Nutritional Status in Non-Cancer Older Adults Experiencing Dry Mouth –Meta-analysis and Systematic Review

Abstract

Objectives:

Older adults are at increased risk of nutritional deficiencies due to age-related physiological changes, chronic diseases, medication side effects, socioeconomic factors, and declining oral health. This systematic review examines the association between hyposalivation and nutritional status in non-cancer older adults.

Data:

The study protocol was registered in PROSPERO (CRD42025645149). Data were extracted from eligible studies, and quality assessment and bias evaluation were conducted. Using a random effects model, a meta-analysis estimated the pooled prevalence of hyposalivation, xerostomia, and malnutrition.

Sources:

A comprehensive search of PubMed, CINAHL, Web of Science, and Embase was performed from inception to December 2024.

Study Selection:

Longitudinal, cross-sectional, and case-control studies were included. After screening 774 potential studies, 14 (11 cross-sectional, two case-control, and one longitudinal cohort) met the inclusion criteria. Heterogeneity was assessed using Cochran’s Q and I² statistics, while publication bias was evaluated with Egger’s test and funnel plots.

Conclusions:

Thirteen studies reported a significant association between hyposalivation and malnutrition in older adults. All studies highlighted impaired chewing, swallowing difficulties, and reduced taste sensitivity. The pooled prevalence of xerostomia was 38% (95% CI: 22–57%) with substantial heterogeneity (I² = 97%), while the estimated prevalence of malnutrition was 55% (95% CI: 34–74%). The findings suggested a strong link between hyposalivation and malnutrition in non-cancer older adults. However, variability in study designs underscores the need for standardized diagnostic criteria and longitudinal studies to explore the interplay between salivary function and nutritional health in aging populations.

INTRODUCTION

The prevalence of oral diseases among older adults is increasing globally, with significant rates of tooth loss, periodontal disease, dry mouth, dental caries, and oral cancer¹. Studies have shown an association between nutritional status and oral health in older people^2–4. Among older adults (NHANES 1999–2004), persons aged 75 years and older were three times more likely to be edentulous and had, on average, four fewer teeth⁵. Researchers also reported that dry mouth or decreased salivary flow rate (hyposalivation) and xerostomia are linked to food avoidance, a low nutritional index, as well as anthropometric indicators of malnutrition, such as reduced triceps skinfold thickness and arm circumference^6–8.

Xerostomia and hyposalivation are common symptoms of various diseases and health conditions that most frequently affect older individuals⁹. While xerostomia refers to the subjective feeling of oral dryness, hyposalivation is the objective outcome of a reduced flow rate¹⁰. A systematic review reported the prevalence of xerostomia as 23% and hyposalivation as 20%, especially among adults with increasing age¹¹. While dry mouth symptoms may worsen with age¹² due to age-related decreases in salivary gland function^{13, 14}, aging alone, in the absence of medications and systemic conditions, did not significantly affect stimulated parotid saliva flow rates, and age-related decline in salivary flow was not evident in elderly individuals¹⁵. Studies have shown that the prevalence of very low unstimulated whole salivary flow rates is higher in women aged 50–69 years and in men aged 60–69 years¹⁶. Hyposalivation is most frequently the result of certain medications, particularly anticholinergics, sympathomimetics, sedative-hypnotics, opiates, antihistamines, and muscle relaxants. The combination of medications in polypharmacy (taking five or more medications) increases the risk of developing dry mouth¹⁷. A study that evaluated over 2 billion patient visits in the United States found that polypharmacy was prevalent in 65.1% of adults over 65 years of age¹⁸. Other causes for hyposalivation include systemic diseases such as Sjögren’s syndrome, obstructive sleep apnea, chronic kidney disease, diabetes, obesity, and head and neck radiation^{13 19–22}.

Saliva is essential for food processing and digestion, as it contains enzymes such as amylase, which breaks down starches into maltose and dextrin^{23 24}, and lipase, which initiates the digestion of dietary fats. These enzymes act as catalysts in the oral cavity, significantly reducing the complexity of macronutrients before they reach the stomach. Salivary amylase also contributes to oral health by binding to streptococci and modulating the adhesion of bacteria on oral surfaces.⁶¹ Saliva aids taste perception, mastication, bolus formation, and swallowing²⁵. Furthermore, salivary proteins can impact food preferences and taste-related behaviors²⁶. The consequences of hyposalivation include difficulties with chewing and swallowing, food breakdown, and bolus formation, which may affect overall dietary intake (the quantity and composition of food and nutrients consumed in total)^{7, 27}. This can lead to a decline in nutritional status, which may ultimately result in malnutrition in older individuals²⁸. Older individuals are often at a greater risk of nutritional deficiencies due to age-related physiological changes, the effects of medications, decreased appetite resulting from diminished taste and smell, low socioeconomic status, and various health conditions^29,30–33. Additionally, a diminished sense of smell (anosmia) or taste (hypogeusia) is common in older adults due to a decreased number, sensitivity, or density of papillae and taste buds on the tongue , and changes in olfactory epithelial cells, respectively. A study indicated that over 60% of individuals aged 65–80 and 80% of those over 80 experience hypogeusia, mainly due to changes in the oral cavity, such as increased hyposalivation, thinner mucosal membranes, reduced acinar cells in salivary glands, and increased fibrous and adipose tissue³⁵.

Poor oral health has been shown to lead to difficulties in chewing and swallowing, which may result in inadequate nutrition and subsequent health issues³⁷. Oral diseases are associated with systemic conditions, including cardiovascular disorders, cognitive impairment, and diabetes³⁸. Oral health is integral to overall well-being and nutrition, supporting essential physiological (digestion, food processing) and social (talking, eating) functions⁴⁰. Recent publications have explored the relationship between oral health status in older individuals and malnutrition; however, information on how hyposalivation affects nutritional status in older adults is scarce¹. In this systematic review and meta-analysis, we examine the association between hyposalivation and nutritional status in older adults.

MATERIAL AND METHODS

2.1. Protocol and Registration

This research was conducted following the guidelines of Preferred Reporting Items for Systematic Review and Meta-analysis (PRISMA)⁴¹. The study was registered in the International Prospective Register of Systematic Reviews (PROSPERO) with the registration number CRD42025645149.

