Comparison of the Relationship Between Dementia and Oral Health Behavior

Background: Dementia is a serious social problem worldwide, and dementia and oral health are closely related. Therefore, we con�rmed the relationship between dementia prevention behavior and the oral health behaviors. Methods: The study was conducted by IRB review at Silla University in Korea (No.1041449-201912-HR-002) and decided that 140 people living in South Korea were eligible. The data analysis used IBM SPS ver. 25.0 (IBM Co., Armonk, NY, USA) and compared oral health knowledge, dementia knowledge, Dementia anxiety and dementia prevention behavior according to oral health behavior. Results: As a result, the people with high oral health behavior had high oral health knowledge and was not relevant in dementia knowledge and anxiety. Also, as the oral health behavior increased, oral health knowledge and dementia prevention behavior tended to get improve. As the oral health knowledge increased, dementia anxiety and dementia prevention behavior tended to get improve. Conclusion: Therefore, in order to improve the prevention of dementia, knowledge transfer that dementia is highly relevant to oral health is more important than anything else.

, and the systemic in ammatory responses induced by periodontitis have been reported to increase the risk of developing dementia [13]. In particular, in a previous study, as the serum markers of the periodontal pathogen P. gingivalis increased, cognitive functions like word memory were lowered [14]. When 10 dementia patients' brain tissues were examined within 12 hours postmortem, P. gingivalisderived LPS was identi ed in the brains of 4 dementia patients [14]. In addition, it has been reported that the bacteria in the bio lm of the teeth can penetrate the brain through the blood ow or the nerves, and Treponema associated with periodontitis has been found in the brain of dementia patients [13]. As such, it has been reported that the systemic in ammatory response due to periodontal disease increases the risk of cognitive impairment and dementia [16], and causes poor oral conditions in dementia patients, such as fewer residual teeth due to severe dental caries [17,18]. In a national cross-sectional study in the United Kingdom, there were 2.6 times more cognitive impairment cases in edentulous patients among people aged 65 years and older [19], and in a large community-based research in Japan, the cases of cognitive impairment was 1.71 times higher in people with fewer residual teeth [20]. In South Korea, a community-based study also found that dementia progressed 1.61 times faster in people with missing teeth and without dentures [21], and a cross-sectional study in the United States reported a link between dental caries and cognitive impairment [22]. Therefore, to prevent the progression of dementia, promoting oral health practice is very important by making people realize that dementia and oral health are closely associated with each other.
To practice oral health, regular oral check-ups and proper brushing should be made a habit. A longitudinal study examining the relationship between oral health care and cognitive function changes over 6 years reported a signi cant correlation between low brushing frequency and progression of cognitive impairment [23]. Brushing is the most basic way to maintain oral health, and as by itself brushing can prevent dementia, efforts should be made to improve one's oral health behavior. Therefore, it is necessary to check people's dementia knowledge, anxiety, and prevention behavior according to the degree of their oral health behavior. Most of the relevant studies to date, however, have con rmed the relationship between dementia and oral disease [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22], and the relationships among dementia knowledge, dementia anxiety, and dementia prevention behavior in elderly people [24]. There have been very few studies on dementia according to oral health behavior. Therefore, this study aimed to investigate the level of oral health behavior; to determine the relationships among dementia knowledge, dementia anxiety, and dementia prevention behavior according to the level of oral health behavior; and to use the study results as fundamental data for dementia prevention.

Methods
This study was conducted by receiving IRB review from the Institutional Review Board of Silla University (No. 1041449-201912-HR-002). Copies of a questionnaire were distributed to middle-aged people living in Gyeongsangnam-do for about a month from January 10, 2020, and were collected immediately after selfadministration. For sample size determination, G*Power 3.1 was used with a 0.01 signi cance level, 95% power, and a 0.15 medium effect size. As a result, the sample size was calculated to be 119, and considering the unclear answers, a total of 140 subjects (61 persons aged 60 years and younger, and 79 persons aged 61 years and older) were determined.

Orla health behavior
The questionnaire on oral health behavior consisted of 20 items formulated by referring to the study by Kim et al. [25], and each item was answered based on a 5-point Likert scale where the higher the score was, the higher the oral health behavior. In this study, the Cronbach's α was 0.87, and based on 85 points with a cumulative percentage of 49.3%, those who got a score of 85 or less were classi ed as belonging to the low-oral-health-behavior group and those who got a score of 86 or higher were classi ed as belonging to the high-oral-health-behavior group.

