves developing an oral frailty assessment
tool.
1. Introduction
When people age, the risk for oral health problems increases
(Chalmers & Ettinger, 2008; Farias et al., 2020; Petersen & Ogawa,
2018). The consequences of oral health problems extend beyond the
mouth and have been linked to numerous adverse general health out-
comes, especially in older people (de Sire et al., 2022; Hakeem et al.,
2020; Hiltunen et al., 2021; Komatsu et al., 2021; Kuo & Lee, 2022;
Patel et al., 2021; Watanabe et al., 2020). To better understand the
consequences of the aging process on oral health and oral function, the
concept of oral frailty has emerged (JapanDentalAssociation, 2019). Yet,
a concept like oral frailty remains highly subjective in the absence of a
carefully articulated and consented denition (Podsakoff et al., 2016).
Therefore, preceding the present study, we analyzed existing denitions
of oral frailty in a scoping review and concluded that these denitions
were not adequately formulated at a conceptual level. In response, we
developed a new denition by synthesizing and conceptualizing the
essence of existing ones. We dened oral frailty as the age-related
functional decline of orofacial structures (Parisius et al., 2022).
While a conceptual denition is essential in understanding what oral
frailty fundamentally is, and how it can be distinguished from other
related phenomena (e.g., oral hypofunction), it does not explain which
components (i.e., latent characteristics) oral frailty consists of. There-
fore, an operational denition is needed to convey the conceptual terms
into observable components of oral frailty. Subsequently, to assess oral
frailty, these components should be formulated in measurable terms
(viz., variables) (Boesjes-Hommes, 1970).
The literature still has ambiguity regarding the operationalization
and assessment of oral frailty. The most widely used oral frailty assess-
ment instrument is the one proposed by Tanaka et al. (2018). It consists
of six components: the number of natural teeth, chewing ability, artic-
ulatory oral motor skills for the "ta" sound, tongue pressure, subjective
difculty in eating tough foods, and subjective difculty swallowing. A
person is considered orally frail when at least three of these six com-
ponents score below a specied threshold. This instrument was devel-
oped in a Japanese cohort. While problems related to oral health in older
people are similar on a global scale, nuances may exist in different
populations. For example, Schimmel et al. (2022) concluded that
although articulatory oral motor skills play an essential role in assessing
orofacial function, the thresholds need to be revised for individuals who
are non-native speakers of Japanese. Furthermore, although researchers
have validated devices for measuring oral functions like tongue move-
ment and bite force in the Japanese population, most of these devices are
unavailable outside of Japan, which can impede cross-cultural research
and limit the generalizability of ndings (Schimmel et al., 2022).
In a recent study conducted in Finland by Hiltunen et al. (2021), oral
frailty showed a signicant association with Fried’s frailty phenotype (i.
e., unintentional weight loss, exhaustion, low physical activity, slow-
ness, and physical weakness) (Fried et al., 2001) and a strong relation-
ship with general health, nutrition, and need for help with activities of
daily living (ADL). Despite these ndings, Hiltunen et al. (2021) also
indicated that there is no international consensus on the components of
oral frailty. Remarkably, compared to Tanaka et al. (2018), oral frailty is
assessed with a different set of components in this study, namely: having
a dry mouth, the presence of food residues in the oral cavity, the
inability to keep the mouth open during an oral examination, unclear
speech, the need for food texture modication (pureed or soft food diet),
and the expression of pain during an oral examination. These compo-
nents are scored dichotomously (yes/no), with the sum reecting the
degree of oral frailty. Furthermore, Hiltunen et al. (2021) point out that,
unlike Tanaka et al. (2018), they cannot conrm that the number of
remaining teeth determines the severity of oral frailty.
The above indicates that there are divergent views among experts in
gerodontology and related elds on the key components of oral frailty,
the methods used to assess it, and the thresholds used in those methods.
Building on our new conceptual denition of oral frailty, this study aims
to establish a consensus among an international panel of experts on the
key components of oral frailty to develop an operational denition based
on their input.
2. Methods
2.1. Study design
We used a three-round modied e-Delphi (Keeney et al., 2011) (see
Data collection and data analysis) to reach a consensus on the components
of oral frailty among international expert panel members. The modied
aspect in this e-Delphi study relates to the rst round in which experts
were provided with a structured questionnaire rather than the more
traditional open-ended questionnaire. In addition, they were given the
option to include their own suggestions. A more detailed explanation
follows under Data collection and data analysis. The letter ’e’ in e-Delphi
refers to its electronic nature, indicating that the entire study is con-
ducted exclusively online. In addition, we followed an ‘all-rounds invi-
tation’ approach (Boel et al., 2021). This implies that experts were
allowed to participate in the second round irrespective of their partici-
pation in the rst round. This study was approved by the Academic
Centre for Dentistry Amsterdam’s ethical commission and registered
under le number #2021–6162.
2.2. Expert-panel members
For this study, 15 experts in the eld of gerodontology from different
regions and countries, were approached. These experts were all part of
our networks organized in international societies and associations such
as IADR (International Association of Dental Research) and ECG (Eu-
ropean College of Gerodontology). An expert was dened as an aca-
demic who is actively researching aspects of oral health in older people.