2.2. Eligibility criteria

The eligibility criteria were formed based on the PEO (Population, Exposure, and Outcome) principle. The Population (P) was non-cancer older adults above 60 years of age. The Exposure (E) was hyposalivation (reduced salivary flow). The Outcome (O) was nutritional status. While some studies also reported xerostomia or oral health indicators, only those that assessed the relationship between hyposalivation and nutritional outcomes were included in the meta-analysis. The search included clinical trials, cross-sectional, case-control, and longitudinal cohort studies. Review articles, case reports, or series, conference papers, and animal studies were excluded. Given that individuals with cancer often experience oral dryness due to radiation treatment⁴² or chemotherapy, and their treatment and nutritional status have specific clinical aspects, we concentrated on studies involving non-cancer older adults⁴³. In contrast, systemic conditions such as diabetes, chronic kidney disease, and polypharmacy were retained, as they represent common comorbidities among older adults and reflect typical clinical scenarios in this age group.

2.3. Focused Question (PEO)

The review aimed to answer the focused question: “Does hyposalivation (E) affect the nutritional status (O) of non-cancer older adults (P)?”

2.4. Information and search strategy

Four indexed databases (PubMed/Medline, Embase, Scopus, and Web of Science) were searched without restrictions by two reviewers (S.S.K and R.C) from inception to December 2024. The combination of the following keywords based on Medical Subject Headings (MeSH) was used: (a) nutritional status, (b) older adults, and (c) xerostomia (Table 1). Additionally, the reference lists of eligible articles, as well as citations of included articles and existing gray literature, were manually searched.

Table 1.

Search Strategy

Database	Search Terms	No of articles
PubMed	(“Nutritional Status”[Mesh] OR nutrition*) AND (elderly OR Aged[Mesh] OR “older adult*” OR aged) AND (Xerostomia[Mesh] OR hyposalivation OR “dry mouth” OR xerostomia)	344
Embase	(‘Nutritional Status’/exp OR nutrition*) AND (elderly OR Aged/exp OR ‘older adult*’ OR aged) AND (Xerostomia/exp OR hyposalivation OR ‘dry mouth’ OR xerostomia)	219
Web of Science	(“Nutritional Status” OR nutrition*) AND (elderly OR Aged OR “older adult*” OR aged) AND (Xerostomia OR hyposalivation OR “dry mouth” OR xerostomia)	211
Cinahl	((MH “Nutritional Status+”) OR nutrition*) AND (elderly OR (MH Aged+) OR “older adult*” OR aged) AND ((MH Xerostomia+) OR hyposalivation OR “dry mouth” OR xerostomia)	180

2.4. Study selection and data collection (Table 1)

Two authors (S.S.K and R.C) performed the title and abstract screening of search results to eliminate irrelevant articles to be examined as full texts. Any disagreement between the two authors was resolved through discussion with the third author (L.X). After a full-text review of eligible studies, 19 articles met the PICO for the final analysis (Fig. 1, Table 2). Data extraction was performed using a standardized data extraction form covering (i) study characteristics (design, country), (ii) patient characteristics (type of sample, gender, age), and (iii) outcome measured (hyposalivation and nutritional status).

Figure 1.

A flow diagram of the search strategy conducted (PRISMA flow of study selection process)

TABLE 2.

Eligible articles excluded with reason.

No	Title	Reason for exclusion
1.	Oral Health and Nutritional Intake in Community-Dwelling 90-Year-Old Japanese People: A Cross-Sectional Study	Full text not available
2.	The association of xerostomia and inadequate intake in older adults	Duplicate
3.	Assessment of Nutritional Status and Associated Risk Factors in Older People	In Arabic
4.	Association of Self-perceived Oral Health Status with ESSPRI reported by patients with Sjögren’s Syndrome	Full text not available
5.	Xerostomia and hyposalivation in orthogeriatric patients with fall history and impact on oral health-related quality of life	Did not find an association between hyposalivation and malnutrition
6.	Digestive and nutritional implications of polypharmacy in older adults	Article unavailable
7.	Xerostomia is Associated with frai and Poor Appetite in Patients on Chronic Hemodialysis	Did not find an association between hyposalivation and malnutrition
8.	Digestive and nutritional implications of polypharmacy in older adults.	Full text unavailable. Abstract submission.
9.	Impact of care level, setting and accommodation costs on a newly developed oral care nursing plan format for elderly patients with care needs - Results from a cross-sectional study.	Did not find an association between hyposalivation and malnutrition.
10.	High prevalence of malnutrition associated with oral health problems among hospitalized adult somatic and psychiatric patients	Did not meet PICO (not elderly adults)
11.	Exploring oral health indicators, oral health-related quality of life and nutritional aspects in 23 medicated patients from a short-term psychiatric ward	Did not meet PICO (not elderly adults)
12.	Drugs and food intake	Did not meet PICO
13.	Drug associated nutritional problems in older person	Did not meet PICO
14.	Oral health status and care of institutionalized old elderly individuals in Lebanon	Did not meet PICO
15.	Nutrition impacts symptoms (NIS) and malnutrition in hospitalized Brazilian patients	Did not meet PICO
16.	Dental health among patients attending an acute care geriatric unit	Did not meet PICO
17.	Caries prevalence, nutrition, and xerogenic medications use among a geriatric population	Did not meet PICO
18.	Frailty index and ten oral conditions in the Coyoacan cohort study: A cross-sectional analysis	Did not meet PICO
19.	Association of Oral Health with Frailty, Malnutrition Risk and Functional Decline in Hospitalized Older Adults: A Cross-Sectional Study	Did not find an association between hyposalivation and malnutrition

2.5. Data analysis

Statistical analyses were conducted using meta-analytical techniques to estimate the pooled prevalence of hyposalivation, xerostomia, and malnutrition deficits across included studies. A weighted proportion was calculated using the random effects model, accounting for study heterogeneity. Heterogeneity was assessed using Cochran’s Q test and I² statistics, where an I² value above 50% indicated moderate to high heterogeneity. A subgroup analysis was conducted to investigate potential sources of variability, including differences in diagnostic criteria, study design, or population characteristics. Sensitivity analysis was conducted by sequentially removing studies to assess the robustness of the results. A publication bias assessment was performed using Egger’s test and visual inspection of funnel plots. Statistical significance was set at p < 0.05, and all analyses were conducted using statistical software such as R or STATA.

2.6. Risk of bias

The Newcastle-Ottawa Scale (NOS) was implemented in our systematic review to assess the quality and risk of bias across the included studies, which comprised cross-sectional, case-control, and cohort designs. This versatile tool evaluates studies based on three primary domains: selection of participants, comparability of study groups, and the assessment of exposures or outcomes. For cross-sectional studies, the NOS examined factors such as the representativeness of the sample, handling of non-respondents, and the validity of exposure and outcome measurements. In the case-control studies, the focus was on the adequacy of case definitions, the representativeness of cases and controls, and the comparability of groups through design or analysis. Cohort studies were evaluated for the representativeness of exposed and non-exposed cohorts, the accuracy of exposure ascertainment, and the adequacy and duration of follow-up. By applying this tool consistently across the diverse study designs included in our review, we ensured a rigorous and standardized evaluation of methodological quality, thereby strengthening the credibility and interpretability of our findings.

