Table 1 Characteristics of the included studies

Food items

 CFS

Chewing function score [31] (Development)

Sato et al., 1989

110 older adults;

mean age: 71.6 years;

female: 58.2%;

sample: random

Selected complete denture wearers in dental clinics

Cross-sectional

Japan

Japanese

20 food items

Easy (1), difficult (0), impossible (0) to chew

Yes, 0–20

Chewing function, unidimensional

 ICA-1990

Index of chewing ability-1990 [32]

Leake, 1990

233 older adults

Independently living elders (secondary data)

Cross-sectional

Canada

English

9 food items, 5-item index

Yes (1) or No (0)

Yes, 0–5

Chewing ability, unidimensional

 ICA-2020

Index of chewing ability-2020 [29]

Montero et al., 2020

118 adults;

age: 30–86 years;

female: 41.5%;

Patients who required rehabilitation in dental hospital

Cohort

Spain

Spanish

5-item index

0 = no difficulty, 1 = little, and 2 = much difficulty

-

 FIQ-Japanese-1994

Food intake questionnaire Japanese-1994 [7]

Hirai et al., 1994

20 older adults;

age: 50–76 years;

female: 45%

Complete denture wearers

Cross-sectional

Japan

Japanese

35 food items

Easily eaten (2), eaten with difficulty (1), “cannot be eaten” or “do not eat” (0)

Yes, weighted score, 0–100%

Masticatory function

 FIQ-Japanese-1998

Food intake questionnaire- Japanese-1998 [33]

Miura et al., 1998

70 older adults;

age: 65–74 years;

female: 51.4%

Residents living in Kawaguchiko, Yamanashi Prefecture

Cross-sectional

 New-FIQ- Japanes

New Food intake questionnaire-Japanese [8]

Koshino et al., 2008

262 older adults;

mean age: 76.7 years;

female: 51.1%

Complete denture wearers

Cross-sectional

Japan

Japanese

25 food items

Easily eaten (2), eaten with difficulty (1), “cannot be eaten” or “do not eat” (0)

Yes, weighted score, 0–100%

Masticatory function, 5 factors, namely hardness, fibrous, slippery, sticky, other factor

 FIQ-Chinese-2012

Food intake questionnaire-Chinese-2012 [38]

Hsu et al., 2012

2244 dental patients;

age: 45 + years;

female: 51.5%

Patients recruited from dental clinics

Cross-sectional

China, Taiwan

Chinese

14 food groups

2 = able to eat, 1 = difficult to eat, 0 = unable to eat

Yes

Masticatory ability

 FIQ-Chinese-2014

Food intake questionnaire-Chinese-2014 [28]

Hsu et al., 2014

332 elders;

age: 65 + years; female: 52.1%;

sample: convenient

Elders recruited from senior citizens’ service center, community dwelling

Cross-sectional

‘easy to chew,’ ‘difficult to chew,’ or ‘unable to chew’

 PDC-Tanzania

Perceived difficulty of chewing- Tanzania [34]

Sarita et al., 2003

850 subjects;

age: 20 + years;

sample: convenient

725 subjects with shortened dental arch and 125 subjects with complete dental arch living in urban and rural areas

Cross-sectional

Tanzania

Tanzanian

20 food items

0 = very easily; 1 = minor problems, adapted; 2 = minor problems, not adapted; 3 = difficult but not avoided; 4 = very difficult but not avoided; 5 = very difficult and avoided; 6 = never used that food

Yes, mean score, 0–5

Difficulty of chewing

 PDC-Sudan

Perceived difficulty of chewing-Sudan [26]

Khalifa et al., 2013

1,888 individuals;

age:16 + years;

female: 59%;

sample: consecutive, proportional sampling

Patients attending outpatient dental hospitals (n = 1659) and dental health centres (n = 229)

Cross-sectional

Sudan

Sudanese

15 food items

0 = very easy; 1 = minor problems, adapted; 2 = minor problems, not adapted; 3 = difficult but not avoided; 4 = very difficult but not avoided; 5 = very difficult and avoided; 6 = have never eaten that food

Yes, 0–15

Difficulty of chewing

 IED

Index of eating difficulty [35]

Zeng et al., 2008

1229 participants;

age: 55 + years;

female: 51.7%;

sample: convenient

Elders attending check-up centre for annual health screening

Cross-sectional

China

Chinese

5 food groups (10 food items)

Yes or No

Yes, 0–5

Eating difficulty, unidimensional

 CFQ-Japanese

Alternate version of the chewing function questionnaire [36]

Baba et al., 2009

491 subjects,

mean age: 63.0 years;

female: 71%;

sample: consecutive

Partially dentate patients who attended the prosthodontic clinic

Cross-sectional

Japan

Japanese

20 food items

Easy (1) or difficult (0) to chew the foods

Yes, 0–20

Chewing function, unidimensional, one construct

CFQ-Chinese

Chewing function questionnaire-Chinese [30]