After receiving information about the study’s aim and procedure, the
experts were asked to participate. The number of Delphi participants
was set a priori at 10 – 15 experts. According to Delbecq & Gustafson
Glenview (1976), in cases where the expertise of the panel members is
relatively homogeneous, a group size of 10 – 15 is considered adequate
for conducting the Delphi process (Delbecq & Gustafson Glenview,
1976; Hsu CCS, 2007; Keeney et al., 2011).
2.3. Data collection and data analysis
Three online questionnaires (viz., round 1 till round 3) were used to
investigate which items the experts considered to be components of oral
K.G.H. Parisius et al.
Archives of Gerontology and Geriatrics 117 (2024) 105181
3
frailty. Two research team members (RG and FL) pilot-tested the ques-
tionnaires before each round. Aspects such as the length of the ques-
tionnaire, clarity of wording, content accuracy, response options,
structure, and overall clarity were reviewed as well. The questionnaires
were distributed using the application Qualtrics version 10.2022
(Qualtrics, Provo, UT). On the questionnaire’s welcome page, experts
were given information about the current round and instructions for
completion. They were given a three-week deadline and received re-
minders as the deadline approached, as well as one week after. A nal
reminder and personal message were sent if no response was received.
These experts were excluded from participating in that current round, if
no action was taken.
Round 1: We identied 17 components of oral frailty in the literature
during our scoping review aimed at developing the conceptual deni-
tion of oral frailty (Parisius et al., 2022). The experts were asked to rate
these 17 components following a structured item assessment (viz., on a
5-point Likert scale ranging from 1. Not at all important to 5. Extremely
important), and to provide a rationale for the score. The members of the
expert panel were given the opportunity to suggest any missing com-
ponents of oral frailty.
Round 2: We presented the components of oral frailty on which
consensus had been reached and allowed the experts to comment on
these. Items that did not reach consensus during round 1 were reiterated
in this round. To encourage convergence, anonymized ratings, expla-
nations, and comments from other panel members were included. Lastly,
the experts were asked to rate the importance of the open-ended items
suggested by their peers of round 1, using the same 5-point Likert scale.
Round 3: The experts received an individual questionnaire to reas-
sess the items on which they diverged from the consensus. The ques-
tionnaire included ratings, comments, and descriptive statistical
feedback from the previous rounds. In this round, the experts had the
opportunity to revise their opinion on these items. In doing so, an
attempt was made to achieve the highest possible consensus level.
If 70% or more of the experts gave an item a score of four or higher
on the 5-point Likert scale, it was considered a consensus that the item is
a component of oral frailty. If 70% or more of the experts rated an item
with a score of three or lower on the 5-point Likert scale, it was agreed
that the item does not qualify for being considered a component of oral
frailty. Any other outcome was considered to be a lack of consensus
(Hsu CCS, 2007; Keeney et al., 2011). The data was analyzed using IBM
SPSS Statistical Package version 27 (SPSS Inc., Chicago, IL). For each
round, expert scores were expressed in frequencies and percentages,
which were presented in tables. A owchart provides an overview of the
study (see Fig. 1).
3. Results
3.1. International Delphi expert panel members
Of the 15 experts invited, 13 agreed to participate in this e-Delphi
Fig. 1. Flowchart operational denition of oral frailty modied 3-round e-Delphi study.
K.G.H. Parisius et al.
Archives of Gerontology and Geriatrics 117 (2024) 105181
4
study, and two experts did not respond to our invitation. In round-1, 10
experts completed the questionnaire, and three did not respond. In
round-2 and round-3, 12 experts completed the questionnaire. Seven
experts are afliated with universities in a European country, four in an
East Asian country, and one in North America. Of the 12 participating
experts, nine hold a professorship, two hold a position as associate
professor, and one leads a research team promoting the independence
and mental health of older adults. The experts’ clinical and/or research
area included one or a combination, of the following: gerodontology,
prosthodontics, oral medicine, oral neurophysiology, and gerontology.
Further details can be found in Table 1.
3.2. Round 1
In the rst round, 17 items were presented to the experts. On six of
the 17 items, consensus to include was achieved, namely: 1) difculty
eating hard or tough foods, 2) decreased ability to swallow solid foods, 3)
decreased ability to swallow liquids, 4) overall poor swallowing function, 5)
impaired tongue movement, and 6) hyposalivation or xerostomia. On ve of
the 17 items, more than 70% of the experts scored three or lower,
leading to a consensus that these items should be left out of the opera-
tional denition of oral frailty. These ve items are: 1) a small number of
remaining teeth, 2) loss of posterior occlusion, 3) age-related oral hygiene
decline, 4) the decline in smooth and prompt actions of the jaw, and 5) a
small number of functioning teeth. No consensus was reached on the
remaining six items.
Therefore, these items, including the scores and the comments given
by the experts, were reiterated in the second round for reconsideration.
Finally, experts suggested 34 possible components of oral frailty for
further examination in round two.