3. RESULTS

3.1. Study selection (PRISMA)

The literature database search retrieved 774 articles; six records were identified manually (Fig. 1). After removing duplicates and eliminating non-relevant reports by reviewing the title and abstract information, 674 articles were assessed for eligibility. Thirty-three full-text articles were selected for full-text eligibility, 19 were excluded for reasons (Table 2), and 14 studies were included in this review.

3.2. General characteristics and study population of included studies (Table 2)

All the included studies were non-randomized cross-sectional, case-control, and longitudinal cohort investigations. Only three out of 14 studies included a control group in their sample^44–46. The mean age range of the study participants was between 62 and 94 years. Anderson et al., Barbe et al., and Dormenval et al. (1998,1999) included hospitalized participants in their studies, whereas others included outpatients and random individuals undergoing hemodialysis, individuals with Sjögren’s syndrome, and older adults living in the respective localities where the study was conducted^46–49. The included studies were conducted in ten countries (Sweden, Germany, Italy, the USA, the Netherlands, Thailand, China, France, Switzerland, and Lebanon).

The included studies reported various methodologies to measure hyposalivation and its impact. Regarding the assessment methods for salivary function, Anderson et al. employed the Revised Oral Assessment Guide (ROAG)⁴⁹. The ROAG is a standardized tool used to evaluate oral health status by assessing key factors, including saliva, teeth, mucosa, and swallowing function. It is commonly employed in clinical settings to identify oral health issues and guide appropriate interventions, particularly in vulnerable populations. Hyposalivation was measured by Barbe et al., Rhodus et al. (1998 and 1999), Samnieng et al., Wu et al., Iwasaki et al., and Dormenval et al. (1998 and 1999) using salivary flow rates^{8, 28, 44–48, 50}. Unstimulated whole saliva (UWS) flow rates were measured using the spitting method^{8, 47, 48} or sialometry⁵¹. Stimulated whole saliva (SWS), essential during meals for bolus formation and digestion, was measured using mastication techniques or citric acid stimulation⁴⁵. Xerostomia was assessed by Khoury et al. and Bossola et al. using the Xerostomia Inventory^{52, 53}. The Xerostomia Inventory (XI) is a comprehensive, self-reported questionnaire designed to evaluate the severity and impact of xerostomia symptoms on an individual’s quality of life. It consists of 11 items, each rated on a five-point Likert scale ranging from “never” to “very often,” covering various aspects of dryness-related discomfort, including difficulties with speech, swallowing, and oral sensation⁵³. Additionally, Kiesswetter et al. and Ambrosio-Palma et al. gathered self-reported data on xerostomia from their participants, whereas Helou et al. conducted oral cavity inspections to assess xerostomia^{51, 54}.

For the assessment of nutritional status, the Mini Nutritional Assessment tool was used in six studies^{8, 46, 50–52, 55}. The Mini Nutritional Assessment (MNA) is a validated tool to evaluate the nutritional status of older adults. It consists of a 6-question screening section (MNA-SF) with a maximum score of 14 and a full assessment section completed if the screening score is ≤11, providing a total score of 30. Scores categorize individuals as having normal nutrition, being at risk of malnutrition, or being malnourished, enabling early identification and intervention⁵⁶. Rhodus et al. (1988, 1991) used 5-day dietary records, which included videotapes of meal trays from 15 meals (5 days), as well as snacks, food from friends or relatives, and vending machine purchases, to document their total dietary intake. Andersson et al. utilized the Subjective Global Assessment (SGA), an instrument that combines a patient’s history and physical examination to grade nutritional status clinically⁴⁹. Patients were categorized as (i) well-nourished, (ii) well-nourished but at risk of undernutrition, (iii) suspected of being undernourished, or (iv) severely undernourished. Other remaining studies used BMI, body weight calculation, and anthropometric measures^{8, 44, 45, 47, 48, 50–55, 57, 58}. (Table 3)

Table 3.

General Characteristics of Included Studies

Author (year) (First author’s last name et al)	Type of Study	Country	Sample size		Age		Type of participants	Assessment for hyposalivation	Assessment for nutritional status
			Cases (No/gender)	Control (No/gender)	Cases (range/mean)	Control (range/mean)
Ambrosio-Palma et al. (2022)	Cross-sectional study	Mexico	100/M=26 F=74	NR	73–88 yrs/81.2 ± 7.5 yrs	NR	Outpatients at a University third-level hospital in Mexico City.	Self-reported	Short-Form Mini Nutritional Assessment (MNA)
Andersson et al. (2004)	Cross-sectional study	Sweden	161/M=44 F=117	NR	65–98 yrs/81.7 yrs	NR	Newly admitted elderly patients in rehabilitation care	Revised Oral Assessment Guide (ROAG)	Subjective Global Assessment (SGA)
Barbe et al. (2018)	Cross-sectional study	Germany	20/M=0 F= 20	12/M=3 F=9	77–91 yrs/84±7 yrs	75–87 yrs/81±7 yrs	Geriatric patients admitted to the orthogeriatric department Exp= with a fall and trauma history. Control= without a fall and trauma history.	Unstimulated whole saliva flow rate (UWSFR) Stimulated whole saliva flow rate (SWSFR) Xerostomia Questionnaire (XQ)	Mini Nutritional Assessment (MNA)
Bossola et al. (2013)	Cross-sectional study.	Italy	75/M=47 F=28	NR	47.2–77/62.1 ± 14.9	NR	Hemodialysis patients	Xerostomia Inventory	Hemodialysis Study Appetite questionnaire
Nelson L. Rhodus et al (1988)	Case-Control Study	USA	28/M=10.7%, F=89.3%	24/M=18.2%, F=81.8%	Above 60 yrs/69.4 yrs	Range = >60yrs/Mean=68.2 yrs	Case=Sjogrens syndrome Control=dental clinic patients	UWS; and Stimulated parotid flow rate with citric acid	Five-day dietary record
Nelson L. Rhodus et al (1991)	Case-Control Study	USA	Free-living: 24/M=10%, F=90% Institutionalized: 21/M=22.5%, F=77.5%	22/M=18.2%, F=77.5%	Free-living: NR/69.4 yrs Institutionalized: NR/69.1 yrs	Range = NR/Mean = 68.2 yrs	Case=Free-living: attending U of Minnesota dental clinics; and Insitutionalized geriatric subjects Control=22 age matched participants	UWS and Stimulated saliva (Parotid)	Five-day dietary record. Videotapes of institutionalized subjects’ meals and copy of quantitative menu.
Samnieng et al (2012)	Cross-sectional and observational study	Thailand	612/M=158, F=454	NR	60 −70 yrs/68.8 yrs± 5.9	NR	Random sampling of elderly lived in Phitsanuloke, Thailand	UWS (spit for 5 min), and SWS (mastication of paraffin for 5 min)	Mini Nutritional Assessment (MNA) questionnaire.
Wu et al (2024)	Cross-sectional study	China	267/M=121, F=155	NR	75–94 yrs/81.4± 4.3 yrs	NR	Randomized cluster sampling of older adults living in rural area of Qingdao, Shandong.	UWS and SWS	Mini Nutritional Assessment-Short Form (MNA-SF); Food Frequency Questionnaire; and 24-hour Food Intake Recall
Khoury et al (2022)	Cross-sectional study	France	87/F=74.7%	NR	90.6 – 105.6 yrs/94.1 yrs±3.0	NR	Participants of PAQUID study (cohort on cerebral and functional aging in France at 25-yr follow-up)	Xerostomia Inventory	Mini Nutritional Assessment (MNA)
Iwasaki et al (2016)	Cross-Sectional study	USA	352/M=174, F=178	NR	80 yrs	NR	Random Japanese	SWS collection and questionnaire	Questionnaire
Dormenval et al (1998)	Cross-sectional study	Switzerland	99/M=30, F=69	NR	75–95 yrs/82.5 ± 4.0 yrs	NR	Hospitalized patients	USFR, SSFR	Questionnaire
Dormenval et al (1999)	Cross-sectional study	Switzerland	99/M=30, F=69	NR	75–95 yrs/82.5 ± 4.0 yrs	NR	Hospitalized patients	USFR, SSFR	Anthropometric measures, questionnaire
Helou et al 2014	Cross-sectional study	Lebanon	115/M=56, F=59	NR	NR/76.2 ±5.6 yrs	NR	Hospitalized patients	Inspection of oral cavity	Mini-Nutritional Assessment Questionnaire
Kiesswetter et al 2019	Longitudinal Cohort Study	Netherland	893/M=474, F=419	NR	55–80 yrs/67.6±6. 1 yrs	NR	Dutch older people	Self-administered questionnaire (22 items)	Body height and weight were measured, and BMI was calculated (9 year follow-up)

