How Common is Dry Mouth? Systematic Review and Meta-Regression Analysis of Prevalence Estimates

Agostini, Bernardo Antonio; Cericato, Graziela Oro; Silveira, Ethieli Rodrigues da; Nascimento, Gustavo Giacomelli; Costa, Francine dos Santos; Thomson, Willian Murray; Demarco, Flavio Fernando

doi:10.1590/0103-6440201802302

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Brazilian Dental Journal

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Article • Braz. Dent. J. 29 (6) • Nov-Dec 2018 • https://doi.org/10.1590/0103-6440201802302 copy

How Common is Dry Mouth? Systematic Review and Meta-Regression Analysis of Prevalence Estimates

Authorship SCIMAGO INSTITUTIONS RANKINGS

Abstract

The aim of this paper is to systematically review the literature to estimate the overall prevalence of xerostomia/hyposalivation in epidemiological studies. An electronic search was carried out up to February 2018 with no language restrictions. A total of 5760 titles were screened and just twenty-nine papers were included in review and the meta-analysis after a two independently reviewers applied the selection criteria. Data were extracted from PubMed and Web of Science databases. Eligibility criteria included original investigations from observational population-based studies that reported the prevalence of xerostomia or data that allowed the calculation of prevalence of xerostomia and/or hyposalivation. Studies conducted in samples with specific health conditions, literature reviews, case reports and anthropological studies, as conferences or comments were excluded. Sample size, geographic location of the study, study design, age of the studied population, diagnosis methods, and evaluation criteria used to determine xerostomia e/or hyposalivation were extracted for meta-analysis and meta-regression. Multivariate meta-regression analysis was performed to explore heterogeneity among studies. The overall estimated prevalence of dry mouth was 22.0% (95%CI 17.0-26.0%). Higher prevalence of xerostomia was observed in studies conducted only with elderly people. Despite diverse approaches to the condition’s measurement, just over one in four people suffer from xerostomia, with higher rates observed among older people. Moreover, the measurement methods used currently may over- or underestimate xerostomia. These findings highlight the need for further work on existing and new clinical measure and will be useful to determine which one is more reliable in clinical and epidemiological perspectives.

Key Words:
xerostomia; dry mouth; hyposalivation; global prevalence; salivary function

PubMed
(((((“Xerostomia”(Mesh)) OR “Xerostomia”(all)) OR “Dry Mouth”(all) OR “Mouth Dryness”(all) OR “Hyposalivation”(all))) AND ((((((((((((((((((((((((“Epidemiological Studies”) OR “Epidemiological Study”) OR “Cross Sectional Study”) OR “Cross Sectional Studies”) OR “Cross-Sectional Study”) OR “Cross-Sectional Studies”) OR “Studies, Cross-Sectional”) OR “Study, Cross-Sectional”) OR “Prevalence Studies”) OR “Prevalence Study”) OR “Studies, Prevalence”) OR “Study, Prevalence”) OR “Cohort Study”) OR “Cohort Studies”) OR “Incidence Study”) OR “Incidence Studies”) OR “Studies, Incidence”) OR “Study, Incidence”) OR “Follow up Studies”) OR “Follow-up Studies”) OR “Follow up Study”) OR “Follow-up Study”) OR “Prevalence”) OR “Incidence”))
Web of Science
((((“Xerostomia” OR “Dry Mouth”) OR “Mouth Dryness”) OR “hypersalivation”) AND (((((((((((((((((((((((“Epidemiological Studies” OR “Epidemiological Study”) OR “Cross Sectional Study”) OR “Cross Sectional Studies”) OR “Cross-Sectional Study”) OR “Cross-Sectional Studies”) OR “Studies, Cross-Sectional”) OR “Study, Cross-Sectional”) OR “Prevalence Studies”) OR “Prevalence Study”) OR “Studies, Prevalence”) OR “Study, Prevalence”) OR “Cohort Study”) OR “Cohort Studies”) OR “Incidence Study”) OR “Incidence Studies”) OR “Studies, Incidence”) OR “Study, Incidence”) OR “Follow up Studies”) OR “Follow-up Studies”) OR “Follow up Study”) OR “Follow-up Study”) OR “Prevalence”) OR “Incidence”))

