SEARCH

SEARCH BY CITATION

Keywords:

  • dry mouth;
  • super-elderly;
  • tooth brushing;
  • cross-sectional study

Abstract

  1. Top of page
  2. Abstract
  3. Introduction
  4. Materials and methods
  5. Results
  6. Discussion
  7. Conclusion
  8. Acknowledgements
  9. Conflict of interest statement
  10. References

Objectives

To identify factors associated with dry mouth.

Background

Dry mouth adversely affects oropharyngeal health, particularly in elderly, and can lead to pneumonia. A better understanding of the epidemiology of dry mouth is therefore important in improving treatment strategies and oral health in high-risk elderly patients.

Methods

We conducted a cross-sectional study involving 383 dependent Japanese elderly individuals (65–84 [n = 167] and ≥85 [n = 216] years) at eight long-term care facilities and hospitals. Thirty-four potential factors associated with dry mouth were examined by multiple logistic regression analysis. The primary outcome was dry mouth, as diagnosed by tongue dorsum moisture.

Results

We identified that body mass index and severity of physical disability were identified as a potential factors associated with dry mouth in the super-elderly (≥85 years) group, whereas severity of physical disability, outcome measurement time, high daily water consumption, mouth breathing, use of antidepressants and diuretics, and high frequency of daily brushing (≥2 times per day; Odds ratio: 5.56; 95% Confidence Interval: 1.52–20.00) were associated with dry mouth in the 65- to 84-year-old group.

Conclusion

To our knowledge, this is the first study to identify a link between frequency of daily brushing and dry mouth and suggests that tooth brushing should be encouraged in high-risk dependent Japanese elderly (65–84 years), particularly those taking antidepressants and/or diuretics.


Introduction

  1. Top of page
  2. Abstract
  3. Introduction
  4. Materials and methods
  5. Results
  6. Discussion
  7. Conclusion
  8. Acknowledgements
  9. Conflict of interest statement
  10. References

Dry mouth is typically characterised by salivary gland hypofunction that leads to a reduced output of saliva. Elderly are most affected by dry mouth, with the reported incidence ranging from 20% to as high as 60%[1-5]. Dry mouth is of particular concern for dependent individuals, as adverse changes in the oral environment can lead to increased oropharyngeal colonisation by respiratory pathogens[6-8]. Recently, Takeshita et al.[9] reported that dry mouth was significantly associated with aspiration pneumonia in a population of institutionalised elderly Japanese patients. Hospitalised patients with dry mouth are also more susceptible to pyrexia [10] and have a two-fold higher risk of death from pneumonia[11]. Owing to the significant impact of dry mouth on health[12], a better understanding of this condition in elderly dependent patients is important for developing treatment and prevention strategies and improving oral health in this population.

The potential factors associated with dry mouth identified to date are the use of xerogenic drugs, systemic disease and cancer irradiation therapy of the head and neck[13, 14]. In elderly, reported predisposing factors of dry mouth include gender and smoking[15, 16]. In addition, several studies have identified an association between age and dry mouth[17, 18, 3], which is of particular concern because of the increasing longevity of populations worldwide. In Japan, super-elderly (≥85 years) are increasing rapidly and Japanese female life expectancy has reached over 85 years. Even less is known about potential factors associated with dry mouth in the super-elderly, who account for a relatively large proportion of institutionalised Japanese patients and exhibit high mortality rates following infection. Despite the identification of these general underlying factors of dry mouth, comprehensive factor analyses including oral health care and lifestyle-related factors have not been conducted in previous studies. Thus, a better understanding of the factors of dry mouth in the super-elderly may have significant public health benefits.

Here, we conducted a cross-sectional study to identify comprehensive factors, including oral health care and lifestyle-related factors, associated with dry mouth in dependent elderly and compared these factors between elderly (65–84 years) and super-elderly (≥85 years) groups.

Materials and methods

  1. Top of page
  2. Abstract
  3. Introduction
  4. Materials and methods
  5. Results
  6. Discussion
  7. Conclusion
  8. Acknowledgements
  9. Conflict of interest statement
  10. References

Study design

We conducted a cross-sectional study consisting of a questionnaire survey and a clinical assessment to identify factors associated with dry mouth in dependent Japanese elderly individuals between March 2010 and February 2011. This study was approved by the ethical committee of Kyushu Dental College.