SWS - Stimulated Whole Saliva, PAQUID STUDY - ongoing cohort to describe the evolution of cognitive functions to identify predictive signs of and risk factors for dementia, and to study dependence in older adults, its risk factors, and consequences.

3.3. Outcome related to hyposalivation and malnutrition

A significant association between hyposalivation and malnutrition was consistently observed across multiple studies, as shown in Table 4. The results based on various methods for measuring xerostomia and nutritional status were as follows: in the study by Ambrosio-Palma et al. (2022), 71% of participants self-reported xerostomia, and hyposalivation was linked to an MNA score of < 8 (risk of malnutrition), suggesting an association with inadequate nutrition (p = 0.035)⁵¹. Similarly, Andersson et al. (2004) found that 56% of patients exhibited low salivary flow, which was associated with undernourishment in 54% of cases (OR = 2.7, 95% CI 1.3–5.4, p = 0.007⁵¹. Barbe et al. (2018) observed that 64% of participants had hyposalivation, 93% reported xerostomia, and 52% were malnourished, indicating a strong connection between dry mouth and reduced nutritional intake (p < 0.05)⁴⁶. Bossola et al. (2013) further supported these findings, showing a significant relationship between xerostomia, poor appetite, and lower BMI (p < 0.0001)⁵³. Nelson L. Rhodus (1988, 1991) conducted two studies that showed both free-living and institutionalized individuals with xerostomia had significantly lower nutritional intake compared to controls, with deficiencies observed across all 12 nutrients analyzed (p < 0.01 and p < 0.001). Samnieng (2012) found that 14.4% of participants had hyposalivation, and those with reduced salivary flow had a significantly lower mean MNA score (p < 0.05)⁸. Wu (2024) also identified that xerostomia was more prevalent among participants classified as malnourished or at risk of malnutrition (p = 0.037)⁵⁰. Khoury (2022) reported a strong association between xerostomia and malnutrition risk, with an odds ratio of 8.79 (p = 0.002)⁵². Additional studies by Dormenval et al. (1998, 1999), Keisswetter et al. (2019), and Iwasaki et al. (2016) confirmed an association between hyposalivation and indicators of poor nutrition such as low BMI, triceps skinfold thickness, and mid-arm circumference^{28, 47, 48, 54}. Helou et al. (2014) concluded that xerostomia was not associated with a significant risk of nutritional deficits (p ≤ 0.05)⁵⁵.

Table 4.

Outcome related to hyposalivation and malnutrition.