3.3. Round 2
In the second round, the expert panel members were presented with
40 items (viz., six items on which no consensus was reached in the rst
round, and 34 items suggested by the experts). More than 70% of the
experts agreed that three of the six previously disagreed items should be
excluded. However, no consensus was reached on the remaining three
items: 1) the occurrence of spillage while eating, 2) reduced occlusal bite
force, and 3) articulatory oral motor skill for "ta". Furthermore, consensus
was reached to include two of the 34 items suggested by the experts: 1)
unable to chew all foods, and 2) speech impairment/ phonatory disorders.
The experts agreed to exclude 14 of the 34 items. No consensus was
reached on the remaining 24 items. Table 2 displays the exact scores and
consensus levels.
3.4. Round 3
During the evaluation of the 51 items in the rst two rounds, a
consensus was reached on including eight items, while 18 items were
agreed to be excluded (Table 2). In the third round, the experts were
provided with an individual questionnaire to reassess their position on
items where they initially stood outside the consensus. A higher
consensus level was achieved for six of the eight items on which experts
agreed to be components of oral frailty. Consensus levels for items
considered components of oral frailty ranged from 90 to 100% after
round three. Experts achieved higher consensus levels on 15 of the 18
items deemed not to be components of oral frailty, with consensus levels
ranging from 80 to 100% after round three. Table 2 contains further
details.
3.5. The operational denition of oral frailty
According to the majority of the experts in this modied e-Delphi
study, the operational denition of oral frailty consists of the following
eight components which can be grouped into four categories: 1)
Table 1
Delphi expert panel.
Expert University Position Expertise
Associate
Prof. Dr.
Limor
Avivi-
Arber
University of
Toronto, Canada
Associate professor
in prosthodontics
and oral
neurophysiology
Prosthodontics and
oral neurophysiology
Prof. Dr.
Joke
Duyck
KU Leuven,
Belgium
Professor of
Gerodontology and
removable
Prosthodontics
Gerodontology,
prosthodontics
Dr. Hirohiko
Hirano
Tokyo
Metropolitan
Institute for
Geriatrics and
Gerontology,
Japan
Director Department
of Dentistry and
Oral Surgery and
research team leader
Elderly independence
promotion
Prof. Dr.
Katsuya
Iijima
The University of
Tokyo, Japan
Professor of Institute
for Future Initiatives
(IFI), Director of
Institute
of Gerontology
(IOG)
Prevention of
sarcopenia-related
frailty, multi-
disciplinary
collaboration,
healthy ageing
Prof. Dr.
Barbara
Janssens
University Gent,
Belguim
Professor of
gerodontology
Oral health
promotion in older
adults, mobile dental
care, health services
research,
interprofessional
collaboration in oral
health.
Prof. Dr.
Anastassia
Kossioni
National and
Kapodistrian
University
of Athens, Greece
Professor of
gerodontology
Gerodontology
Prof. Dr.
Chia-Shu
Lin
National Yang
Ming Chiao Tung
University,
Taiwan
Professor Brain Neuroimaging,
Behavioral Dentistry,
Geriatric Dentistry,
Orofacial Pain
Prof. Dr.
Gerald
McKenna
Queen’s
University
Belfast, Northern
Ireland
Chair of Oral Health
Services Research
and Gerodontology,
Centre for Public
Health
Gerodontology,
Prosthodontics,
Restorative Dentistry,
Nutrition
Prof. Dr. hc.
Frauke
Müller
University of
Geneva,
Switzerland
Professor of
Gerodontology and
removable
Prosthodontics
Gerodontology and
removable
Prosthodontics
Prof. Dr.
Martin
Schimmel
University of
Bern, Switzerland
Chair of
Reconstructive
Dentistry and
Gerodontology
Prosthodontics,
Gerodontology,
Implantology,
Orofacial Function.
Prof. Dr.
Anita
Visser
University
Medical Center
Groningen,
University of
Groningen, The
Netherlands;
Radboud
University
Medical Center,
Radboud
University
Nijmegen The
Netherlands
Professor in geriatric
dentistry
Maxillofacial
prosthodontist.
Gerodontology,
Maxillo facial
prosthodontics.
Associate
Prof. Dr.
Yutaka
Watanabe
Hokkaido
University, Japan
Associate Professor
of Gerodontology,
Department of Oral
Health Science,
Faculty of Dental
Medicine
Epidemiology,
geriatrics, and
dentistry
K.G.H. Parisius et al.
Archives of Gerontology and Geriatrics 117 (2024) 105181
5
mastication (difculty eating hard or tough foods, and inability to chew all
types of foods); 2) swallowing (decreased ability to swallow solid foods,
decreased ability to swallow liquids, and overall poor swallowing function);
3) oral motor skill (impaired tongue movement, and speech or phonatory
disorders), and 4) salivation (hyposalivation or xerostomia).
4. Discussion
This modied three-round e-Delphi study aimed to reach a consensus
on the components that should be included in the operational denition
of oral frailty.
