Most studies on ETS exposure of non-smoking adolescents have focused on the prevalence of respiratory or mental diseases. However, we aimed to determine the association between ETS and oral health status in adolescents. The results of this study found that non-smoking adolescents who experienced ETS exposure more than once had various oral symptoms regardless of the sex.
The mechanism behind these results can be explained by the results of previous studies. One study reported that ETS exposure may lead to a decrease in saliva flow rate and salivary α-amylase activity along with an increase in peroxidase activity, indicating the incidence of oxidative stress [19]. Another study reported that ETS exposure could lead to elevation of interleukin-1beta, albumin, and aspartate aminotransferase levels in saliva [20]. Considering these mechanisms, abnormal oral health symptoms in non-smoking adolescents could result from ETS exposure.
The present study also reports that the association between ETS exposure and oral health is statistically significant even when adolescents have different oral health management behaviors. However, the adverse effects of ETS exposure on oral health symptoms of adolescents can be reduced by good health habits, such as brushing teeth more often and consuming soda less frequently.
Previous studies have shown that adolescents who brush their teeth twice or more a day have significantly lower incidence of caries and counts of decayed, missing, or filled teeth [21]. These preventive oral health behaviors may lower the effects of ETS exposure. Lifestyle factors such as drinking soda also lead to negative oral health symptoms. Increased soda consumption is significantly associated with the prevalence of dental erosion, according to a previous study [22, 23].
Additional subgroup analyses of the locations and frequencies of ETS exposure confirmed that there was a statistically significant occurrence of oral health symptoms in both sex groups when they experienced ETS exposure at home. Furthermore, frequent ETS exposure at other indoor locations was associated with oral health symptoms. However, a significant association between frequent ETS exposure at school and oral health symptoms when compared with non-school ETS exposure, was observed only in female adolescents.
A previous study with a purpose similar to that of our study showed that children of parents who smoked a higher number of cigarettes reported higher cotinine concentrations than children of non-smoking parents [13]. Furthermore, another study showed that adults who experienced ETS exposure for more than two hours per day had a higher risk of cardiovascular disease than adults who experienced it for less than two hours per day [24]. As shown in these studies, the frequency of ETS could become an important factor that determines the wellness of individuals who are exposed to ETS.
Finally, the present study examined the association between ETS exposure and the prevalence of these three oral symptoms. There was a significant association between ETS and dental pain and gum bleeding in the male adolescent group and tooth fracture, dental pain, and gum bleeding in the female adolescent group. These results based on sex differences are similar to those of several previous studies, which show a stronger association of ETS with numerous diseases in the female group than in the male group; however, this should be interpreted cautiously and investigated further [25, 26].
This study has several limitations that should be considered. First, cross-sectional data were used. Therefore, the association between variables could be confirmed; causality could not be determined. Second, the results were derived from self-reported data. We specifically assessed the oral health symptoms of an individual, ETS frequencies, socioeconomic status, and health behavior covariates based on self-reported data. This finding may have been subject to recall bias [27]. Hence, the data may not have been accurately measured and may not be reliable. To provide more reliable results, future research should be conducted using the results of clinical examinations to assess the oral health status and levels of ETS exposure. Third, there might be factors such as individual lifestyle and personal traits, which co-vary with the oral symptoms of an adolescent and are not considered in this research model.
Despite these limitations, our study has several strengths. First, we used nationally representative data that were suitable for generalizing the results of the study to the overall South Korean adolescent population in middle and high schools. Furthermore, KYRBWS is an anonymous web-based survey that is likely to obtain relatively honest responses [28]. Third, in South Korea, few studies have been performed on the associations between ETS and oral health of adolescents, which analyzes these relationships in multi-dimensional aspects.