Author	Measurement of hyposalivation	Outcome of hyposalivation	Measurement of nutritional Status	Outcome of nutrition status	Statistical Analysis	P value	Software Used	Result	Confounding factors
Ambrosio-Palma et al. (2022)	Self-reported	71% = Self-reported xerostomia	Mini Nutritional Assessment Short-Form (MNA-SF) (<8 = Risk of malnutrition)	MNA-SF score = <8	Logistic regression models	p<0.05 Xerostomia p= 0.05 Nutritional status p=0.035	SPSS	Hyposalivation is associated with inadequate nutrition status and is more likely to contribute to malnutrition in individuals with oral dysphagia.	Oropharyngeal dysphagia
Andersson et al. (2004)	ROAG	Low salivary flow in 56% of patients. (p=0.026)	SGA	Undernourishment in 54% of the patients.	Odds ratios (ORs) with 95% confidence intervals (CIs) were estimated. Univariate and multiple logistic regression analyses.	p=0.007	SPSS	Low saliva flow was associated with the presence of undernourishment. (OR 2.7, 95% CI 1.3—5.4.)	Alterations on the Tongue
Barbe et al. (2018)	Unstimulated whole saliva flow rate (UWSFR) Stimulated whole saliva flow rate (SWSFR) Xerostomia Questionnaire (XQ)	64% = hyposalivation, 93% = xerostomia.	Mini Nutritional Assessment	39% = risk of malnutrition 52% = Malnutrition	Mean (SD) values, Spearman, Wilcoxon signed-rank test and Mann–Whitney U-test, ORs	p<0.05	SPSS Statistics 24	Dry mouth is associated with reduced and changed nutritional intake.	Fall history
Bossola et al. (2013)	Xerostomia Inventory	Median XI score = 18	Hemodialysis Study Appetite questionnaire	38.9% patients had very poor/poor appetite	Univariate analysis, multiple linear regression analysis	XI score was significantly associated with appetite, p<0.0001	SYSTAT 7.0, SPSS	Xerostomiais independently associated with appetite, leading to avoidance of food and low BMI.	Age
Nelson L. Rhodus (1988)	UWS = 0.1ml/min for 10min. Stimulated parotid: 2 drops of 2% citric acid on the tongue with Curby cup, for 10 min.	Case: labial salivary gland biopsy Control: UWS and SWS was >0.5ml/min	Self-reported pre- and post-5-day dietary record interviews	Of the twelve nutrients analyzed, SS group is deficient at 100%, relative to RDA (US Recommended Dietary Allowance	Student’s t-test	p<0.01	PRUCAL/program for nutritional analysis. NR for statistical software.	Group with xerostomia had significantly lower nutritional intake as compared with controls.	Sjögren’s Syndrome
Nelson L. Rhodus (1991)	UWS = a quantity of less than .5ml/min SWS=parotid stimulation by 2 drops of citric acid on the tongue, <0.1ml/min	All cases both free-living (100%, n=24) and institutionalized (100%, n=21) exhibited xerostomia.	Free-living: Pre- and Post-dietary record interviews, 5 day dietary record (self-reported). Institutionalized: Copy of quantitative menu, videotapes of meals and snacks, etc. Then, data translated into computer codes for analysis of nutrient levels, using PRUCAL program.	Both Free-living & institutionalized had significantly lower nutritional intakes for all twelve nutrients compared to the control group.	Student’s T-test and Chi-square analysis	p<0.001	PRUCAL for nutritional analysis/NR for statistical software.	Association between xerostomia and inadequate nutritional intake in seniors was apparent	Medication Use Chronic systemic diseases
Samnieng (2012)	UWS: 5min spitting, hyposalivation if flow rate <0.1ml/min SWS: chew paraffin block for 5 min, hyposalivation if flow rate <0.5ml/min	14.4% (n=88) had hyposalivation.	Mini Nutritional Assessment (MNA) questionnaire with 18 items. Score ranges 0–30: Normal nutritional status = >23.5 Questionable nutritional status = 17–23 Malnutrition if score = <16	Mean MNA score was 21.5 (3.0). Normal nutrition: 7.7% Risk of malnutrition (questionable): 67.1% Malnutrition: 25%	Chi-square tests, Analysis of Variance (ANOVA), Analysis of Covariance (ANCOVA), Multiple logistic regression analysis	p<0.05	SPSS 17 software	Subjects who were classified as hyposalivation had a lower mean MNA score (20.7) compared with those who were classified as normal salivation (22.6, p<0.05) Nutritional status was associated with hyposalivation	Oral function problems (Swallowing, speaking, teasting and chewing)
Wu (2024)	UWS: spit in a tube for 5 mins. SWS: wait 10 minutes after UWS test, chew parafilm, the spit in a tube for 5 mins. Saliva volume is then calculated gravimetrically after collection.	Xerostomia: 127 subjects (46.0%); More frequently reported by malnourished group than by those who were not (p=0.037)	Mini Nutritional Assessment-Short Form (MNA-SF) Score between 0–14. In this study, Malnutrition Group =0 – 11 points (includes malnourished & at risk of malnutrition) Well-nourished group = 12–14 points	Malnutrition group = 112 (40.6%) participants; where Malnourished =2.2%, at risk of malnutrition =38.4%.	The Kolmogorov-Smirnov test; Mann-Whitney and Chi-square tests; Spearman’s rank correlation analysis Multiple regression analysis	p<0.05	SPSS	This study revealed a statistically significant difference in xerostomia between the two groups (Well-nourished vs Malnourished), with more participants in the malnutrition group experiencing xerostomia.	Decreased oral function (swallowing, chewing) Frequency of exercise Stroke; Intake of vegetables and fruits.
Khoury (2022)	Xerostomia Inventory “subjective feeling of dry mouth”	Xerostomia = 21 participants (24.1%)	Mini Nutritional Assessment (MNA) questionnaire with 18 items. Score ranges 0–30: Normal nutritional status = >23.5 Questionable nutritional status = 17–23 Malnutrition if score = <16	Malnutrition or risk of malnutrition (MNA <24) = 23 participants (26.4%)	Univariate and multivariate logistic regressions	p<0.05	SAS and R software	Xerostomia (OR = 8.79. 95% CI = 2.38–39.10; p = 0.002) was found to be associated with malnutrition or risk of malnutrition.	Female (vs male) Institutionalized (vs living at home) Number of medications per day Number of posterior occluding pairs
Dormenval et al (1998)	USFR (0.1ml/min) and SSFR (0.5ml/min) were collected by spitting every 2 mins for 6 mins and self-reported oral dryness during day and night	USFR=17%, SSFR=26%; USFR decreased in patients with daytime oral dryness (P=0.03), and SSFR decreased in those with nighttime dryness (P<0.01)	BMI, mid-arm circumference, triceps skinfold thickness, and serum albumin level	BMI, mid-arm circumference, and triceps skinfold thickness were significantly lower in patients with daytime dry mouth	Multivariate analysis of variance	P=0.05	NR	Xerostomia is linked to poor nutrition and general health	Increased number of medications
Iwasaki et al (2016)	SWS: Chew a 1-g piece of paraffin wax for 3 min and to expectorate secreted saliva into a test tube.	11.4% (n = 36) had hyposalivation	Brief-type self-administered diet history questionnaire calculated based on the Standard Tables of Food Composition in Japan	Lower nutritional intake reported in hyposalivation group	independent t-tests, χ2-tests, multivariable analysis	P<0.05	STATA	Hyposalivation was associated with malnutrition	Chewing and swallowing difficulty Lower income Diabetes Psychological distress
Dormenval et al (1999)	USFR and SSFR were collected by spitting every 2 mins for 6 mins. Reduced USFR and SSFR were 0.1ml/min and 0.5ml/min, respectively	17% had reduced USFR; 26% had reduced SSFR.	BMI, mid-arm circumference, triceps skinfold thickness, and serum albumin level	50% of the patients have malnutrition	Pearson chi-square test; Student’s t-test	P<0.05	N/R	Hyposalivation leading to eating difficulties is associated with malnutrition	Poor Dental or Prosthetic status
Helou et al 2014	NR	74.8% complained of xerostomia	Mini-Nutritional Assessment (MNA): good nutritional status score >23.5, At risk of malnutrition 17–23.5, undernourished score <17	6% undernutrition; 37.4% risk of malnutrition mean MNA score 23.6 ±4	Bivariate analyses, multiple logistic regression	p≤0.05	SPSS	Xerostomia is not associated with risk of nutritional deficit	Low level of eudcation Use of more than three drugs/day; Lack the ability to shop or prepare meals Avoidance of certain foods
Kiesswetter et al 2019	Self-reported	24% reported xerostomia	Self-reported involuntary WL≥5% in the previous 6 months and/or low BMI. Low BMI means <20kg/m2 in <70 years and 22kg/m2 >70 years	32.7% of people who reported oral problems (n=107) had xerostomia with malnutrition	Chi2-tests	p>0.05	SPSS	Xerostomia was more pronounced in people with incident malnutrition	Toothache while chewing Poor self-rated oral health