4.1. Consensus
In the present study, a total of 51 components were reviewed by eld
experts, including 17 sourced from literature and 34 newly suggested
items brought in by experts in the rst round of the e-Delphi study. The
experts determined that eight (16%) of the 51 items should be included
in the operational denition through consensus. Upon closer examina-
tion, the eight items can be grouped into four categories (Fig. 2):
mastication (difculty eating hard or tough foods and inability to chew all
types of foods); swallowing (decreased ability to swallow solid foods,
decreased ability to swallow liquids, and overall poor swallowing function);
oral motor skill (impaired tongue movement, and speech or phonatory dis-
orders); and salivation (hyposalivation or xerostomia). Consistent with the
conceptual denition of oral frailty, (Parisius et al., 2022) these com-
ponents reect the age-related functional decline in orofacial structures
and are commonly mentioned in scientic literature as factors associ-
ated with the general health decline of older people. This is supported by
a recent systematic review by Dibello et al. (2022), who found that
factors similar to the eight components identied in this study are
associated with adverse health outcomes in older individuals, including
mortality, physical frailty, functional disability, reduced quality of life,
hospitalization, and falls. The output of the present study will primarily
serve to develop an instrument to assess oral frailty, which will help to
investigate if and how oral frailty is associated with adverse health
outcomes. This knowledge is essential as it opens the possibility of
exploring interventions to prevent or reverse the deterioration of oro-
facial structures and improve oral frailty. However, when an assessment
shows that any of these oral functions (mastication, swallowing, oral
motor skill, and salivation) are deteriorating, a closer examination is
needed to determine the root cause. For example, swallowing problems
can have several causes beyond orofacial structures and thus oral frailty
(McCarty & Chao, 2021).
Of the 51 items, the experts agreed that 18 items (35%) should not be
part of the operational denition of oral frailty. These 18 items can be
condensed into four categories: dental status (the use of complete den-
tures, poor t of dentures, reduced occlusal vertical dimension, loss of pos-
terior occlusion, a small number of remaining teeth, and a small number of
functioning teeth); diet and eating (change in diet, food avoidance behavior,
Table 2
Final results after 3 rounds: components of oral frailty.
Source* Final
consensus
level
Final
result
COMPONENTS ON WHICH A CONSENSUS IS REACHED
1 The impaired functional
movement of the tongue.
L 100 incl
2 Decreased ability in swallowing
solid foods
L 100 incl
3 Oral dryness: hyposalivation and/
or xerostomia.
L 100 incl
4 Difculty in eating hard and/or
tough foods.
L 100 incl
5 Unable to chew all types of foods E 100 incl
6 Speech impairment/phonatory
disorders
E 92 incl
7 Decreased ability in swallowing
liquids.
L 90 incl
8 Overall poor swallowing function. L 90 incl
9 Loss of posterior occlusion. L 100 excl
10 Age-related physical frailty. L 100 excl
11 Reduced occlusal vertical
dimension
E 100 excl
12 Cognitive decline E 100 excl
13 Lower motivation to keep oral
health
E 100 excl
14 Age-related cognitive decline. L 92 excl
15 Breathing in coordination with
chewing and swallowing
E 92 excl
16 The use of complete dentures E 92 excl
17 Poor t of dentures E 92 excl
18 Change in diet E 92 excl
19 Increase in the number of
masticatory cycles
E 92 excl
20 Low eating-related quality of life E 92 excl
21 Food pocketing in the cheeks E 92 excl
22 Low number of remaining teeth. L 90 excl
23 Age-related oral hygiene decline. L 90 excl
24 Low number of functioning teeth. L 90 excl
25 Food avoidance behavior E 83 excl
26 The decline in smooth and prompt
actions of the jaw.
L 80 excl
27 The decline in smooth and prompt
actions of the lips.
L 80 excl
COMPONENTS ON WHICH NO CONSENSUS IS REACHED
28 Adaptive eating behaviors E 67 excl
29 Wet voice E 67 excl
30 Unhealthy periodontal condition E 67 excl
31 Reduced sensibility of the oral
mucosa
E 67 excl
32 Altered (deteriorated) quality of
saliva
E 67 excl
33 The occurrence of spillage while
eating.
L 67 excl
34 Oral diadochokinesis E 67 excl
35 Lack of facial expression E 67 excl
36 Physical frailty E 67 excl
37 Altered (dysgeusia) or lost
(ageusia) sense of
E 67 excl
38 Orofacial muscular activity E 59 excl
39 Choking while eating E 58 excl
40 Regular aspiration of liquid or
solid food
E 58 excl
41 Decreased ability in reducing food
into proper size for swallowing
E 58 excl
42 Drooling E 58 excl
43 Natural mechanical cleaning of
the mouth
E 58 excl
44 Weight loss E 58 excl
45 Articulatory oral motor skill for
"ta"
L 58 excl
46 Malnutrition E 50 excl
47 Sarcopenia E 50 excl
Table 2 (continued )
Source* Final
consensus
level
Final
result
48 Inability to keep the oral cavity
clean
E 50 excl
49 Coughing while eating E 50 excl
50 Reduced occlusal (bite) force L 50 excl
51 Maladaptive eating behaviors E 50 excl
incl =consensus on items to be included in the operational denition; excl =
consensus on items to be excluded from the operational denition.