Author and year	Reason for exclusion
Abdullah 2015	Convenience/specific sample
Acevedo et al. 1996	Comments/abstracts of conferences
Allen and Locker 1997	No prevalence data
Almas et al. 2003	Convenience/specific sample
Almstahl et al. 2012	Convenience/specific sample
Anusavice 2002	No access to full text
Arcury et al. 2009	Convenience/specific sample
Atchinson et al. 1993	Convenience/specific sample
Bai and Lin 2006	Full text in Chinese
Barbagli et al. 2014	No prevalence data
Benaryeh et al. 1985	Convenience/specific sample
Bergdahl 2000	Convenience/specific sample
Bergdahl and Bergdahl 2001	Convenience/specific sample
Bergdahl and Bergdahl 2002	Convenience/specific sample
Bhattacharyya and Kenpes 2015	Prevalence data not clear
Billings 1993	Review
Billings et al. 1996	Convenience/specific sample
Cabrera et al. 2007	Convenience/specific sample
Castrejon-Perez et al. 2017	Convenience/specific sample
Chopra et al. 2015	Convenience/specific sample
Coccia et al. 2015	No access to full text
El Osta et al. 2014	Convenience/specific sample
Elishoov et al. 2005	Full text in Hebrew
Enoki et al. 2014	Convenience/specific sample
Evans et al. 2000	Prevalence data not clear
Farah et al. 2008	Convenience/specific sample
Field et al. 2000	Convenience/specific sample
Field et al. 2001	Convenience/specific sample
Field et al. 2001	No access to full text
Flink 2007	No access to full text
Flink et al. 2008	Convenience/specific sample
Flink et al. 2000	Convenience/specific sample
Foerster et al. 1998	Convenience/specific sample
Fure 1998	Non-representative sample
Fure 2003	Non-representative sample
Gerdin et al. 2005	Convenience/specific sample
Ghezzi and Ship 2003	Non-representative sample
Gilbert et al. 1993b	Same sample of an included study
Goaz et al. 1994	Comments/abstracts of conferences
Gois et al. 2018	Convenience/specific sample
Guignon and Novy 2015	Comments/abstracts of conferences
Hahnel et al. 2014	Convenience/specific sample
Hassel et al. 2010	Non-representative sample
Author and year	Reason for exclusion
Ichikawa et al. 2011	No prevalence data
Ikebe et al. 2011	Convenience/specific sample
Ikebe et al. 2006	Convenience/specific sample
Ikebe et al. 2007	Convenience/specific sample
Ikebe et al. 2006	Convenience/specific sample
Ikebe et al. 2001	Convenience/specific sample
Ikebe et al. 2002	Convenience/specific sample
Imazato et al. 2006	Convenience/specific sample
Inoue et al. 2006	Convenience/specific sample
Iwabuchi et al. 2012	Convenience/specific sample
Johanson et al. 2015	Same sample of an included study
Johanson et al. 2009	Same sample of an included study
Khalifa et al. 2012	Convenience/specific sample
Kreher et al. 1987	Convenience/specific sample
Kreher et al. 1991	Convenience/specific sample
Lee et al. 2014	Convenience/specific sample
Leung et al. 2016	Convenience/specific sample
Lewis et al. 1993	No prevalence data
Locker 1997	Same sample of an included study
Marino et al. 2015	No prevalence data
Mizutani et al. 2015	Convenience/specific sample
Nally 1990	Editorial
Narhi 1994	Same sample of a study already included
Navazesh et al. 1996	Convenience/specific sample
Ohara et al. 2015	Same sample of a study already included
Ohara et al. 2011	Convenience/specific sample
Pedersen et al. 2015	No prevalence data
Porter 2010	Review
Pujol et al. 1998	Convenience/specific sample
Ramsay et al. 2015	Convenience/specific sample
Ramsay et al. 2015	Convenience/specific sample
Ramsay et al. 2018	Convenience/specific sample
Russell and O’Grady 1990	Full text in Hungarian
Salako and Farsi 2000	Comments/abstracts of conferences
Schein et al. 1999	Convenience/specific sample
Sorensen et al. 2018	Convenience/specific sample
Sreebny and Valdini 1988	Convenience/specific sample
Thomson et al. 1999	Same sample of an included study
Thomson et al. 2000	No prevalence data
Thomson et al. 2006	Same sample of a study already included
van Eijk et al. 2013	Letter to editor
Villa and Abati 2011	Convenience/specific sample

