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The Connection between Hand Washing and Brushing Teeth
J Dent Hyg Sci 2023;23:132-41
Published online June 30, 2023;
© 2023 Korean Society of Dental Hygiene Science.

Ra-Ae Bak1 , Sun-Jung Shin2 , Hee-Jung Park3 , Jin-Young Jung4 , Hwa-Young Lee5 , and Nam-Hee Kim6,†

1Department of Dental Hygiene, Yonsei Graduate School, Wonju 26493, 2Department of Dental Hygiene, Gangneung-Wonju National Uinversity, Gangneung 25457, 3Department of Dental Hygiene, Kangwon National University, Samcheok 25949, 4Hallym Research Institute of Clinical Epidemiology, Hallym University, Chuncheon 24252, 5Graduate School of Public Health and Healthcare Management, The Catholic University of Korea, Seoul 06591, 6Department of Dental Hygiene, Mirae Campus, Yonsei University, Wonju 26494, Korea
Correspondence to: Nam-Hee Kim,
Department of Dental Hygiene, Mirae Campus, Yonsei University, 1 Yonseidae-gil, Wonju 26494, Korea
Tel: +82-33-760-5570, Fax: +82-33-760-2919, E-mail:
Received May 15, 2023; Revised June 8, 2023; Accepted June 9, 2023.
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License ( which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Background: The purpose of this study was to identify the connection between handwashing and toothbrushing, focusing on eating habits, and to verify whether eating habits can be used as an action cue for forming health habits.
Methods: This was a cross-sectional study using secondary data from the 2019 community health survey. The participants included 229,099 adults aged 19 years or older, representative of the South Korean people. We employed two dependent variables: one was washing hands, and the other was brushing teeth. Eating habits was a major independent variable. Socioeconomic variables, such as age, gender, income, occupation, economic activity, education, and residence were adjusted as confounders. Multivariate logistic regression was performed to calculate adjusted odds ratio and 95% confidence intervals.
Results: Most of the participants had good health behaviors: those who wash their hands and brush their teeth were each approximately 80%. Our finding indicated that brushing teeth and washing hands can be connected with eating habits. After adjusting for confounders, it was found that people who wash their hands before meals (compared to those who did not wash their hands before meals) had a higher toothbrushing rate after meals (i.e., socioeconomic status) (Adjusted Odds Ratio: 2.0, Confidence Intervals: 1.9 to 2.1).
Conclusion: Those who practice either washing hands before meals or brushing teeth after meals were found to have a connection between washing hands and brushing teeth based on the results of practicing other health behaviors. This implies that eating habits can be connected as a behavior cue to promote health habits, such as washing hands before meals and brushing teeth after meals.
Keywords : Behavioral cue, Brushing teeth, Eating habits, Health behavior, Washing hands


World Health Organization emphasizes the importance of hand washing after returning home and before and after the meal to prevent infectious diseases1). This hand washing campaign has been more emphasized since the Coronavirus disease 2019 (COVID-19) outbreak, and currently, such hand washing practice has improved after the COVID-19 pandemic in Korea2). Hand washing is also known to contribute to prevention of foodborne diseases and food poisoning and interruption of the spread of diseases3).

A previous study that supported the importance of hand washing before the meal has suggested the necessity of connecting two behaviors. For example, a study that investigated the association between the number of hand washings before distributing foods at school cafeteria and the incidences of Staphylococcus aureus, a bacteria that causes food poisoning, pneumonia, and sepsis, has demon-strated the importance of hand washing before the meal4). In addition, a study that analyzed detection of Staphy-lococcus aureus from cooking appliances and ingredients handled by cooks’ hands has emphasized the necessity of practicing hand washing to prevent cross infection5).

