Examining the relationship between oral health indicators, obesity, and Xerostomia in older adults

Abstract

Introduction and objective

Obesity is becoming a hot topic for people and governments around the world, with many countries even considering it an epidemic. A group of researchers has made new findings about the link between obesity and oral health, making the issue even more sensitive than before. According to the findings, clear signs of periodontal disease are seen in people with a body mass index (BMI) above 30. Also, xerostomia is actually a subset of oral health that can significantly affect various aspects of oral health. Saliva plays an important role in maintaining oral health by keeping your mouth moist, cleaning your teeth, and fighting bacteria. Therefore, this study aimed to explore the association between obesity indicators, general oral health variables, and xerostomia.

Methods

This cross-sectional study involved 439 adults aged 50 years or older. Data were collected using a structured questionnaire consisting of five sections: (I) demographic information, (II) oral health (issues such as loose teeth, tooth loss, use of dentures/implants, bleeding gums - self based on reported questionnaires and dental examination), (III) general health, (IV) overweight and/or obesity ( based on BMI- Height and weight measurement by a final year dental student), and (V) xerostomia (self-reported questionnaires). Statistical analysis was performed using the SPSS 24 software, with methods including T-test, Kruskal-Wallis, ANOVA, Chi-Square test, Pearson correlation coefficient, and logistic regression. A significance level of P < 0.05 was set for analyzing relationships.

Results

The study included 312 female and 127 male participants. The average age, body mass index (BMI kg/m²) and waist-to-height ratio (WHtR- cm/cm) of the group were 67.8 ± 11.5 years, 24.4 ± 2.1 kg/m², and 0.54 ± 0.4, respectively. The mean of the xerostomia questionnaire XI was 33.21 ± 6.56. Regarding xerostomia (self-reported questionnaires), 21.8% of respondents reported mild symptoms, 11.4% moderate symptoms, and 6.4% severe symptoms. The prevalence of xerostomia was highest in the age group of 80 years or older.

People with tooth mobility reported more xerostomia than patients without tooth mobility. 41.5% vs. 27.2% (P = 0.01). Xerostomia was reported statistically significantly more frequently in patients with hypertension (P = 0.01), diabetes (P = 0.04), and myocardial infarction (P = 0.01). Patients who reported good general health had significantly less xerostomia than patients with bad general health (P = 0.04). In this study, BMI and WHtR had no significant relationship with xerostomia (P = 0.61, 0.24, respectively). However, a statistically significant association was found between WHtR and BMI with the number of missing teeth, i.e., the higher the tooth loss, the lower the BMI and WHtR (P = 0.01).

Conclusion

The study concludes that the prevalence of xerostomia is 39.6%, as reported by participants. Age emerged as a critical factor influencing this condition, while BMI and WHtR showed no direct relationship with xerostomia itself but were significantly related to tooth loss patterns. Notably, the highest prevalence of xerostomia was observed in patients with pulmonary disease (Asthma and respiratory allergies, COPD (Chronic Obstructive Pulmonary Disease).

Introduction

Saliva plays an essential role in maintaining oral health. Beyond protecting against bacterial and fungal infections, it delivers nutrients and digestive enzymes, softens mucous membranes, facilitates chewing, swallowing, and speech, and aids in tooth remineralization processes [1, 2]. Saliva is secreted by the parotid, submandibular, and sublingual glands, along with numerous smaller glands dispersed throughout the oral cavity. These glands activate at specific intervals in response to sensory, gustatory, or olfactory stimuli [3].

Salivary production varies based on stimulation levels, peaking after meals and diminishing during sleep. Healthy individuals produce an average of 1000–1500 mL of saliva daily [3].

Decreased saliva production significantly compromises quality of life [4, 5] by causing progressive dental caries, poor denture stability, traumatic ulcers, halitosis, and infections such as candidiasis, while also impairing essential functions including mastication, swallowing, and speech [6, 7].

Xerostomia refers to either reduced salivary flow or impaired salivary gland function [8], often stemming from salivary gland changes or systemic imbalances [8–10]. While not classified as a disease itself, xerostomia represents a symptom of underlying pathological conditions that can negatively impact patients by affecting daily activities such as chewing, swallowing, denture use, and speaking [11]. Prevalence rates have varied widely in studies, ranging from 0.9% to as high as 64%, with most reports focusing on populations over 50 years old and limited measurement of objective xerostomia [6].