Author and year (# ref)	Country	Participants	Age of participants	Study design	Xerostomia/ Hyposslivation assessment	Xerostomia/ Hyposalivation criteria	Cases of Xerostomia/ Hyposalivation	Total Sample	Prevalence
Alaraudanjoki et al. 2016 ³3 Alaraudanjoki V, Laitala ML, Tjäderhane L, Pesonen P, Lussi A, Ronkainen J. Influence of Intrinsic Factors on Erosive Tooth Wear in a Large-Scale Epidemiological Study. Caries Res 2016;50:508-516.	Finland	Adults	46	Cohort	Unstimulated salivary flow rate	Unstimulated salivary flow rate <0.1 mL/min	31	1,944	0.2*
Antila et al. 1998 ¹³13 Anttila SS, Knuuttila ML, Sakki TK. Depressive symptoms as an underlying factor of the sensation of dry mouth. Psychosom Med 1998;60:215-218.	Finland	Adults	55	Cross-sectional	Self-reported	Frequency (‘Sometimes’ ‘Often’)	232	774	30.0
		Adults	55	Cross-sectional	Stimulated salivary flow rate	Stimulated salivary flow rate <0.7 mL/min	312	774	40.3*
		Adults	55	Cross-sectional	Unstimulated salivary flow rate	Unstimulated salivary flow rate <0.1 mL/min	123	772	15.9
Benn et al. 2015 ⁽⁵⁾5 Benn AM, Broadbent JM, Thomson WM. Occurrence and impact of xerostomia among dentate adult New Zealanders: findings from a national survey. Aust Dent J 2015;60:362-367.	New Zealand	Adults/Elderly	>18	Cross-sectional	Self-reported	Frequency (‘Always’ ‘Frequently)	455	3475	13.1*
Caplan and Hunt 1996 ²⁸28 Caplan, DJ; Hunt, RJ. Salivary flow and risk of tooth loss in an elderly population. Community Dent Oral Epidemiol 1996;24:68-71.	United States of America	Elderly	>65	Cross-sectional	Stimulated salivary flow rate	Stimulated salivary flow rate < 1 mL/min	173	490	35.3*
Castrejón-Pérez et al. 2012 ²2 Castrejon-Perez RC, Borges-Yáñez SA, Gutiérrez-Robledo LM, Ávila-Funes JA. Oral health conditions and frailty in Mexican community-dwelling elderly: a cross sectional analysis. BMC Public Health 2012;12:773.	Mexico	Elderly	>70	Cohort	Self-reported	Presence/Absence	378	838	45.1*
da Silva et al. 2017 ³⁵35 da Silva, L; Kupek ,E; Peres, KG. General health influences episodes of xerostomia: a prospective population-based study. Community Dent Oral Epidemiol 2017;45:153-159.	Brazil	Adults	20-59	Cohort	Self-reported	Frequency (‘Regular’ “Irregular’) according to “Frequently” or “Always” answers to the question ‘How often do you experience dry mouth?’ in 2009 and 2012.	134	1222	11.0*
Ekback et al. 2009 ¹⁴14 Ekback G; Astrom AN; Klock K; Ordell S; Unell L. Variation in subjective oral health indicators of 65-year-olds in Norway and Sweden. Acta Odontol Scand 2009;67:222-232.	Norway	Elderly	65	Cross-sectional	Self-reported	Frequency (‘Sometimes’ ‘Often’ ‘Seldom’)	1,201	4,062	29.6*
	Sweden	Elderly	65	Cross-sectional	Self-reported	Frequency (‘Sometimes’ ‘Often’ ‘Seldom’)	1,685	6,078	27.7*
Gilbert et al. 1993 ¹⁰10 Gilbert GH, Heft MW, Duncan RP. Mouth dryness as reported by older Floridians. Community Dent Oral Epidemiol 1993;21:390-397.	United States of America	Elderly	>65	Cross-sectional	Self-reported	Presence/Absence	234	600	39.0*
Hay et al. 1998 ²⁶26 Hay, EM, Thomas, E; Pal, B; Hajeer, A; Chambers, H; Silman, AJ. Weak association between subjective symptoms or and objective testing for dry eyes and dry mouth: results from a population based study. Ann Rheum Dis 1998;57:20-24.	United States of America	Adults/Elderly	18-75	Cross-sectional	Self-reported	Classification based on 3 questions: Does your mouth feel dry every day? Have you had recurrent or persistent swelling of your salivary glands as an adult? Do you frequently have to take a drink in order to swallow?	61	341	17.9*