Setting

This study was conducted at eight long-term care facilities and hospitals located in the Tohoku, Kanto, Chubu and Kyushu districts of Japan.

Participants

Eligible participants for this study were dependent Japanese elderly (≥65 years) who were unable to live without daily assistance and had entered a hospital or institution for long-term care. All of the participants at the eight long-term care facilities and hospitals who met the inclusion criteria were enrolled in the study. Patients were excluded from the study, if they had oral cancer, received intraoral radiation therapy at any time in the past, or salivary gland disease. The study population consisted of 383 dependent Japanese elderly individuals. All patients or their families provided written informed consent prior to participation in this study.

Primary outcome

The primary outcome was dry mouth, as diagnosed by tongue dorsum moisture, as previously described[19]. In this study, dry mouth was determined by measuring tongue dorsum moisture using the Kiso-Wet Tester (Kiso Science, Yokohama, Japan), which is based on ultrathin-layer chromatography[19, 9]. The measurements were performed by dentists 2–3 h after the last meal by placing the tester vertically on the tongue dorsum approximately 1 cm from the tongue tip for 10 s and recording the height of the moistened area. A height of <3 mm was classified as dry mouth.

Potential factors associated with dry mouth

The following potential factors associated with dry mouth were examined according to six categories: (i) individual characteristics: gender; age; primary nursing care level, a five-level graded system based on assessed care needs under the Japanese long-term care insurance system[20], body mass index (BMI), serum albumin, dementia, history of stroke/cerebral infarction, level of physical disability (severe vs. mild/moderate), Barthel Index score (0–100; for assessment of daily functioning)[21], hypertension, diabetes mellitus, depression, Parkinson's disease, history of respiratory disease, length of stay and ingestion intake; (ii) institutional characteristics: institution and outcome measurement time (morning vs. afternoon); (iii) oral care characteristics: oral hygiene status and frequency of daily brushing; (iv) lifestyle characteristics: daily hours of sleep, daily water consumption and smoking status; (v) oral health characteristics: total number of teeth, number of untreated decayed teeth, occlusion, use of dentures, mouth breathing, habitual open-mouth posture, and repetitive saliva swallowing test (RSST)[22], clinical swallowing examination, observations of eating and swallowing[23] and frequency of thirst; and (vi) medication characteristics: total number of medications and types of medications (antiparkinson drug, diuretic, antidepressant, antihypertensive and oral antidiabetic agent).

Statistical analysis

The prevalence of dry mouth in the sample was calculated after dividing patients into the age groups of 65–84 and ≥85 years. Univariate regression analysis was performed using the presence or absence of dry mouth as a dependent variable and the 34 factors described earlier as independent variables. In each group, median values of continuous variables, with the exception of BMI (18.5 kg/m2)[24] and daily water consumption (1000 ml/day)[25, 26], were used as cut-off values. Cut-off points of BMI and daily water consumption are used according to the previous studies because they can be easy to apply to daily clinical practice. Variables that resulted in a p-value of <0.2 in the univariate regression analysis, potential confounding and clinically important factors, such as age, gender, dementia and the frequency of daily brushing, were further subjected to multiple logistic regression analysis. Multiple logistic regression analysis was conducted to examine the relationship between potential factors and dry mouth. The odds ratios were calculated together with the 95% confidence interval (CI). All statistical analyses were performed with STATA/SE, version 10 for Windows (Stata Corp. LP, College Station, TX, USA). The level of statistical significance was set at p < 0.05.

Results

  1. Top of page
  2. Abstract
  3. Introduction
  4. Materials and methods
  5. Results
  6. Discussion
  7. Conclusion
  8. Acknowledgements
  9. Conflict of interest statement
  10. References

Demographic characteristics and incidence of dry mouth

The demographic characteristics of all study participants are shown in Table 1. Participants were predominantly women (77.5%), and the mean patient age was 85.9 ± 7.2 years. Dry mouth was detected in 179/383 (46.7%) of the dependent elderly study participants. Among elderly (65–84 years) and super-elderly (≥85 years), the incidence of dry mouth was 67/167 (40.1%) and 112/216 (51.9%), respectively.

Table 1. Characteristics of the study participants based on age
CharacteristicAll patients (n = 383)65–84 years (n = 167)≥85 years (n = 216)
  1. a

    Mean ± SD.