The development of xerostomia has a multifaceted range of causes, due to its complex mechanisms involving the control of salivation and glandular function. Risk factors commonly cited include medication usage, systemic diseases, head and neck radiation therapy, smoking and alcohol consumption habits, dehydration, and mental health conditions such as depression [7]. Among these causes, anticholinergic medications are recognized as a primary contributor to xerostomia [12]. Depression further exacerbates oral health problems by disrupting proper dental care routines and is closely linked to issues like xerostomia, dental decay, and periodontal disease. The condition is more prevalent among women and tends to increase with age [13, 14].

Research by Villa et al. [15] identified xerostomia as secondary to reduced saliva secretion while highlighting its possible associations with fungal infections (e.g., candidiasis), dental decay, halitosis, altered taste perception, and a burning sensation in the oral cavity.

Evidence suggests that certain chronic diseases may significantly contribute to the development of xerostomia and/or reduced saliva production [16–20]. Beyond this association with chronic diseases, there is also a well-documented link between xerostomia and long-term use of specific medications. Research by Wiener et al. (21), Van Putten et al. [22], and Freitas et al. [23]. highlights that anticholinergics, diuretics, antipsychotics, some types of analgesics, and antibiotics are among the drugs commonly associated with this condition.

Despite its clinical significance, xerostomia remains underdiagnosed and undertreated due to poor recognition by healthcare providers. Obesity, an established risk factor for systemic disease, correlates strongly with xerostomia and other oral pathologies, including dental caries, periodontitis, and tooth loss [24]. Critically, obesity frequently coexists with dyslipidemia, hypertension, and hyperglycemia in metabolic syndrome, a multifactorial disorder driven by sedentary behavior, aging, genetic predisposition, and nutritional imbalances. Emerging evidence directly links abdominal obesity to reduced dentition functionality, revealing profound interconnections between oral health and metabolic dysregulation [25]. The global rise in obesity prevalence has consequently amplified metabolic syndrome incidence, characterized by central adiposity, insulin resistance, hypertensive states, and dyslipidemic profiles.

Obesity is becoming a hot topic for people and governments around the world, with many countries even considering it an epidemic. A group of researchers has made new findings about the link between obesity and oral health, making the issue even more sensitive than before. According to the findings, clear signs of periodontal disease are seen in people with a body mass index (BMI) above 30. Some aspects of the study are still not clear, such as how much factors such as gender, age, smoking history and genetics really play a role in this relationship, but this still does not reduce the need for lifestyle changes. Researchers have found that the intake of sugary substances is higher in obese people than in others, and this problem is considered a factor in the development of periodontal disease. When a significant portion of the diet consists of useless calories, a person’s desire to consume foods containing important micronutrients decreases, while these same micronutrients are very important for having healthy gums and preventing tooth decay. The researchers in this study decided to examine the saliva of a group of women whose body mass index was in the range of 27 to 32. The final findings showed that a specific bacteria called “Selenomonas noxia” was present in 98.4% of the samples. Diets with a high glycemic index are the most important factor in the formation of this bacteria, and this bacteria is found in the mouths of overweight or obese people [24–26].

Also, findings from earlier research by the same group indicate that impaired chewing function may be linked to obesity, reiterating the relationship between functional teeth count and abdominal obesity. Moreover, poor oral health has been associated with heightened risks of various conditions such as aspiration pneumonia, cardiovascular diseases, diabetes, and others [27].

Xerostomia is actually a subset of oral health that can significantly affect various aspects of oral health. Saliva plays an important role in maintaining oral health by keeping your mouth moist, cleaning your teeth, and fighting bacteria. When saliva production is reduced, it can lead to increased risks such as tooth decay (dry mouth can make it easier for bacteria to grow and plaque to form, leading to tooth decay), gum disease (reduced saliva can cause inflammation and infection of the gums), oral infections (dry mouth can increase the risk of fungal infections such as oral thrush), and difficulty eating and swallowing. Therefore, this study aimed to explore the association between obesity indicators, general oral health variables, and xerostomia.

Methods

The study employed an analytical and cross-sectional design involving a sample of 500 adults aged 50 years or older, who were selected from the general population (Convenience Sampling).