L =Components sourced from literature; E =Components suggested by experts;
* 17 of the components were extracted from literature in our previously con-
ducted scoping review (Parisius et al., 2022), 34 of the components were sug-
gested by the experts.
K.G.H. Parisius et al.
Archives of Gerontology and Geriatrics 117 (2024) 105181
6
low eating-related quality of life, food pocketing in the cheeks, increase in the
number of masticatory cycles); age-related factors (age-related physical
frailty, cognitive decline, age-related cognitive decline, lower motivation to
keep oral health, and age-related oral hygiene decline); and oral motor skill
(breathing in coordination with chewing and swallowing, and the decline in
smooth and prompt actions of the jaw).
The experts had reasons for omitting these items despite them being
closely related to the included items. For example, items such as dif-
culty in eating hard or tough foods (included) and an increase in the number
of masticatory cycles (excluded) can be considered associated with one
another, as they both essentially reect masticatory impairment. The
excluded item is worded in a more technical manner, which causes it to
lose the essence of the matter, namely the ability to chew hard food. It is
further difcult to standardize, as the number of cycles per chewing
sequence not only depends on age and dental state but also on the type of
bolus chewed. The item that was included (difculty in eating hard or
tough foods) is more precisely worded within this context.
Additionally, nine items (viz., the use of complete dentures, poor t
of dentures, change in diet, food avoidance behavior, low eating-related
quality of life, age-related physical frailty, cognitive decline, lower
motivation to keep oral health, and age-related oral hygiene decline)
were excluded as they were considered too general or do not directly
reect the age-related decline of orofacial structures. Therefore, these
items do not align with the conceptual denition of oral frailty (Parisius
et al., 2022).
In summary, items were omitted due to their lack of relevance to the
concept of oral frailty or when having overlap with other items. In in-
stances of overlapping terminology, the item deemed most clear and
concise by the experts was retained.
The partial resemblance among some of the eight included items is
not an issue at this point. The four categories (mastication, swallowing,
oral motor skill, and salivation) along with the eight included items will
primarily serve as a guiding framework for developing the oral frailty
assessment tool; which our next study will focus on.
4.2. No consenus
The experts did not reach a consensus on 24 of the 51 items (47%).
This means that less than 70% of the experts agreed on whether or not
these items should be incorporated into the operational denition.
Although the absolute majority of the experts (i.e., between 51% and
69%) scored six items (viz., oral diadochokinesis, regular aspiration of
liquid or solid food, decreased ability in reducing food into proper size for
swallowing, orofacial muscular activity, articulatory oral motor skill for
“ta”, and choking while eating) with a 4 or higher, they were still omitted
from the operational denition due to the pre-determined 70%
consensus level. This implies that by omitting these items, potentially
essential aspects are left out of the operational denition. However,
upon closer inspection, it can be concluded that these items are either
extensions of or synonymous with items already included. The omission
of oral diadochokinesis may surprise some clinicians as it is commonly
assessed in clinical practice (e.g., in Japan) (Hara et al., 2013; Iijima
et al., 2017; Kugimiya et al., 2020; Sakayori et al., 2016; Satake et al.,
2019; Takeuchi et al., 2021; Watanabe et al., 2018; Watanabe et al.,
2017). However, in the context of an operational denition, the item
oral diadochokinesis would be too narrow in terms of speech and
phonation difculties and tongue movement. Difculty with speech and
tongue movement may also be related to the perceptual processing of
intra-oral stimuli. The oral diadochokinesis assessment only focuses on
motor aspects. Experts were unable to reach a consensus on this item due
to these considerations.
The highest degree of disagreement existed on another six items
(viz., coughing while eating, reduced occlusal (bite) force, maladaptive
eating behaviors, inability to keep the oral cavity clean, sarcopenia, and
malnutrition), with a response distribution in which 50% of the experts
scored 4 or higher and 50% scored 3 or lower. This reveals that the view
on these items remained inconsistent after three Delphi rounds. This
justies the omission of these six items. However, the great divergence
in the experts’ opinions on these aspects suggests a need for more
research and solid evidence.
The remaining 12 items received a score of 3 or lower from the
majority of experts (i.e., between 51% and 69%), meaning that these
items are not seen as adequate components of the operational denition
of oral frailty. Although a consensus was not reached on these particular
items, their exclusion from the operational denition does not under-
mine the overall assessment of the absolute majority of experts.
Despite their exclusion, however, it is fair to say that further inves-
tigation is needed on the excluded items and their association with oral
frailty, since research in this emerging eld is still in progress.
4.3. Comparison to existing instruments to assess oral frailty
As previously stated, Tanaka et al.’s oral frailty assessment method
(Tanaka et al., 2018) is the most commonly used. Our operational
denition shares similar components (viz., unable to chew all foods, dif-
culty in eating hard and/or tough foods, overall poor swallowing function)
with three components used by Tanaka et al., namely: chewing ability,
subjective difculty in eating tough foods, and subjective difculty in swal-
lowing. Regarding the other components, Tanaka et al. tend to rely more
heavily on technical or clinical measures (viz., tongue pressure and the
number of natural teeth), in contrast to our more function-oriented
approach. It is worth noting that there exists quite a difference in
research aims between this study and the study conducted by Tanaka
et al. The aim of the latter was assessing mortality risk, and for this, oral
function and oral health measures that are commonly used in Japan
were utilized. On the other hand, our objective is to develop an assess-
ment tool designed specically for the assessment of oral frailty.