Washing the hands before the meal is important to prevent infectious materials from entering into the mouth through the hands. In the same context, toothbrushing is a healthy oral hygiene behavior to remove the risk factors for oral diseases caused by food debris in the mouth after the meal6,7). Toothbrushing removes food debris and dental plaques from the teeth surfaces and those stuck between teeth and increases resistance to infections by promoting keratinization of the gingival epithelium8). Also, tooth loss due to oral diseases has social-psychological effects as it causes loss of chewing ability and decreases nutrient intakes, leading to the poor quality of meal, dissatisfaction with pronunciation and appearance, and poor quality of life9). Toothbrushing is a representative behavior that prevent these oral disease10,11).

Hypothesis of our study is supported by previous studies that have reported the association between toothbrushing and hand washing. For example, the studies had empha-sized the association between hand washing and tooth-brushing by demonstrating that low practice of hand washing resulted in low frequency of toothbrushing, and suggested plans to increase the frequency of practicing those behaviors by connecting these behaviors12-17).

Meanwhile, as food (eating) is a basic human need, we practice this behavior every day to take nutrient necessary for physical activities18,19). Regular breakfast is also adva-ntageous for nutrient intakes and health conditions20), and since quality as well as quantity of nutrients are associated with the morbidity or longevity, eating plays an important role in the quality of life21).

The three behaviors (i.e., handwashing, eating and tooth-brushing) are referred to as healthy behaviors because we practice these behaviors every day and these are closely related to health. Thus, we thought that these behaviors can be connected to each other as action cues to make them habits if there is any association between the three beha-viors. For example, hand washing before eating is a habit, and eating can be an action cue for the handwashing beh-avior. In the same manner, for a person who has the ‘meal’ and brushes his/her teeth, ‘an action for eating’ can al-ready be an action cue for toothbrushing behavior. Likewise, the principle is that repeated exposure to any associated behaviors can become a habit naturally as a precedent action becomes an action cue (motivation) that leads the subsequent action22). Therefore, the investigators of this study thought that there is a chance to advocate associated actions such as ‘handwashing before eating’ and ‘tooth-brushing after eating’ based on eating behavior if eating meals can become an action cue for hand washing and toothbrushing. This study was conducted to demonstrate this possibility.


This study aimed to assess the association between handwashing and toothbrushing based on eating meals and to demonstrate whether eating every day can be used as a factor developing healthy habits.

Materials and Methods

1.Study participants

This is a cross-section study and used data of the 2019 Community Health Survey (CHS) from the Korea Disease Control and Prevention Agency for analysis. The CHS is the questionnaire generating community health data of community based on the Regional Public Health Act and Enforcement Decree of the Regional Public Health Act. A population of this study included 229,099 adults aged at least 19 years over the country for analysis.

2.Study design and method

This study used two dependent variables: ‘hand washing before eating’ and ‘toothbrushing after eating.’ For ‘hand washing before eating,’ the question was ‘how many time have you washed your hands before eating?’ The answers were categorized into ① do and ② don’t. For ‘tooth-brushing after eating,’ the question was ‘have you brushed your teeth yesterday after having a breakfast?’ The answer was categorized into ① do and ② don’t.

‘How many days a week do you eat breakfast annually’ and sociodemographic variables were used as independent variables. For the question about ‘how many days a week do you eat breakfast annually,’ the answer was classified into ① do and ② don’t.

Sociodemographic variables included gender, age, household monthly income, occupation, participation in economic activity, education level, and administrative dis-tricts (Dong, Eup/Myeon). Gender was categorized into ① man and ② woman, and age was categorized into ① 19∼34 years, ② 35∼44 years, ③ 45∼54 years, ④ 55∼64 years, and ⑤ ≥65 years. Household monthly income was categorized into ① low, ② lower-middle, ③ upper-mi-ddle, and ④ high. Occupation was classified into ① ma-nagers and professionals, ② office workers, ③ service providers and sales workers, ④ agricultural and fishery workers, ⑤ machine operators, ⑥ daily labors, and ⑦ other (solders, housewives, students, retakers, and unem-ployed). Participation in economic activity was catego-rized into ① active and ② inactive, and education level was categorized into ① middle school graduates or lower level, ② high school graduates, and ③ college graduates or higher level. Administrative districts (Dong, Eup/ Myeon) were classified into ① Dong and ② Eup/Myeon (Table 1).