Participants aged 50 years or older who volunteered to participate in the study were included in the study and individuals who were unable to answer the questions, who were not fully literate and did not understand the questions, and who were under 50 years of age were excluded from the study [24].

The study ensured participants’ autonomy by allowing them to withdraw their participation at any stage after the interview commenced. Each participant was briefed on the study’s purpose and provided with a questionnaire if they agreed to participate. Confidentiality was guaranteed, with assurances that all collected information would only be used for statistical analysis. To foster cooperation, the research objectives were clearly explained, highlighting both the harmlessness of participation and the secure handling of data. This research was approved by the Ethics Committee of Kerman University of Medical Sciences and its Research Deputy Office (Code IR.KMU.REC.1401.445, Registration No. 401000591).

A questionnaire was designed by the researchers for this purpose. (Appendix 1). The questionnaire was developed by two dental specialists and one statistician. To verify its validity and reliability, it was reviewed by four faculty experts for scientific relevance, clarity of content, and comprehension. Adjustments were made based on their feedback and relevant literature. Additionally, the questionnaire was tested in two weeks’ time on ten patients for face validation and further refinements. Cronbach’s alpha coefficient (0.72) confirmed its reliability.

The questionnaire consisted of five sections: Demographic Information (age, gender, educational, smoking habits), Oral Health (issues such as loose teeth, tooth loss, bleeding gums, and xerostomia- self-reported the Dry Mouth Questionnaire XI and dental examination), General Health (factors included high blood pressure, diabetes, cholesterol levels, osteoporosis, heart conditions, digestive or nervous disorders, use of anti-anxiety/antidepressant medications - based on self-reporting), physical activity levels, general health perception, and consumption of fresh fruits and vegetables, overweight and/or obesity [measurements included height, weight, and waist circumference - based on BMI- Height and weight measurement by a final year dental student]) [24].

Loose teeth were evaluated using the Grace & Smales Mobility Index. This method involved placing each tooth between the ends of two metal instruments (e.g., dentist mirror handles) and assessing movement in the bucolingual direction: Grade 0: No apparent mobility, Grade 1: Mobility less than 1 mm in the bucolingual direction, Grade 2: Mobility greater than 1 mm but less than 2 mm, Grade 3: Mobility exceeding 2 mm or presence of vertical movement. Each participant’s dental status was documented based on whether teeth were sound, decayed, filled, or missing. The remaining teeth count was determined as the total sum of sound, decayed, and filled teeth after excluding third molars (assessed using the DMFT index) (clinical examination). Oral examinations were conducted with participants seated in a relaxed position. In addition, oral and dental examinations were performed by a senior student using a mirror, a flashlight, and a sterile gas [24].

Xerostomia Inventory is an 11-item tool utilizing a 5-point graded response format to evaluate the severity of xerostomia symptoms on a continuous scale. Scores range from 0 to 44, where higher scores correspond to more severe symptoms. The categorization of scores is as follows: 0–11 indicates no xerostomia, 12–22 reflects mild xerostomia, 23–33 signals moderate xerostomia, and 34–44 corresponds to severe xerostomia [24].

Body Mass Index (BMI kg/m²) was computed using the formula: weight in kilograms divided by height in meters squared. The World Health Organization classifies nutritional status such as very severe wasting (≤ 15), severe wasting (15–15.9), underweight (16–18.4), healthy weight (18.5–24.9), overweight (25–29.9), moderate obesity (30–34.9), severe obesity (35–39.9), and morbid obesity (≥ 40). Since BMI does not consider body fat distribution, the waist-to-height ratio (WHtR- cm/cm) was also analyzed to complement the findings [24].

The Waist-to-Height Ratio (WHtR), calculated as waist circumference (cm) divided by height (cm), is a stronger predictor of obesity-related cardiovascular risk than BMI. Clinically significant thresholds include WHtR ≥ 0.5 for general cardiometabolic risk and ≥ 0.6 for adults > 50 years [24]. Gender-stratified classifications are:

• Very Thin: <0.34 (both sexes).

• Healthy Thin: 0.35–0.42 (men), 0.35–0.41 (women).

• Healthy: 0.43–0.52 (men), 0.42–0.48 (women).

• Overweight: 0.53–0.57 (men), 0.49–0.53 (women).

• Obese: 0.58–0.62 (men), 0.54–0.57 (women).

• Morbidly Obese: ≥0.63 (men), ≥ 0.58 (women).

