
Smoking affects teeth and periodontal tissues in various ways, such as the thermal or physical stimulation of cigarettes. However, the most critical pathological issue is that chemical and molecular interaction by cigarettes increases periodontal inflammation and induces potential benign and malignant oral diseases (e.g., oral cancer)1). Cigarette smoke is the most common cause of exposure to chemical carcinogens among people. Worldwide, one in five cancer deaths is caused by smoking or secondhand smoke (SHS)2).
Non-smokers can also be exposed to cigarette smoke. According to a study by Oberg et al.3), 33% of male non-smokers, 35% of female non-smokers, and 40% of children were exposed to involuntary smoking. SHS increases the risk of stroke and heart disease4) and induces or aggravates asthma and allergy. Prolonged exposure to SHS can also increase the risk of chronic obstructive pulmonary disease (COPD)5). A previous study of children and adolescents aged between 9 and 18 years reported that SHS among children and adolescents increased the risk of cardiovascular diseases6).
SHS negatively affects not only systemic health but also oral health7). SHS can change normal bacterial flora of the oral cavity and nasopharynx and cause upper respiratory infection8). In addition, SHS is associated with alveolar bone loss, risk of severe periodontitis, and dental implant failures9-11). In particular, exposure to SHS affects mineralization in a developing tooth12) and is associated with dental caries among children and adolescents13). Experience of SHS in children and adolescents is a factor that increases the level of nicotine dependence and makes it more difficult to quit smoking14,15). Since oral problems due to SHS are more likely to lead to persistent oral diseases, various studies on SHS in adolescents are required.
Studies regarding SHS and oral health in adolescents have reported the association between SHS and pain and gingival bleeding16), the association between exposure to SHS and risk of dental caries13), and the association between the smoking status of parents and the oral health of their children17). However, only few studies reported effects of SHS on oral symptoms and their association by classifying them into dental and gingival diseases and determined the association between the frequency of SHS exposure and oral symptoms.
This study aimed to determine the trends in SHS of adolescents by employing data from the 17th Korea Youth Risk Behavior Web-based Survey in 2021 (hereinafter referred to as 17th Youth Health Survey) that included Korean adolescents as a population and to identify the independent association between the level of SHS and oral symptoms.
The 17th Youth Health Survey was a government-approved undertaking (approval number 117058) based on the National Health Promotion Act. This data has been deidentified and is anonymous. Therefore, it is not human-subject research. Also, It was conducted in full accordance with the World Medical Association Declaration of Helsinki, and written informed consent was obtained on a web page before the start of the Internet survey from all participants or their parents/guardians in cases where the subject was aged <18 years.
This is a secondary data analysis study that employed data from the 17th Youth Health Survey. It was an online anonymous, self-recording survey, and raw data were provided according to the procedures for usage on the Website. The 17th Youth Health Survey employed stratified cluster sampling to select samples between the first year of middle school and high school seniors among the entire Korean students, and the survey was administered after obtaining consent to participation from the samples. In addition, students with a long absence, special needs, and literacy problems were excluded, and data from the final 54,848 were employed.
This study used subjective oral symptoms I, II, and III from the oral health domain of the 17th Youth Health Survey, and experiencing one of those symptoms was selected as the dependent variable. For subjective oral symptoms, symptoms for the recent 12 months were investigated. Symptoms I and II corresponded to symptoms of dental caries18): ‘tooth pain when eating or drinking hot or cold foods (subjective oral symptom I)’ and ‘throbbing tooth pain (subjective oral symptom II).’ Subjective oral symptom III includes ‘sore or bleeding gums’ which is a known symptom for gum diseases19).
Also, independent variables of this study were home, school, public indoor places, and SHS frequency among smoking domains of the 17th Youth Health Survey.
Sociodemographic characteristics (sex, grade, area of residence, subjective household economic class, father’s educational level, and mother’s educational level), oral health behavior (brushing after lunch, daily frequency of brushing teeth), and frequency of snack intake (fast food, carbonated drinks, and sweet drinks for the recent 7 days) that can affect the results were selected as confounding variables.