Variables Description in the Analysis

Variable Definition
Dependent variables Washing hands before eating
① Washing hands all the time
② Washing hands frequently (=do)
③ Washing hands occasionally
④ Washing hands hardly (=don’t)
Brushing teeth after breakfast
① Do
② Don’t
Independent variables Eating breakfast
① 5∼7 times a week
② 3∼4 times a week (=do)
③ 1∼2 times a week
④ Hardly eat breakfast (=don’t)
① Man
② Woman
① 19∼34
② 35∼44
③ 45∼54
④ 55∼64
⑤ ≥65
Household monthly income
① Less than 3 million won (=lower)
② Less than 5 million won (=lower-middle)
③ Less than 7 million won (=upper-middle)
④ More than 7 million won (=high)
① Managers and professionals
② Office workers
③ Service and sales workers
④ Agricultural and fishery workers
⑤ Machine operators
⑥ Daily labors
⑦ Other (soldiers, housewives, students, etc)
Economic activity
① Active
② Inactive
① Middle school
② High school
③ University
① Dong
② Eup/Myeon

3.Statistical analysis

Cross analysis was performed to test the association between sociodemographic characteristics and hand washing, eating, and toothbrushing, and the distribution between variables was demonstrated. Multivariate logistic regre-ssion analysis was performed to investigate that how much and how differently independent variables affect hand washing and toothbrushing. For statistical analysis, data were analyzed using the SAS Institute (SAS Institute, Cary, NC, USA). A significance level was set to be 0.05.


1.Proportion of practicing hand washing,eating, and toothbrushing bysociodemographic characteristics

Of the total subjects, 77.1% of subjects were found to have breakfast, of which 87.3% and 92.3% were found to wash their hands before eating breakfast and brush their teeth after eating breakfast, respectively. However, of those who washed their hands before eating, 93.3% were found to brush their teeth after eating breakfast (Table 2).

Proportion of Practicing Hand Washing, Eating, and Toothbrushing by Sociodemographic Characteristics

Variable Total Washing hands before eating Eating breakfast Brushing teeth after breakfast