Static Analysis

The study-specific database housed the collected data, which were analyzed using SPSS v.24 (IBM, Statistics, NY, USA). Categorical variables were presented as frequencies and percentages, while quantitative variables were summarized using means and standard deviations. Given the large sample size, the central limit theorem justified treating quantitative variables as normally distributed. Associations between categorical variables were assessed via chi-squared tests, while Kruskal-Wallis tests analyzed ordinal data. Parametric ANOVA, combined with Bonferroni post-hoc correction, evaluated the impact of quantitative variables on qualitative ones, and Pearson’s correlation coefficient measured variable correlations. The diagnostic utility of the Xerostomia Inventory was explored through univariate and adjusted multinomial logistic regression to calculate xerostomia risk (OR). Statistical significance was set at p ≤ 0.05.

Results

In this study, 500 forms were distributed, of which 439 were completed (Response Rate = 87.8%). The sample consisted of 312 women and 127 men. The mean age of the participants in the study was 67.8 ± 11.5. The mean BMI was 24.4 ± 2.1 and WHtR was 0.4 ± 0.54. Table 1.

Table 1.

Demographic characteristics of the participants in the study

Variable		No	%
Gender	Male	127	29
	Female	312	71
Average age	67.8 ± 11.5
Job	Employed	334	76
	Unemployed	105	24
Marital statue	Married	341	77
	Single	98	23
Education	School diploma ≥	334	76
	School diploma <	105	24
Month income	5 million ≥	350	80
	5 million <	89	20
Smoking	Yes	52	12
	No	387	88
BMI(kg/m²)	30 >	354	80
	30 ≤	85	20
WHtR(cm/cm)	0.6 >	347	79
	0.6 ≤	92	21

Table 2 shows the participants’ responses to general questions. The most common systemic diseases were diabetes, hypertension, and hyperlipidemia. 278 respondents described their general health as good. In addition, 302 did not do any regular physical exercise and 256 did not consume fresh fruits or vegetables daily.

Table 2.

Responses of study participants to general questions

Variable		No	%
Do you exercise daily?	Yes	137	31
	No	302	69
Do you eat fruits and vegetables daily?	Yes	183	42
	No	256	58
How would you rate your general health?	Good	278	63
	Bad	161	37
Which of the following diseases do you suffer from?	Diabetes	89	20
	Blood pressure	64	14
	Thyroid problems	25	5
	Rheumatoid arthritis	21	5
	Depression	15	3.5
	Osteoporosis	14	3
	Blood lipids	48	10
	GI problem	21	5
	Kidney problems	12	3
	Heart attack	26	6
	Stroke	16	4
	Pulmonary	22	5
	Parkinson’s	2	0.5

Regarding oral health, 210 respondents had experienced tooth mobility, 40% of participants do not brush their teeth., and 80% of participants do not dental floss their teeth. Table 3.

Table 3.

Responses of study participants to oral health questions

Variable		No	%
How many times have you visited the dentist in the past year?	I didn’t have any visit	283	54
	≤ Once	189	43
	>Once	12	3
How many times do you brush your teeth a day?	I don’t brush my teeth	173	40
	≤ Once	245	55
	>Once	21	5
How many times do you floss your teeth a day?	I don’t floss my teeth	351	80
	≤ Once	64	14
	>Once	24	6
Do you use mouthwash?	Yes	39	8
	No	400	92
How would you rate your oral hygiene status?	Good	145	32
	Average	92	21
	Poor	202	47
Number of teeth extracted	1 ≥	42	10
	1 <	397	90
Decayed	1 ≥	72	17
	1 <	367	83
Filled	1 ≥	50	11
	1 <	389	89
Tooth mobility	Yes	210	48
	No	229	52
Gingival bleeding	Yes	302	69
	No	137	31

Regarding xerostomia (based on questionnaire), 172 respondents answered positively to the question “Do you feel xerostomia?” The mean of the xerostomia questionnaire XI was 33.21 ± 6.56. A total of 267 respondents xerostomia reported 96 mild, 50 moderate, and 28 severe xerostomia. The complete data is shown in Table 4 and therefore the prevalence of xerostomia was reported as 39.6% based on the patients’ statements.

Table 4.