This study used PASW Statistics 18.0 (IBM Corp., Armonk, NY, USA) to analyze data. Since the 17th Youth Health Survey used samples selected via stratified clustering probability sampling, a complex sample design, data were analyzed by creating analysis plan files that reflected weight, stratification variables, and cluster variables. This can prevent the results from being biased that may occur from the general statistics handling method, and the weighted data can allow the results to be interpreted for the population. A p-value of 0.05 was considered statistically significant. Multicollinearity for all independent variables was identified, and variables with a variance inflation factor ≤10 were used for analysis. Data analysis is described below in detail.
Frequency analysis of complex sampling was conducted for sociodemographic characteristics, frequency of SHS, and subjective oral symptoms.
Chi-squared test of complex sampling was used to analyze the frequency of SHS by sociodemographic characteristics.
Chi-squared test of complex sampling was used to analyze subjective oral symptoms by sociodemographic characteristics.
Multiple logistic regression analysis of complex sampling was used to determine the association between the frequency of SHS and subjective oral symptoms.
In this study, 51.7% were male students and 51.0% were middle school students, and 43.4% and 42.7% had fathers and mothers who graduated from university, respectively. The subjective economic class was highest in ‘middle,’ accounting for 49.0%, and the subjective academic class was highest in ‘high,’ accounting for 37.1%. The proportion of those who experienced subjective oral symptoms was 45.6%, who reported at least one of oral symptoms I, II, and III. Regarding places of SHS, most students reported that they were not exposed to SHS at home, school, and public indoor places. However, 23.3%, 7.9%, and 40.0% were exposed to SHS at home, school, and public indoor places at least once a week, respectively (Table 1).
Sociodemographic Characteristics Derived from the 2021 Korea Youth Risk Behavior Web-Based Survey (n=54,848)
Characteristic | n | Weighted %±standard error |
---|---|---|
Demographic variable | ||
Sex | ||
Adolescent male | 28,401 | 51.7±1.1 |
Adolescent female | 26,447 | 48.3±1.1 |
Academic level | ||
Middle school | 30,015 | 51.0±0.7 |
High school | 24,833 | 49.0±0.7 |
Sociological factors | ||
Father’s educational level | ||
Middle-school graduation or lower | 558 | 0.9±0.0 |
High-school graduation | 8,665 | 15.3±0.3 |
University or college graduation or higher | 22,958 | 43.4±0.5 |
I don’t know | 7,680 | 12.9±0.2 |
No father, missing data | 14,987 | 27.4±0.5 |
Mother’s educational level | ||
Middle-school graduation or lower | 453 | 0.8±0.0 |
High-school graduation | 10,147 | 18.2±0.3 |
University or college graduation or higher | 22,722 | 42.7±0.5 |
I don’t know | 6,929 | 11.7±0.2 |
No mother, missing data | 14,597 | 26.7±0.5 |
Economic factors | ||
Subjective economic class | ||
High | 21,568 | 40.1±0.4 |
Middle | 27,077 | 49.0±0.3 |
Low | 6,203 | 10.9±0.2 |
Academic factors | ||
Subjective academic class | ||
High | 20,528 | 37.1±0.3 |
Middle | 16,903 | 31.0±0.2 |
Low | 17,417 | 31.9±0.3 |
Oral symptom factors | ||
Oral symptoms |
||
Oral symptoms class I | 16,724 | 30.6±0.2 |
Oral symptoms class II | 11,456 | 21.1±0.2 |
Oral symptoms class III | 10,322 | 19.1±0.2 |
Oral symptoms class I, II, or III | 24,846 | 45.6±0.3 |
Secondhand smoking factors (times/week) | ||
Home | ||
No secondhand smoking | 41,671 | 76.7±0.2 |
1∼2 | 5,726 | 10.2±0.1 |
3∼4 | 3,114 | 5.5±0.1 |
5∼6 | 1,211 | 2.1±0.1 |
≥7 | 3,126 | 5.5±0.1 |
School | ||
No secondhand smoking | 50,661 | 92.1±0.3 |
1∼2 | 2,595 | 4.9±.1 |
3∼4 | 814 | 1.5±0.1 |
5∼6 | 283 | 0.5±0.0 |
≥7 | 495 | 0.9±0.1 |
Other etc. (PC room, shopping mall) | ||
No secondhand smoking | 33,223 | 60.0±0.3 |
1∼2 | 12,515 | 23.0±0.2 |
3∼4 | 5,694 | 10.6±0.2 |
5∼6 | 1,506 | 2.8±0.1 |
≥7 | 1,910 | 3.7±0.1 |
Total (home+school+other etc.) | ||
No secondhand smoking | 25,751 | 46.8±0.3 |
1∼2 | 19,035 | 34.8±0.3 |
3∼4 | 6,671 | 12.2±0.2 |
5∼6 | 2,223 | 4.0±0.1 |
≥7 | 1,168 | 2.2±0.1 |
aOral symptoms class I: tooth pain when eating, Oral symptoms class II: throbbing tooth pain, Oral symptoms class III: sore and bleeding gums.