Fan et al., 2021

211 elders;

mean age: 77.1 years, female: 69.7%; sample: purposive

Elders from a dental hospital, an elderly home and three community elderly centres

Cross-sectional

China

Chinese

10 food items

Impossible (1), difficult (2), easy (3) to chew

Yes, 10–30

Chewing function, unidimensional

 FIAQ

Food intake ability questionnaire [37]

Kim et al., 2009

308 adults;

age: 20 + years;

female: 63.6%

Patients in dental hospitals

Cross-sectional

Korea

Korean

30 food items

Cannot chew at all (1), difficult to chew (2), cannot either way (3), can chew some (4), can chew well (5)

Yes, average score, 1–5

Masticatory function

 FIAQ-key food version

Food intake ability questionnaire- key food version [37]

Kim et al., 2009

308 adults;

age: 20 + years

female: 63.6%

Patients in dental hospitals

Cross-sectional

Korea

Korean

5 food items

Cannot chew at all (1), difficult to chew (2), cannot either way (3), can chew some (4), can chew well (5)

Yes, average score, 1–5

Masticatory function

 MACE

Masticatory ability assessment for community-dwelling elderly [27]

Miura et al., 2013

761 elderly subjects; age: 65–84 years;

female: 55.1%;

Independent community-dwelling elders

Cross-sectional

Japan

Japanese

9 food items

Easy (2), slightly difficult (1), very difficult (0), nonresponse

Yes, 0–18

Masticatory ability, unidimensional

Chewing problems

 MPI

Masticatory problem index [39]

Tsuga et al., 1998

160 elders;

age: 80-year-old;

female: 53.8%;

sample: random

Elders living in their own homes, not institutionalized and could travel to the clinical examination

Cross-sectional

Sweden

Swedish

13 items related to chewing problems

–

Yes

Masticatory problem

 Subset-OHIP

Subset of

the oral health impact profile [40]

Cusson et al., 2015

1,789 older adults;

age: 67–84 years;

sample: random

Community-dwelling adults

Cross-sectional

Canada

English

7 items related to chewing problems

Always, often, occasionally, rarely, never

Yes, 0–28

Masticatory efficiency, unidimensional

 SMDOA

Screening for masticatory disorders in older adults [41]

Cavalcanti et al., 2019

295 older adults;

age: 60 + years;

female: 86.4%;

sample: convenient

Adults in social centers for epidemiological screening purpose

Cross-sectional

Brazil

Portuguese

9 items related to chewing problems

No,

Yes-sometimes,

Yes-always

No. Detect change in chewing function

Masticatory disorders, unidimensional. Two factors: 1. chewing function 2. masticatory perception

Food items and chewing problems

 CFQ-Croatian

Chewing

function questionnaire-Croatian [44]

Peršić et al., 2013

224 participants;

age:19–85 years;

female: 48.0%

sample: convenient

Dental students and prosthodontic patients for daily clinical practice and research

Cohort

Croatia

Croatian and English

10 items, including food items and items related to chewing problems

0 = never, 1 = hardly ever, 2 = occasionally, 3 = fairly, 4 = very often or extreme difficulties

Yes, 0–40

Chewing function, unidimensional

 CFQ-Albanian

Albanian

version of chewing-function questionnaire [43]

Bimbashi et al., 2016

205 subjects;

age:19–86 years;

female: 53.2%

sample: random (36), consecutive (61), convenient (108)

General population, dental students and prosthodontic patients for research and clinical trials

Cohort

Republic of Kosovo

Albanian

 QMFQ-Persian

Persian version of the quality of masticatory function questionnaire [42]

Khodaeian et al., 2016

62 edentulous patients;

age: 45–75 years;

female: 50%; sample: convenient

Complete denture wearers referred from hospitals

Cross-sectional

Iran

Persian

27 items, including food items and items related to chewing problems

“always = 1” to “never = 5” or “a lot = 1” to “no difficulty = 5”

Yes, 27–135

Masticatory function, five domains: masticatory problems with dentures, problems while consuming apple and carrot, meat products, fruits and vegetables, and changes need for better swallowing

One global question

 SMF-Yanagisawa

Self-reported masticatory function [45]

Yanagisawa et al. 2010

2668 adults;

age: 40–75 years;

female: 59.1%;

sample: convenient

Community residents recruited by mail

Cross-sectional

Japan

Japanese

1 global question. “Can you bite tightly with your back teeth and dentures?”

Yes, I can bite tightly on both sides; Yes, but only on one side; No, I cannot on either side

No

Masticatory function

 SMF-Ueno

Self-reported masticatory status (function) [46]

Ueno et al., 2018

2356 adults;

age: 40–75 years;

female: 67.9%;

sample: convenient

Community residents recruited on-site or by mail

Cross-sectional

Japan

Japanese