Responses of study participants to the questions of the Xerostomia questionnaire XI

Question	Yes		No
	No	%	No	%
Do you feel xerostomia?	172	39.6	267	60.4
I have trouble swallowing some foods	168	38	271	62
I feel my mouth dry when I eat	223	51	216	49
I drink fluids to help with swallow foods	129	30	310	70
I wake up at night to drink water	145	33	294	67
I suck on candy to relieve xerostomia.	98	23	341	77
I feel my eyes are dry	196	45	243	55
My lips are dry	214	49	225	51
I have trouble eating dry foods	187	43	252	57
I feel my mouth is dry	198	45	241	55
The skin on my face becomes dry	234	53	205	47
I feel dry inside my nose	183	42	256	58

26% of men reported mild xerostomia and 21% moderate xerostomia, while 8.2% of women reported moderate xerostomia and 2.6% reported severe xerostomia. (P = 0.001). Age was a significant factor. The prevalence of xerostomia was highest in the age group of 80 years or older, with 57.1% reporting xerostomia, compared to 32.1% in the 65–79 years old group and 22.5% in the 50-year-old group. (P = 0.01).

Patients with tooth mobility reported more xerostomia than patients without tooth mobility. 41.5% vs. 27.2% (P = 0.01). Xerostomia was reported statistically significantly more frequently in patients with hypertension (P = 0.01), diabetes (P = 0.04), and myocardial infarction (P = 0.01). In addition, xerostomia was significantly more reported in respondents who had a depressive illness, with 56.2% reporting some degree of xerostomia.

Patients who reported good general health had significantly less xerostomia than patients with bad general health (P = 0.04).

In this study, BMI and WHtR had no significant relationship with xerostomia (P = 0.61, 0.24, respectively). However, a statistically significant association was found between WHtR and BMI with the number of missing teeth, i.e., the higher the tooth loss, the lower the BMI and WHtR (P = 0.01).

After adjusting for age and gender, logistic regression analysis showed that the highest rate of xerostomia was related to patients who had lung disease [P = 0.001-OR = 1.51 (2.92–1.02)]. Also, between tooth mobility [P = 0.02-OR = 1.51 (2.92–1.02)], diabetes [P = 0.01-OR = 1.45 (2.82–1.02)], general health [P = 0.04-OR = 2.01 (3.21–1.12)], and depression [P = 0.04-OR = 1.91 (3.35–1.34)] with xerostomia, there was a significant relationship Table 5.

Table 5.

Association between Xerostomia and general health and oral health after adjusting for age and gender

Variable	Univariate OR (95% CI)	P value	Adjusted OR (95% CI)	P value
Tooth mobility- Have vs. Not have	2.11(1.42–3.52)	*0.01	1.52(1.02–2.92)	*0.02
Diabetes- Have vs. Not have	1.65(1.23–2.3)	*0.01	1.45(1.02–2.82)	*0.01
Bone disease- Have vs. Not have	2.99(1.42–4.32)	*0.01	1.78(1.12–3.02)	0.21
Pulmonary disease- Have vs. Not have	3.21(2.12–5.12)	*0.001	2.31(1.72–3.61)	*0.001
Depression- Have vs. Not have	2.41(1.12–3.15)	*0.02	1.91(1.34–3.35)	*0.03
Oral Health Status- Good vs. Bad	1.85(1.12–3.42)	*0.04	1.65(1.12–3.25)	0.07
General Health- Good vs. Bad	2.51(1.52–4.65)	*0.01	2.01(1.12–3.21)	*0.04
Obesity- BMI 30 ≤ vs. 30 >	2.71(1.31–3.01)	*0.02	1.74(1.43–3.12)	*0.01
Smoking- Yes vs. No	2.32(1.13–2.98)	*0.001	1.60(1.17–3.15)	*0.01
Income- 5 million ≥ vs. 5 million <	2.54(1.41–3.45)	0.06	1.78(1.10–2.51)	0.14
Education- School diploma ≥ vs. School diploma <	2.21(1.51–2.89)	0.08	1.60(1.32–3.45)	0.09
Diet- Healthy vs. Unhealthy	2.52(1.31–4.23)	*0.04	1.34(1.37–2.78)	*0.01
Physical activity- Yes vs. No	2.74(1.78–4.21)	*0.001	1.11(1.41–2.80)	*0.01
DMFT- 5 ≤ vs. 5 >	2.42(1.11–4.45)	*0.03	1.21(1.01–3.09)	*0.01
Dental visits- Yes vs. No	2.53(1.20–4.67)	0.12	1.23(1.22–3.71)	0.42
Brushing habits- Yes vs. No	2.55(1.41–3.99)	0.05	1.21(0.81–2.67)	0.05

* P value < 0.05 is significant

The study found that people who took antidepressants, antihistamines, antipsychotics, decongestants, opioids and antihypertensives reported more dry mouth, although no significant association was found (P > 0.05).