The frequency of SHS by sociodemographic characteristics was analyzed and showed a higher proportion of female students than male students.
In high school students, the highest proportion of those who had fathers and mothers with middle school graduation or lower were exposed to SHS at least 3 times a week (p<0.05). In addition, the frequency of SHS was highest in a group with ‘low’ subjective economic class and subjective academic class (p<0.05) (Table 2).
Frequency of Secondhand Smoking by Sociodemographic Characteristics in Korean Adolescents (n=54,848)
Characteristic | Frequency of secondhand smoking per week (weighted %±standard error) | |||||
---|---|---|---|---|---|---|
0 (none) | 1∼2 | 3∼4 | 5∼6 | ≥7 | p | |
Demographic factors | ||||||
Sex | <0.001 | |||||
Adolescent male | 53.0±0.4 | 31.4±0.3 | 10.2±0.2 | 3.3±0.1 | 2.1±0.1 | |
Adolescent female | 40.3±0.4 | 38.4±0.3 | 14.2±0.2 | 4.8±0.1 | 2.3±0.1 | |
Academic level | <0.001 | |||||
Middle school | 46.0±0.4 | 37.0±0.3 | 11.7±0.2 | 3.7±0.1 | 1.6±0.1 | |
High school | 47.7±0.5 | 32.5±0.4 | 12.6±0.3 | 4.4±0.2 | 2.7±0.1 | |
Sociological factors | ||||||
Father’s educational level | <0.001 | |||||
Middle-school graduation or lower | 34.0±2.1 | 33.5±2.0 | 18.8±1.7 | 7.7±1.2 | 5.9±1.0 | |
High-school graduation | 40.8±0.5 | 34.5±0.5 | 15.4±0.4 | 6.4±0.3 | 2.8±0.2 | |
University or college graduation or higher | 46.8±0.4 | 37.3±0.4 | 11.2±0.2 | 3.1±0.1 | 1.6±0.1 | |
I don’t know | 46.3±0.6 | 35.3±0.6 | 12.5±0.4 | 4.1±0.2 | 1.9±0.2 | |
No father, missing data | 51.9±0.5 | 30.4±0.4 | 11.1± 0.3 | 3.9±0.2 | 2.7±0.2 | |
Mother’s educational level | <0.001 | |||||
Middle-school graduation or lower | 37.2±2.3 | 29.8±2.2 | 17.7±2.0 | 9.4±1.5 | 6.0±1.0 | |
High-school graduation | 41.0±0.5 | 36.0±0.5 | 15.0±0.4 | 5.3±0.2 | 2.7±0.2 | |
University or college graduation or higher | 46.8±0.4 | 37.3±0.4 | 11.0±0.2 | 3.3±0.1 | 1.6±0.1 | |
I don’t know | 47.4±0.7 | 34.4±0.6 | 12.8±0.4 | 3.7±0.3 | 1.7±0.2 | |
No mother, missing data | 51.9±0.5 | 30.4±0.4 | 11.1±0.3 | 3.9±0.2 | 2.7±0.2 | |
Economic factors | ||||||
Subjective economic class | <0.001 | |||||
High | 49.9±0.4 | 34.4±0.4 | 10.6±0.2 | 3.2±0.1 | 1.9±0.1 | |
Middle | 46.2±0.4 | 35.5±0.3 | 12.4±0.2 | 4.0±0.1 | 1.9±0.1 | |
Low | 38.2±0.7 | 33.2±0.7 | 17.1±0.5 | 7.2±0.4 | 4.2±0.3 | |
Academic factors | ||||||
Subjective academic class | <0.001 | |||||
High | 47.9±0.5 | 36.0±0.4 | 11.0±0.2 | 3.2±0.1 | 1.8±0.1 | |
Middle | 47.9±0.5 | 34.2±0.4 | 12.3±0.3 | 3.8±0.1 | 1.8±0.1 | |
Low | 44.6±0.5 | 34.0±0.4 | 13.4±0.3 | 5.1±0.2 | 2.9±0.1 |
p-values were analyzed using chi-squared test.