Hocberg et al. 1998 ¹¹11 Hochberg MC, Tielsch J, Munoz B, Bandeen-Roche K, West SK, Schein OD. Prevalence of symptoms of dry mouth and their relationship to saliva production in community dwelling elderly: the SEE project. Salisbury Eye Evaluation. J Rheumatol 1998;25:486-491.	England	Elderly	65-84	Cohort	Self-reported	Classification based on 2 questions: Does your mouth usually feel dry? Do you wake at night feeling so dry in your mouth that you need to drink fluids?	427	2,482	17.2
	England	Elderly	65-84	Cohort	Stimulated salivary flow rate	Stimulated salivary flow rate < 1 mL/min	373	2,482	15.0*
Iwasaki et al. 2016 ⁷7 Iwasaki M, Yoshihara A, Ito K, Sato M, Minagawa K, Muramatsu K. Hyposalivation and dietary nutrient intake among community-based older Japanese. Geriatr Gerontol Int 2016;16:500-507.	Japan	Elderly	80	Cohort	Self-reported	Presence/Absence	62	352	17.6
		Elderly	80	Cohort	Stimulated salivary flow rate	Stimulated salivary flow rate <0.5 mL/min	36	352	10.2*
Jacobsson et al. 1989 ¹²12 Jacobsson LT, Axell TE, Hansen BU, Henricsson VJ, Lieberkind K, Lilja B, et al. Dry eyes or mouth - an epidemiological study in Swedish adults, with special reference to primary Sjogren’s syndrome. J Autoimmun 1989; 2:521-527.	Sweden	Adults	52-72	Cohort	Self-reported	Classification based on 2 questions: Do you often feel a gritty or sandy sensation in your eyes? Do you wake up at night feeling so dry in the mouth that you need to drink water?	247	705	35.0
		Adults	52-72	Cohort	Unstimulated salivary flow rate	Unstimulated salivary flow rate <0.1 mL/min	39	109	35.8*
Johanson et al. 2012 ¹1 Johansson AK1, Johansson A, Unell L, Ekbäck G, Ordell S, Carlsson GE. Self-reported dry mouth in Swedish population samples aged 50, 65 and 75 years. Gerodontology 2012;29:e107-e115.	Sweden	Elderly	75	Cohort	Self-reported	Frequency (‘Sometimes’ ‘Often’ ‘Seldom’)	1,325	3,539	37.4
		Elderly	75	Cohort	Self-reported	Frequency (‘Sometimes’ ‘Often’ ‘Seldom’)	2,064	3,591	57.5
		Elderly	75	Cohort	Self-reported	Frequency (‘Sometimes’ ‘Often’ ‘Seldom’)	2,249	3,611	62.3
		Elderly	75	Cohort	Stimulated salivary flow rate	Stimulated salivary flow rate <0.7 mL/min	311	1072	29.0*
Kongstad et al. 2013 ¹⁹19 Kongstad, J; Ekstrand, K; Qvist, V; Christensen, LB; Cortsen, B; Gronbaek, M; et al. Findings from the oral health study of the Danish Health Examination Survey 2007-2008. Acta Odontol Scand 2013;71:1560-1569.	Denmark	Adults/Elderly	18-96	Cross-sectional	Self-reported	Frequency (‘Sometimes’ ‘Often’ ‘Seldom’)	634	4,402	14.4
		Adults/Elderly	18-96	Cross-sectional	Stimulated salivary flow rate	Stimulated salivary flow rate <0.5 mL/min	132	4,402	3.0*
Lee et al. 2016 (²⁹29 Lee, YS; Kim, HG; Moreno, K. Xerostomia among older adults with low income: nuisance or warning? J Nurs Scholarsh 2016;48:58-65.	Korea	Elderly	>65	Cross-sectional	Self-reported	Presence/Absence	3,943	9,84	40.1*
Locker 1995 ³⁴34 Rawal Hoffman, HJ; Bainbridge, KE. Prevalence and Risk Factors of Self-Reported Smell and Taste Alterations: Results from the 2011-2012 US National Health and Nutrition Examination Survey (NHANES). Chem Senses 2016;41,69-76.	Canada	Adults	>50	Cross-sectional	Self-reported	Presence/Absence	180	611	29.5*
Mochida et al. 2018 ⁴¹41 Mochid,a Y; Yamamoto, T; Fuchida, S; Aida, J; Kondo, K. Does poor oral Health status increase the risk of falls?: The JAGES project longitudinal study. Plos One2018;13:e0192251.	Japan	Elderly	>65	Cohort	Self-reported	Presence/Absence	6256	38529	16.2*