Discussion

One study revealed that 172 participants affirmed experiencing xerostomia, with an average Dry Mouth Questionnaire XI score of 33.21 ± 6.56. Of all respondents, 265 did not report xerostomia, while 96 experienced mild cases, 50 reported moderate symptoms, and 28 had severe xerostomia. Based on self-reported data, xerostomia prevalence stood at 39.6%. Among men, 26% experienced mild symptoms and 21% moderate symptoms. In contrast, among women, 8.2% reported moderate cases and 2.6% severe cases. Age was a significant factor; the condition was most prevalent among individuals aged 80 years or older (57.1%), compared to 32.1% in the 65–79 age group and 22.5% in the 50–64 age group.

The prevalence of xerostomia has been reported to range between 12% and 63% across different studies. Notably, women are more frequently affected than men [28–30].

Nederfors et al. [37], meanwhile, studied xerostomia prevalence in Swedish adults relative to age, gender, and medications and found subjective dryness in 28.3% of women and 21.3% of men. Their results highlighted the influence of aging and medication intake as key contributing factors.

Bergdahl et al. [31] studied the prevalence of xerostomia and its associated factors, they found that 3.7% of the people had xerostomia, including 5.5% of women and 1.6% of men.

In a study conducted by Pajukoski et al. [30] on the prevalence of symptomatic xerostomia in outpatients and inpatients, it was observed that 57% of outpatients and 63% of inpatients complained of xerostomia. The most important factor underlying xerostomia in outpatients was respiratory diseases and in inpatients was decreased salivary flow. These two problems were more common in females.

Bergdahl et al. [31] reported in another study that 3.7% of participants experienced xerostomia; this included a higher prevalence among women (5.5%) compared to men (1.6%). Of those reporting dryness, approximately 66% had symptomatic manifestations.

The research conducted by Pérez-González et al. [24] identified that 30.7% of participants experienced xerostomia. However, the findings from this study were not connected to those of Hijaw et al. [32].

Logistic regression analysis revealed an association between xerostomia and a range of systemic diseases and psychiatric conditions. Among individuals taking anti-anxiety or antidepressant medications, the risk of experiencing xerostomia was 3.33 times higher in the univariate model and 2.26 times higher in the adjusted model. Regarding general health, xerostomia was observed in 5.40% of patients with hypertension, likely influenced by both the condition’s effects on saliva production and the medications used for treatment.

A greater prevalence of xerostomia was reported among diabetic respondents, aligning with findings from López-Pintor et al. [27]. Similarly, in a study by Pérez-González et al. [24], no significant correlation was found between body mass index (BMI) or waist-to-hip ratio (WHtR) and xerostomia. However, an association existed between tooth loss and both BMI and WHtR. This observation supports results from a 2016 meta-analysis, which noted that obese individuals were 1.49 times more likely to experience tooth loss (33).

Overweight and obesity are linked to an increased risk of numerous medical conditions, such as cardiovascular and cerebrovascular diseases, hypertension, gastrointestinal disorders, certain cancers, gallbladder disease, dyslipidemia, osteoarthritis, and diabetes mellitus. Beyond these systemic effects, obesity significantly impacts oral health, contributing to issues like periodontal disease, dental caries, tooth wear, and xerostomia [34]. Tavares et al. [31] highlighted a connection between oral and dental health with broader public health implications, although evidence remains insufficient to establish definitive conclusions.

In this study, after adjusting for age and sex, the highest incidence of xerostomia was identified among patients with pulmonary diseases (Asthma and respiratory allergies, COPD (Chronic Obstructive Pulmonary Disease). Significant associations were also noted between xerostomia and factors such as dental mobility, diabetes, general health status, and depression.

One hypothesis may be that dry mouth is more prevalent in people with pulmonary disease, mouth breathing, and medication use.