Subjective oral symptoms by sociodemographic characteristics among adolescents were investigated, and subjective oral symptoms I, II, and III showed significant differences in sex, grade, father’s and mother’s educational level, subjective economic class, and subjective academic class (p<0.001). Especially, more female students (50.40.3%) reported at least one of oral symptoms I, II, and III compared to male students (41.0±0.3%). High school students (47.5±0.4%), students who had fathers (51.8±2.2%) and mothers (56.0±2.4%) with middle school graduation or lower, and those with low subjective economic class (53.3±0.7%) and low subjective academic class (46.6±0.4%) showed a higher percentage of experiencing subjective oral symptoms (Table 3).
Sociodemographic Characteristics and Subjective Oral Symptoms among Korean (n=54,848)
Characteristic | Proportions experiencing oral symptoms (weighted %±standard error) | |||
---|---|---|---|---|
Class I |
Class II |
Class III |
Class I, II, or III | |
Demographic factors | ||||
Sex | ||||
Adolescent male | 27.8±0.3 | 18.0±0.3 | 16.6±0.2 | 41.0±0.3 |
Adolescent female | 33.5±0.3 | 24.7±0.3 | 21.8±0.3 | 50.4±0.3 |
p-value | <0.001 | <0.001 | <0.001 | <0.001 |
Academic level | ||||
Middle school | 29.8±0.3 | 19.0 ±0.3 | 17.7±0.2 | 43.7±0.5 |
High school | 31.3±0.3 | 23.6±0.3 | 20.6±0.3 | 47.5±0.4 |
p-value | <0.001 | <0.001 | <0.001 | <0.001 |
Sociological factors | ||||
Father’s educational level | ||||
Middle-school graduation or lower | 35.9±2.0 | 25.9±1.9 | 26.6±2.1 | 51.8±2.2 |
High-school graduation | 30.9±0.5 | 22.5±0.5 | 20.1±0.5 | 47.1±0.6 |
University or college graduation or higher | 32.2±0.3 | 22.3±0.3 | 20.0±0.3 | 47.7±0.4 |
I don’t know | 27.7±0.6 | 17.8±0.5 | 16.8±0.4 | 41.5±0.6 |
No father, missing data | 28.6±0.4 | 19.9±0.4 | 17.7±0.3 | 42.5±0.5 |
p-value | <0.001 | <0.001 | <0.001 | <0.001 |
Mother’s educational level | ||||
Middle-school graduation or lower | 39.0±2.4 | 25.8±1.9 | 27.0±2.2 | 56.0±2.4 |
High-school graduation | 30.6±0.5 | 22.1±0.4 | 20.1±0.4 | 46.8±0.5 |
University or college graduation or higher | 32.2±0.3 | 22.4±0.3 | 19.9±0.3 | 47.8±0.4 |
I don’t know | 27.6±0.6 | 17.9±0.5 | 16.6±0.5 | 41.1±0.7 |
No mother, missing data | 28.6±0.4 | 19.9±0.4 | 17.7±0.3 | 42.5±0.5 |
p-value | <0.001 | <0.001 | <0.001 | <0.001 |
Economic factors | ||||
Subjective economic class | ||||
High | 29.1±0.4 | 19.4±0.3 | 18.0±0.3 | 43.3±0.4 |
Middle | 30.5±0.3 | 21.4±0.3 | 19.0±0.3 | 45.7±0.4 |
Low | 36.3±0.6 | 27.4±0.6 | 23.8±0.6 | 53.3±0.7 |
p-value | <0.001 | <0.001 | <0.001 | <0.001 |
Academic factors | ||||
Subjective academic class | ||||
High | 31.3±0.4 | 21.1±0.3 | 19.3±0.3 | 46.3±0.4 |
Middle | 28.6±0.4 | 20.3±0.3 | 18.2±0.3 | 43.7±0.4 |
Low | 31.6±0.4 | 22.4±0.3 | 19.7±0.3 | 46.6±0.4 |
p-value | <0.001 | <0.001 | <0.001 | <0.001 |
p-values were analyzed using chi-squared test.