USFR- - unstimulated salivary flow rate, SSFR - stimulated salivary flow rate, BMI - body mass index, UWS - unstimulated whole saliva, SWS - stimulated whole saliva, ROAG - Revised Oral Assessment Guide, NST - Nutritional Screening Tool, WL – weight loss

The meta-analysis (Figs. 2, 3, 4) evaluated the prevalence of hyposalivation/xerostomia and malnutrition deficits across multiple studies, involving 2,340 participants. The findings provide insight into the variability of reported prevalence rates and highlight the need for standardized diagnostic approaches.

Figure 2. Forest plot of malnutrition deficit event proportion in older adults.

Forest plot displaying the proportion of older adults with malnutrition across individual studies included in the review. The blue squares represent the effect size for each study, with horizontal lines indicating 95% confidence intervals. The diamond at the bottom reflects the pooled prevalence estimate using a random-effects model.

Figure 3. Forest plot indicating hyposalivation and nutritional events proportion within older adults.

Forest plot summarizing the prevalence of both hyposalivation and nutritional deficiency among older adults in each included study. Individual study estimates are shown with 95% confidence intervals. The overall pooled proportion is shown as a red diamond.

Figure 4.

Forest plot indicating hyposalivation/xerostomia event proportion within older adults

For hyposalivation/xerostomia, the pooled prevalence, as estimated using the random effects model, yielded a broader estimate of 38% (95% CI: 22–57%). The analysis revealed substantial heterogeneity (I² = 97%, τ² = 1.7687, p < 0.01), indicating significant variability among studies, likely due to differences in patient populations, diagnostic criteria, and methodologies. These results suggest that xerostomia is a prevalent condition; however, the wide range of reported estimates underscores the need for further research to understand the contributing factors better.

Regarding malnutrition deficits, individual study proportions varied widely from as low as 0.10 (Iwasaki et al., 2016) to as high as 0.93 (Samnieng et al., 2012b), highlighting significant differences in reported prevalence. The random effects model provided a more conservative estimate of 0.55 [0.34, 0.74], reflecting broader uncertainty. This high heterogeneity suggests notable differences among studies, potentially influenced by variations in population characteristics, study design, or measurement methods. The wide confidence interval in the random effects model underscores this variability, emphasizing the need for cautious interpretation and further investigation into the sources of inconsistency.

When specifically examining the relationship between hyposalivation and nutritional deficits, the reported proportions varied significantly, with Nelson L. Rhodus et al. (1991) reporting the highest prevalence at 0.67 [0.55, 0.78], while other studies, such as Iwasaki et al. (2016) and Wu et al. (2024), reported much lower proportions around 0.10–0.14. Given the high heterogeneity (I² = 94%), the random effects model provided a slightly adjusted estimate of 0.22 [0.14, 0.34], accounting for study variations. The broad confidence interval in the random effects model suggests substantial variability, likely due to differences in sample populations, diagnostic criteria, or study methodologies. This high heterogeneity underscores the need for careful interpretation and additional research to explore the underlying factors contributing to these variations.

3.4. Consequences of hyposalivation in older adults

Fig. 5 summarizes hyposalivation-related damage reported by all included studies. Low nutrient intake was the most common consequence among the participants of most of the included studies (n = 13; 92.80%), followed by difficulties with swallowing (n = 8; 50%) and chewing (n = 6; 37.50%).

Figure 5.

Consequences of hyposalivation in elderly

3.5. Risk/association of hyposalivation

Of the 14 studies reviewed, nine identified a relationship between hyposalivation and an increased risk of systemic health diseases. Ambrosio-Palma et al., Andersson et al., Bossola et al. Dormenval et al. (1998). Nelson et al. (1991) and Samnieng et al. reported that medication intake was associated with the occurrence of hyposalivation^{8, 45, 47, 49, 51, 53}. (Fig. 6).

Figure 6.

Common risks/associations of hyposalivation and malnutrition in the elderly

3.6. Risk/association of malnutrition

Issues with oral health, such as root caries, periodontitis, burning mouth syndrome, mucosal ulcerations, and dysgeusia or hypogeusia, as well as problems with oral function, including difficulty with chewing, swallowing, and altered taste perceptions, were identified as having an association with malnutrition in almost all the included articles. (Fig. 6)

3.7. Results of risk of bias

The risk of bias assessment for the included studies was conducted using the Newcastle-Ottawa Quality Assessment Scale, tailored for cross-sectional, case-control, and cohort study designs. Among the 10 cross-sectional studies, scores ranged from 5 to 10, reflecting varying degrees of methodological quality. Studies like Wu et al. (2024) and Khoury et al. (2022) achieved the highest scores of 9 and 10, respectively, indicating robust sampling, strong ascertainment of exposure, and thorough statistical testing^{50, 52}. These studies effectively minimized biases related to sample representation and outcome measurement, enhancing the reliability of their findings. In contrast, Anderson et al. (2004) scored only five due to gaps in sample size management, a lack of response rate reporting, and a limited assessment of outcomes, which may introduce selection and information bias⁴⁹. Other studies, such as those by Barbe et al. (2018) and Dormenval et al. (1998, 1999), scored moderately (7/10), suggesting adequate handling of exposure and outcomes but room for improvement in addressing non-respondent bias and representativeness^46–48. Rhodus (1988) demonstrated strong methodological rigor in the two case-control studies, scoring 8/10⁴⁴. This study excelled in case definition, comparability between cases and controls, and consistent exposure assessment. However, Rhodus (1991) scored 6/10, highlighting issues with the representativeness of the cases and the incomplete handling of non-respondents, which may have limited its generalizability⁴⁵. The single cohort study by Kiesswetter et al. (2019) was assessed using a modified Newcastle-Ottawa scale, scoring 8/9. This study displayed strengths in exposure ascertainment, follow-up adequacy, and outcome assessment, ensuring a high level of reliability⁵⁴. However, slight limitations in exposure representativeness were noted, suggesting potential for improvement in this domain. Overall, the assessment revealed that while most studies demonstrated acceptable to high methodological quality, a few exhibited limitations that could affect the robustness of their findings. This variability highlights the need for cautious interpretation of the evidence, particularly from studies with lower scores. (Tables 5, 6, and 7)

Table 5.