Orla health knowledge
The questionnaire on oral health knowledge consisted of 10 items formulated by referring to the study by Shin [26]. In this study, the Cronbach's α was 0.41.

Dementia knowledge
The questionnaire on dementia knowledge consisted of 12 items: 3 on the cause of dementia, 3 on the dementia symptoms and diagnosis, 4 on the prevention and treatment of dementia, and 2 on dementia patient care, all of which were developed by Seoul City [27]. The Cronbach's α was 0.57 at the time of development, and 0.45 in this study.

Dementia anxiety
The questionnaire on dementia anxiety consisted of 5 items formulated by referring to the study by Park et al. [28], and each item was answered based on a 5-point Likert scale where the lower the score was, the lower the dementia anxiety. In this study, the Cronbach's α was 0.87.

Dementia prevention behavior
For dementia prevention behavior, the instrument developed by Lee et al. [29] was used, which consisted of 12 items: 4 on stress management, 3 on disease management, 3 on lifestyle habits, and 2 on diet. Each item was answered based on a 5-point Likert scale where the higher the score was, the better the dementia prevention behavior. In this study, the Cronbach's α was 0.72.

Statistical Analysis
For statistical analysis, IBM SPSS ver. 25.0 (IBM Co., Armonk, NY, USA) was used. The oral health behavior was analyzed through frequency analysis, and the comparison of oral health knowledge and dementia knowledge according to the level of oral health behavior was conducted using chi-square test and independent t-test. The comparison of dementia anxiety and dementia prevention behavior according to the level of oral health behavior was conducted using Mann-Whitney t-test, a non-parametric analysis method. For the comparison of the associations among the variables, correlation analysis was conducted.

Oral health behavior
For the results of the examination of the subjects' oral health behavior, item 2 ("I get treatment immediately if I have toothache") had the highest level while item 18 ("I do not eat tough and hard foods as much as possible") had the lowest level as seen in Table 1. For the results of the examination of the subjects' oral health knowledge according to their oral health behavior level, there were signi cant differences between the high-and low-oral-health-practice groups in item 3 ("When brushing, the brush head should be inserted between the teeth to clean them thoroughly"), item 4 ("The tongue should also be cleaned during brushing"), and item 9 ("The use of toothpaste containing uoride is effective in preventing tooth decay"), and in the total score for oral health knowledge as seen in Table 2 (P < 0.001). For the results of the examination of the subjects' dementia knowledge according to their oral health behavior level, there was a signi cant difference only in item 2 ("Alzheimer's disease is the most common cause of dementia") as seen in Table 3 (P < 0.01). By chi-square test, ≠ independent t-test Dementia anxiety according to the level of oral health behavior There were no signi cant differences in all the items on dementia anxiety according to the level of oral health behavior, showing that the dementia anxiety is very high regardless of oral health behavior as seen in Table 4. For the results of the examination of the dementia prevention behavior according to the level of oral health behavior, there were signi cant differences in item 4 ("Do you read newspapers or magazines?"), item 5 ("Do you eat enough vegetables or fruits?"), and item 7 ("Do you manage disease well?"), and in the total score for dementia prevention behavior as seen in Table 5 (P < 0.001). Oral health behavior was positively correlated with oral health knowledge and dementia prevention behavior, while oral health knowledge was positively correlated with dementia anxiety and dementia prevention behavior as seen in Table 6 (P < 0.001).