  2. BMI, body mass index; RSST, repetitive saliva swallowing test.

Kiso-Wet value
<3 mm179 (46.7%)67 (40.1%)112 (51.9%)
≥3 mm204 (53.3%)100 (59.9%)104 (48.1%)
Gender
Male86 (22.5%)52 (31.1%)34 (15.7%)
Female297 (77.5%)115 (68.9%)182 (84.3%)
Age (years)a85.9 ± 7.279.3 ± 4.391.0 ± 4.2
BMI (kg/m2)a20.2 ± 3.519.9 ± 3.420.5 ± 3.6
Serum albumin (g/dl)a3.62 ± 0.413.70 ± 0.433.56 ± 0.39
Dementia294 (76.8%)63 (67.7%)181 (83.8%)
History of stroke/cerebral infarction173 (45.2%)81(48.5%)92 (42.6%)
Level of physical disability
Severe141 (36.8%)75 (44.9%)66 (30.6%)
Mild/Moderate242 (63.2%)92 (55.1%)150 (69.4%)
History of respiratory disease86 (22.5%)45(26.9%)41 (19.0%)
Length of stay (months)a30.4 ± 34.623.8 ± 30.635.5 ± 36.6
Outcome measurement time
Morning201 (52.5%)82 (49.1%)119(55.1%)
Afternoon182 (47.5%)85(50.9%)97(44.9%)
Frequency of daily brushing (times/day)a2.1 ± 1.01.9 ± 0.92.2 ± 1.0
Daily hour of sleepa8.67 ± 1.948.25 ± 1.789.00 ± 2.01
Daily water consumption (ml)a829.8 ± 365.5767.3 ± 383.7878.1 ± 343.9
Total number of teetha7.9 ± 8.79.4 ± 8.96.7 ± 8.4
Mouth breathing108 (28.2%)51(30.5%)57 (26.4%)
RSST (times)a2.8 ± 2.13.5 ± 2.02.2 ± 2.0
Total number of medicationsa7.8 ± 4.07.6 ± 3.57.9 ± 4.3

Factors associated with dry mouth

Multiple logistic regression analysis identified five factors that were significantly associated with dry mouth among all study participants: odds ratios of low BMI, severity of physical disability, high daily hours of sleep, mouth breathing and administration of diuretics are 0.55 (0.33–0.92), 2.61 (1.40–4.86), 1.85 (1.02–3.35), 1.90 (1.06–3.41) and 1.82 (1.02–3.26), respectively (Table 2). In the elderly (65–84 years) group, seven factors were significantly associated with dry mouth: odds ratios of severity of disability, outcome measurement time, frequency of daily brushing, daily water consumption, mouth breathing, and the use of diuretics and anti-depressants were 7.53 (2.00–28.39), 5.16 (1.18–22.59), 5.56 (1.52–20.0), 5.32 (1.61–17.54), 3.85 (1.19–12.54), 7.63 (2.24–25.95) and 4.89 (1.22–19.53), respectively. In the super-elderly (≥85 years) group, two factors were significantly associated with dry mouth: Odds ratios of low BMI and the severity of physical disability were 0.46 (0.22–0.95) and 2.42 (1.02–5.72), respectively.

Table 2. Factors associated with dry mouth in elderly based on multiple logistic regression analysis
VariableAll patients (n = 383) OR (95% CI)p value65–84 years old (n = 167) OR (95% CI)p value≥85 years old (n = 216) OR (95% CI)p value
  1. a

    p < 0.05.

  2. b

    p < 0.01.