Quality assessments for cross-sectional studies included (NEWCASTLE – OTTAWA QUALITY ASSESSMENT SCALE).

Cross sectional studies (n=10)	Selection	Comparability	Outcome	Total Score
	Representativeness of the sample	Sample size	No-respondents	Ascertainment of the exposure	The subject in different outcome groups	Assessment of outcome	Statistical test	Max = /10
Ambrosio-Palma et al. (2022)	*	*	-	**	*	*	*	7
Anderson et al. (2004)	*	-	-	**	-	*	*
5
Barbe et al. (2018)	*	-	-	**	**	*	*	7
Bossola et al. (2013)	-	-	-	**	*	**	*	6
Samnieng et al. (2012)	*	-	-	**	**	**	*	8
Wu et al. (2024)	*	*	-	**	**	**	*	9
Khoury et al. (2022)	*	*	*	**	**	**	*	10
Iwasaki et al. (2016)	*	*	-	**	**	**	*	9
Dormenval et al. (1998)	*	-	-	**	*	**	*	7
Dormenval et al. (1999)	*	-	-	**	*	**	*	7
Helou et al. (2014)	*	-	-	**	**	**	*	8

Table 6.

Quality assessments for case-control studies included (modified Newcastle - Ottawa quality assessment scale).

Case-control studies (n=2)	Selection				Comparability	Exposure			Total Score
	Case definition adequate	Representativeness of cases	Controls	Definition of controls	Case and controls on the basis of the design or analysis	Ascertainment	Same method for case and controls	Non-response rate
Rhodus (1988)	*	*	*	*	**	-	*	*	8
Rhodus (1991)	*	-	*	*	**	-	-	*	6

Table 7.

Quality assessments for cohort studies included (modified Newcastle - Ottawa quality assessment scale).

Cohort study (n=1)	Selection	Comparability	Outcome	Total Score
	Representativeness of the exposed cohort	non-exposed cohort	Ascertainment of exposure	Outcome of interest was not present at the start	Cohorts	Assessment	Was follow-up long enough	Adequacy of follow up of cohorts	Max = /9
Kiesswetter et al. (2019)	*	*	-	*	**	*	*	*	8

4. Discussion

Most evidence presented in this systematic review supporting the association between oral health and malnutrition is based on findings from cross-sectional studies. Of the fourteen studies reviewed, thirteen identified a positive correlation between hyposalivation and nutritional deficiencies in older adults^{8, 28, 44–54}. Saliva flow measurements consistently demonstrated reduced salivary output among older adults, with UWS decreasing by 40% and SWS by 15%⁵⁹. These findings align with earlier research emphasizing the importance of assessing UWS and SWS saliva when evaluating hyposalivation, and its nutritional implications^{59, 60}. Most patients from the included studies were older adults, with a mean age above 65. Increasing age may be associated with numerous physiological changes impacting nutritional status, salivary gland function, and saliva composition. Histological changes in the glands related to aging often include a reduction in the number of acini and an increase in fatty and fibrous tissue¹⁵. Changes in saliva composition due to aging may involve decreased levels of calcium and mucins, elevated ionic concentrations, and reduced IgA levels, which can negatively impact oral health, taste perception, and food intake^{12, 15}. Furthermore, aging can influence the synthesis of salivary proteins and the glycosylation of mucins, thereby compromising oral defense mechanisms^{15, 61}. As a result, salivary output may diminish, leading to decreased salivary secretion, a key component necessary for oral health and digestion¹². In contrast, some other studies suggested that healthy older adults without systemic diseases or medication influences may not experience significant reductions in saliva flow. Yeh et al. (1998) found that in a non-medicated subpopulation, the age-related decreases were less pronounced compared to substantial age-related decreases in UWS and stimulated submandibular/sublingual saliva flow rates in a community-based population. Our previous publications also suggested that factors other than aging, such as medication use and systemic health conditions, may play a more substantial role in salivary gland function^{62, 63}. These findings highlight the importance of considering individual health status and external factors when evaluating salivary gland function in older populations.

Hyposalivation may be paired with xerostomia; they are not necessarily correlated⁶⁴. Xerostomia is particularly prevalent among older adults, with medication use being a major contributing factor. Polypharmacy poses a higher risk of anticholinergic burden and an increased likelihood of experiencing dry mouth^65–67. A cross-sectional study involving older hospitalized patients demonstrated a significant correlation between reduced salivary secretion, symptoms of hyposalivation and compromised nutritional and general health, which adversely impacted appetite, dietary intake, and oral comfort⁷. Rhodus⁴⁴ has characterized malnourishment associated with xerostomia by noting that individuals with xerostomia exhibited significantly lower nutritional intakes across all nutrients below recommended levels based on the US Dietary Guidelines, compared to controls. Besides its impact on the mechanical processing of food, xerostomia significantly alters the sensory experience of eating. Individuals with burning mouth syndrome, a condition frequently accompanied by xerostomia⁶⁸, often experience discomfort during meals, leading to an aversion to diverse, nutrient-rich foods and the preference for processed foods that lack essential nutrients like protein, fiber, vitamins, and minerals, adding to deficiencies, especially in iron, vitamin B12, and folic acid^69–71. The study by Yoshida et al. examined the prevalence and associated factors of xerostomia and hyposalivation among 894 community-dwelling older adults in Japan aged 65–84 years⁹. Their findings revealed that hyposalivation was more prevalent in women and was linked to the use of medications affecting the digestive system, as well as systemic and metabolic factors; thus, diminished salivary function was associated with an increased risk of nutritional deficiencies. As dietary quality declines due to these factors, systemic health deteriorates further, creating a feedback loop where poor nutrition exacerbates deterioration in both oral and systemic health^{8, 28, 50}.

Our review identified published evidence on the association between impaired salivary function and malnutrition. Malnutrition in older adults is a significant public health concern, with various risk factors identified across studies. These include advanced age, rural residence, economic vulnerability, chronic pain, previous hospitalization, and lack of health insurance⁷². Depression, cognitive decline, and the presence of chronic diseases also contribute to malnutrition risk^{33, 72}. Other factors include frailty, excessive polypharmacy, poor self-reported health status, eating dependencies, and institutionalization³³. Age-related changes, such as decreased gastric motility and flexibility, impaired nutrient absorption, and systemic inflammation, contribute to early satiety, reduced food intake, and the anorexia of aging⁵⁷ .