Our operational denition only partially aligns with the instrument
developed by Hiltunen et al. (2021). While we share similarities in some
components, such as experiencing a dry mouth, requiring food texture
modication, and having unclear speech, there are notable differences
as well. Specically, our e-Delphi study experts have excluded items
equivalent to the presence of food residues in the oral cavity, the inability to
keep the mouth open during an oral examination, and the expression of pain
Fig. 2. Categorized components of oral frailty.
K.G.H. Parisius et al.
Archives of Gerontology and Geriatrics 117 (2024) 105181
7
during an oral examination.
4.4. Study limitations and strengths
A modied e-Delphi design was a practical choice for a study
involving participants from different geographical locations worldwide.
Electronic surveys allowed experts to participate at their convenient
time and from their international location, reducing the logistical
challenges and costs associated with in-person meetings. On the other
hand, this design also has its downsides regarding open discussions.
Although we gave experts outside the consensus a possibility to recon-
sider their position based on the arguments of fellow experts, the lack of
face-to-face interaction and real-time discussion can make it difcult for
experts to fully engage with each other’s arguments and perspectives.
Mainly when experts had contrasting scores, a more open verbal dis-
cussion might have led to a higher consensus level. However, when
panel members’ views differ strongly, the dynamics in a physical group
setting could lead to group pressure, resulting in a false consensus
(Mullen, 2003). Our modied e-Delphi design has the advantage that
group pressure through expert interaction plays only a minor role, if at
all.
Despite the international scope of this study, the location of the ex-
perts was not representative, as seven of the experts are from Europe,
four from East Asia, and one from North America. A broader perspective
on the operational denition of oral frailty could have been gathered if
experts from the Middle East, South America, Africa, and Australia had
also been included. However, average life expectancy varies widely from
country to country, and the population of older people with it. The top
ten countries with the highest average life expectancy consist of ve
European and ve Asian countries, while African countries are among
the bottom ten in this regard (Worldometers.info, 2023). It seems logical
that geriatrics may not be a research priority in countries with lower
average life expectancy, and a small population of older people makes it
difcult to nd experts to represent these regions.
In this study, we followed an ’all-rounds invitation’ approach (Boel
et al., 2021). Two experts who had not participated in the rst round
were thus allowed to join the second round. This raises concerns about
the effect of this approach on the nal outcome of this e-Delphi study,
considering these two experts did not share their views in the rst round.
Boel et al. (2021) examined the difference in response rate and nal
outcome between two approaches to a 3-round e-Delphi study. The rst
(most common) approach was to invite individuals only if they partic-
ipated in a previous round (respondents-only), and the second (alter-
native) approach was to invite individuals for each round, regardless of
their participation in the previous round (all-rounds invitation). Results
showed no difference between the ’respondents-only’ and ’all-rounds’
groups in mean (SD) scores, nor in the percentage of critical votes.
However, a higher overall response rate was found in the ’all-rounds
group’ (61%) compared to the ’respondents-only group’ (46%). Thus, it
can be concluded that the "all-rounds invitation approach" does not
affect the nal result of the e-Delphi study and is even more favorable in
terms of response rate. In this e-Delphi study, the response rate
improved from 77% in the rst round to 92% in the second and third
rounds.
It should be noted that research on this topic is still evolving and that
research evidence on oral frailty is limited outside Japan. Therefore, this
operational denition is primarily based on expert opinion and may be
subject to revision in the future as new evidence emerges. Our opera-
tional denition of oral frailty only includes physical components. It is
important to note that this denition will be associated with social, and
psychological components and background characteristics (e.g. sex,
education, income, marital status). To fully understand these associa-
tions further studies may be necessary. From a theoretical point of view,
it seems that oral frailty is related to other types of frailty (e.g. physical
frailty, psychological frailty). However, this has not yet been studied.
Before we suggest this in our work, we will conduct a study examining
the associations between our oral frailty assessment tool (based on the
operational denition presented in the current study) and other types of
frailty using well-known and frequently cited assessment tools.
Despite the limitations mentioned above, this operational denition
helps to establish a better understanding of the concept of oral frailty by
explicitly dening it in terms of observable components. Operational
denitions also allow for the objective measurement of concepts and
facilitate the replication of studies by other researchers, helping to build
a stronger foundation of knowledge in the eld. This is particularly
important when studying a complex and multidimensional concept such
as oral frailty, which may have multiple meanings and interpretations
(Parisius et al., 2022). An updated measure of oral frailty may now be
indicated, given the nature of the study results. The upcoming study will
be dedicated to the development and psychometric evaluation (s.a.
reliability, construct validity, and criterion validity) of a novel oral
frailty assessment tool. The outcome of this e-Delphi study will lay the
groundwork for devising an instrument to measure oral frailty.