Pérez-González et al. [24] corroborated earlier research that xerostomia is more prevalent among individuals who rate their overall health as poor or very poor. Xerostomia was also common in those with hypertension, diabetes, bone diseases, heart conditions, pulmonary disease, and gastrointestinal diseases. For instance, xerostomia was present in 40.5% of patients with hypertension due to its impact on saliva quality and quantity.

Similarly, diabetic individuals showed higher rates of xerostomia consistent with findings by López-Pintor et al. [18].

Psychotropic drugs are well-documented contributors to xerostomia, as demonstrated by Johansson et al. [35]. Abdullah et al. [36] also observed higher rates of xerostomia in patients on antidepressants.

Storbeck et al. [37] found that a variety of medications, including antihypertensive drugs, were associated with xerostomia in a dose-dependent manner. Such drugs can reduce salivary flow, impair salivary clearance, and heighten the risk of dental caries and pulp disease [38].

Some studies [e.g., Khongsirisombat et al. [20] vs. Torres et al. [39] show conflicting results on obesity and dry mouth. A meta-analysis or systematic review could help reconcile these.

Regarding overall health, xerostomia was reported in 40.5% of patients with hypertension, potentially stemming from its impact on both the quality and quantity of saliva [23]. Furthermore, a greater occurrence of xerostomia was noted among individuals with diabetes, consistent with the observations made by López-Pintor et al. [24]. Fornari et al.’s [40] study found that 19.1% of individuals reported experiencing xerostomia. This prevalence was higher among elderly people with diabetes and those managing chronic conditions or using continuous medication. Gastrointestinal illnesses were also linked to an increased likelihood of xerostomia.

In terms of difficulty swallowing due to xerostomia symptoms, this study observed that 38.3% of participants had trouble swallowing certain foods, while 29.4% needed liquids to aid food consumption—a vital indicator of xerostomia presence. By comparison, Fornari et al.’s [40] research reported that 13% encountered swallowing difficulties and 14.7% drank liquids to assist in consuming food.

Among adult and elderly populations studied by Thomson et al. [30], the prevalence of xerostomia was documented at 10%. In another study by Proto et al. [40], 24.8% reported experiencing xerostomia symptoms primarily attributed to medication usage. The findings of this study contrast with those of Freitas et al. [39], where 59% of elderly individuals reported experiencing xerostomia for most of the day. Similarly, research by Islas-Granillo et al. [40] found a higher prevalence, with 68.3% of elderly participants suffering from xerostomia. In a separate survey by Nicklander et al. [41] involving 566 individuals, 42.4% were on some form of medication, and among them, 17.92% reported xerostomia symptoms. It has been consistently demonstrated through research that medications and underlying health conditions significantly impact the occurrence of xerostomia. This underscores the importance of healthcare professionals thoroughly documenting patients’ medical histories and medication usage.

For instance, a study by Fornari et al. [40] highlighted a significant association between diabetes and xerostomia. Patients with uncontrolled diabetes are thought to experience higher rates of xerostomia due to increased diuresis or polyuria, which can interfere with saliva production [42].

Additionally, Carda et al. [43] revealed that 76.4% of individuals with type 2 diabetes exhibited xerostomia symptoms, while another study reported a 49.2% prevalence of xerostomia among 120 elderly diabetic patients [19].

However, not all studies align on certain associations. Fornari et al. [40], for example, did not find a statistically significant link between xerostomia and conditions such as depression, anxiety, hypertension, or thyroid disease, though other studies have reported such correlations [30, 39, 40].

Thomson et al. [44] identified a strong relationship between xerostomia and the use of specific medications, including antidepressants, iron supplements, and analgesics. Those prescribed antidepressants were found to be up to 22 times more likely to experience xerostomia.

Marquezin et al. [44] and Villa et al.‘s [5] findings further support these observations. They noted that commonly used medications among participants such as antihypertensives, antidiabetics, antidepressants, and sedatives are significant contributors to xerostomia. The simultaneous use of multiple drugs exacerbates their impact through pharmacodynamic and pharmacokinetic interactions, increasing the likelihood of dryness symptoms.

Conclusion

The study concludes that the prevalence of xerostomia is 39.6%, as reported by participants. Age emerged as a critical factor influencing this condition, while BMI and WHtR showed no direct relationship with xerostomia itself but were significantly related to tooth loss patterns. Notably, the highest prevalence of xerostomia was observed in patients with pulmonary disease. Also, it is recommended that xerostomia screening be performed in elderly patients with pulmonary disease/diabetes and interventional studies (e.g., saliva substitutes in high-risk groups) be conducted to better investigate dry mouth.