Consistent with this review’s findings, hyposalivation can hinder the food processing experience of older adults due to a lack of lubrication and impaired textural perception of food, ultimately impacting food intake⁷³. Saliva plays a critical role in bolus formation by combining food particles into a cohesive, slippery mass, facilitating safe and efficient swallowing. The water content of saliva hydrates food, while mucins and glycoproteins provide lubrication to prevent damage to the oral and esophageal tissues. Pedersen et al. (2002) emphasized the multifaceted roles of saliva in gastrointestinal processes, particularly its role in bolus lubrication, which enhances the efficiency of chewing and swallowing. Hyposalivation leads to difficulties with chewing and swallowing (dysphagia), which can manifest as oropharyngeal dysphagia, characterized by difficulty initiating a swallow due to issues in the oral cavity or throat. Symptoms may encompass pain during swallowing, the sensation of food being stuck, coughing or gagging when swallowing, and recurrent pneumonia due to aspiration. A meta-analysis analyzed dysphagia and pneumonia across five studies, encompassing a total of 5,314 patients⁷⁴. They revealed that the incidence of pneumonia was over nine times more likely to develop in patients with dysphagia compared to those without dysphagia.

Saliva’s role extends to sensory enhancement, as it dissolves flavor molecules, allowing them to interact with taste receptors. This interaction enables the perception of complex flavors, including sweet, sour, salty, bitter, and umami. A comprehensive review by Zhang et al. (2022) delves into the properties and functions of saliva during oral processing. The authors discuss the secretion mechanisms of saliva, detailing its physical and chemical characteristics, including its composition, which is approximately 98% water and 2% organic and inorganic substances. The interactions between saliva and food components affecting taste are examined, providing insights into how saliva contributes to the overall eating experience. Declines in taste and smell are closely linked to malnutrition in older adults, significantly reducing appetite, altering macronutrient intake, and affecting food enjoyment and overall dietary quality. Sensory impairments can negatively impact the quality of life and increase the risk of adverse outcomes, such as protein-energy malnutrition, sarcopenia, and frailty^{75, 76}. Olfactory impairment increases dramatically from the fifth decade of life, often resulting in anosmia after 90 years⁷⁷, and can significantly impact food intake and quality of life⁷⁸. Fluitman et al. reported that olfactory decline in older adults is associated with decreased protein intake and a shift toward calorie-dense, low-nutrient foods⁷⁹. Similarly, diminished taste perception, particularly in detecting umami and salty flavors, leads to poor dietary diversity and inadequate intake of essential micronutrients such as zinc, vitamin D, and folate²⁸. These sensory changes often co-occur with xerostomia, further reducing food enjoyment and impairing flavor perception⁵⁵ . Age-related degeneration, including the loss of olfactory receptor neurons, reduced sensory cell regeneration, and decreased taste bud functionality, contributes to sensory declines. Chronic conditions, such as diabetes²⁸, Parkinson’s disease⁵⁵, Alzheimer’s disease⁷⁹ , and chronic kidney disease⁴⁹, impair sensory pathways, reducing the ability to detect and appreciate flavors and smells. Polypharmacy⁵⁷, common in older adults, also exacerbates sensory impairments through side effects such as dry mouth and altered taste perception⁴⁹. These factors create a cycle of reduced dietary intake and worsening nutritional status.

Hyposalivation in older adults consists of a complex, bidirectional relationship with nutritional status. On one hand, loss⁸⁰ and reduced salivary flow impair chewing, swallowing, and taste perception, making it difficult to eat a wide variety of foods and often leading to reduced nutrient intake and malnutrition. On the other hand, the underlying factors that increase the risk of malnutrition in older adults, such as chronic systemic diseases, polypharmacy, and medical interventions, are also well-known causes of hyposalivation. Recognizing this bidirectional relationship is crucial to understanding how dry mouth and malnutrition can mutually exacerbate each other in geriatric populations.

As the global population ages, there is a growing need for the early identification of individuals at risk through routine oral health assessments and the use of screening tools, such as salivary flow measurements and evaluations of functional tooth units. The absence of functional tooth units reduces the ability to properly process food, leading to a preference for softer, easier-to-chew foods that are typically calorie-dense but nutrient-poor. The 2024 Oral Health Surveillance Report, published by the Centers for Disease Control and Prevention, reported that the average number of permanent teeth among older adults in the United States decreases with age. Adults aged 65 to 74 have an average of 21.7 teeth, while those aged 75 and older have an average of 19.8 teeth. Missing teeth, edentulism, and inadequate prosthetic rehabilitation limit the ability to ingest and process a wide variety of foods, contributing to eating discomfort and restricted dietary variety, which further increases malnutrition risks. Interventions such as patient and caregiver education, saliva substitutes, dental prosthetics to restore masticatory function, and dietary modifications can enhance food intake and nutrient absorption. Properly designed dentures or dental implants are crucial in restoring masticatory efficiency, allowing older adults to consume a more balanced diet that includes nutrient-rich foods such as raw vegetables, fruits, and proteins. Although dentition status was not consistently reported across all included studies, several did reference chewing difficulty, edentulism, or prosthetic use. The lack of standardized dental data represents a limitation in evaluating the impact of oral function on nutrition. Future studies should prioritize comprehensive dental assessments to better understand the relationship between salivary function, dentition, and nutritional health status. Additionally, living arrangements can impact access to care, dietary patterns, and support systems; the core association between salivary flow and nutritional status remains relevant across settings. Nonetheless, stratifying community-dwelling and institutionalized older adults could offer more nuanced insights, and we have noted this as a limitation. Effective management requires collaboration among healthcare providers, including dentists, dietitians, and primary care physicians, to develop comprehensive care plans that address the unique needs of older adults, ultimately improving their nutritional status and quality of life.

Conclusions:

Based on the included articles, this review confirmed a significant association between hyposalivation and malnutrition. Hyposalivation impairs essential functions such as chewing, swallowing, and taste perception, which can result in food avoidance and subsequent nutritional deficiencies. The primary contributors to reduced intake include compromised systemic health and dental conditions, including the total number of teeth and denture use. Notably, older adults experiencing hyposalivation encounter more significant difficulties in meeting their nutritional needs compared to those without hyposalivation. The study highlighted the importance of adopting a multidimensional approach to addressing and managing dry mouth in older populations.

Clinical significance:

This review highlights the association between hyposalivation and malnutrition in non-cancer older adults. Dry mouth impairs oral function, leading to poor nutrient intake and an increased risk of malnutrition. Early detection and management of hyposalivation are crucial to prevent nutritional problems. The variability in prevalence suggests a need for standardized diagnostic tools and further research to understand better nutritional health concerns associated with hyposalivation, as well as to improve patients’ overall health and quality of life.