Do Don’t Do Don’t Do Don’t
Total 229,099 197,901 (86.4) 31,165 (13.6) 176,625 (77.1) 52,470 (22.9) 188,383 (92.3) 15,785 (7.7)
Gender Man 102,572 (44.8) 73,147 (46.2) 17,286 (68.0) 76,998(48.7) 13,435 (50.1) 81,693 (48.1) 8,849 (60.4)
Woman 126,527 (55.2) 103,696 (53.8) 9,529 (32.0) 97.056 (51.3) 16,169 (49.9) 106,411 (51.9) 6,904 (39.6)
Age 19∼34 34,474 (15.0) 20,810 (19.6) 3,438 (22.8) 14,710 (15.2) 9,538 (38.8) 21,787 (19.4) 2,500 (27.7)
35∼44 31,816 (13.9) 22,963 (17.6) 2,607 (13.5) 17,746 (14.6) 7,824 (27.0) 23,702 (17.0) 1,905 (17.6)
45∼54 40,198 (17.6) 31,148 (21.1) 4,178 (20.0) 28,623 (20.9) 6,703 (21.3) 33,220 (21.3) 2,147 (17.0)
55∼64 48,064 (21.0) 40,139 (20.1) 5,228 (18.7) 41,724 (22.5) 3,643 (9.5) 42,851 (20.4) 2,556 (14.3)
≥65 74,547 (32.5) 61,783 (21.6) 11,364 (25.0) 71,251 (26.8) 1,896 (3.4) 66,544 (21.9) 6,645 (23.4)
Income Lower 88,467 (38.6) 70,058 (28.7) 12,276 (33.9) 75,060 (31.5) 7,274 (20.9) 75,197 (29.1) 7,193 (32.8)
Lower-middle 47,649 (20.8) 36,174 (24.1) 4,853 (22.9) 332,939 (23.2) 7,734 (26.7) 38,308(24.0) 2,758 (22.8)
Upper-iddle 38,050 (16.6) 28,361 (21.8) 3,681 (19.8) 25,179 (20.7) 6,863 (25.1) 30,084 (21.7) 1,989 (19.7)
High 54,933 (24.0) 42,250 (25.4) 6,005 (23.4) 40,522 (24.6) 7,733 (27.3) 44,515 (25.2) 3,813 (24.7)
Occupation Managers and professionals 23,194 (10.1) 17,364 (14.2) 1,961 (11.1) 14,390 (12.6) 4,935 (18.7) 18,150(13.9) 1,175 (12.0)
Office workers 19,696 (8.6) 14,142 (11.5) 1,773 (10.2) 11,465 (10.0) 4,450 (16.7) 14,960 (11.5) 955 (9.9)
Service and sales workers 30,083 (13.1) 23,040 (13.8) 2,420 (10.9) 20,219 (12.5) 5,241 (16.9) 24,044 (13.6) 1,416 (11.3)
Agricultural and fishery workers 25,354 (11.1) 21,238 (3.6) 3,611 (4.2) 24,011 (4.4) 838 (0.9) 22,289 (3.5) 2,560 (5.2)
Machine operators 21,196 (9.3) 15,171 (10.6) 3,035 (14.9) 15,013 (11.2) 3,193 (11.0) 16,764 (11.1) 1,442 (12.3)
Daily labors 21,672 (9.5) 17,228 (8.3) 2,647 (9.7) 17,543 (8.9) 2,332 (6.8) 18,487 (8.5) 1,388 (8.2)
Other (soliders, housewives, students) 87,590 (38.3) 68,660 (38.0) 11,368 (39.0) 71,413 (40.4) 8,615 (29.0) 73,221 (37.9) 6,807 (41.1)
Economic activity Active 141,960 (62.0) 108,611 (62.3) 15,470 (61.1) 102,936 (59.8) 21,145 (71.4) 115,221 (62.4) 8,979 (59.2)
None 87,056 (38.0) 68,232 (37.7) 11,345 (38.9) 71,118 (40.2) 8,459 (28.6) 72,883 (37.6) 6,774 (40.8)
Education Middle school 80,883 (35.3) 66,696 (22.1) 12,016 (26.6) 75,634 (26.8) 3,078 (6.1) 71,743 (22.5) 7,018 (24.2)
High school 65,466 (28.6) 50,414 (29.6) 7,348 (31.2) 48,363 (30.1) 9,399 (28.8) 53,899 (30.0) 3,916 (28.1)
University 82,527 (36.1) 59,733 (48.3) 7,451 (42.2) 50,057 (43.1) 17,127 (65.1 62,462 (47.5) 4,819 (47.7)
Residence Dong 128,724 (56.2) 96,306 (80.4) 13,841 (79.2) 90,071 (79.2) 20,076 (84.4) 102,433 (80.4) 7,843 (78.5)
Eup/Myeon 100,375 (43.8) 80,537 (19.6) 12,974 (20.8) 83,983 (20.8) 9,528 (15.6) 85,671 (19.6) 7,910 (21.5)
Hands washing Yes 197,901 (86.4) NA NA 151,320 (87.3) 25,523 (86.0) 165,284 (88.0) 11,559 (75.8)
No 31,165 (13.6) NA NA 22,734 (12.7) 4,081 (14.0) 22,631 (12.0) 4,184 (24.2)
Eating breakfast Yes 176,625 (77.1) 151,320 (80.1) 22,734 (78.3) NA NA 161,706 (80.7) 12,348 (69.3)
No 52,470 (22.9) 25,523 (19.9) 4,081 (21.7) NA NA 26,209 (19.3) 3,395 (30.7)
Tooth brushing Yes 188,383 (92.3) 165,284 (93.3) 22,632 (85.5) 161,706 (93.3) 26,209 (88.2) NA NA
No 15,785 (7.7) 11,559 (6.7) 4,184 (14.5) 12,348 (6.7) 3,395 (11.8) NA NA

NA: not applicable.