5. Conclusion
The ndings of this e-Delphi study suggest that oral frailty can be
operationally dened by eight components, grouped into four categories
namely: 1) mastication (difculty eating hard or tough foods, and
inability to chew all types of foods); 2) swallowing (decreased ability to
swallow solid foods, decreased ability to swallow liquids, and overall
poor swallowing function); 3) oral motor skill (impaired tongue move-
ment, and speech or phonatory disorders), and 4) salivation (hypo-
salivation or xerostomia).
Based on the ndings of this study, a revised method for assessing
oral frailty is recommended using these four categories as the
foundation.
CRediT authorship contribution statement
Karl G.H. Parisius: Writing – review & editing, Visualization,
Writing – original draft, Project administration, Methodology, Investi-
gation, Formal analysis, Conceptualization. Merel C. Verhoeff: Writing
– review & editing, Visualization, Supervision. Frank Lobbezoo:
Writing – review & editing, Visualization, Supervision, Methodology,
Conceptualization. Limor Avivi-Arber: Writing – original draft, Visu-
alization, Investigation. Joke Duyck: Writing – review & editing,
Visualization, Investigation. Hirohiko Hirano: Writing – review &
editing, Visualization, Investigation. Katsuya Iijima: Writing – review
& editing, Visualization, Investigation. Barbara Janssens: Writing –
review & editing, Visualization, Investigation. Anastassia Kossioni:
Writing – review & editing, Validation, Investigation. Chia-Shu Lin:
Writing – review & editing, Visualization, Investigation. Gerald
McKenna: Writing – review & editing, Visualization, Investigation.
Frauke Müller: Writing – review & editing, Visualization, Investigation.
Martin Schimmel: Writing – review & editing, Visualization, Investi-
gation. Anita Visser: Writing – review & editing, Visualization, Inves-
tigation. Yutaka Watanabe: Writing – review & editing, Visualization,
Investigation. Robbert J.J. Gobbens: Writing – review & editing,
Visualization, Supervision, Methodology, Investigation.
Declaration of Competing Interest
The authors have no nancial or any other type of personal conict
of interest regarding the content of this study. This study was funded by
the Dutch Organization for Scientic Research (Nederlandse Organisatie
voor Wetenschappelijk Onderzoek – NWO); grant number 023.015.022.
The funder was not involved in the design, methods, data collection,
analysis, or preparation of this study. The content is solely the authors’
responsibility and does not necessarily reect the views of the Dutch
Organization for Scientic Research.
K.G.H. Parisius et al.
Archives of Gerontology and Geriatrics 117 (2024) 105181
8
Acknowledgements
The authors thank Dr. Nao Takano for her contribution to translation
and language support, for the experts requiring assistance.
References
Boel, A., Navarro-Comp´
an, V., Landew´
e, R., & van der Heijde, D. (2021). Two different
invitation approaches for consecutive rounds of a Delphi survey led to comparable
nal outcome. Journal of Clinical Epidemiology, 129, 31–39.
Boesjes-Hommes, R. W. (1970). The valid operationalisation of concepts; a proposition.
Meppel: Boom.
Chalmers, J. M., & Ettinger, R. L. (2008). Public health issues in geriatric dentistry in the
United States. Dental Clinics of North America, 52(2), 423–446. vii-viii.
Delbecq, A. L. VdVAH, & Gustafson Glenview, D. H (1976). Group techniques for
program planning: A guide to nominal group and Delphi processes. Group &
Organization Studies, 1(2), 256, 256.
de Sire, A., Ferrillo, M., Lippi, L., et al. (2022). Sarcopenic dysphagia, malnutrition, and
oral frailty in elderly: A comprehensive review. Nutrients, 14(5).
Dibello V., Lobbezoo F., Lozupone M., et al. Oral frailty indicators to target major adverse
health-related outcomes in older age: A systematic review. GeroScience. 2022.
Farias, I., Sousa, S. A., Almeida, L. F. D., Santiago, B. M., Pereira, A. C., &
Cavalcanti, Y. W. (2020). Does non-institutionalized elders have a better oral health
status compared to institutionalized ones? A systematic review and meta-analysis.
Ciencia & Saude Coletiva, 25(6), 2177–2192.
Fried, L. P., Tangen, C. M., Walston, J., et al. (2001). Frailty in older adults: Evidence for
a phenotype. The Journals of Gerontology Series A, Biological Sciences and Medical
Sciences, 56(3), M146–M157.
Hakeem, F. F., Bernab´
e, E., Fadel, H. T., & Sabbah, W. (2020). Association between oral
health and frailty among older adults in Madinah, Saudi Arabia: A cross-sectional
study. The Journal of Nutrition, Health & Aging, 24(9), 975–980.
Hara, S., Miura, H., & Yamasaki, K. (2013). Oral diadochokinesis among Japanese aged
over 55 years: Analysis of standard values. Nihon Ronen Igakkai Zasshi. Japanese
Journal of Geriatrics, 50(2), 258–263.
Hiltunen K., M¨
antyl¨
a P., Vehkalahti M.M. Age- and time-related trends in oral health care
for patients aged 60 years and older in 2007-2017 in public oral health services in
Helsinki, Finland. International Dental Journal 2021.