aTooth pain when eating, bthrobbing tooth pain, csore and bleeding gums.
Correlation between the frequency of SHS and subjective oral symptoms among adolescents was analyzed, and a group with exposure to SHS at least once a week showed a statistically significant increase in the risk of experiencing subjective oral symptoms I, II, and III compared to a group with no exposure to SHS (p<0.05). Especially, the risk of experiencing at least one of three oral symptoms (I, II, and III) increased 1.407 times in those with exposure to SHS only one or two times a week compared to the group with no exposure to SHS (Table 4).
Secondhand Smoke Patterns and Subjective Oral Symptoms among Korean Adolescents: Web-Based Survey on Adolescents Health Behavior in 2021 (n=54,848)
Odds ratio (95% confidence interval) |
||||
---|---|---|---|---|
Oral symptom I | Oral symptom II | Oral symptom III | Oral symptom I, II, or III | |
Secondhand smoke (times/week) | ||||
None | 1 | 1 | 1 | 1 |
1∼2 | 1.330 (1.275∼1.389) | 1.350 (1.280∼1.425) | 1.279 (1.215∼1.347) | 1.407 (1.351∼1.466) |
3∼4 | 1.417 (1.336∼1.503) | 1.487 (1.391∼1.590) | 1.545 (1.444∼1.653) | 1.519 (1.437∼1.605) |
5∼6 | 1.643 (1.493∼1.807) | 1.855 (1.683∼2.045) | 1.543 (1.396∼1.705) | 1.778 (1.620∼1.951) |
≥7 | 1.504 (1.332∼1.699) | 1.794 (1.585∼2.029) | 1.694 (1.480∼1.938) | 1.545 (1.376∼1.734) |
aAdjusted by sociodemographic characteristics (sex, grade, area of residence, subjective household economic class, father’s educational level, and mother’s educational level), oral health behavior (brushing after lunch, daily frequency of brushing teeth), and frequency of snack intake (fast food, carbonated drinks, and sweet drinks for the recent 7 days).
This study investigated the trends in SHS among adolescents by employing data from the Korea Youth Risk Behavior Web-based Survey and demonstrated that more frequent exposure to SHS increases the risk of subjective oral symptoms among adolescents.
In this study, 53.2% of subjects experienced SHS exposure at least once a week. Each country has reported problems with exposure to SHS among adolescents. In 2017, a study of U.S. adolescents showed an annual increase in exposure to SHS, and 55% of the subjects reported that they had experienced SHS. This is consistent with the results of this study20). However, a study that analyzed the 2012 Korea Youth Risk Behavior Web-based Survey21) reported that 40.6% of students experienced SHS at least once a week, which implies that the proportion of adolescents who were exposed to SHS has increased gradually. Interestingly, the proportion of those exposed to SHS at home decreased, while a higher proportion of those exposed to SHS in public places has been reported22,23). In this study, 23.3% were exposed to SHS at home at least once a week, while 40.0% were exposed to SHS in public places, such as PC rooms or shopping malls. Another previous study has reported that the proportion of those exposed to SHS due to close friends was higher than those exposed to SHS at home24). Exposure to SHS can be a critical factor that induces adolescents to smoke22). A previous study reported that exposure to SHS during the adolescent period increases the likelihood of smoking during adulthood and the number of cigarettes25). To protect adolescents from SHS, a legal system that does not allow individuals to smoke in public places or places where adolescents frequently visit is deemed necessary. In the United Kingdom the rate of children’s exposure to SHS has decreased since the law banning smoking in public places26).