2.The association between eating breakfast and handwashing before eating breakfast

Subjects who ate breakfast were 1.1 times more likely to wash their hands compared to those who did not have breakfast (Adjusted Odds Ratio [aOR]: 1.1, Confidence Intervals [CI]: 1.1~1,2). Those who participated in socioe-conomic activity (Adjusted Odds Ratio [aOR]: 1.7, [CI]: 1.4∼2.0) and had higher education level (Adjusted Odds Ratio [aOR]: 1.8, [CI]: 1.7∼1.9) were more likely to practice hand washing before eating (Table 3).

The Association with Eating Breakfast and Washing Hands

Variable Washing hands

Crude Adjusted

OR (95% CI) OR (95% CI)
Eating breakfast Do 1.1 (1.1∼1.2) 1.1 (1.1∼1.2)
Don’t (ref) NA NA
Gender Man (ref) NA NA
Woman 2.5 (2.4∼2.6) 2.7 (2.6∼2.8)
Age 19∼34 0.7 (0.6∼0.7) 0.7 (0.7∼0.8)
35∼44 (ref) NA NA
45∼54 0.8 (0.8∼0.9) 0.9 (0.8∼1.0)
55∼64 0.7 (0.6∼0.7) 1.0 (0.9∼1.1)
≥65 0.7 (0.6∼0.7) 1.0 (0.9∼1.1)
Income Lower 0.8 (0.7∼0.8) 0.9 (0.8∼1.0)
Lower-middle 1.0 (0.9∼1.0) 1.0 (0.9∼1.0)
Middle-high (ref) NA NA
High 1.0 (0.9∼1.0) 1.0 (0.9∼1.0)
Occupation Managers and professionals 1.5 (1.4∼1.6) 1.1 (1.0∼1.2)
Office workers 1.3 (1.2∼1.4) 1.0 (0.9∼1.1)
Service and sales workers 1.4 (1.4∼1.6) 1.1 (1.0∼1.2)
Agricultural and fishery workers (ref) NA NA
Machine operators 0.8 (0.8∼0.9) 0.9 (0.9∼1.0)
Daily labors 1.0 (1.0∼1.1) 0.9 (0.8∼0.9)
Other (soliders, housewives, students, etc) 1.1 (1.1∼1.2) 1.4 (1.2∼1.7)
Economic activity Active 1.1 (1.0∼1.1) 1.7 (1.4∼2.0)
None (ref) NA NA
Education Middle (ref) NA NA
High 1.2 (1.1∼1.2) 1.4 (1.3∼1.4)
University 1.4 (1.3∼1.4) 1.8 (1.7∼1.9)
Residence Dong 1.1 (1.0∼1.1) 1.0 (0.9∼1.0)
Eup/Myeon (ref) NA NA

Values are presented as n (%).

ref: reference, NA: not applicable.

3.The association between eating breakfast and toothbrushing after eating breakfast

Subjects who ate breakfast were 1.8 times more likely to brush their teeth compared to those who did not have breakfast (OR: 1.8, CI: 1.7∼1.9). Subjects who washed their hands before eating breakfast were 2 times more likely to brush their teeth after eating breakfast compared to those who did not wash their hands before eating break-fast (OR: 2.0, CI: 1.9∼2.1). Those who are office workers (OR: 1.8, CI: 1.6∼2.0), participated in economic activity (OR: 1.3, CI: 1.2∼1.4), and had higher education level (OR: 1.4, CI: 1.3∼1.6) were more likely to practice tooth-brushing a lot after eating breakfast (Table 4).