Discussion
Oral health is closely related to dementia, and in particular, poor chewing ability leads to preference for soft, easy-to-eat foods high in saturated fat and cholesterol rather than hard-to-chew brous foods or foods high in essential trace elements. As the former is far from a Mediterranean diet that prevents dementia, and actually increases the risk of dementia [30,31], persistent oral care is necessary. Oral health behavior is a concept that re ects oral-health-related quality of life in a broad sense, and most people have high awareness of the importance of oral health but very low oral health behavior [32].
Therefore, it is necessary to examine the relationships among dementia knowledge, dementia anxiety, and dementia prevention behavior in groups with high and low oral health behavior scores. In this study, the subjects' oral health behavior scores were 83.03 on average, and based on 85 points, with a cumulative percentage of 49.3%, those who got a score of 85 or less were classi ed as belonging to the low-oral-health-behavior group, and those who got a score of 86 or higher were classi ed as belonging to the high-oral-health-behavior group. For the results of the examination of the subjects' oral health knowledge according to their oral health behavior level, the group with high oral health behavior had high oral health knowledge. This is consistent with a study [33] that reported that a high interest in oral health and high behavioral awareness lead to high oral health behavior. In the study by Kim and Yang [34], more than half of the subjects had high interest in dementia and high awareness that they were likely to develop it, but their subjective awareness of dementia was relatively low. It was found that in more than 90% of the cases, information on dementia was obtained from mass media and the patients' relatives. Related to this, Kim [35] stressed the necessity of systematic education about dementia from experts because acquiring dementia information through mass media and through one's family and relatives was not related to dementia awareness. In this study, the subjects' dementia knowledge was not related to their oral health behavior level, and low scores were obtained in 4 of the 12 items on oral health behavior while high scores were obtained in only 2 of such items. In addition, it was con rmed that the subjects' dementia knowledge was not high, with 7 items having less than 60% correct answers. As such, active education to increase dementia knowledge is necessary.
Compared to the subjects' dementia knowledge, their dementia anxiety was very high, with a score of 4 or higher in all the items. Dementia anxiety refers to an emotional response that recognizes the fear of developing dementia [36], and the subjects answered that they feared losing their identity due to dementia [37]. The reason for fear of dementia was the family burden [24] or family damage [28] that it may entail or cause. In Germany, 41.1% of the subjects in a study were concerned about dementia [38], and in South Korea, 78.2% of the subjects in a study reported that they feared dementia [28]. As such, dementia anxiety was very high in all the items on such, regardless of the level of oral health behavior. As the dementia prevention behavior, however, was higher in the group with higher oral health behavior than in the group with low oral health behavior, the oral health behavior should be improved to increase the dementia prevention behavior. In this study, the higher the oral health behavior was, the higher the oral health knowledge and dementia prevention behavior, and the higher the oral health knowledge was, the higher the dementia anxiety and dementia prevention behavior were as well.
Therefore, to improve dementia prevention behavior, transfer of the knowledge that dementia is highly related to oral health is most important, and the oral health knowledge and oral health behavior should be improved to enhance the dementia prevention behavior. In this study, the relationship between dementia anxiety and dementia prevention behavior was not con rmed, but in the 3-year follow-up study by Mah, Binns, and Steffens [39], the higher the dementia anxiety was, the greater the risk of dementia. In particular, the elderly people with severe anxiety were 2.35 times more likely to develop dementia. A 12year follow-up study by Johansson et al. [40] also reported that the risk of dementia was twice as high in the high-stress group than in the low-stress group. As there is a close relationship between dementia anxiety and dementia prevention behavior, in-depth research on the association between them is considered necessary in the future.

Conclusions
This study examined the associations among oral health knowledge, dementia knowledge, dementia anxiety, and dementia prevention behavior according to the level of oral health behavior. Through the study results, it was con rmed that high oral health behavior increases oral health knowledge and dementia prevention behavior, and high oral health knowledge increases dementia anxiety and dementia prevention behavior. Therefore, to prevent dementia, active education is required on the relationship between dementia and oral health, and efforts should be made to improve people's oral health behavior.

Limitation
The limitations of this study are that the samples were drawn through convenience sampling from a region and the sample size is small; thus, there is a limit to the generalization of the study results. The relationships among oral health behavior, dementia knowledge, dementia anxiety, and dementia prevention behavior cannot be categorized into causal relations; therefore, further research on this should be conducted.

List Of Abbreviations
Not applicable.
Declarations i. Ethics approval and consent to participate The study was approved by Institutional Review Board of Silla University'(No. 1041449-201912-HR-002).
Informed consent was obtained from all individual participants included in the study. All methods have been carried out in accordance with the relevant guidelines and regulations.
ii. Consent for publication Not applicable.
iii. Availability of data and material The data sets generated and/or analyzed during the current study are not publicly available for reasons of personal and organizational integrity but are available from the corresponding author on reasonable request.

iv. Competing interests
The authors declare that they have no competing interests.

v. Funding
No nancial support was received for this study.
vi. Authors' contributions Y.R Kim wrote the main manuscript text and H.K Kang and M.G Soong prepared tables 1-6. All authors reviewed the manuscript.

vii. Acknowledgements
Not applicable.