In this study, the risk of experiencing at least one oral symptom has increased in a group with exposure to SHS at least one time compared to the group with no exposure to SHS. Exposure to SHS only once or twice a week increased the risk of experiencing oral symptoms 1.466 times. Also, this study showed the highest risk of oral symptoms I and II when the frequency of exposure to SHS was 5 to 6 times a week (odds ratio [OR]: 1.643, OR: 1.855, respectively). The risk of oral symptom III (sore and bleeding gums) successively increased as the frequency of exposure increased. A previous study that analyzed data from the Korea National Health and Nutrition Examination Survey27) reported that the effects of SHS on periodontal diseases in adults are not clear compared to first-hand smoking, but it should be considered as a risk factor. In addition, a study of American adults showed a 29% increase in severe periodontitis in those who were exposed to SHS for 1 to 25 hours per week, and the odds were twice higher in those exposed to SHS for 26 hours or longer per week than those who were not exposed to SHS10). However, a study of adolescents also reported the association between SHS and periodontal diseases. A study by Choi et al.16) reported that adolescents who were exposed to SHS at home or in public places had a higher rate of experiencing gingival pain and bleeding than those who were not exposed to SHS, which supports the results of this study.
Smoking increases the risk of periodontal diseases, and cotinine, a key metabolite of nicotine, damages host reaction, activates Porphyromonas gingivalis, the causative organism of periodontal disease, and is known to induce periodontal diseases28). Cotinine has a half-life of 19 to 30 hours29) and is used as a biochemical index for smoking28). According to a previous study, the level of cotinine, a key metabolite of nicotine, in the saliva of children who were exposed to SHS increases30). In the case of SHS, the cotinine level in the saliva is 1∼7 ng/mL, which can be 10 ng/ml or greater for severe SHS31). Given the association between SHS and the incidence of periodontal disease, dental institutions should determine smoking status, including SHS, when seeing adolescents with oral symptoms, such as tooth pain or bleeding gums as a plan to prevent periodontal diseases in adolescents and educate not only adolescents but also their caregivers about first-hand smoking during the adolescent period and the effects of SHS on oral health.
Since this study investigated data from adolescent students, we were not able to identify data from adolescents who did not go to school. Also, the respondents might be less honest about sensitive questions regarding SHS. In addition, since there is a high probability of having statistically significant results because of a large number of subjects due to the nature of big data, caution should be taken when interpreting the study results. Another limitation is that sub-variables among investigation items, known to be related to SHS, such as relationships with friends, were not various. Nevertheless, this study analyzed representative data from the survey that included the entire adolescent population and identified status and trends in SHS among adolescents. This study also reviewed the association between the level of SHS and oral symptoms.
In future research, it is necessary to investigate the reality of SHS among adolescents by including those who do not go to school, and not only the frequency of SHS, but also the length of stay in a place where an individual is exposed to SHS, and various SHS-related factors, such as first-hand smoking, should be identified to investigate their associations with oral symptoms.
None.
Conflict of interest
No potential conflict of interest relevant to this article was reported.
Ethical approval
The 2021 Youth Risk Behavior Web-based Survey (17th survey) was a government-approved undertaking (approval number 117058) based on the National Health Promotion Act.
Author contributions
Conceptualization: Eun Bi Sim. Data acquisition: Eun Bi Sim. Formal analysis: Bo Young Park and Eun Bi Sim. Supervision: Bo Young Park and Eun Bi Sim. Writing-original draft: Bo Young Park and Eun Bi Sim. Writing-review & editing: Bo Young Park and Eun Bi Sim.
Funding
None.
Data availability
The datasets used and/or analyzed during the current study available from the corresponding author on reasonable request.
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