Narhi et al. 1993 (¹⁸18 Narhi TO Ainamo, A; Meurman, JH. Salivary yeasts, saliva, and oral mucosa in the elderly. J Dent Res 1993;72:1009-1014.	Finland	Elderly	>75	Cohort	Self-Reported	Presence/Absence	40	341	11.7
		Elderly	>75	Cohort	Unstimulated salivary flow rate	Unstimulated salivary flow rate <0.1 mL/min	143	306	46.7
		Elderly	>75	Cohort	Stimulated salivary flow rate	Stimulated salivary flow rate <0.8 mL/min	82	307	26.7*
Nederfors 1996 (³⁷37 Nederfors,T; Isaksson, R; Mornstad, H; et al. Prevalence of perceived symptoms of dry mouth in an adult Swedish population-relation to age, sex and pharmacotherapy. Community Dent Oral Epidemiol1997;25: 211-216.	Sweden	Adults	20-80	Cross-sectional	Self-reported	Presence/Absence	851	3,313	25.7*
Ohara et al. 2016 ²⁷27 Ohara, Y; Hirano, H; Yoshida, H. Prevalence and factors associated with xerostomia and hyposalivation among community-dwelling older people in Japan. Gerodontology 2016;33:20-27.	Japan	Elderly	>65	Cross-sectional	Self-reported	Presence/Absence	311	894	34.8
		Elderly	>65	Cross-sectional	Unstimulated salivary flow rate	Weight <0,1 g	103	894	11.5*
Ostesberg et al. 1992 ²⁰20 Osterberg, T; Birkhed, D; Johansson, C; Svanborg, A. Longitudinal study of stimulated whole saliva in an elderly population. Scand J Dent Res 1992;100:340-345. Ostesberg et al. 1984 ⁴⁰40 Osterberg, T; Landahl, S; Hedegard, B. Salivary flow, saliva, pH and buffering capacity in 70-year-old men and women. Correlation to dental health, dryness in the mouth, disease and drug treatment. J Oral Rehabil 1984;11:157-170.	Sweden	Elderly	>70	Cohort	Stimulated salivary flow rate	Stimulated salivary flow rate <0.2 mL/min	39	975	4.0*
		Elderly	>70	Cohort	Self-reported	Presence/Absence	201	996	20.2
		Elderly	>70	Cohort	Stimulated salivary flow rate	Stimulated salivary flow rate <0.1 mL/min	303	996	30.4*
Quandt et al. 2011 ³⁶36 Quandt, SA; Savoca, MR; Leng, X; et al. Dry mouth and dietary quality in older adults in North Carolina. J Am Geriatr Soc 2011;59:439-445.	United States of America	Elderly	>60	Cross-sectional	Self-reported	Frequency (‘Always’ ‘Frequently)	158	622	25.4*
Rawal et al. 2016 ³³33 Locker, D, Xerostomia in older adults: a longitudinal study. Gerodontology1995;12:18-25.	United States of America	Adults	>40	Cross-sectional	Self-reported	Presence/Absence	513	3,603	14.2*
Reichart 2000 ⁸8 Reichart PA. Oral mucosal lesions in a representative cross-sectional study of aging Germans. Community Dent Oral Epidemiol 2000;28:390-398.	Germany	Adults	>35	Cross-sectional	Self-reported	Presence/Absence	7	1,367	0.1*
So et al. 2010 ¹⁷17 So JS, Chung SC, Kho HS; Kim YK; Chung JW. Dry mouth among the elderly in Korea: a survey of prevalence, severity, and associated factors. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2010;110:475-483.	Korea	Elderly	>55	Cross-sectional	Self-reported	Classification based on 9 questions.	261	1,012	25.8*
Thomson et al. 1999 ¹⁵15 Thomson WM; Chalmers JM; Spencer AJ; Ketabi M. The occurrence of xerostomia and salivary gland hypofunction in a population-based sample of older South Australians. Spec Care Dentist 1999;19:20-23.	Australia	Elderly	75	Cohort	Self-reported	Frequency (‘Always’ ‘Frequently)	140	684	20.5
		Elderly	75	Cohort	Unstimulated salivary flow rate	Unstimulated salivary flow rate <0.1 mL/min	151	684	22.1*
Thomson et al. 2006 ⁴4 Thomson WM, Poulton R Broadbent, JM Al-Kubaisy S. Xerostomia and medications among 32-year-olds. Acta Odontol Scand 2006;64:249-254.	New Zealand	Adults/Elderly	26 and 32	Cohort	Self-reported	Frequency (‘Always’ ‘Frequently)	95	950	10.0*