Limitations

The study faced constraints due to non-cooperation from some participants and an incomplete number of returned questionnaires. Other limitations include the small sample size, and it is recommended that a study with a larger sample size be conducted. It also appears that there was a slight bias in the selection of some of the samples. Another limitation of the study is its lack of generalizability to the entire population due to the small sample size, use of questionnaire to asses dry mouth, weak medical history taking. On the other hand, in this study, dry mouth was measured using a questionnaire, and it is recommended that saliva be measured in other studies to allow for better comparisons.

Appendix

Dear visitor, Hello, the following questionnaire was designed to investigate the relationship between oral health and obesity variables with xerostomia. Please read the questions and answer them carefully. It is worth noting that your information will remain confidential and will only be analyzed statistically. Thank you.

Gender: Male □ Female □.

Age:

Marital status: Married □ Single □.

Weight:

Height:

Waist circumference:

Occupation: Student □ Employee □ Freelance □ Retired □ Housewife □ Unemployed □.

Education level: Associate ’s degree □ Diploma □ Post-graduate degree □ Bachelor ’s degree □ Master ’s degree and above □.

Monthly income: 1 to 3 million Tomans □ 3–5 million Tomans □ More than 5 million Tomans □.

How many times have you visited the dentist in the past year? Once □ 2 times □ More than 2 times □ No visits □.

How many times do you brush your teeth a day? I don’t brush my teeth □ Once □ Twice □ Three times □.

How many times do you floss your teeth a day? I don’t use it □ Once □ Twice □ Three times □.

Do you use mouthwash? Yes □ No □ Name of mouthwash:

Do you exercise daily? Yes □ No □.

Do you eat fruits and vegetables daily? Yes □ No □.

How would you rate your general health? Good □ Bad □.

Do you smoke? Yes □ No □.

How would you rate your oral hygiene status? Good □ Average □ Poor □.

Number of teeth extracted: Decayed: Filled:

Loose teeth: Yes □ No □.

Bleeding gums: Yes □ No □.

Toothache: Yes □ No □.

Implants: Yes □ No □.

Which of the following diseases do you suffer from? Diabetes □ High blood pressure □ Thyroid problems □ Rheumatoid arthritis □ Depression and/or anxiety □ Osteoporosis □ High blood pressure □ Gastrointestinal diseases □ Anticoagulants □ Kidney problems □ Heart attack □ Stroke □ Heart failure □ Lung problems □ Parkinson’s □ Other diseases (list).

Do you have xerostomia? Yes □ No □.

I have trouble swallowing some foods. Yes □ No □.

I feel my mouth is dry when I eat. Yes □ No □.

I drink fluids to help me swallow food. Yes □ No □.

I wake up at night to drink water. Yes □ No □.

I suck on candy to relieve xerostomia. Yes □ No □.

I feel my eyes are dry. Yes □ No □.

My lips are dry. Yes □ No □.

I have trouble eating dry foods. Yes □ No □.

I feel my mouth is dry. Yes □ No □.

My skin is dry. Yes □ No □.

I feel dry inside my nose. Yes □ No □.

Authors’ contributions

Raziyehsadat Rezvaninejad: wrote the main manuscript text Mahdie Zeinali: data collection Amirreza Fatemi: data collection Maryam Alsadat Hashemipour: wrote the main manuscript text.

Funding

This research received no external funding.

Data availability

The datasets utilized and/or analyzed in this study are available from the corresponding author upon reasonable request.

Declarations

Ethics approval and consent to participate

This research was approved by the Ethics Committee of Kerman University of Medical Sciences and its Research Deputy Office. All experimental protocols were conducted according to relevant guidelines and regulations, including the Declaration of Helsinki. Verbal informed consent was obtained from all participants after a detailed explanation of the study objectives was provided by the researchers. Confidentiality regarding participant information is strictly maintained. The authors extend their gratitude to the Vice Deputy of Research at Kerman University of Medical Sciences for financial support (Registration No. 401000591). This project received ethics approval under code IR.KMU.REC.1401.445.

Consent for publication

Not applicable.

Competing interests

The authors declare no competing interests.