The Association with Eating Breakfast and Brushing Teeth

Variable Brushing teeth

Crude Adjusted

OR (95% CI) OR (95% CI)
Eating breakfast Do 1.9 (1.8∼1.9) 1.8 (1.7∼1.9)
Don’t (ref) NA NA
Washing hands Do 2.3 (2.2∼2.5) 2.0 (1.9∼2.1)
Don’t (ref) NA NA
Gender Man (ref) NA NA
Woman 1.6 (1.6∼1.7) 1.6 (1.6∼1.7)
Age 19∼34 0.7 (0.7∼0.8) 0.8 (0.8∼0.9)
35∼44 (ref) NA NA
45∼54 1.3 (1.2∼1.4) 1.3 (1.2∼1.4)
55∼64 1.5 (1.4∼1.6) 1.6 (1.5∼1.8)
≥65 1.0 (0.9∼1.0) 1.3 (1.2∼1.4)
Income Lower 0.8 (0.8∼0.9) 0.9 (0.8∼1.0)
Lower-middle 1.0 (0.9∼1.0) 1.0 (0.9∼1.1)
Middle-high (ref) NA NA
High 0.9 (0.9∼1.0) 1.0 (0.9∼1.0)
Occupation Managers and professionals 1.7 (1.6∼1.9) 1.7 (1.6∼1.9)
Office workers 1.7 (1.5∼1.9) 1.8 (1.6∼2.0)
Service and sales workers 1.8 (1.6∼1.9) 1.7 (1.6∼1.9)
Agricultural and fishery workers (ref) NA NA
Machine operators 1.3 (1.2∼1.4) 1.6 (1.4∼1.7)
Daily labors 1.5 (1.4∼1.7) 1.5 (1.4∼1.7)
Other (soliders, housewives, students) 1.3 (1.2∼1.4) 1.7 (1.3∼2.1)
Economic activity Active 1.1 (1.1∼1.2) 1.3 (1.0∼1.7)
None (ref) NA NA
Education Middle (ref) NA NA
High 1.1 (1.1∼1.2) 1.3 (1.2∼1.4)
University 1. (1.0∼1.1) 1.4 (1.3∼1.6)
Residence Dong 1.1 (1.1∼1.2) 1.0 (1.0∼1.1)
Eup/Myeon (ref) NA NA

Values are presented as n (%).

ref: reference, NA: not applicable.



This study investigated the association between hand washing before eating breakfast and toothbrushing after eating breakfast based on eating breakfast as healthy behaviors of adults aged at least 19 years over the country, by using data of 2019 CHS. Of those who ate breakfast, 87.3% washed their hands before eating breakfast (Table 2), and those who ate breakfast were 1.1 times more likely to wash their hands compared to those who did not eat breakfast (OR: 1.1, CI: 1.1∼1.2) (Table 3).

Also, subjects who had breakfast were 1.8 times (OR: 1.8, CI: 1.7∼1.9) more likely to brush their teeth compared to those who did not eat breakfast. Those who washed their hands were 2.0 times (CI: 1.9∼2.1) more likely to brush their teeth compared to those who did not wash their hands (Table 4).

2.Key results and comparison with the results of previous studies

Analysis performed based on occupation showed that those who are managers, professionals, and relevant workers, office workers, service providers, and sales workers (clas-sified as indoor workers) were more likely to practice toothbrushing and hand washing compared to those who are agricultural and fishery workers, which was not stati-stically significant. With regard to eating breakfast, the proportion of individuals who ate breakfast was much higher in managers, professionals, relevant workers, office workers, service providers, and sales workers than those who are agricultural and fishery workers. Since office workers or managers have higher education compared to agricultural and fishery workers23), educational level can affect the practice of healthy behaviors. In previous studies, the pro-portions of subjects who washed their hands24) and brushed their teeth25) were much higher in the group of office workers compared to non-office workers, and the propo-rtion of eating breakfast was higher in factory workers26). Similarly, this study showed that agricultural and fishery workers tend to practice healthy behaviors little.