	Checklist item
	1	2	3	4	5	6	7	8	9
Alaraudanjoki et al. 2016 (3)	yes	yes	yes	no	yes	yes	yes	yes	yes
Antila et al. 1998 (13)	yes	yes	yes	yes	yes	yes	yes	yes	yes
Benn et al. 2015 (5)	yes	yes	yes	yes	yes	yes	yes	yes	yes
Caplan and Hunt 1996 (28)	yes	yes	yes	yes	no	yes	yes	yes	yes
Castrejon-Perez et al. 2012 (2)	yes	yes	yes	yes	yes	yes	yes	yes	yes
da Silva et al. 2017 (35)	yes	yes	yes	yes	yes	yes	yes	yes	yes
Eckback et al. 2009 (14)	yes	yes	yes	yes	yes	yes	yes	yes	yes
Gilbert et al. 1993 (10)	yes	yes	yes	yes	yes	yes	yes	yes	yes
Hay et al. 1998 (26)	unclear	yes	yes	yes	yes	yes	yes	yes	yes
Hocberg et al. 1998 (11)	yes	yes	yes	yes	yes	yes	yes	yes	yes
Iwasaki et al. 2016 (7)	yes	yes	no	yes	yes	yes	yes	yes	no
Jacobsson et al. 1989 (12)	unclear	yes	yes	yes	yes	yes	yes	no	yes
Johanson et al. 2012 (1)	yes	yes	yes	yes	yes	yes	yes	yes	yes
Kongstad et al. 2013 (19)	yes	yes	yes	yes	yes	yes	yes	yes	yes
Lee et al. 2016 (29)	yes	yes	yes	yes	yes	yes	yes	yes	yes
Locker 1995 (34)	yes	yes	yes	yes	yes	yes	yes	yes	yes
Mochida 2018 (41)	yes	yes	yes	yes	yes	yes	yes	yes	yes
Narhi et al. 1993 (18)	yes	yes	yes	yes	yes	yes	yes	yes	yes
Nederfors 1996 (37)	yes	yes	yes	yes	yes	yes	yes	yes	yes
Ohara et al. 2016 (27)	yes	yes	unclear	yes	yes	yes	yes	yes	yes
Ostesberg et al. 1992 (20)	yes	yes	yes	yes	yes	yes	yes	yes	yes
Ostesberg et al. 1984 ⁴⁰40 Osterberg, T; Landahl, S; Hedegard, B. Salivary flow, saliva, pH and buffering capacity in 70-year-old men and women. Correlation to dental health, dryness in the mouth, disease and drug treatment. J Oral Rehabil 1984;11:157-170.	yes	yes	yes	yes	yes	yes	yes	yes	yes
Quandt et al. 2011 (36)	yes	yes	yes	yes	yes	yes	yes	yes	yes
Rawal et al. 2016 (33)	yes	yes	yes	yes	yes	yes	yes	yes	yes
Reichart 2000 (8)	yes	yes	yes	yes	yes	yes	yes	yes	yes
So et al. 2010 (17)	yes	yes	yes	yes	yes	yes	yes	yes	yes
Thomson et al. 1999 (15)	yes	yes	yes	yes	yes	yes	yes	yes	yes
Thomson et al. 2006 (4)	yes	yes	yes	yes	yes	yes	yes	yes	yes