  3. OR, odds ratio; CI, confidence interval; BMI, body mass index; RSST, repetitive saliva swallowing test.

Gender
Male1 1 1 
Female0.80 (0.43–1.50)0.4861.20 (0.38–3.76)0.7570.48 (0.18–1.30)0.150
Age (years)
65–741 1   
75–851.02 (0.43–2.41)0.9721.36 (0.43–4.23)0.601  
≥851.59 (0.67–3.73)0.290    
BMI (kg/m2)
<18.51 1 1 
≥18.50.55 (0.33–0.92)0.023a1.04 (0.34–3.12)0.9510.46 (0.22–0.95)0.035a
Serum albumin (g/dl)
<3.71 1 1 
≥3.71.64 (0.90–2.99)0.1040.63 (0.20–1.94)0.4201.63 (0.74–3.58)0.224
Missing0.77 (0.33–1.79)0.5450.98 (0.16–5.94)0.9830.74 (0.22–2.48)0.623
Dementia
No1 1 1 
Yes1.53 (0.80–2.95)0.1990.74 (0.21–2.57)0.6392.24 (0.81–6.19)0.119
History of stroke/cerebral infarction
No1 1 1 
Yes1.03 (0.62–1.70)0.9082.25 (0.81–6.23)0.1180.64 (0.31–1.31)0.217
Level of physical disability
Mild/Moderate1 1 1 
Severe2.61 (1.40–4.86)0.003b7.53 (2.00–28.39)0.003b2.42 (1.02–5.72)0.045a
History of respiratory disease
No1 1 1 
Yes1.34 (0.67–2.68)0.4010.80 (0.21–3.05)0.7422.08 (0.76–5.66)0.153
Length of stay (months)
<221 1 1 
≥220.78 (0.43–1.44)0.4350.51 (0.14–1.87)0.3101.11 (0.53–2.32)0.785
Outcome measurement time
AM1 1 1 
PM1 .00 (0.49–2.02)0.9945.16 (1.18–22.59)0.029a0.60 (0.24–1.53)0.289
Frequency of daily brushing (times/day)
≥21 1 1 
<21.67 (0.83–3.33)0.1475.56 (1.52–20.00)0.010a1.28 (0.44–3.70)0.657
Daily hours of sleep
<91 1 1 
≥91.85 (1.02–3.35)0.042a0.66 (0.23–1.92)0.4462.23 (0.97–5.13)0.058
Daily water consumption (ml)
<10001 1 1 
≥10001.45 (0.80–2.60)0.2175.32 (1.61–17.54)0.006b1.18 (0.54–2.58)0.679
Mouth breathing
No1 1 1 
Yes1.90 (1.06–3.41)0.031a3.85 (1.19–12.54)0.025a1.33 (0.60–2.97)0.483
RSST (times)
<31 1 1 
≥30.59 (0.26–1.34)0.2100.77 (0.18–3.30)0.7230.47 (0.18–1.24)0.127
Missing0.68 (0.37–1.24)0.2120.65 (0.20–2.14)0.4770.49 (0.22–1.07)0.074
Type of medication Antiparkinson drug
No1 1 1 
Yes1.87 (0.90–3.87)0.0912.59 (0.92–7.32)0.0720.70 (0.27–1.83)0.466
Diuretic
No1 1 1 
Yes1.82 (1.02–3.26)0.044a7.63 (2.24–25.95)0.001b1.18 (0.56–2.51)0.663
Antidepressants
No1 1 1 
Yes1.21 (0.62–2.36)0.5854.89 (1.22–19.53)0.025a1.06 (0.38–2.96)0.911
Antihypertensive
No1 1 1 
Yes1.07 (0.65–1.76)0.7940.99 (0.38–2.63)0.9901.04 (0.53–2.04)0.903
Oral antidiabetic agent
No1 1 1 
Yes0.73 (0.36–1.47)0.3791.17 (0.36–3.78)0.7910.78 (0.27–2.23)0.637

Discussion

  1. Top of page
  2. Abstract
  3. Introduction
  4. Materials and methods
  5. Results
  6. Discussion
  7. Conclusion
  8. Acknowledgements
  9. Conflict of interest statement
  10. References

Our cross-sectional study of 383 dependent Japanese elderly identified several potential factors associated with dry mouth. Among these novel potential factors identified in this study, we found that tooth brushing frequency was associated with the incidence of dry mouth in elderly <85 years old. To our knowledge, this is the first study to identify a link between tooth brushing frequency and the incidence of dry mouth. It is likely that mechanical stimulation of the salivary glands during brushing promotes the discharge of saliva, leading to a greater coating of the tongue dorsum with saliva. This finding is indirectly supported by a study indicating that brushing increased salivary flow in persons with medication-induced dry mouth[27], a response that is likely associated with in the generation of activating impulses to both major and minor residual salivary tissues following stimulation of oral and pharyngeal regions, causing salivation[27, 28]. Notably, this factor was not significant in the ≥85-year-old group, a finding that may have been due to the generally reduced function of the salivary gland in these individuals. However, in interpreting this finding, it is also important to consider that brushing itself may not obviate dry mouth, as individuals with better self-care are likely to have better all-round general and oral health. Thus, further study is needed to clarify the relationship between tooth brushing and dry mouth.