More subjects of this study practiced hand washing and toothbrushing as they participated in economic activity and had higher education level. This is supported by a previous study that reported that the level of practicing healthy behavior is increased as the socioeconomic level is higher, which positively affects the subjective health level27). However, this result also implies the possibility of that environment and infrastructure of the community, surrou-nding the corresponding jobs, might impact on practicing healthy behavior of those who had the jobs28).

In addition, this study reviewed the association between eating breakfast and hand washing, eating breakfast and toothbrushing, and hand washing and toothbrushing to de-termine the interconnectivity between healthy behaviors. Consequently, like the result that practice of healthy behaviors is increased as the health belief is higher29), we found that an individual who performs one healthy behavior also tends to practice other healthy behaviors naturally owing to a belief in health and hygiene. Therefore, a factor affecting health promoting behaviors that enable people to recognize the importance of health and enhance the healthy lifestyles and the ability to manage health is health recognition that is aware of health-related behaviors30). This means that health promoting behaviors at individual levels originating from such health recognition and health belief is important.


Practicing three or more healthy behaviors has more positive effects than practicing a part of relevant behaviors31). Likewise, since practicing hand washing before the meal, having a meal, and practicing toothbrushing together can have complementary influences on nutrient intakes, preve-ntion of infectious diseases, and prevention of oral diseases, it is necessary to build habits to establish positive influe-nces that can build such healthy behaviors.

In addition, as hand washing and toothbrushing can be practiced using public restrooms and sinks, environment and opportunity to practice the three behaviors continuously by establishing relevant facilities near the dining area. An effort is required to create environment that can facilitate better health promoting behaviors.


This study has some limitation. Since CHS used as study data did not include variables that show presence of lunch and dinner, we were not able to investigate the association between hand washing and toothbrushing by meal time. Thus, this study analyzed eating breakfast and practice of toothbrushing after eating breakfast only. Second limitation was that this study could not consider the un-measured confounding the practice of hand washing or toothbrushing. It should be considered to subgroup analysis with eating breakfast. It may have endogenous issues for those who eat breakfast every day.

Despite of these limitations, this study has demonstrated the intercorrelation between hand washing, having meals, and toothbrushing that had never been studied. This study demonstrated that more subjects who ate breakfast washed their hands and brushed their teeth compared to those who did not eat breakfast, and more subjects who washed their hands brushed their teeth compared to those who did not wash their hands. Therefore, eating behavior is considered a cue that promotes hand washing and toothbrushing and can be used to induce consistent health promoting beha-viors by applying it.

The subjects who practiced one of behaviors (hand washing before eating and toothbrushing after eating) also practiced another behavior, showing that there is association between the two behaviors. To encourage an individual to practice hand washing and toothbrushing sequentially (e.g., hand washing before eating and tooth-brushing after eating), eating meals can be used as a cue and applied for habit formation of health promoting be-haviors.


The research was supported by a fund (Reseach No. 2022-11-003) by Research of Korea Disease Control and Prevention Agency.

Conflict of Interest

No potential conflict of interest relevant to this article was reported.

Ethical Approval

This study was approved by the Institutional Review Board of Yonsei University Mirae Campus (IRB No. 1041849-202211-SB-216-02).

Author contributions

Conceptualization: Ra-Ae Bak and Nam-Hee Kim. Data acquisition: Ra-Ae Bak. Formal analysis: Ra-Ae Bak. Funding: Ra-Ae Bak. Supervision: Sun-Jung Shin, Hee- Jung Park, Jin-Young Jung, Hwa-Young Lee, and Nam- Hee Kim. Writing-original draft: Ra-Ae Bak. Writing- review & editing: Ra-Ae Bak and Nam-Hee Kim.

Data availability

Data were obtained from the 2019 CHS (

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