Methodological characteristics	Prevalence % (95%CI)	p value^a	Heterogeneity Explained (R²)
Age of the participants		0.259	10.52%
Only adults	19.3 (12.8-25.7)
Only elders	25.4 (20.0-30.9)
Adults and Elders	10.8 (4.2-17.5)
Geographic location		0.187	2.79%
Europe	20.4(14.7-26.2)
Australasia	18.6(10.6-26.7)
Americas	27.1 (18.7-35.5)
Heterogeneity Explained by final model (R²)^b: 15.81%

Methodological characteristics	Xerostomia	p^a	Hyposalivation	p^a
Methodological characteristics	Prevalence % (95%CI)	p^a	Prevalence % (95%CI)	p^a
Age of the participants		0.469		0.220
Only adults	20.8(10.6-30.9)		26.0(-0.5-56.0)
Only elders	27.2(21.4-33.0)		20.0(13.0-27.0)
Adults and elders	13.4(11.3-15.5)		3.0(2.0-4.0)
Geographic location		0.327
Europe	22.7(13.2-32.2)		20.0(14.0-26.0)	0.238
Australasia	22.3(14.0-30.6)		15.0(8.0-21.0)
Americas 25.9(17.2-34.7) 35.0(31.0-40.0)
Heterogeneity (I²):	99.8%		99.4%
Heterogeneity Explained (R²)^b:	13.82%		9.15%

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[1] Correspondence: Flávio Fernando Demarco, Rua Gonçalves, 457, 5º andar, 96015560 Pelotas, RS, Brasil. Tel: +55-53-3222-6690. e-mail: flavio.demarco@ufpel.edu.br