We also identified that antidepressants and diuretics were factors associated with dry mouth in elderly (65–84 years) group. Our results are consistent with those of Persson et al.[29], who examined salivary flow rates in elderly and found that psychotropic and diuretic agents were the most potent at reducing saliva production. A higher incidence of dry mouth was also reported for elderly men taking antidepressants combined with diuretics and in elderly woman prescribed diuretics[30, 16]. Presently in Japan, clear protocols for tooth brushing frequency have not been established with respect to the care of institutionalised elderly. Our study supports the implementation of guidelines for tooth brushing more than twice per day in dependent elderly, particularly those taking antidepressants and/or diuretics. Further longitudinal studies are needed to determine the most effective frequency of brushing for lowering the incidence of dry mouth in dependent elderly.

A low BMI was associated with the incidence of dry mouth in the super-elderly patients. Although BMI did not markedly differ between the elderly and super-elderly group, it is possible that a low BMI in the latter group is more indicative of deterioration of bodily function, disability severity and food intake. This speculation is supported by a study reporting that the perception of dry mouth in elderly participants (mean age, 66 years) was significantly associated with low BMI[31], and a report that in elderly men requiring care (mean age, 84 years), dry mouth was associated with the degree of incapacity and type of feeding (oral ingestion vs. tube feeding)[32]. We also identified severity of disability is a factor associated with dry mouth in both elderly and super-elderly patients.

The identification of a relationship between mouth breathing and dry mouth is not surprising, as tongue dorsum moisture would reasonably be expected to be lowered by constant exhalation through the mouth. Such an association was identified in a study of Finnish elderly[33]. For mouth-breathing individuals, face muscle and breathing training might help to reduce the frequency that the mouth is open during the day, and potentially lowering moisture loss. Finally, our finding that dry mouth is associated with high daily hours of sleep may be related to sleeping with an open mouth[34] or because of the differential influence of the parasympathetic and sympathetic nervous systems on the flow of saliva. One possible approach for limiting this potential factor is to more closely monitor and adjust the sleeping hours of dependent individuals. Although the high daily consumption of water was associated with dry mouth, the relationship between cause and effect is not clear, as it is conceivable that the feeling of dryness would lead to increased water consumption.

Our study has several strengths. First, this was a multi-institutional study with a relatively large sample size that included individuals over the age of 85 years (super-elderly) for whom limited information is available. Second, we analyzed a comprehensive set of factors that included detailed epidemiological and clinical information. Finally, the participants came from a wide variety of areas within Japan and represent a wide cross-section of the dependent elderly population in Japan, enhancing the generalisability of the findings. A few limitations of the study also warrant mention. First, as this was a cross-sectional study, causative relationships between factors and dry mouth were difficult to assess. Second, the dosing regimen and duration for medications administered to study participants were not examined. To confirm the relevance of the association between medications and dry mouth, a follow-up survey of patients is needed.

Conclusion

  1. Top of page
  2. Abstract
  3. Introduction
  4. Materials and methods
  5. Results
  6. Discussion
  7. Conclusion
  8. Acknowledgements
  9. Conflict of interest statement
  10. References

Our cross-sectional study involving dependent elderly identified that severity of physical disability, mouth breathing, high daily water consumption, use of antidepressants and diuretics, and frequency of daily brushing were potential factors associated with dry mouth in dependent elderly (65–84 years). In contrast, only low BMI and severe disability were associated with dry mouth in dependent super-elderly (≥85 years). Our study also has detected a link between tooth brushing frequency and dry mouth and suggests that establishing oral hygiene programmes for dependent elderly (65–84 years) may reduce the incidence of dry mouth, particularly among those taking antidepressants and/or diuretics. Future cohort studies are needed to confirm the relationships between the factors identified here and dry mouth.

Acknowledgements

  1. Top of page
  2. Abstract
  3. Introduction
  4. Materials and methods
  5. Results
  6. Discussion
  7. Conclusion
  8. Acknowledgements
  9. Conflict of interest statement
  10. References

There are no financial conflicts of interest, and the authors declare that they do not have any association with any parties who may have vested interests in the results of this article. This study was supported by a Health Sciences Research Grant (Comprehensive Research on Aging and Health, 22-005) from the Ministry of Health and Labour and Welfare of Japan.

References

  1. Top of page
  2. Abstract
  3. Introduction
  4. Materials and methods
  5. Results
  6. Discussion
  7. Conclusion
  8. Acknowledgements
  9. Conflict of interest statement
  10. References