Hiltunen, K., Saarela, R. K. T., Kautiainen, H., Roitto, H. M., Pitk¨
al¨
a, K. H., & M¨
antyl¨
a, P.
(2021b). Relationship between Fried’s frailty phenotype and oral frailty in long-term
care residents. Age and Ageing, 50(6), 2133–2139.
Hsu CCS B.A. The Delphi technique: Making sense of consensus. 2007;Vol. 12, Article 10.
doi:https://doi.org/10.7275/pdz9-th90.
Iijima, K., Tanaka, T., Takahashi, K., et al. (2017). Strong association between declines in
oral functions and sarcopenia among Japanese community-dwelling elderly in
Kashiwa study: Designing a new concept ’oral frailty’. Journal of the American
Geriatrics Society, 65, S69.
JapanDentalAssociation. (2019). Manual for oral frailty at dental clinics 2019. Tokyo,
Japan: Japan Dental Association. https://www.jda.or.jp/dentist/oral_ail/pdf/ma
nual_all.pdf.
Keeney, S., McKenna, H., & Hasson, F. (2011). The Delphi technique in nursing and health
research. Wiley.
Komatsu, R., Nagai, K., Hasegawa, Y., et al. (2021). Association between physical frailty
subdomains and oral frailty in community-dwelling older adults. International
Journal of Environmental Research and Public Health, 18(6).
Kugimiya, Y., Watanabe, Y., Ueda, T., et al. (2020). Rate of oral frailty and oral
hypofunction in rural community-dwelling older Japanese individuals.
Gerodontology.
Kuo, Y. W., & Lee, J. D. (2022). Association between oral frailty and physical frailty
among rural middle-old community-dwelling people with cognitive decline in
Taiwan: A cross-sectional study. International Journal of Environmental Research and
Public Health, 19(5).
McCarty, E. B., & Chao, T. N. (2021). Dysphagia and swallowing disorders. Medical
Clinics of North America, 105(5), 939–954.
Mullen, P. M. (2003). Delphi: Myths and reality. Journal of Health Organization and
Management, 17(1), 37–52.
Parisius, K. G. H., Wartewig, E., Schoonmade, L. J., Aarab, G., Gobbens, R., &
Lobbezoo, F. (2022). Oral frailty dissected and conceptualized: A scoping review.
Archives of Gerontology and Geriatrics, 100, Article 104653.
Patel, J., Wallace, J., Doshi, M., et al. (2021). Oral health for healthy ageing. The Lancet
Healthy Longevity, 2(8), E521–e527.
Petersen, P. E., & Ogawa, H. (2018). Promoting oral health and quality of life of older
people - the need for public health action. Oral Health & Preventive Dentistry, 16(2),
113–124.
Podsakoff, P. M., MacKenzie, S. B., & Podsakoff, N. P. (2016). Recommendations for
creating better concept denitions in the organizational, behavioral, and social
sciences. Organizational Research Methods, 19(2), 159–203.
Sakayori, T., Maki, Y., Ohkubo, M., Ishida, R., Hirata, S., & Ishii, T. (2016). Longitudinal
evaluation of community support project to improve oral function in Japanese
elderly. The Bulletin of Tokyo Dental College, 57(2), 75–82.
Satake, A., Kobayashi, W., Tamura, Y., et al. (2019). Effects of oral environment on
frailty: Particular relevance of tongue pressure. Clinical Interventions in Aging, 14,
1643–1648.
Schimmel, M., Domioni, T., Bukvic, H., Arakawa, I., Seifert, E., & Abou-Ayash, S. (2022).
Oral diadochokinesis and associated oro-facial function in young and old German
mother-tongue speakers: A cross-sectional study. Gerodontology, 39(1), 33–40.
Takeuchi, N., Sawada, N., Ekuni, D., & Morita, M. (2021). Oral diadochokinesis is related
to decline in swallowing function among community-dwelling Japanese elderly: A
cross-sectional study. Aging Clinical and Experimental Research, 33(2), 399–405.
Tanaka, T., Takahashi, K., Hirano, H., et al. (2018). Oral frailty as a risk factor for
physical frailty and mortality in community-dwelling elderly. The Journals of
Gerontology: Series A, 73(12), 1661–1667.
Watanabe, Y., Arai, H., Hirano, H., et al. (2018). Oral function as an indexing parameter
for mild cognitive impairment in older adults. Geriatrics & Gerontology International,
18(5), 790–798.
Watanabe, Y., Hirano, H., Arai, H., et al. (2017). Relationship between frailty and oral
function in community-dwelling elderly adults. Journal of the American Geriatrics
Society, 65(1), 66–76.
Watanabe Y., Okada K., Kondo M., Matsushita T., Nakazawa S., Yamazaki Y. Oral health
for achieving longevity. Geriatrics & Gerontology International. 2020.
Worldometers.info. Life expectancy by country and in the world (2023) - Worldometer.
https://www.worldometers.info/demographics/life-expectancy/. Published 2023.
Accessed Web Page.
K.G.H. Parisius et al.
